Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: neilep on 28/01/2007 23:13:32

Title: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 28/01/2007 23:13:32
In this country (UK) Diesel is more expensive than petrol (gasoline !...sheesh!! Ok US peeps!!)...but...you get many more miles to the gallon with diesel than petrol.

me is not a mechanic or a petro chem engineer..me is a wooly four legged trans-gender sheep.

Is it possible (in a john and jane fashion) to explain the differences between the two fuels and also the mechanics of the different engines !

How far would I get if I put petrol (gas...sheesh !!) in a diesel engine ?...and the other way round ?

I suppose I could wiki the answers but that would negate the premise of this forum and me wants to know the answers.

Spank Ewe

neil
xx

[MOD - Subject edited for clarity - CS]
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 28/01/2007 23:33:27
Deisel is like kerosene and it is not as explosive as gas, so it doesn't have as much energy potential as petrol, whereas the gas has a higher energy potential.

If you put diesel into a regular gas powered engine, it would probably run crudy if at all!  I believe that I have that the right way!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: elegantlywasted on 29/01/2007 15:20:01
Ha! A friend of mine did this, very funny.. and expensive.

First of all the nozzle sizes are different, diesel gas will not fit into a regular engine, but a regular gas (petrol) pump will fit into a diesel tank.


Now when that happens  you will be able to drive for a few clicks, then the engine will shudder then die. And it will cost you lots of money, lots.


Now in a bit of research I found this site http://www.straightdope.com/mailbag/mdieselvsgas.html (http://www.straightdope.com/mailbag/mdieselvsgas.html) It explains everything in more detail.


It basically explains the difference between the two types of engines. Gasoline is burned in a spark ignition system. Essentially the vapour of the gas and air mix, compress and then a spark is added and we have combustion... and exhaust. Now a diesel engine is burned in a compression ignition engine. Where air is drawn into the engine and the fuel and air compress (higher than regular fuel) and it self ignites.


Now from what I understand, and I am no mechanic (i've only dated a few) gasoline going into a diesel engine is a far worse (regular gas doesn't self ingnite) so you wont go anywhere and possibly will ruin your fuel pump and you will need to have all of the fuel lines in your car flushed out.


Diesel going into a gasoine engine will cause you have to flush the lines, but if you haven't put a large amount of diesel into the fuel tank the car should run, it may however shudder alot and run kindo of crappily (is that a word?) But if you have added alot or diesel, expect your car to stop, and a bill for mucho expensive car repairs.]
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: eric l on 29/01/2007 16:23:23
Sometimes a little amount (less than 5 %) of gasoline is added to diesel fuel to prevent parafin gelling in winter times.  This can only count as an emergency measure !
Diesel engines generally draw in air, rather than a mix of air and gasoline.  The compression heats up the air, and the fuel is injected into the combustion chamber as the piston nears the top dead center.
Under certain conditions, gasoline (petrol) engines can "diesel", which means they do not need a spark to ignite (the residual heat in the spark plug will be enough to ignite the compressed and hot mixture).  If this happens, even shutting off the engine will not stop it.  Unlikely to happen with modern engines, and almost impossible when you have fuel injection rather than mixing air and gasoline (petrol) in a carburetor. 
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 29/01/2007 16:41:54
Good Job you two....I have a post around here somewhere where we were discussing the differences in the two fuels and types of engines.. both me boys are mechanics... and hubby drives a big rig and knows a great deal about these engine...
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: daveshorts on 29/01/2007 17:05:22
Both petrol and diesel are hydrocarbons, they are mae up of hydrogen and carbon. Hydrogen and carbon make up chains eg:

CH3-CH2 - CH2 ...

Although the chains are not allways straight, they can have brances and rings etc.

the big difference between the two is that petrol has 5-10 carbon atoms in it where as diesel has 17-20. this has various effects the first being that because diesel has longer chains they tangle and stick together better so it has a higher boiling point - it doesn't evaporate so quickly. This also means it is not nearly as flamable, because you have to evaporate the fuel to get it well mixed with air in order to burn. Hence you can drop a lighted match into diesel and it won't burn.

This difference in property makes how you ignite the two fuels in an engine different.
In a petrol engine you compress the air an fuel a bit, in order to get more of it in the cylinder then use the spark plug to cause ignition firing the piston down the cylinder.

With diesel a spark is not nearly enough to ignite it, what you do instead is compress the fuel and air very violently causing it to heat enormously and ignite.

There are two reasons diesels get a better mpg than petrol.
1. the fuel is denser so you get more of it in a litre.
2. The high compression cycle is in fact intrinsically more efficient.

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 29/01/2007 17:11:15
 Cool Dave..Could you explain the compression cycle a tad bit??
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 30/01/2007 00:14:34
Deisel is like kerosene and it is not as explosive as gas, so it doesn't have as much energy potential as petrol, whereas the gas has a higher energy potential.

If you put diesel into a regular gas powered engine, it would probably run crudy if at all!  I believe that I have that the right way!

Thank Ewe Karen mam...very helpful indeed

YAYYYYYYYYYYYY !!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 30/01/2007 00:15:49
Ha! A friend of mine did this, very funny.. and expensive.

First of all the nozzle sizes are different, diesel gas will not fit into a regular engine, but a regular gas (petrol) pump will fit into a diesel tank.


Now when that happens  you will be able to drive for a few clicks, then the engine will shudder then die. And it will cost you lots of money, lots.


Now in a bit of research I found this site http://www.straightdope.com/mailbag/mdieselvsgas.html (http://www.straightdope.com/mailbag/mdieselvsgas.html) It explains everything in more detail.


It basically explains the difference between the two types of engines. Gasoline is burned in a spark ignition system. Essentially the vapour of the gas and air mix, compress and then a spark is added and we have combustion... and exhaust. Now a diesel engine is burned in a compression ignition engine. Where air is drawn into the engine and the fuel and air compress (higher than regular fuel) and it self ignites.


Now from what I understand, and I am no mechanic (i've only dated a few) gasoline going into a diesel engine is a far worse (regular gas doesn't self ingnite) so you wont go anywhere and possibly will ruin your fuel pump and you will need to have all of the fuel lines in your car flushed out.


Diesel going into a gasoine engine will cause you have to flush the lines, but if you haven't put a large amount of diesel into the fuel tank the car should run, it may however shudder alot and run kindo of crappily (is that a word?) But if you have added alot or diesel, expect your car to stop, and a bill for mucho expensive car repairs.]

YAYYYYYYYYYYYY !!

Thank EWE Meg...and me appreciates the excellent link also...me knows stuff now ..YAYYYYYYYY !!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 30/01/2007 00:16:53
Sometimes a little amount (less than 5 %) of gasoline is added to diesel fuel to prevent parafin gelling in winter times.  This can only count as an emergency measure !
Diesel engines generally draw in air, rather than a mix of air and gasoline.  The compression heats up the air, and the fuel is injected into the combustion chamber as the piston nears the top dead center.
Under certain conditions, gasoline (petrol) engines can "diesel", which means they do not need a spark to ignite (the residual heat in the spark plug will be enough to ignite the compressed and hot mixture).  If this happens, even shutting off the engine will not stop it.  Unlikely to happen with modern engines, and almost impossible when you have fuel injection rather than mixing air and gasoline (petrol) in a carburetor. 

Excellent Eric...Many many thanks indeed !!....as always..a font of knowledge....YAYYYYYYYYYYY !!!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 30/01/2007 00:19:37
Both petrol and diesel are hydrocarbons, they are mae up of hydrogen and carbon. Hydrogen and carbon make up chains eg:

CH3-CH2 - CH2 ...

Although the chains are not allways straight, they can have brances and rings etc.

the big difference between the two is that petrol has 5-10 carbon atoms in it where as diesel has 17-20. this has various effects the first being that because diesel has longer chains they tangle and stick together better so it has a higher boiling point - it doesn't evaporate so quickly. This also means it is not nearly as flamable, because you have to evaporate the fuel to get it well mixed with air in order to burn. Hence you can drop a lighted match into diesel and it won't burn.

This difference in property makes how you ignite the two fuels in an engine different.
In a petrol engine you compress the air an fuel a bit, in order to get more of it in the cylinder then use the spark plug to cause ignition firing the piston down the cylinder.

With diesel a spark is not nearly enough to ignite it, what you do instead is compress the fuel and air very violently causing it to heat enormously and ignite.

There are two reasons diesels get a better mpg than petrol.
1. the fuel is denser so you get more of it in a litre.
2. The high compression cycle is in fact intrinsically more efficient.



This is wonderful Dave...THANK EWE so much....don't suppose you have any idea how hot Diesel gets to ignite under those conditions ?...are we talking about a lot lot lot hotter than petrol ?...does that mean Diesel engines run a lot hotter too ?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: daveshorts on 31/01/2007 14:35:57
If you compress a gas it gets hotter, If you have ever pumped up a bicycle tyre enthusiastically you may have noticed the pump getting hotter..

Apparantly petrol will burn with a flame at -45 °C but diesel will not do so until 65 °C which is a big difference. This is why you couldn't ignite diesel with a spark unless you really pre-heated it.

Interestingly diesel will spontaineously ignite with no flame at 210 °C but petrol not until 265 °C, so a diesel probably wouldn't ignite if you filled it with petrol, and vice versa.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 31/01/2007 18:15:21
It basically explains the difference between the two types of engines. Gasoline is burned in a spark ignition system. Essentially the vapour of the gas and air mix, compress and then a spark is added and we have combustion... and exhaust. Now a diesel engine is burned in a compression ignition engine. Where air is drawn into the engine and the fuel and air compress (higher than regular fuel) and it self ignites.

Now from what I understand, and I am no mechanic (i've only dated a few) gasoline going into a diesel engine is a far worse (regular gas doesn't self ingnite) so you wont go anywhere and possibly will ruin your fuel pump and you will need to have all of the fuel lines in your car flushed out.
Diesel going into a gasoine engine will cause you have to flush the lines, but if you haven't put a large amount of diesel into the fuel tank the car should run, it may however shudder alot and run kindo of crappily (is that a word?) But if you have added alot or diesel, expect your car to stop, and a bill for mucho expensive car repairs.
Diesel fuel has a much lower Octane Number than gasoline. They infact have to behave in an opposite way: gasoline have to resist compression together with air as much as possible, without spontaneously ignite. Diesel have to ignite when compressed with air, as easily as possible. In the case of Diesel fuel this caracteristic is called Cetane Number.

If you put diesel fuel in a gasoline engine, it will ignite too early before the piston arrives at his maximum point, and this will cause an increase in the top temperature of the piston, fusing it; or can cause detonation, which can destroy the piston. This is worse than replacing pipes and fuel pump, believe me! However, modern engines have a lot of sensors to monitor the correct functioning, and this will not probably happen easily.

Anyway, your explanation of the two different kind of engines was very good, my compliments to you!

