Naked Science Forum
Non Life Sciences => Technology => Topic started by: Petrochemicals on 18/04/2024 19:50:31
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Today the motor is averaging 52mpg, this is city driving, traffic lights, junctions, etc. Only a week ago it was averaging 44mpg for the same type of driving. The numbers are via the cars display?
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Hi.
I don't really know where your figures came from. My car hasn't improved its fuel economy this week compared to last week. 52 mpg sounds unrealistically high for the average motor car, what country did the figures come from and is it all downhill there?
Best Wishes.
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Oddly, I concur with PC!
For no reason I can think of, Britain's motorways have suddenly become congestion-free and the cities seem devoid of idiots.
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That's an interesting observation, Alan. Here in Ireland we have had an alarming increase in road deaths over the last two years. There appears to be no shortage of idiots here, maybe we could export some if you feel your country is running short?!!. Driving on an idiot free road/motorway could be actually enjoyable instead of apoplexy inducing. On the mileage question, the boss' car(Renault clio hybrid) will do ~50 to the gallon - I can testify to this as I have been driving it recently as my 20year old Honda civic has gone to the great service station in the sky. The clutch hydraulics failed and I could not source a replacement master cylinder. Now I will have to choose the least worst of the current range of overly complex motors.
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More averaging needed.
I was getting little more than 4% variation if I exclude the one year where my driving was materially different:
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Not sure where ES is based, but 50 mpg is a reasonable target for a smallish European car using British gallons of gasoline, equivalent to 37.5 miles per USG.
I use a medium (for Europe) SUV - a Skoda Yeti 2 liter diesel that generally averages 52 mpg between weekly fillups but has crept up to 55 this week, despite thrashing around the M25 (London peripheral route) and in and out of central London.
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Hi.
I don't really know a lot about cars.
I have a red one with 7 seats but I don't usually put all the seats down. So I reckon it has the fuel economy of a 5 seater on average.
I've also noticed the trip computer displays an economy of 0.1 mpg while I'm waiting at the traffic lights. The hand-brake is holding, so I reckon that's because the earth is moving through space all the time.
It runs on tyres. This car has a diesel injection engine while my old one had a petrol injection engine. I can use the same tyres, the engine just injects them differently.
Not sure where ES is based
It's a fairly ordinary house with a B rating for energy efficiency but I can't always park the car close to my house and I don't know what efficiency the other houses offer.
Best Wishes.
(perhaps I should keep my day job and not consider a career as a comedian).
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Hi.
I don't really know where your figures came from. My car hasn't improved its fuel economy this week compared to last week. 52 mpg sounds unrealistically high for the average motor car, what country did the figures come from and is it all downhill there?
Best Wishes.
From the car computer display thing. It is a modern car with the small 1 litre eco turbo boost engine. From the uk, round trips so there is as much up as down, standard city driving. Things i think could factor:
1)humidity
2)oxygen content
3)air temperature
4)road surface temperature
5)fresh air as opposed to used air? As in smog, maybe based on wind?
6) car temperature?
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The presence of headwinds/tailwinds could produce such a discrepancy in motive efficiency, it's hardly likely that the brake thermal efficiency of the engine could be that erratic. Most of one's fuel goes to counter wind resistance assuming careful driving without redhot discs. Note to ES regarding comedy: I had similar aspirations once as Alan had made reference to my "rampant wit"!
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My travels are almost always out and back the same day. Whether this is effectively a radial or mostly an arc around the M25, I would be very surprised if, just for one week, the wind changed through exactly 180 degrees every day whilst I was visiting my client's premises for a couple of hours!
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Cyclonic pattern winds. I know I am "scraping the barrel" to find a cause of the discrepancy, what do you propose?
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The presence of headwinds/tailwinds could produce such a discrepancy in motive efficiency, it's hardly likely that the brake thermal efficiency of the engine could be that erratic. Most of one's fuel goes to counter wind resistance assuming careful driving without redhot discs. Note to ES regarding comedy: I had similar aspirations once as Alan had made reference to my "rampant wit"!
1)humidity
2)oxygen content
3)air temperature
4)road surface temperature
5)fresh air as opposed to used air? As in smog, maybe based on wind?
6) car temperature?
7)air density/pressure
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I would only rate 1,3 and 7 as having any significant effect, but way less than a STRONG headwind/tailwind.
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I would only rate 1,3 and 7 as having any significant effect, but way less than a STRONG headwind/tailwind.
