Naked Science Forum
General Science => General Science => Topic started by: neilep on 24/04/2007 00:37:52
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Hello,
I'm Neil.
Cars are great..especially when travelling distances !!...they get you from A to B in sheer automotive
unburdened fun & luff !!
I use mine every day and I do a lot of motorway driving (USA Peeps: Motorway = Highway...sheesh !!)
Often I have many miles of no traffic so I go ahead and play with my cruise control...(in fact..it's very handy when in a controlled speeding zone )
Is it more efficient to use it rather than using my foot ?
I presume the cpu must be making thousands of calculations a second or is it just as simple as it being tied into the speedometer and not many decisions are being made at all ?
i don't know...do you ?
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Efficient, as in fuel-wise?
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Efficient, as in fuel-wise?
yes Sir Seany Sir !!
Thanks for helping me to clarify it.
Hugs the Seany !!
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Well.. I think it is more efficient.
For instance, if you want to go at a steady pace, of 70mph, but by using your foot. Then, you constantly have to press the pedal, let go a bit, press the pedal, let go a bit.. This will use more petrol, and is less efficient, just like starting a car up, is the most fuel-consuming action.
If you go at a steady pace of 70mph using cruise control, the machine does the letting go and pressing the pedal, on it's own, but it's a lot more accurate, as to when to press and let go. Thus, it'll be more efficient for fuel.
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I am surprised that you find anywhere in the UK, particularly in the south-east, where traffic is so light that it is safe to use cruise control.
Cruise control can improve fuel efficiency over normal driving, but it is not optimal efficiency. In order to optimise fuel consumption, one would normally allow speed to be picked up when travelling downhill and some of the speed to be used to help coast up the next gradient, and so running at something closer to constant power than constant speed (a lot depends on exactly what speed you are travelling - at very high speeds, the increase in downhill speed will lose more in aerodynamic drag - but if you are trying to optimise fuel consumption, then you would not be travelling at those speeds).
Another reason for trying to build up speed on downhill stretches is that you want to spend as much time as possible in top gear, while running at the lowest speed consistent will allowing youself to use top gear. If you have built up momentum on the downhill run, this will allow you to take the next uphill gradient without dropping a gear.
The other thing to bear in mind is that using cruise control makes steering more difficult, as you will not as easily be able to use torque to pull you around corners (not so much of a problem in those parts of the US where you have miles and miles of absolutely straight roads, but there are not many places in the UK you could find that).
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I am surprised that you find anywhere in the UK, particularly in the south-east, where traffic is so light that it is safe to use cruise control.
The UK isn't really a very traffic-jammed place. Go to Italy or somewhere, you can't drive. Bumpy roads, tons of traffic - hell. Places such as South Korea, tons of cars, take you about 1 hour to travel 10 miles. The UK's traffic is really light.
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I am surprised that you find anywhere in the UK, particularly in the south-east, where traffic is so light that it is safe to use cruise control.
The UK isn't really a very traffic-jammed place. Go to Italy or somewhere, you can't drive. Bumpy roads, tons of traffic - hell. Places such as South Korea, tons of cars, take you about 1 hour to travel 10 miles. The UK's traffic is really light.
Many years since I have been in Italy, but my recollection is that the Italian autostrada are no more crowded than British motorways (some crowded areas, e.g. around Venice - but some areas of the UK can be crowded). Off the motorways, the roads are crowded, but speeds are generally high, if a bit dangerous at times.
Can't comment about Asia.
But in any case, except maybe for the very early hours of the morning, I don't think there is anywhere in Europe I would consider to be safe to use cruise control. Even though UK motorways, most of the time, have a relatively steady flow of traffic, there are just too many occasions to have to slow down or react to events that one cannot hold a steady speed, and having you foot constantly on the throttle makes you more responsive to changes in the driving environment.
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I am surprised that you find anywhere in the UK, particularly in the south-east, where traffic is so light that it is safe to use cruise control.