By the way, why are you "elegantlywasted"?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 31/01/2007 18:26:52
This is wonderful Dave...THANK EWE so much....don't suppose you have any idea how hot Diesel gets to ignite under those conditions ?...are we talking about a lot lot lot hotter than petrol ?...does that mean Diesel engines run a lot hotter too ?
As Dave said, Diesel engines have a higher compression rate, because the higher it is, the greater the thermodynamical efficiency (gasoline cannot be compressed so much together with air, but Diesel engines compress air without fuel!).
So, Diesel engines run, intrinsically, hotter than gas engines; but they usually run at lower rpm, with a bit more fuel than what is required and have heavier pistons; these 3 things prevent them to get too hot.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 31/01/2007 18:35:41
THANK YOU ALBERTO...and THANK YOU DAVE.


I really appreciate the explanations. Very helpful...and because of you..I now know.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ukmicky on 01/02/2007 20:44:02
The problem with desiel is less energy is released when it ignites ,so deisel cars have less power, so there drivers tend put their foot down a bit more and in the end they end up filling up more than petrol car owners.  And on top of that they polute more than petrol driven cars.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 02/02/2007 00:09:57
The problem with desiel is less energy is released when it ignites ,so deisel cars have less power, so there drivers tend put their foot down a bit more and in the end they end up filling up more than petrol car owners.  And on top of that they polute more than petrol driven cars.

Is that a fact ?...me did not know this !!

The premise behind this thread is because I am doing silly miles a week seeing my clients...and my car ?...a petrol guzzling  automatic 7 seater people carrier !!!.....my car takes £60 average to fill....surely there must be some compromise in pollution if I can do a lot less fuel stops and also save me money. I am thinking seriously about getting just a really small diesel...Toyota Yaris...or even  hyundai getz (with a 5 year warranty thrown in).

whajafink matey ?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 02/02/2007 02:37:57
Hey what does the hyundai  look like.. I have a huge gas guzzler also..8 passenger mini van.. I like my gas guzzler as far as comfort goes, but gas stinks.. LOL
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 02/02/2007 03:36:50
Hey what does the hyundai  look like.. I have a huge gas guzzler also..8 passenger mini van.. I like my gas guzzler as far as comfort goes, but gas stinks.. LOL

The Hyundai is a just a really small car..I need it to be small car. I need it to be small for all the miles I do...and parking is hard with a people carrier. We don't have any of the space you have Karen mam.....But it does need to carry my exhibition cabinet and banner....

ho hum !!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 02/02/2007 04:09:25
Is that big enough to carry your things..? Mine only seats one more then yours
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 02/02/2007 13:06:20
The problem with desiel is less energy is released when it ignites ,so deisel cars have less power, so there drivers tend put their foot down a bit more and in the end they end up filling up more than petrol car owners.  And on top of that they polute more than petrol driven cars.
Sorry Michael but I think what you say is not correct.
Diesel engines have a greater torque than petrol engines with the same cc. So, If they could run at the same rpm, their power would actually be greater. Infact they actually releases more energy than petrol engines when the same amount of air/fuel mix ignites, because of the greater intrinsic efficiency.
To compare how much fuel a Diesel consumes against a petrol fuel, we should have two engines with the same cc and the same weight of the cars.

Having said this, I personally hate Diesels, however, because of how much they pollute. Have you ever noticed that strange, bleach-like smell coming from modern diesel's exaust? If you haven't, try to do it. That is the smell of nitrogen dioxyde: NO2. Have you ever heard of the poison carbon monoxide CO? Ok. NO2 is 500 times more poisonous. And it's also carcinogenic. Nano particles of the smoke are carcinogenic too. Why these informations are not revealed? When will governments stop being paid from car companies and will tell us the truth?  [:(!]
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 03/02/2007 04:24:09
JEESE LOUISE THAT'S SCARY! I had no Idea it was that much higher in poisons.. and carcenogens.. Yikes. I knew they all held them but that is a lrge amount over the others!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: daveshorts on 03/02/2007 14:25:09
Modern diesels are really nice, I drove a ford Focus estate about 6 years ago and it drove like a nice petrol engine (unless you are possibly a racing driver) and used very little fuel.

On a similar note, about 5 years ago I went on a science tour with a long wheelbase transit, and a petrol mondeo  estate, and despite the fact the van is huge and aerodynamiclly far worse they both cost the same in fuel.. do the maths.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 03/02/2007 15:18:33
I think Diesel is the way...and the engines are getting better and better...after all..if they were really that bad they would be banned wouldn't they ?...or am I being naive ?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: eric l on 03/02/2007 15:40:21
I remember the days when the rotary piston engine (Wankel-engine)was heralded as the engine of the future.  What has happened to it ? 

At another moment, gasturbines were "te engine of the future" - it must have been in the late 1960's that a gas turbine powered car was racing at Le Mans.  Never heard of it again.  If i'm not mistaken, the latest winner at Le Manswas a Dieselpowered Audi.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ukmicky on 03/02/2007 22:53:05
The problem with diesel is less energy is released when it ignites ,so diesel cars have less power, so there drivers tend put their foot down a bit more and in the end they end up filling up more than petrol car owners.  And on top of that they polute more than petrol driven cars.
Sorry Michael but I think what you say is not correct.
Diesel engines have a greater torque than petrol engines with the same cc. So, If they could run at the same rpm, their power would actually be greater. Infact they actually releases more energy than petrol engines when the same amount of air/fuel mix ignites, because of the greater intrinsic efficiency.
To compare how much fuel a Diesel consumes against a petrol fuel, we should have two engines with the same cc and the same weight of the cars.

Having said this, I personally hate Diesels, however, because of how much they pollute. Have you ever noticed that strange, bleach-like smell coming from modern diesel's exaust? If you haven't, try to do it. That is the smell of nitrogen dioxyde: NO2. Have you ever heard of the poison carbon monoxide CO? Ok. NO2 is 500 times more poisonous. And it's also carcinogenic. Nano particles of the smoke are carcinogenic too. Why these informations are not revealed? When will governments stop being paid from car companies and will tell us the truth?  [:(!]
But petrol car produces more BHP per litre , jump into a 1600 diesel and then a 1600 petrol and see which one accelerates faster ,the petrol will win everytime.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 05/02/2007 08:22:11
The problem with diesel is less energy is released when it ignites ,so diesel cars have less power, so there drivers tend put their foot down a bit more and in the end they end up filling up more than petrol car owners.  And on top of that they polute more than petrol driven cars.
Sorry Michael but I think what you say is not correct.
Diesel engines have a greater torque than petrol engines with the same cc. So, If they could run at the same rpm, their power would actually be greater. Infact they actually releases more energy than petrol engines when the same amount of air/fuel mix ignites, because of the greater intrinsic efficiency.
To compare how much fuel a Diesel consumes against a petrol fuel, we should have two engines with the same cc and the same weight of the cars.

Having said this, I personally hate Diesels, however, because of how much they pollute. Have you ever noticed that strange, bleach-like smell coming from modern diesel's exaust? If you haven't, try to do it. That is the smell of nitrogen dioxyde: NO2. Have you ever heard of the poison carbon monoxide CO? Ok. NO2 is 500 times more poisonous. And it's also carcinogenic. Nano particles of the smoke are carcinogenic too. Why these informations are not revealed? When will governments stop being paid from car companies and will tell us the truth?  [:(!]
But petrol car produces more BHP per litre , jump into a 1600 diesel and then a 1600 petrol and see which one accelerates faster ,the petrol will win everytime.
As I said, you cannot compare an engine's power in this way, because power is not only given by the mechanical energy from a single cycle (at the same capacity = cc), but from rpm also. You cannot compare, for example a 1600 diesel which max rpm is 4000 and a 1600 petrol which max rpm is 6000; to do this theoretically, you should multilply the diesel power by 6000/4000.

Furthermore, a diesel vehicle is usually lighter than a petrol one of the same cc, so, if you want to compare the power' engine from the vehicle's acceleration, you should also multiply the diesel power by W1/W2 where W1 is the diesel vehicle's weight and W2 the petrol vehicle's weight.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ukmicky on 05/02/2007 15:25:31
Quote
Furthermore, a diesel vehicle is usually lighter than a petrol one of the same cc, so, if you want to compare the power' engine from the vehicle's acceleration, you should also multiply the diesel power by W1/W2 where W1 is the diesel vehicle's weight and W2 the petrol vehicle's weight.

Sorry i think you will find diesel vehicles are much heavier than petrol equivalent.

A diesel engine may be simpler than a petrol and requires less ancillary components due to the simplicity of its design however the diesel engine runs at a much higher temperature and compression ratio than the petrol variant and therefore requires a much heavier and stronger block which adds greatly to the overall weight of the vehicle.

Also diesel engine's tend to be low revving units and deliver their torque low down in a very narrow band of their rev range meaning they tend to run out of steam very very quickly compared to the petrol equivalent.  Yes get one if you live in the countryside and need low down pulling power for your four wheel drive or if your often towing caravans up steep hills.
Diesel engines also tend to require more frequent servicing in order to prevent their performance from dropping and without them frequent services they also tend to pollute quite a bit more than petrol . They smell more,run on the most unpleasant stuff you can get on your hands or clothes,their noisier especially when they first start and after a few years of service.
Their very inefficient after high millages and cost more to insure and purchase. Why would anyone want one.


Petrol engines are much lighter than diesel engines with many of their components being made out of alloy and are higher reeving compared to diesel counterparts, Their supremely more responsive with the deliverance of their power and they deliver that power across a much broader spectrum of the rev range .  Petrol WINS everytime ask Aston Martin,Ferrari or Porsche .
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: rosy on 05/02/2007 17:14:07
The AA have already done all the maths here:
http://www.theaa.com/motoring_advice/running_costs/index.html

It appears at a cursory glance that for the cheapest end of the range diesels have running costs of maybe 1p/mile more than petrol cars whereas at the upper end of the cost range diesels provide significantly better value.

Of course, since this is the AA there's no information whatever about emmissions of carbon, SOx, whatever.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 05/02/2007 20:37:42
Quote
Furthermore, a diesel vehicle is usually lighter than a petrol one of the same cc, so, if you want to compare the power' engine from the vehicle's acceleration, you should also multiply the diesel power by W1/W2 where W1 is the diesel vehicle's weight and W2 the petrol vehicle's weight.