3 and 5 i think will be the same thing too! Catalytic converters run on a fuel rich mix in the engine, so a slight uptick in oxygen persentage may yield results, especially if the fuel air mix is set for a high atmospheric pressure/ low humidity/low temperature senario, that is if these modern cars themselves do not automatically adjust for humidity, temperature and pressure
As alan points out, a round trip is unlikely to yield wind or gradient advantage. Talking of gradients, i have often wondered if someone who lives in london achieves better mileage than someone who lives in sheffield, as the latter is quite hilly, all that braking to keep within the speed limit must add up. Its not all down hill from here though.
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Problem with London is empty bus lanes and a 20 mph speed limit practically everywhere, so even when the traffic is moving you rarely get out of third gear.
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Problem with London is empty bus lanes and a 20 mph speed limit practically everywhere, so even when the traffic is moving you rarely get out of third gear.
That is the problem everywhere, exept london has this wonderous thing called the underground, you can quite easily live in london without a car at the same time as removing pollution and doing your bit to lower global warming. If only they had put similar infrastructure into all the other congested cities, Birmingham and Manchester wouldnt have the longest commute times in the uk. Ah well, I supose it would have cost ?100 billion plus.
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In the 1980s in the USA car manufacturers started to put computers into cars to collect information on performance.
These first computers were manufacturer specific until the industry made a common specification and added Diagnostic data collection.
The specification is known as OBD "On Board Diagnostics" , the USA spec. and there are others JOBD and EOBD (Japanese , European).
When a fault is sensed the onboard computer stores a special OBD "lookup error code" you can find online.
e.g. P1003
Then it switches on the "check engine" light on the dashboard to alert a driver or mechanic to take a look with the OBD reader tool.
I changed the fuel filter in a Holden Captiva diesel recently, unlike the old days before 2000 , there were electric data and power source leads into the filter housing top and bottom, I had to also change the master cylinder and re bleed the brakes because the other master cylinder sinks the pedal to the floor, it had data connectors onto the master cylinder for the ABS unit.
Anyhow, all vehicles on the road legally must have some form of OBD. You can buy particular OBD readers from good engineering and industrial tool stores.
You will find the OBD data connection port in your car usually to the wall side of the driver in the bottom of the dashboard or just under it if not covered by a plastic inset plate.
Today the motor is averaging 52mpg, this is city driving, traffic lights, junctions, etc. Only a week ago it was averaging 44mpg for the same type of driving. The numbers are via the cars display?
Diesel (drained water from the fuel filter, service done on time)?
or petrol (unleaded , unleaded premium) ?
Does the engine blow more smoke than before and seem less powerful (spark plugs) , (piston rings over 250,000 km's)?
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Exhaust gas return valve clean?
Bad hydraulic lifters (tappets worn tips on manually tuned valve system)?
Excess carbon build up "on" cylinder - cylinder head internal, it causes loss of correct fuel ignition "moment".
A rare and vague possibility is a fuel leak. Done Any work on the fuel lines (non screw in lines use a special plug clipping tool). Start the car on a clean level cement area, take a look under it before you start it front and at the back where the tank is underneath, run it for five minutes idling , give it a few revs for a moment, nothing hard (tap the accelerator a few times just after starting ) . When time is up find if fuel and drips have formed on the ground as a stain under the vehicle.
A less common one is water leaking into the cylinders from a blown head gasket. If you must get this tested (there are off the shelf special test kits) always take the vehicle to a "reputable mechanic" not simply down the road!
When I got the Captiva, the guy told me it only has 177,000 km's on the clock and it was serviced regularly and recently.
When I test drove it the brake pedal sank to the floor a number of times, and the automatic transmission skipped over a gear to the top gear.
When I tried to find the transmission oil level I couldn't get a reading, it took two litres to fill it, the correct quantity is 2.5l , the engine oil was black as night (no service there if it ever was changed). The fuel filter was black as night, a wonder the engine ran with any power! It was a bit more powerful after the fuel filter was changed.
I'm getting it to pink slip test for the rego soon.
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london has this wonderous thing called the underground
Which would be a Good Thing if the suburban stations had big enough car parks!
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london has this wonderous thing called the underground
Which would be a Good Thing if the suburban stations had big enough car parks!
The idea of a light railway is there are more stations and you walk to a local station.
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Diesel (drained water from the fuel filter, service done on time)?
or petrol (unleaded , unleaded premium) ?
It still fluctuates so nothing mechanical. It's petrol, so I have wondered about the quality of fuels, whether light distilates are being boiled off or burned, or simply a different quality of fuel or contamination. I feel it is definatley something to do with the air, the humidity content, smog etc.
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Diesel (drained water from the fuel filter, service done on time)?
or petrol (unleaded , unleaded premium) ?