Sorry i think you will find diesel vehicles are much heavier than petrol equivalent.
Sorry Michael, you are right. I made a mistake, I intended: "...a diesel vehicle is usually heavier than...", exactly for the reasons you write. Apologize!
Quote
A diesel engine may be simpler than a petrol and requires less ancillary components due to the simplicity of its design however the diesel engine runs at a much higher temperature and compression ratio than the petrol variant and therefore requires a much heavier and stronger block which adds greatly to the overall weight of the vehicle.
Also diesel engine's tend to be low revving units and deliver their torque low down in a very narrow band of their rev range meaning they tend to run out of steam very very quickly compared to the petrol equivalent.  Yes get one if you live in the countryside and need low down pulling power for your four wheel drive or if your often towing caravans up steep hills. Or if you never need to feel a quick response whilst travel quickly.
Diesel engines also tend to require more frequent servicing in order to prevent their performance from dropping and without them frequent services they also tend to pollute quite a bit more than petrol . They smell more,run on the most unpleasant stuff you can get on your hands or clothes,their noisier especially when they first start and after a few years of service.
Their very inefficient after high millages and cost more to insure and purchase. Why would anyone want one.
Because modern diesels makes more km with 1 litre of fuel, and because diesel fuel cost less than petrol (at least here!). Of course they don't consider the long-term costs, as you pointed out.
Quote
Petrol engines are much lighter than diesel engines with many of their components being made out of alloy and are higher reeving compared to diesel counterparts, Their supremely more responsive with the deliverance of their power and they deliver that power across a much broader spectrum of the rev range . Petrol WINS everytime ask Aston Martin,Ferrari or Porsche.
At the moment, the higher rate power/weight is of petrol's engines, but, if we don't look at the most performant (sport/race) engines, and we are not interested in high rpm, low fumes ecc., diesels are better. Furthermore diesel engines are improving faster than the corrisponding petrol ones; this is the reason there are much more diesels now than 10 years ago, and it's the reason there will be more. Here in Italy, most modern cars sold are diesel ones! If no improvement on petrol engine's efficiency will be made in a few years, you can be sure that we will see diesels on races too, in the future!
When I bought my car 4 years ago, a 1600 petrol Alfa 147, I made a "nostalgic" choice, because if I bought a diesel one (JTD 1900), I would have had a faster car (acceleration and speed), with lower fuel used! (However, I use GPL, more than petrol).
If I had to buy a new car now, I would still buy a petrol one but only because I hate how much diesels pollute, and because I want to listen to the "real" sound of an engine.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ukmicky on 05/02/2007 23:36:57
Hi Alberto

Diesel was once very cheap over here in the UK now its on par and on some occasions more expensive than petrol,but these days everything in the UK is expensive.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 07/02/2007 01:05:44
The same here. [:-'(]
Bye Michael.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: chris on 12/02/2007 10:32:21
This is a really interesting thread, but the one thing we've not done is to explain in any great detail how diesel engines versus petrol engines actually work.

Petrol engines have sparkplugs. The fuel is drawn into the cylinder pre-mixed with air, or injected as the cylinder fills with air as the piston is descending (this is the induction stroke). The piston then begins to ascend again (compression stroke), compressing the cylinder contents, which is the petrol/air mixture. At just before top dead centre (TDC) the sparkplug fires, igniting the compressed mixture, which begins to burn.

Burning hydrocarbons in air produces gaseous products (chiefly oxides of carbon, and water). Since gases take up more volume than liquids, the contents of the cylinder expand as they burn, forcing the piston back down inside the cyclinder (the power stroke). The piston then re-ascends the cylinder, pushing the exhaust gases out through the exhaust valves, and then begins a new induction cycle. (Please note that this is the schema for a four-stroke engine).

A turbo or super-charged engine works slightly differently. In this case power is taken from the engine (usually by driving an impeller in the exhaust) and use to drive a compressor. This forces air into the cylinder during the induction stroke. Because the cylinder contains more air it can burn more fuel and hence produce more energy. And because the amount of air forced into the cylinder increases as the engine speeds up that's why you experience an initial lag in pick up when you put your foot down at low engine speeds.

A diesel engine is different. This has no sparkplugs and instead relies on sheer heat to ignite the fuel. During the induction stroke, the descending piston pulls just air into the cylinder, which is compressed as the piston ascends. Just as a bike pump gets hot when you inflate a tyre, the air being compressed inside the cyclider heats up. In the average engine it probably reaches 700-900 degrees C. Diesel engines have a higher compression ratio, at 20:1, than petrol engines, which usually compress at about a 10:1 ratio.

When the piston gets to the top of the cylinder, the fuel is injected as a fine (atomised) mist. The intense heat of the compressed air causes the fuel to burn, again producing gaseous (high-volume) products that drive the piston down, generating power. A turbocharger in this context works similarly to a petrol turbo - a compressor forces in more air, increasing the compression in the cylinder, the amount of oxygen in the cylinder and hence the amount of fuel that can be burned in the cylinder. The more fuel you burn the more energy you liberate.

Chris

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 12/02/2007 20:41:01
This is a really interesting thread,




THANK YOU very much Chris.....You've dotted the 'i 's and crossed the 't's

Those diesel engines run HOT !!!

many thanks
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 13/02/2007 02:21:24
Burning hydrocarbons in air produces gaseous products (chiefly oxides of carbon, and water). Since gases take up more volume than liquids, the contents of the cylinder expand as they burn, forcing the piston back down inside the cylinder (the power stroke). The piston then re-ascends the cylinder, pushing the exhaust gases out through the exhaust valves, and then begins a new induction cycle. (Please note that this is the schema for a four-stroke engine).

In my understanding, this would not be very significant.  Most of the volume of matter in the cylinder is already gaseous (mostly air).  The big expansion, as I understood it, was because of the input of heat from combustion, and a hot gas takes more room than a cold gas (which is why, with turbocharged cars, they like to add intercoolers, so you start the air off cooler, so there is even more expansion when the mixture heats up).
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: chris on 13/02/2007 12:15:22
Sure, but you need to consume energy to cool incoming air, pack more air into a cylinder in the first place and then compress it (in a diesel engine this is referred to as adiabatic compression). Burning the fuel liberates large amounts of gas AND heat, both of which cause expansion within the cylinder and hence the ability to extract "work".

Chris

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 13/02/2007 19:26:46
As a long term diesel car driver (since 1988) I am, err how do I put this politely - ummmm amazed will do - at the ignorance on here about diesel.
Chris and daveshorts seem to be the only contributors who have the slightest idea of anything to do with diesel.

As for Louise (I think) and the carcinogens? Well my flabber is well and truly ghasted, has she been sniffing petrol?

1 Diesels are way more efficient than petrol engines; my son has a 999cc petrol car that struggles to do much over 40(imperial)MPG and is slow and a pain to drive anywhere as any overtaking has to be planned a week in advance. My daughter drives a similar sized car (same make, but later slightly larger model) that has much more equipment inc. air con etc but it has a 1910cc turbo diesel engine. It does well 50mpg overall and is a pleasure to drive in any type of traffic and cruises easily (on my private test track of course) at 100mph when the engine is doing just 3000rpm. It is way faster, accelerates much quicker (and stronger) and does around 30-40% more to the gallon.

2 Diesel engines used to be much heavier than petrols until makers like Peugeot/Citroen started the trend to dieselising petrol engines with the XUD engine in the mid 80's. Diesel engines now are usually less than 10% heavier than their petrol equivalent.

3 Diesel engines are not about BHP a purely artificial measure of power that is simply the torque (the real strength of an engine that does the work) times RPM times a constant.
Torque is therefore the real measure of how "good" and engine is and diesels typically have over twice the torque of equivalent petrol engine and develop it at half the RPM.
This is NOT a failing as some of you seem to think, but an advantage. Diesels do not HAVE to rev to do useful amounts of work as petrols do and revs are what kill engines as wear increases exponentially as RPM rises. Double the revs and you get 4 times the wear.  This is why diesel engines last much much longer than petrols allied to the fact that diesel fuel lubricates whilst petrol destroys lubrication by washing away the engine oil from the cylinder walls. The "lack" of revs is irrelevant as diesels can pull far higher gearing (how many small petrol engined cars are doing 3000RPM @ 100MPH like my daughter's car - in fact how many petrol cars of any size do that??)

4 Diesel emissions are worse in some respects that petrol but way better in others. CO2 is much lower CO is absent (you can't commit suicide with a diesel exhaust) PM10 particulates may be higher (it depends on the car and the quality of fuel used) but PM2.5s and PM5s are not thought to be any worse than petrol (yes petrols emit particulates too) and current thinking is that the smaller particulates are worse for health as they lodge lower in the respiratory tract and lungs - so petrol fumes might be equally bad for us in that respect, especially now that more diesels are being fitted with particulate traps and petrols aren't.

5 Diesels do NOT run hotter, because they are more thermally efficient than petrols, more heat is converted into power/torque so the engines actually run cooler, even though the combustion temperature is higher.

6 Petrol apologists always conveniently forget about all the nasties in petrol - benzene for one. Benzene is a known carcinogen so toxic that there is NO safe exposure level and petrol gives off benzene even when the engine isn't running. Petrol is also volatile and downright dangerous just look at any car that crashes in any US action film - it has exploded in flames before it even hits the barrier - that just couldn't/wouldn't/doesn't happen with diesel. As someone said you can throw a match in a bucket of diesel and it will go out - just don't try it with a bucket of petrol.

All major car makers, even the US ones (but they won't admit it at home) see diesel as the way to go. Audi even Grand Slammed the Le Mans series with a Tdi diesel car last year and Peugeot are entering a Hdi competitor this year. The Audi was so superior that the petrolheads are trying to change the rules so they have even the slightest chance of winning.

Diesel is the future and once anybody has tried a good one (there are still some bad ones left) few ever go back to petrol.

www.dervhead.com

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 14/02/2007 01:25:41
Scanner has some points, but I don't agree with them all.

No question that diesel has come a long way, but then so too has petrol.

The question of benzene in petrol is, I believe, and unfortunate side effect of having gone unleaded (the old leaded petrols had far less benzene in them, but politically it was not considered wise to make too big a fuss over benzene levels in unleaded if the government were going to sell the idea of replacing leaded petrol with unleaded).

Diesel certainly has much going for it, but it is at best an interim solution, and is politically unlikely to be satisfactory (not least because most political pressure groups want to move away from any petrochemical fuel – although whether they succeed in that is another matter).

The argument that diesels will still provide the same performance as petrol is not in my experience true, although there is no doubt that the gap is closing.  Diesels, with their high torque, can provide quite a bit of flexibility, but the engines still are less responsive to sudden demands for more power.  This is even true when one looks at high compression, long stroke,  petrol engines do not have the responsiveness of square bored engines, but have better efficiency.  Diesel engines just take this to the extreme.

Ofcourse, some of the difference is down to marketing – since diesels are marketed for fuel economy and longevity, they will not be optimised for raw performance.  Given the convergence of the capabilities of the two technologies, it may well be that we are close to designing petrol engines with the same efficiency as diesel, and diesel engines with the same performance as petrol, but the buyers for each market would be looking for different things.

And, yes, a lot of the old reputation that diesels had of being smelly and dirty is now out of date (at least for modern diesel cars) – that is, unless you are going to fill them up with vegetable oil, which can be used to fuel diesels, although it is illegal because motor tax has not been paid on the vegetable oil.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 14/02/2007 18:05:10
First of all, hi scanner! Welcome on this Forum!
As a long term diesel car driver (since 1988) I am, err how do I put this politely - ummmm amazed will do - at the ignorance on here about diesel.
Chris and daveshorts seem to be the only contributors who have the slightest idea of anything to do with diesel.
As for Louise (I think) and the carcinogens? Well my flabber is well and truly ghasted, has she been sniffing petrol?
I'm italian and I have some problems in understanding these terms. However I said that Diesel vehicles pollute the air, more than petrol vehicles (and all people breath the air, not only diesel's drivers); I work in Sanity Department, you can believe me.
Quote
1 Diesels are way more efficient than petrol engines; my son has a 999cc petrol car that struggles to do much over 40(imperial)MPG and is slow and a pain to drive anywhere as any overtaking has to be planned a week in advance. My daughter drives a similar sized car (same make, but later slightly larger model) that has much more equipment inc. air con etc but it has a 1910cc turbo diesel engine. It does well 50mpg overall and is a pleasure to drive in any type of traffic and cruises easily (on my private test track of course) at 100mph when the engine is doing just 3000rpm. It is way faster, accelerates much quicker (and stronger) and does around 30-40% more to the gallon.
As I already said.
Quote
3 Diesel engines are not about BHP a purely artificial measure of power that is simply the torque (the real strength of an engine that does the work) times RPM times a constant.
Torque is therefore the real measure of how "good" and engine is and diesels typically have over twice the torque of equivalent petrol engine and develop it at half the RPM.
As I already said (more or less).
Quote
This is NOT a failing as some of you seem to think, but an advantage. Diesels do not HAVE to rev to do useful amounts of work as petrols do and revs are what kill engines as wear increases exponentially as RPM rises. Double the revs and you get 4 times the wear. 
One moment! This would be true only with tha same piston elongation, because it would mean higher piston's speed (yes, there is not only the piston's movement, but here are the most important wears), but, as you said, petrol engines usually have shorter piston elongation than the corresponding diesels ones.
Quote
This is why diesel engines last much much longer than petrols allied to the fact that diesel fuel lubricates whilst petrol destroys lubrication by washing away the engine oil from the cylinder walls.
This could be true for old petrol engines (without electronic ignition) starting at cold weather. Furthermore, you don't consider all the problems in the long term in a diesel engine; remember that the pressure inside the cylinders is higher and the injectors (for example) causes problems in the long term.
Quote
PM10 particulates may be higher (it depends on the car and the quality of fuel used) but PM2.5s and PM5s are not thought to be any worse than petrol (yes petrols emit particulates too) and current thinking is that the smaller particulates are worse for health as they lodge lower in the respiratory tract and lungs - so petrol fumes might be equally bad for us in that respect, especially now that more diesels are being fitted with particulate traps and petrols aren't.
Which diesel engines are you talking about? Euro 4 or 5 or what? Most of the present diesel engines are Much worse than the petrol ones for what concerns particulates.
Quote
6 Petrol apologists always conveniently forget about all the nasties in petrol - benzene for one. Benzene is a known carcinogen so toxic that there is NO safe exposure level and petrol gives off benzene even when the engine isn't running. 
Most of Benzene and aromatic compounds were replaced by MTBE metil-terz-butil ethere (non-aromatic).
Quote
Petrol is also volatile and downright dangerous just look at any car that crashes in any US action film - it has exploded in flames before it even hits the barrier
I usually don't believe very much on US action films [:)] It's quite improbable that this happens, actually. Anyway, it's certainly more probable with petrol than with diesel.
Quote
Diesel is the future...
I hope not, with these diesels...
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 14/02/2007 19:49:29
Thank you for the welcome Lightarrow but I can agree with few if any of the points you make.

I don't know what a Sanity Department does but it clearly doesn't do much to do with engine emissions in the real world.

Fact Petrol fumes kill in minutes diesel fumes MAY kill in decades

Fact Petrol washes lubricant off the cylinder walls in all types of engine the ignition system is irrelevant

Fact Wear increases as the square of engine speed - I accept that different bore stroke ratios will have some effect on ultimate wear, but negligible compared the overall rate of wear. In addition petrols have to be driven at higher revs all the time to achieve the same progress as a diesel, this is both tiring and more intrusive than the relaxed drive in a diesel.

Fact Petrols were actively developed for most of the last century - diesel development only really began in the mid 1980's and is now leaping ahead at many times the rate of petrol development, which has really hit a plateau.

Fact ALL major car makers see diesel as the only way forward with the IC engine, as it is able to run on the widest range of fuels. To produce Ethanol for spark ignition engines to run on, consumes almost as much energy as the fuel releases in use, production of Bio-diesel is much more energy efficient.

Fact Petrol is a volatile, explosive (1000 times more explosive than gunpowder), toxic down right dangerous fuel that in most countries (certainly the UK) is subject to specific and rigorous storage regulation because it is just so damn dangerous.
Diesel is benign, safe and in the case of bio-diesel, bio degradeable, so no special storage regulations apply.

Fact Diesel does not pollute MORE than petrol, just differently, they both pollute and the pollutants in petrol emissions kill much much quicker.
It is strange just how much diesel pollutants are exaggerated and how petrol pollutants are conveniently overlooked
WHY? What vested interests are harmed by any criticism of petrol?

Question?? So diesel injectors cause problems in the long term? Is that the same long term over which PETROL injectors give problems and longer than the SHORT term that petrol spark plugs and ignition systems give problems?.
All engines develop problems, diesels do not develop them any sooner overall than petrols - indeed I would suggest that most breakdown services would tell you it is much longer.
The AA (UK breakdown service) have said that 85% of all the breakdowns they attend are related to the High Tension IGNITION system, so therefore if follows that 85% of ALL breakdowns can only happen with Spark Ignition (i.e. Petrol) cars.

Particulates You persist in believing that petrols do not emit particulates. I will be generous and accept that this is because you have been convinced by the vested interests who defend petrol, that only PM10s matter.
Many would argue, as I said earlier, that PM2.5s and PM5 are far more dangerous as they penetrate deeper into the lungs. The main producers of the smaller particulates are petrol engines.

Benzene and MTBE - so petrol is now SAFER because (known carcinogen with NO safe exposure level) benzene has been replaced by "non-aromatic" MTBE - WOW!!!! I suggest you go off and do a Google and find out just what problems MTBE has caused in the USA.

Finally, if you think petrol is safer than diesel, I'll make you a deal.

We each take 10 litres of fuel - You petrol - Me diesel and we'll walk out into the middle of a nice open space. We will then pour our can of fuel onto the ground, stand in the middle of the puddle and strike a match.

The one who is able to come back here and write about it wins.





Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Hadrian on 14/02/2007 23:39:10
Quote
We each take 10 litres of fuel - You petrol - Me diesel and we'll walk out into the middle of a nice open space. We will then pour our can of fuel onto the ground, stand in the middle of the puddle and strike a match.

The one who is able to come back here and write about it wins.


Well after a few hours I dropped my match and you what, the petrol was all gone? Funny that....LOL  [;D]
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 14/02/2007 23:50:34
SMSLOL

Same with the Bio-diesel; Ohh except that it hasn't left a poisoned toxic patch on the ground and released a lethal dose of Benzene into the atmosphere.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Hadrian on 14/02/2007 23:55:34
emmmmmmmmm  i love the smell of Benzene in the morning............LOL

you got me there OK but still i did not burn and i got back first to write... so do i win still LOL  [;D]  



Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 15/02/2007 00:03:48
If you read the rules it said "Stand in the puddle and light a match".

If you wait for it to evaporate.....

Either

1 I've lit my match and got back here (safely) to post a reply long before you possibly could.

or

2 You are no longer stood in said puddle, because said puddle is no longer there and I win by default.

or

3 You play by the rules and get crispy.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: skelo on 15/02/2007 00:23:45
emmmmmmmmm  i love the smell of Benzene in the morning............LOL

you got me there OK but still i did not burn and i got back first to write... so do i win still LOL  [;D]  





Lets alter the rules slightly.

To save any possible cheating, how about both of us choose a liquid. Either petrol or diesel, i choose the diesel.

I pour diesel over myself, you get the farmer to pour petrol over you. I light a match immediately after pouring the fuel over myself, the farmer then lights a match immediately after pouring the petrol over yourself then drops it on your fur coat.

Let see who becomes sunday lunch.

I really don't understand, why there is so much anti-diesel argument here. Scientists are supposed to see through the lies and hypocrisy, and base there judgements on fact and logic.

Can you guys not see the simple facts put in front of you?
Diesel is the fuel of the current, and the future.

Cheers
Skelo
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 15/02/2007 08:28:05
Thank you for the welcome Lightarrow but I can agree with few if any of the points you make.
I don't know what a Sanity Department does but it clearly doesn't do much to do with engine emissions in the real world.
This clearly show that you are talking about another planet. Sanity departments (at least here in Italy!) are continuously studying, sampling, making conferences on this subject. If you don't believe what I say, we have nothing to discuss anylonger.
Maybe you sell diesel vehicles or you are pushing for it...
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 15/02/2007 08:45:02
I really don't understand, why there is so much anti-diesel argument here. Scientists are supposed to see through the lies and hypocrisy, and base there judgements on fact and logic.
Can you guys not see the simple facts put in front of you?
Diesel is the fuel of the current, and the future.
About the fuel for the future I certainly don't stand for petrol; I would prefer alcohols. About diesel, I really hope that, at least, NOx emissions will go down drastically, soon.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: daveshorts on 15/02/2007 10:09:01

Well after a few hours I dropped my match and you what, the petrol was all gone? Funny that....LOL  [;D]
Yes causing the production of low level ozone and trashing some DNA with all the benzene released.

Neither petrol or diesel are particularly nice, I have to say I would prefer diesel in many of the ways that scanner has said. but both fuels are unpleasent overall, and produce lots of CO2 and in the long term finding something that will work electrochemically (eg a in fuel cell) means we are not thermodynamically limited to a 30-40% efficiency.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 15/02/2007 12:23:21
Thank you for the welcome Lightarrow but I can agree with few if any of the points you make.
I don't know what a Sanity Department does but it clearly doesn't do much to do with engine emissions in the real world.
This clearly show that you are talking about another planet. Sanity departments (at least here in Italy!) are continuously studying, sampling, making conferences on this subject. If you don't believe what I say, we have nothing to discuss anylonger.
Maybe you sell diesel vehicles or you are pushing for it...

Studying, sampling and making conferences about what exactly? As you have clearly not studied or sampled much petrol emissions if you think they are safer than diesel ones.
have you studied or sampled much of the emissions from the new "petrols that work like diesels but still have the most unreliable bit the High-tension ignition system" the FSI and other direct injection engines they produce NOX as well. Diesel virtually eliminate their NOX with EGR (Exhaust Gas recirculation, in case your sampling and studying hasn't got that far).
I fear the Italian version of SANITY (I wonder if you mean Sanitary?) is way out of step with Audi, VW, BMW, GM, Ford, Citroen, Peugeot, Renault and even Errrrr FIAT who all see diesel as the only way of meeting both CO2 and air quality standards.