It still fluctuates so nothing mechanical. It's petrol, so I have wondered about the quality of fuels, whether light distilates are being boiled off or burned, or simply a different quality of fuel or contamination. I feel it is definatley something to do with the air, the humidity content, smog etc.
It is considered the humidity and moisture from air , BUT , the reason is the underground storage tanks at petrol stations must have a breather vent (not simply each motor vehicle). Too , it is each station must adhere to quality control but for one reason or another it can be a problem.
BUT, again finally, a diesel filter is not quite the same as a petrol filter in terms of water, truth is though to cut it short ,either will cease to allow flow to the engine fuel controls if enough water is caught.
Diesel vehicles use very good blocking filters in a filter reservoir and have a drain screw.
Diesel is coloured (refinery must add a dye colour) but water is clear and heavier.
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The idea of a light railway is there are more stations and you walk to a local station.
At the age of 80, I am not inclined to walk 50 miles to the nearest London Underground station to make a 9 am meeting tomorrow. I could probably manage the 5 miles to the main line station if there was no hurry but the last time I arrived there it was closed due to strike action so I had to drive 200 miles to the job - turned out to be quicker and cheaper than the train anyway, even though it wasn't subsidised by the taxpayer (me).
Some years back a Department of Health survey discovered that there were fewer disabled people in London than almost anywhere else in the UK, with rural Northern Ireland scoring particularly high. My group was tasked to investigate the anomaly. It turned out that the definition of "disabled" was the question "Can you walk to a bus stop?"
Meanwhile, be cautious of weekly fuel consumption figures unless you drive at least 500 miles a week. Fuel tank float monitors are notoriously vague and nonlinear as the inferred volume depends on the starting level and the shape of the tank. Even if you have credibly calibrated injectors or a flow monitor, a lot depends on the ambient air temperature at startup, and overtaking on a hill will have a startling effect: most cars cruise at around 10% of maximum power and a short burst at 100% makes a huge difference to the short-term average consumption.
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At the age of 80, I am not inclined to walk 50 miles to the nearest London Underground station to make a 9 am meeting tomorrow
I wouldn't call that local. It's more about the time than the distance, even if you drive you have to find a parking spot at a station, you can still have spent 10 minutes extra, may as well drive straight there at that. Even if you only live around a mile away that can still be a 20 minute plus walk in the freezing driving rain. It needs to be 10 minutes tops, ideally within 500m of your door or stations 1km apart with lines spaced similarly. Quick accelleration and breaking and you can cross a city much faster than you can drive.
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1km apart with lines spaced similarly. Quick accelleration and breaking and you can cross a city much faster than you can drive
You need 30s stops at each station, and acceleration > 0.15g is not acceptable. There's little difference in practice if the city is well planned.
The real frustration with public transport is short-haul flying. I can't afford the time or cost of a train to Glasgow but although the Airbus covers the distance in 50 minutes, the overall trip door-to door takes as long as driving. Quickest, and still cheaper than the train, is the old Cessna - provided the engine starts.
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There's little difference in practice if the city is well planned.
Triple carriageways with flyover and slip roads plus their embankments and free flow junctions, but then you get to the problem of the majority of the city consisting of roadway rather than anything else. You could tunnel, but the upheaval of the upheaval and the cost is something governments tend to shy away from. Maybe we should start building cities in the air starting with pavements at the 3rd storey.
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Future "cities" will be very different. Office blocks are a 20th century excrescence from the days before telephones, there will be no need for high densities of manual workers, most retail and all wholesale will be from automated warehouses....I think the city is doomed to extinction. And if we are to live sustainably, a much-reduced population will be living in villages with a pub and a post office/ local government/registrar's office where the church used to be.
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Future "cities" will be very different. Office blocks are a 20th century excrescence from the days before telephones, there will be no need for high densities of manual workers, most retail and all wholesale will be from automated warehouses....I think the city is doomed to extinction. And if we are to live sustainably, a much-reduced population will be living in villages with a pub and a post office/ local government/registrar's office where the church used to be.
Only Alan if it is cheaper, money rules Alan, bankers I think will be replaced completely, computers already do much stock trading, their is no need for an opening or closing bell now, nor do they need to be in the same area, as you say, communications render New your as Close as Canary Warf .
Modern cities are beginning to etracate businesses from the centre to the outskirts, with high density housing taking their place, even though the centre was once sensible for commuting, many people commute past their own centre anyway to another or somewhere else and businesses are not constrained in florspace or tax rates. This though is all the more reason for a good light railway system in any major connurbation.