Alcohol is a dead end it is expensive and energy hungry to produce and wasteful of huge areas of land - much more land is needed to produce the same energy value of alcohol than of bio-diesel. It is also more dangerous and more difficult to store and more wasteful in use due to losses by evaporation.

However, Yes you are right on one point - if you can't see that and can't see past your clear and undoubted prejudices - you have nothing more to say on a matter you clearly have little relevant knowledge of.

And NO I do not sell diesels - I drive them with a clear conscience and the sooner I can drive anywhere using waste vegetable oil as fuel my conscience will be even clearer
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ROCKETRON on 15/02/2007 18:56:57
 I noticed on the BBC website that they are providing a link to this site on the “Petrol versus diesel” debate. When I looked at this debate I was utterly amazed that the BBC obviously didn’t get anybody with a modicum of knowledge to look at the ridiculous anti-diesel statements being stated as fact on this website. It seems to me that with the exception of Scanner who actually explained the real facts, most of you are quoting from the Jeremy Clarkson school of thought and have probably never actually had much to do with the modern “euro3/4” diesel engined car. While no internal combustion engine can ever be considered green the diesel engine certainly has more going for it than the petrol engine in terms of overall pollution and when run on bio-diesel is relatively green. It should be remembered also that the smaller particulates are also produced by petrol engined cars but as they are not visible from the exhaust it is often assumed that petrol cars don’t produce any particulates but because you can actually see the larger,less harmfull,particulates from the exhaust of the diesel it is assumed that they must be more polluting. Their high torque at low revs and high gearing certainly makes them feel much better to drive than a similar sized petrol engined car and the fact that they also do about 33% more miles than the petrol car on the same amount of fuel and hold their value better can only be a bonus and prove that most people don’t hold the views of people on this forum.. 

 
 
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 15/02/2007 19:02:22
Thank you for the welcome Lightarrow but I can agree with few if any of the points you make.
I don't know what a Sanity Department does but it clearly doesn't do much to do with engine emissions in the real world.
This clearly show that you are talking about another planet. Sanity departments (at least here in Italy!) are continuously studying, sampling, making conferences on this subject. If you don't believe what I say, we have nothing to discuss anylonger.
Maybe you sell diesel vehicles or you are pushing for it...
Studying, sampling and making conferences about what exactly? As you have clearly not studied or sampled much petrol emissions if you think they are safer than diesel ones.
It's not my opinion.
Quote
have you studied or sampled much of the emissions from the new "petrols that work like diesels but still have the most unreliable bit the High-tension ignition system" the FSI and other direct injection engines they produce NOX as well.
Pressures inside an FSI petrol engine are about 10 times lower than those in a corresponding common rail diesel. So NOx are much lower.
Quote
Diesel virtually eliminate their NOX with EGR (Exhaust Gas recirculation, in case your sampling and studying hasn't got that far).
You are dreaming. You don't even realize the difference in smell from a diesel engine exausts and a petrol engine. I studied and made chemistry and I can tell you the smell from diesel exausts means great amounts of NO2. If you don't believe it, make this simple experiment: dissolve a piece of metallic copper in nitric acid and observe the red smoke it forms; then remember the smell it has. Then look up a chemistry book looking for all the physical, chemical and tossicological properties of NO2.
Quote
I fear the Italian version of SANITY (I wonder if you mean Sanitary?) is way out of step with Audi, VW, BMW, GM, Ford, Citroen, Peugeot, Renault and even Errrrr FIAT who all see diesel as the only way of meeting both CO2 and air quality standards.
What car companies and governements told us are not what data analysis show...Furthermore, they make us focus our attention on the CO2 problem, instead of much worse problems. Do keep breathing particulates and NOx at these levels and we won't have to worry about dissolving poles, because we will all be ill before.
Quote
Alcohol is a dead end it is expensive and energy hungry to produce and wasteful of huge areas of land - much more land is needed to produce the same energy value of alcohol than of bio-diesel. It is also more dangerous and more difficult to store and more wasteful in use due to losses by evaporation.
Bio-diesel comes directly as liquid from trees? Making it needs energy too. Alcohol is not more volatile and more difficult to store than petrol.
Quote
However, Yes you are right on one point - if you can't see that and can't see past your clear and undoubted prejudices - you have nothing more to say on a matter you clearly have little relevant knowledge of.
And NO I do not sell diesels - I drive them with a clear conscience and the sooner I can drive anywhere using waste vegetable oil as fuel my conscience will be even clearer
Maybe your conscience, but not the air we all breathe, unfortunately.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 15/02/2007 20:07:30
I'll connect a pipe to my diesel exhaust and you connect one to your petrol exhaust and then breath it in for a few minutes - I'll have a cough (maybe)- you won't have a cough you'll have a funeral.

I repeat: petrol emissions kill instantly and there are millions of suicides (including a good friend of mine) to conclusively prove that.

Diesel emissions MAY kill in decades and even that hasn't been proved yet and neither you nor anybody else can produce one single person who can be conclusively proved to have died solely as a result of diesel exhaust fumes.

If that friend of mine had followed my advice and had a diesel car he might still be alive, he certainly wouldn't have died in his car.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: rosy on 15/02/2007 21:56:52
As has been remarked in this and another thread, this forum thread has been linked from some BBC page somewhere... I don't know where, since no-one's posted the link.

This is rather unfortunate since this forum (being an entirely open discussion area) contains quite a lot of interesting and well argued material posted by individuals who have serious background knowledge or a good record in checking their facts, in response to questions about interesting areas or science and research. However, the diesel/petrol debate is sufficiently contentious (and enough people have a stake in terms of wanting to believe they've made the right choice of car) to fall prey to the not uncommon problem of people with Strongly Held Views shouting louder, longer and more often than those with a more measured viewpoint.

I can only remark, for the benefit of anyone who hadn't already grasped this fact, that all open discussion areas are only as informative as the people posting to them are informed. Some contributors are pretty reliable, and I shall cite Chris and Daveshorts as examples because I know both (and their trackrecords) fairly well, although this is by no means meant to cast aspersions on anyone else (or not anyone in particular).

For new vistors... the quality of debate on this thread is depressingly low, overendowed with ad hominem attacks, and not in my view (as a site regular) typical of this forum.. tho' it's not unheard of either.
Whilst I'm addressing any new visitors, I may as well point out that as well as the forum this site has a load of other content, including a lot of articles on various scientific topics and podcasts of the Naked Scientists radio show, neither of which are afflicted with underinformed rants.

(Apologies, I'm going to cross post this to the feedback thread too.)
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: elegantlywasted on 15/02/2007 22:02:00
I'll connect a pipe to my diesel exhaust and you connect one to your petrol exhaust and then breath it in for a few minutes - I'll have a cough (maybe)- you won't have a cough you'll have a funeral.

I repeat: petrol emissions kill instantly and there are millions of suicides (including a good friend of mine) to conclusively prove that.

Diesel emissions MAY kill in decades and even that hasn't been proved yet and neither you nor anybody else can produce one single person who can be conclusively proved to have died solely as a result of diesel exhaust fumes.

If that friend of mine had followed my advice and had a diesel car he might still be alive, he certainly wouldn't have died in his car.


Uhh I have a small problem with the statement that petrol emissions kill "instantly"... Years ago, a friend of the family, on a bet (he was 8) put him mouth to a tail pipe of his fathers Ford while the car was running. Although he was terribly sick (nasty cough for months) and had some pretty nasty burns to his face, he isnt dead. Actually he plays for the farm team of an NHL hockey team... Definatly isn't dead, definatly now a professional athelete.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: elegantlywasted on 15/02/2007 22:02:58
And rosy... excellent post.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: daveshorts on 15/02/2007 22:18:28
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emmision annoyingly.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 15/02/2007 23:17:11
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emmision annoyingly.

CO2 is far less toxic than CO, but as far as I am aware it is still toxic (i.e. you will die sooner breathing in an atmosphere of CO2 than breathing in an inert atmosphere - e.g. N2 or He).
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 16/02/2007 00:02:47
Here is the link to the BBC page with the link to this Topic.
http://www.bbc.co.uk/radio4/science/homeplanet_20070213.shtml
If you object to having this forum quoted in this way please take it up with the Producers of the Programme - "Pier Productions"



Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emission annoyingly.


Correct IF a catalyst is fully warmed up and working properly, the catalytic effect being temperature critical (that's why your car has to be fully warmed up for the MOT test). However that takes quite a while, much longer than most people think and in cold weather it can be 15 miles or so depending on driving conditions and until that happens a cat equipped car is actually pumping out more harmful emissions than a non cat equipped one because fitment of the cat causes it to run less efficiently - approx 10% worse.

CO is toxic it combines with something in the blood, Red Corpuscles maybe? and prevents them forming Oxyhaemoglobin  and making Carboxyhaemoglobin instead (perhaps any haematologist who reads this could verify/correct my recollections from schooldays).

CO2 is not toxic but inert (SFAIK) and would kill in just the same way as any inert atmosphere that did not contain any oxygen. It is the lack of oxygen that kills not the CO2 - it's how CO2 fire extinguishers works as well.

How ever little CO a modern fully warmed up catalyst equipped petrol engine produces it is still more than any diesel exhaust emits, as diesels always operate with an excess of Oxygen and CO can only form when there is a deficit of Oxygen (once again SFAIK).

Modern diesels operating on modern Ultra low sulphur diesel or even better totally sulphur free bio-diesel easily meet the same emission standards as catalyst equipped petrol engines whilst using much less fuel and producing much less CO2 and they do not need a Lambda sensor and all the inherently unreliable electronics associated  with it to do so.
Less fuel = Less emissions = Less trouble for the planet and all who live on it.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 17/02/2007 14:01:42
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.
In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emission annoyingly.
Correct IF a catalyst is fully warmed up and working properly, the catalytic effect being temperature critical (that's why your car has to be fully warmed up for the MOT test). However that takes quite a while, much longer than most people think and in cold weather it can be 15 miles or so depending on driving conditions and until that happens a cat equipped car is actually pumping out more harmful emissions than a non cat equipped one because fitment of the cat causes it to run less efficiently - approx 10% worse.
CO is toxic it combines with something in the blood, Red Corpuscles maybe? and prevents them forming Oxyhaemoglobin  and making Carboxyhaemoglobin instead (perhaps any haematologist who reads this could verify/correct my recollections from schooldays).
CO2 is not toxic but inert (SFAIK) and would kill in just the same way as any inert atmosphere that did not contain any oxygen. It is the lack of oxygen that kills not the CO2 - it's how CO2 fire extinguishers works as well.
How ever little CO a modern fully warmed up catalyst equipped petrol engine produces it is still more than any diesel exhaust emits, as diesels always operate with an excess of Oxygen and CO can only form when there is a deficit of Oxygen (once again SFAIK).
Modern diesels operating on modern Ultra low sulphur diesel or even better totally sulphur free bio-diesel easily meet the same emission standards as catalyst equipped petrol engines whilst using much less fuel and producing much less CO2 and they do not need a Lambda sensor and all the inherently unreliable electronics associated  with it to do so.
Less fuel = Less emissions = Less trouble for the planet and all who live on it.
Yes, catalized petrol engines produces CO before the catalitic exaust is hot; but diesel engines produces NO2 always. CO is extremely toxic, we all know; NO2 is extremely toxic AND carcinogenic; it also gives a combined effect with HC (uncombusted hydrocarbons).
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 17/02/2007 16:48:02
Please supply a link to any information that NOX is carcinogenic as that is news to me and I have never heard it suggested anywhere else than in this forum.

In fact a google turns up this reference

Quote
   
How likely are nitrogen oxides to cause cancer?

The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified nitrogen oxides for potential carcinogenicity.
that took all of 2 seconds to find..................and if THEY especially the EPA can't find a link how can you?

You really do need to take your, blinkers off and get real. Stating LIES as facts just shows you up as misinformed and muddle-headed.

And just so you know, petrols also produce uncombusted hydrocarbons not only diesels, so don't try that form of smearing to try and make your weak and unsubstantiated case stick either.

Diesels pollute, but petrols pollute more simply because they produce much more exhaust volume from a more polluting fuel.

I think you should go away and do some up to date "sampling and studying" before sharing your "knowledge" with the world.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: snipez999 on 17/02/2007 21:10:30
Hi there.
I own a diesel car, but was a petrolhead by habit for over 20 years.
I'm no techy, by any means, but if my car can do twice the mpg of my old petrol car; go twice as long between services; need less replacement parts; reach peak torque in half the engine revs and be safer for everyone concerned in the (God forbid) case of a serious accident (by carrying less easily combustible fuel) then isn't that a good thing?
 
 
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 17/02/2007 21:29:58
I think one question one has to ask is which NOX?

Nitrous oxide (technically not an NOX because it is N2O) has long been used in medicine, and I have not heard of it being linked as a carcinogen.

In theory, I suppose any gaseous oxide, being an acid, can cause all sorts of cellular damage, and dissolved NO2 would be one of the more potent acids.

NO is a normal part of our metabolism, although that simply means that in the right doses it will not be significantly harmful, but equally many things that are a natural part of our metabolism, if absorbed in excess, can indeed be harmful.

So, I think one should maybe be more careful than simply to lump all NOXs together (excepting that they are all potent acids, just as SOXs or even, to a lesser extent, COXs are).

As for accusing people of lying, I do not think that is in order at all.  We all have our own sources of knowledge, and whether in one case you are in error, or another case Alberto is in error - it is a very different matter to suggest that the error was by malicious intent (which is what the word 'LIES' implies).
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ROCKETRON on 17/02/2007 21:51:30
Lightarrow i have never heard of NO2 being "extremely toxic and carcinogenic" and certainly not on the same scale as CO as suggested in your post. Scanners quote from Google sounds about right to me. As i said in my previous post i am surprised that the BBC is linking to this site about a debate between petrol and diesel when people are just quoting from normal press bias against diesels and quoting theories as fact.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 17/02/2007 22:13:58
NO2 may not be listed as a carcinogen, but it does seem consistently listed as a major component in photochemical smog, which certainly does have a range of health issues associated with it, even if it may be debateable if cancer is high on that list.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 17/02/2007 22:14:17
Sorry if it isn't true it's a lie, but just to placate anybody who thinks that is too strong I'll settle for terminological inexactitude and for my taste too many terminological inexactitudes are spread in the (unfathomable to me) crusade some supposedly knowledgeable people seem to have against diesel.
They seem happy to completely misrepresent and exaggerate every perceived fault of diesel but conveniently ignore all the (too my mind) far more serious faults of petrol - Volatility, flammability, toxicity, benzene http://www.epa.gov/ttn/atw/hlthef/benzene.html or MTBE http://www.epa.gov/oms/consumer/fuels/mtbe/mtbe.htm (both total environmental disasters) wastefulness and last but not least excessive CO2 emissions.

Whatever the oil industry try to do the "improve" petrol's green credentials just seem to make it ever worse for the environment.

Diesel is a safer, more economical fuel that releases less overall in the way of harmful emissions.
Cars powered by diesel are less tiring to drive due to the more relaxed way they provide motive power. They are far easier to drive in an economical manner and far more likely to actually return the MPG figure claimed for them, unlike the petrol-hybrid white elephants
http://www.consumeraffairs.com/news04/2005/hybridwatch02.html

So far as I'm concerned diesel in the form of bio-diesel is the only fuel that offers any large scale  long term hope for the internal combustion engine.

Whether or not that is a good thing is another argument......................

 
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 17/02/2007 22:17:16
NO2 may not be listed as a carcinogen, but it does seem consistently listed as a major component in photochemical smog, which certainly does have a range of health issues associated with it, even if it may be debateable if cancer is high on that list.
If NOX from diesel is the cause of photochemical smog why is the most vehemently anti-diesel city on earth Los Angeles (where is is virtually impossible to own a diesel car) so afflicted with photochemical smog?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 17/02/2007 22:23:59
If NOX from diesel is the cause of photochemical smog why is the most vehemently anti-diesel city on earth Los Angeles (where is is virtually impossible to own a diesel car) so afflicted with photochemical smog?

I did not use the words "from diesel", only that NO2 (whatever its source) is considered a major component of photochemical smog.

One reason why Los Angelas is one of the cities (there are a few others) that is particularly badly effected by photochemical smog is because the mountains around the city do not allow proper dispersal of the pollutants, so they get seriously concentrated into the valley in which Los Angeles sits.  If Los Angeles were situated elsewhere, with a different geography, the same levels of pollution pumped into the atmosphere would be more widely dispersed, and cause fewer local problems.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 17/02/2007 22:39:14
You may not have done, but others on here seem convinced that diesel produces most if not all the NOX in the world - possibly even whilst smoking a cigarette or two, sat in front of an open (or gas) fire or in a house heated by gas or electricity.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 17/02/2007 22:53:40
You may not have done, but others on here seem convinced that diesel produces most if not all the NOX in the world - possibly even whilst smoking a cigarette or two, sat in front of an open (or gas) fire or in a house heated by gas or electricity.

From what I read, it seems that NO2 in photochemical smog is caused substantially by NO2 and O3 production caused by an interaction of NO, unburnt hydrocarbons, and sunlight.  Most of the NO2 does not seem to be directly coming from the exhaust of vehicles, but as a secondary product created in the atmosphere.

Thus, pumping out high levels of NO alone will not do it, it requires both the NO and the hydrocarbons.

As has been indicated here, the vehicles that produce a lot of one, tend to produce less of the other.  Thus one might argue the worst case scenario is for a mix of vehicles each adding their own contribution.  Where that leaves us with regard to which type of vehicle is more to blame for the outcome is a more difficult question.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 17/02/2007 23:33:36
Well I trust Alberto will believe you..........

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 18/02/2007 01:06:11
Well I trust Alberto will believe you..........

I am not some supreme being that expects unquestioning belief, and should you or Alberto choose not to believe me (for whatever reason), I should not be mortally offended, nor accuse you or he of heresy or blasphemy.  The only thing I do ask is the you trust that I am telling the truth as I know it (and being human, I am as susceptible to error as anybody else).  I just ask that nobody assume malice or deliberate lies, even if maybe they cannot find cause to agree with me.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 18/02/2007 12:31:22
Fair enough no one could ask more than that.

If Alberto wants something to worry about this substance http://www.dhmo.org/ (http://www.dhmo.org/) kills far more people every day than any exposure to NOX from whatever source.

It destroys landscape, infrastructure and technology with equal ease.

All in all it is deadly stuff and we are considering replacing IC engines with motive sources that are said to produce this as their only emission.

Are we mad?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 18/02/2007 13:06:13
If Alberto wants something to worry about this substance http://www.dhmo.org/ (http://www.dhmo.org/) kills far more people every day than any exposure to NOX from whatever source.

It destroys landscape, infrastructure and technology with equal ease.

All in all it is deadly stuff and we are considering replacing IC engines with motive sources that are said to produce this as their only emission.

Are we mad?

LOL - I first heard about that some many, many years ago - but I do think it still holds a valuable lesson in human gullability.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Hadrian on 18/02/2007 14:27:26
Quote

I am not some supreme being that expects unquestioning belief, and should you or Alberto choose not to believe me (for whatever reason), I should not be mortally offended, nor accuse you or he of heresy or blasphemy.  The only thing I do ask is the you trust that I am telling the truth as I know it (and being human, I am as susceptible to error as anybody else).  I just ask that nobody assume malice or deliberate lies, even if maybe they cannot find cause to agree with me.




i can say that you are one great chap who i have enjoyed a scrap or two with in the past and you never took prisioners on the way and i vary much respect you for it...  


Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: neilep on 18/02/2007 21:30:02
Can I just say that me is well happy for asking my question.

Everyone is being so nice and lovely !!!..

Big Big soppy hugs all round.

YAYYYYYYYYYY !!!!






*if you detect even a soupcon of sarcasm...then ewe may be right*
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 18/02/2007 22:48:27
If ewer happy then sow are we.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 19/02/2007 12:19:17
Please supply a link to any information that NOX is carcinogenic as that is news to me and I have never heard it suggested anywhere else than in this forum.
In fact a google turns up this reference
Quote
   
How likely are nitrogen oxides to cause cancer?
The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified nitrogen oxides for potential carcinogenicity.
that took all of 2 seconds to find..................and if THEY especially the EPA can't find a link how can you?
You really do need to take your, blinkers off and get real. Stating LIES as facts just shows you up as misinformed and muddle-headed.
And just so you know, petrols also produce uncombusted hydrocarbons not only diesels, so don't try that form of smearing to try and make your weak and unsubstantiated case stick either.
Diesels pollute, but petrols pollute more simply because they produce much more exhaust volume from a more polluting fuel.
I think you should go away and do some up to date "sampling and studying" before sharing your "knowledge" with the world.

NOx reacts with amines in biological compounds/tissues forming nitrosamines, which are powerful carcinogens:

http://en.wikipedia.org/wiki/Nitrosamines
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 19/02/2007 12:50:14
I also would like to precise something:
1. I certainly don't say petrol engines don't pollute; infact I said that, in case, I would prefer alcohol engines (not hydrogen because it would need a lot of energy and so pollution, to get it).
2. I'm not against all diesel engines in general, but against most of the existing ones, because most of vehicle's pollution comes from them (especially lorries, I presume), for example HC, NOx and particulate. Of course petrol engines also produce a huge amount of pollution, but most comes from existing diesels, because most of them are not modern engines (Euro 4, Euro 5, with antiparticulate filters ecc.).
3. In no way I have an interest in imposing my beliefs; I'm only expressing my ideas, which comes from what I have get through different kinds of information means; if they will result to be wrong, I will accept it; it wouldn't be the first time I have something to learn, and a Forum is exactly a place and a mean to exchange ideas and informations. Isnt'it?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 19/02/2007 16:59:20
So now you claim NOX MAY be a carcinogen IF it reacts with something else - MAYBE.

That is not what you stated as FACT earlier.

Diesels may produce most pollution and it may be the bigger ones that produce most - trucks etc - BUT can you imagine the pollution if all those trucks had petrol engines? What is your alternative to that?

Alcohol may be a good idea but have you studied just how much energy is needed and how much pollution is caused by it's production?
Bio-diesel is far cheaper and easier to produce and produces far more energy at far lower cost. The huge boom in diesel ownership in recent years (certainly in the UK) means that most diesels are less than 3 years old. If all the older ones are to be scrapped think of all the pollution produced when their replacements are manufactured and all the pollution involved in disposing of them.

Pollution produced by use of a car (whatever sort of engine it is fitted with) is relatively small compared to manufacture and disposal.

It is for this reason that hybrids like the Prius are very "UNGREEN" because of the huge extra pollution involved in making and disposing of their battery packs every few years.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 19/02/2007 20:16:52
Pollution produced by use of a car (whatever sort of engine it is fitted with) is relatively small compared to manufacture and disposal.

It is for this reason that hybrids like the Prius are very "UNGREEN" because of the huge extra pollution involved in making and disposing of their battery packs every few years.

The battery packs on the prius are Nickel Metal Hydrides, which are still cleaner to dispose of then the lead acid batteries on conventional cars.

I am not sure where you get the idea that the batteries have a short design life, although NHM batteries inherently have a problem with high levels of self discharge, and so can present problems with vehicles that are infrequently used.  I believe the Toyota will be moving to Lithium Ion batterry technology in 2009, which has far less of a self discharge problem.

The other advantage that has not been mentioned about hybrid and electrical cars is the use of electrical (regenerative) braking.  Aside from the energy efficiency this introduces, it also reduces the amount of brake dust generated - which itself is a pollutant.

Ofcourse, all of this depends on the type of driving you are doing - and if you are doing the kind of driving that inherently requires little braking, then this is not an issue.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 20/02/2007 17:01:42
The other advantage that has not been mentioned about hybrid and electrical cars is the use of electrical (regenerative) braking.  Aside from the energy efficiency this introduces, it also reduces the amount of brake dust generated - which itself is a pollutant.
Ofcourse, all of this depends on the type of driving you are doing - and if you are doing the kind of driving that inherently requires little braking, then this is not an issue.
However, the energy lost by acceleration/braking is infact quite a relevant amount of the total energy used, for a car, so the use of electrical braking would considerably reduce a car's fuel consumption, in my opinion.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 20/02/2007 17:29:00
So now you claim NOX MAY be a carcinogen IF it reacts with something else - MAYBE. That is not what you stated as FACT earlier.
NO and NO2 are free radicals. It means: very reactive compounds.
Quote
Diesels may produce most pollution and it may be the bigger ones that produce most - trucks etc - BUT can you imagine the pollution if all those trucks had petrol engines?
Yes, I can imagine it: much less particulates, less HC and NOx. Of course this wouldn't exactly mean pure air, but certainly a little bit better.
Quote
What is your alternative to that?
Alcohol may be a good idea but have you studied just how much energy is needed and how much pollution is caused by it's production?
Not very much, using cellulose fermentation.
Quote
Bio-diesel is far cheaper and easier to produce and produces far more energy at far lower cost. The huge boom in diesel ownership in recent years (certainly in the UK) means that most diesels are less than 3 years old. If all the older ones are to be scrapped think of all the pollution produced when their replacements are manufactured and all the pollution involved in disposing of them. Pollution produced by use of a car (whatever sort of engine it is fitted with) is relatively small compared to manufacture and disposal.
Are you saying that if we have poisonous things the best solution would be to keep them and keep us poisoned? It's a strange way of thinking! (And I'm not referring to diesels only, but to things in general).
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 20/02/2007 22:51:44
You seem to be one of the few people who think NOX is so dangerous in the concentrations produced by diesels and indeed that diesels are a major source. I reckon more NOX is produced by cigarettes and more directly ingested (i.e. straight into the lungs)than from diesels.

Yes and much more Benzene, much more sub-PM10 particulates, much higher overall volume of emissions, more Co, shorter engine life with earlier/higher combustion of lubrication oil causing more smoke, much more rapid exhaustion of a finite resource.

Huge areas of land and enormous distillation plants would be needed to produce enough fuel for thirsty spark ignition truck engines.......... you really cannot be serious, as somebody once said and I still hold that the dangers inherent with making and transporting alcohol are not worth the risk, just one bad accident could kill more people in one go than in years of use.

Whole life costs! You cannot just count "use" toward whether something is "good" or "bad" you have to count from making it to disposing of it as well. The ill effects of getting rid of an old one and making a new one can easily outweigh the ill effects of using one that is maybe not quite as "good" as it could be.

So diesel is now "poisonous" is it - just what is petrol then?
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: another_someone on 21/02/2007 03:16:09
However, the energy lost by acceleration/braking is infact quite a relevant amount of the total energy used, for a car, so the use of electrical braking would considerably reduce a car's fuel consumption, in my opinion.

In urban traffic, this is certainly the case; but I think one of the reasons why the Prius has proved a little disappointing for some (although it is still very early in the evolution cycle for that technology) is that the same does not hold true for long motorway drives, and it depends upon the type of driving you are doing as to how significant regenerative braking would be.  For Americans in particular, who in may parts of the country don't even have much in the way of bends in the road, and they can just drive on cruise control (something that would be considered highly dangerous in most of Britain, especially the south-east), the benefits of regenerative braking would be marginal at best.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 21/02/2007 08:14:17
In urban traffic, this is certainly the case; but I think one of the reasons why the Prius has proved a little disappointing for some (although it is still very early in the evolution cycle for that technology) is that the same does not hold true for long motorway drives, and it depends upon the type of driving you are doing as to how significant regenerative braking would be.  For Americans in particular, who in may parts of the country don't even have much in the way of bends in the road, and they can just drive on cruise control (something that would be considered highly dangerous in most of Britain, especially the south-east), the benefits of regenerative braking would be marginal at best.
Yes, I forgot that in America, everything is different!
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: lightarrow on 21/02/2007 08:19:23
You seem to be one of the few people who think NOX is so dangerous in the concentrations produced by diesels and indeed that diesels are a major source. I reckon more NOX is produced by cigarettes and more directly ingested (i.e. straight into the lungs)than from diesels.

Yes and much more Benzene, much more sub-PM10 particulates, much higher overall volume of emissions, more Co, shorter engine life with earlier/higher combustion of lubrication oil causing more smoke, much more rapid exhaustion of a finite resource.

Huge areas of land and enormous distillation plants would be needed to produce enough fuel for thirsty spark ignition truck engines.......... you really cannot be serious, as somebody once said and I still hold that the dangers inherent with making and transporting alcohol are not worth the risk, just one bad accident could kill more people in one go than in years of use.

Whole life costs! You cannot just count "use" toward whether something is "good" or "bad" you have to count from making it to disposing of it as well. The ill effects of getting rid of an old one and making a new one can easily outweigh the ill effects of using one that is maybe not quite as "good" as it could be.

So diesel is now "poisonous" is it - just what is petrol then?
Scanner, I sincerely don't want to go on with this discussion with you and not because I finished my arguments.
Bye.
Alberto.
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 21/02/2007 09:58:11
Of course you haven't finished with your arguments because you don't have a valid position to argue from. All you do is repeat your opinion of flawed and biased data. IF diesel was anywhere near as poisonous as you claim it would be banned just as tetra-ethyl lead was in petrol and benzene has partially been - 1% of petrol can still be a KNOWN (not suspected or just plain possible-maybe) carcinogen.
A move away from diesel as the MAIN motive fuel to petrol or even alcohol would result in a huge overall increase in pollutants especially CO2. Your "solution" would be totally unsustainable.

Until we can stop using the IC engine all together, we need to continue using the one which has the least OVERALL ill-effects and at present most sensible observers agree that is the diesel and that is why research into making it even cleaner is progressing so fast.

Please update your "studying and sampling" to drag yourself kicking and screaming into the 21st century - both diesel engines and diesel fuel have improved hugely in the last few years and I consider your views need to catch up.

Goodbye

Stefano
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: paul.fr on 21/02/2007 21:08:05

Scanner, I sincerely don't want to go on with this discussion with you and not because I finished my arguments.
Bye.
Alberto.

No offence, but i have to say it's about time...


Paul
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: ukmicky on 22/02/2007 01:19:51
Quote
BY SCANNER Until we can stop using the IC engine all together, we need to continue using the one which has the least OVERALL ill-effects and at present most sensible observers agree that is the diesel and that is why research into making it even cleaner is progressing so fast
You are kidding of course, YOU CAN NOT BE SERIOUS ,you talk about people on this forum being blinkered in regards to their bias towards petrol and yet you are doing the same with you bias towards diesel.


I ASK EVERYONE TO DO A BASIC GOGGLE SEARCH ON "How toxic is diesel compared to petrol 2006 "
 
You will find that every study performed by every health organisation on the dangers of diesel pollution , even the world health organisation report that diesel pollution is many times more hazardous to life than petrol.Did you know that diesel is the number one air poluter in California even though it is nowhere near the number one fuel which is petrol.
The World Health Organization has concluded that, globally,particulate matter causes 460,000 premature deaths each year. Diesel engines generate primary particulate emissions – accounting for 20 percent of direct PM10emissions nationally. EPA has projected that by 2010, direct PM10emissions frommobile sources will be over 600,000 tons, with diesel engines contributing nearly 70percent.
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THIS WEBSITE GIVES A GOOD BASIC RUNDOWN

For over ten years the U.S. Environmental Protection Agency(EPA) has worked to reduce the amount of emissions that die-sel trucks and buses are allowed to release, due to the threat posed to human health and the environment. Much less has been done to clean up diesel fuel and diesel engines than gaso-line alternatives. Diesel fuel not only contains a higher portion of dangerous substances compared to gasoline (as a result of less refining), but also the high-heat combustion in diesel engines allows a larger portion of these substances to form and be released. The high heat in diesel engines creates NOx. NOx reacts with sunlight and Volatile Organic Compounds (VOCs)to form smog, which triggers asthma. The Clean Air Network estimated that in 1997, smog triggered370,000 asthma attacks, and 9,600 emergency room visits in Pennsylvania. Fourteen Americans die every day from asthma. SO2 contributes to par-ticulate matter (soot) and when inhaled, particles of soot get lodged deep in the lungs causing in-fection, and potentially cancer and premature death. CO de-prives the heart, brain, lungs, and other tissues of oxygen.Diesel exhaust contains more than 40 toxic substances, many more than are found in gasoline. The U.S. EPA stated that die-sel exhaust is a ‘likely human carcinogen’, or cancer-causing agent. Studies in California suggest that over 70% of all cancers attributed to air pollution are caused by diesel exhaust.Carcinogens in diesel exhaust include arsenic and benzene. Other toxics include formaldehyde, cyanide, dioxin, ammonia,and 1-3 butadiene which, can cause long-term health problems such as lung, kidney,and nervous system damage, and short-term effects such as skin and eye irritation,and aggravated respiratory problems
http://www.cleanair.org/Air/diesel_factsheet1_danger.pdf
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Diesel fuel contains more energy per litre than petrol and coupled with the fact that diesel engines are more efficient than petrol engines, diesel cars are more efficient to run. Diesel fuel contains no lead and emissions of the regulated pollutants (carbon monoxide, hydrocarbons and nitrogen oxides) are lower than those from petrol cars without a catalyst. However, when compared to petrol cars with a catalyst, diesels have higher emissions of nitrogen oxides and much higher emissions of particulate matter.
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http://www.ace.mmu.ac.uk/eae/Air_Quality/Older/Cars.html
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While diesel vehicles make up only about 10% of vehicles on the road, they are responsible for belching out 80% of traffic emission problems.
http://www.medicalobserver.com.au/displayarticle/index.asp?articleID=7332&templateID=105&sl=1
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Swedish consultancy agency Ecotraffic report ,showed  that the cancer potency of diesel exhaust is more than twice that of petrol cars. If only particulate emissions are considered, the carcinogenic effect of one new diesel car is equivalent to 24 new petrol cars and 84 new CNG cars on the road.
According to a study conducted by the German Federal Environment Agency, diesel is "several dozen" times more cancer-causing than petrol.
http://www.cseindia.org/dte-supplement/air20040331/toxic_risk.htm

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There is no real debate that breathing diesel fumes is hazardous to the publics health. Compared to auto emissions, which are bad enough, diesel fumes are especially noxious
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The World Health Organization reports that three million people now die each year from the effects of air pollution. This is three times the number who die each year in auto accidents.
A 1999 study by Southern California's South Coast Air Quality Management District (SCAQMD) found that diesel soot accounts for 71 percent of the cancer risk from all toxic air contaminants.
Only 2 percent of all vehicles on the road in the U.S. run on diesel, yet diesels account for 27 percent of the smog-forming pollution and 66 percent of the soot produced by all of the nation's motor vehicles.
Over 30 human epidemiological studies have found a link between diesel exhaust and lung cancer.http://www.aacog.com/schoolbus/Parents/Parents.asp


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Diesel engines emit huge quantities of particulate matter, nitrogen oxides and more than 40 toxic compounds that have been linked to cancer and other serious health impacts. Particulate matter is associated with increased asthma emergencies, bronchitis, various cardiopulmonary ailments, cancer, heart disease and premature death. Nitrogen oxides contribute to ground-level ozone formation, smog, and nutrient pollution in waterways. Up to half of the particulate matter measured in the nation’s largest cities comes from diesel tailpipes. Roughly one-quarter of the nation’s nitrogen oxides come from diesel engines. Diesel exhaust (or diesel particulate) has been found to be carcinogenic by the U.S. Environmental Protection Agency, the California Air Resources Board, the World Health Organization and other public health agencies around the world.
http://www.nrdc.org/air/transportation/trk0600.asp

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http://72.32.110.154/media/pressReleases/001120a.asp

http://www.arb.ca.gov/research/diesel/dpm_draft_3-01-06.pdf


http://www.cseindia.org/aboutus/press_releases/press_20040728.htm

I could go on and on but every study or report from every major heath organisation basically concludes that petrol burning cars pollute less and the pollution that they do give out is less hazardous to our health than diesel, so i may as well leave it as that apart from.

Personally over the years i have driven a hundred or so different diesel powerered vehicles and have driven many thousands of miles in them through my work , but give me the choice and i would have jumped into a petrol car or van everytime because Ive prefer the refinement and responsiveness of the petrol . Also when it comes to health and the dangers of different types of fuels i prefer to listen to the experts like  the U.S. Environmental Protection Agency for example.

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Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Karen W. on 22/02/2007 07:33:31
I live in California and Let me tell you!! LA has tons of diesel cars etc.. Not to mention High numbers of Big Rigs delivering through there daily... Me Husband Having been one !!! There are plenty of disel powered vehicles there despite the veiw taken earlier on there not being accessible or something in LA with their smog factors.. BUNK!!! I am no expert, but LA IS FULL of diesels all varieties!!!

  Michael YOU ROCK!! LOL
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: scanner on 22/02/2007 18:47:11
UKmicky I don't deny diesel pollutes or that petrol pollutes or that they pollute differently.

But US research does not apply in the EU as many factors are different not least the quality of fuel. US diesel is dirty unrefined stuff and is not comparable to EU standard fuel in any way - especially bio-diesel and modern high-tech diesels like V-Power and Ultimate. Once again you are only referring to particulates from diesel - PM10s - petrol produces PM2.5s and PM5s why do you ignore these and their ill effects?
NOX yes diesel produces NOX but in very low concentrations and less now than ever dues to ever better EGR systems. But over all diesel produces less total emissions as it's greater efficiency burns less fuel in the first place.

If things are really so bad why is diesel overhaulling petrol hand over fist as the major motive fuel in the EU?

So
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diesel exhaust is a ‘likely human carcinogen’
is it? Just what is the 1% benzene in petrol then?
I am puzzled by the reference to benzene in diesel exhaust, where would that come from there is no benzene in diesel. It is added to petrol to improve octane ratings - diesel doesn't have or need an octane rating and the very reason it is added to petrol is why it WOULDN'T be added to diesel.

All your quotes relate to the USA and as such are a red herring as those conditions do not translate to the EU as very different circumstances apply and have done for a long time. In any case the EPA is well known for inflating it's case against diesel and totally ignoring the ill-effects of petrol.


OK so you prefer petrol engines, so do such paragons of logical thought as Jeremy Clarkson and Tiff Needell. I would be interested to know exactly which models of diesel car you have driven and how recently that was and when you last drove a petrol van as they are now an endangered species.




Ohh and Karen could you let me know EXACTLY what fraction of 1% of the CARS (not trucks, pick-ups or RVs)in LA are diesel powered? UKmicky states that less than 2% of ALL VEHICLES in the USA are diesel powered, so if you take out all the trucks pick-ups and RVs that cannot leave many % to be cars.

Perhaps the California Dept of Transportation could let you have the figure. I don't think it will take that long to add up.

If it is more than I think, I must say how impressed I am with the good sense of some of your countrypersons.

Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Morepower on 27/05/2008 19:29:56
Sorry to restart an old thread. I read it all with great interest and I can see both sides of the argument. Neither fuel is healthy and I use both fuels. Petrol in my Motorcycle and Diesel in my car. Now as far as I was taught whilst I worked in the Coal mines dust and particulates were a risk to health and I know people who have died from mining related illnesses. We were always told that if you can see the dust it would be filtered out by our bodies defences and the smaller non visible particles were the highest risk. So when we are looking at particulate emissions surely we need to look at total volume regardless of size and be aware that the smaller particulates have a higher health risk. Again we also need to look at not only emissions per liter of fuel used but also per mile or kilometer. If a diesel can go 30% further per liter than petrol we need to look at it over the amount of fuel used and the distance involved. OK cities are hard work due to volume of traffic but we need to look at ways of reducing the number of vehicles in our cities with options based round less localised pollution. I know electric trams and other public transport has emissions which are away from the urban population but as with LA in the US this lack of ventilation or flow of air over the traffic jams will harm more people who come into contact with it.Electric city transport systems powered by rural wind farms are as clean as we can get at the moment. But I digress.
The energy in diesel is potentially greater than in Petrol and in recent months diesel engined cars have not only won world endurance races but European touring car races and these cars are based on the ones we drive. OK they may be tuned engines but they are all 2 litre and turbo charged, which is as close as any race car will get to being similar to ones we drive.

http://www.fiawtcc.com/fiawtcc/season/2008/sport_sto1565962.shtml

As you can see if you look at the link these diesel cars are beating petrol engined ones so power is not too much of a problem with good engine management as these engines are limited to 4100 RPM and have limited boost and fuel pressure applied to them. Now I think unfortunately Diesel will be the fuel we look to more in the future and the US market has not got the volume of diesel vehicles partly due to the poor agricultural quality fuel they use, which almost all the more efficient European and Japanese vehicles now cannot use.There are no top spec European diesel engined cars in the US due to the poor quality fuel. Also as a small by product of US fuel pumps which use one fuel gun for all the fuels which causes the first part of any change in fuel required to take the residue of the other fuel in the lines. Mixing petrol with diesel or vise versa is not good. I was also confused with the comment about Benzine in diesel emissions as Benzine is there to increase octane rating and diesel uses Cetane numbers for its rating and benzine has a negative effect on diesels cetane ratings. I do not argue either fuel is unhealthy but long term bio fuels will be more common and bio diesel in modern engines will become cleaner and exhaust gas recycling to clean up the harmful particulates will become more effective as will the use of catalysts which may not be good for the environment when we make them but will cut down on poisoning due to the use of internal combustion engines.

I do not want to get too wrapped up in the whole argument of either fuel as I have not got the experience of a petrochemical scientist or work in the industry. But from a simplistic point of view if we use less fuel per mile and can use technology to reduce emissions of any type I am in favour of that. Petrol has a limited life and E85 fuels are not an answer with older vehicles as they take a lot to convert over as they use more fuel by volume then petrol alone and fuel injected engines in some cases cannot be adjusted to flow enough E85 and it has a lower energy output per litre to work fully where more modern Diesel fuels will work with older diesel vehicles as the basic principle has not changed and the energy per litre will stay fairly constant.   
Title: Re: What is the difference between diesel fuel and petrol (gasoline)?
Post by: Morepower on 27/05/2008 20:04:24
Deisel is like kerosene and it is not as explosive as gas, so it doesn't have as much energy potential as petrol, whereas the gas has a higher energy potential.


Diesel has a higher energy content than Petrol.
1 gallon of gasoline = 124,000 Btu

1 gallon of heating oil or diesel fuel = 139,000 Btu

If you have to make a point please get it right and the above quote doesn't allow for the newer European low sulphur fuels which now have helped evolve diesels in Europe so far that they now cannot be sold in the USA due to the poor quality fuel sold in much of the USA. It is almost the same grade as used in farm vehicles (called Red Diesel in the UK) and the stuff used in 3rd world countries.