Cruise control can improve fuel efficiency over normal driving, but it is not optimal efficiency. In order to optimise fuel consumption, one would normally allow speed to be picked up when travelling downhill and some of the speed to be used to help coast up the next gradient, and so running at something closer to constant power than constant speed (a lot depends on exactly what speed you are travelling - at very high speeds, the increase in downhill speed will lose more in aerodynamic drag - but if you are trying to optimise fuel consumption, then you would not be travelling at those speeds).
Another reason for trying to build up speed on downhill stretches is that you want to spend as much time as possible in top gear, while running at the lowest speed consistent will allowing youself to use top gear. If you have built up momentum on the downhill run, this will allow you to take the next uphill gradient without dropping a gear.
The other thing to bear in mind is that using cruise control makes steering more difficult, as you will not as easily be able to use torque to pull you around corners (not so much of a problem in those parts of the US where you have miles and miles of absolutely straight roads, but there are not many places in the UK you could find that).
The thing is I see people in the evening and often do not leave to come home as late as 11pm...at those times (from 9pm onwards)..I do in fact have stretches of driving joy ! [:)]
It does become very useful along a particular 5 mile stretch of the M1 where they are widening both sides which currently has a controlled speeding zone of 40 mph...this is to continue until December 2008 and I use it up to three times a week...and so...it is only used on the motorway where changing lanes and steering hardly comes into play.
THANK YOU George for your excellent post.
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I am surprised that you find anywhere in the UK, particularly in the south-east, where traffic is so light that it is safe to use cruise control.
The UK isn't really a very traffic-jammed place. Go to Italy or somewhere, you can't drive. Bumpy roads, tons of traffic - hell. Places such as South Korea, tons of cars, take you about 1 hour to travel 10 miles. The UK's traffic is really light.
I won't travel just fourteen miles south across the river into South London(Fulham for example) unless my appointment is no earlier than 9pm !
To arrive at the same place say before 7pm is absurdly ridiculous in the extreme as it has taken me (on more than one occasion) three hours to travel that far ! ....You can not travel anywhere within the North and South Circular Road at rush hour without just becoming gridlock !!
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It does become very useful along a particular 5 mile stretch of the M1 where they are widening both sides which currently has a controlled speeding zone of 40 mph...this is to continue until December 2008 and I use it up to three times a week...and so...it is only used on the motorway where changing lanes and steering hardly comes into play.
I know that stretch all too well - it is about 5 miles from home, and my local motorway (and has caused an increase of traffic on the local parallel roads).
Southbound, mostly not that much of a problem; but for some reason, northbound can come to a grinding halt from many miles before you hit the road works.
The other problem is that overnight they tend to shut off two of the exits - the one's that I would be using.
All of that work is to support the additional traffic load expected by the expansion of Luton airport - so not only will we actually not have a better motorway (i.e. they spend millions of pounds to allow the motorway to be just as bad with the extra traffic load as it is today with todays traffic load), but we will have to contend with extra air traffic from Luton (which is 4 miles away).
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I presume the cpu must be making thousands of calculations a second or is it just as simple as it being tied into the speedometer and not many decisions are being made at all ?
i don't know...do you ?
Cruise control predates the use of microprocessors in cars.
The only real decision the computer will have to make is whether to change gear - the speed is simply locked with the speedometer.
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I know that stretch all too well - it is about 5 miles from home, and my local motorway (and has caused an increase of traffic on the local parallel roads).
Southbound, mostly not that much of a problem; but for some reason, northbound can come to a grinding halt from many miles before you hit the road works.
The other problem is that overnight they tend to shut off two of the exits - the one's that I would be using.
All of that work is to support the additional traffic load expected by the expansion of Luton airport - so not only will we actually not have a better motorway (i.e. they spend millions of pounds to allow the motorway to be just as bad with the extra traffic load as it is today with todays traffic load), but we will have to contend with extra air traffic from Luton (which is 4 miles away).
I was tonight caught in that traffic half a kilometere before the slip road to leave the M25 to join it !!..it took me two hours to travel 45 miles to Milton Keynes...I left to come home at 9pm and it took 50 minutes !
So, with Luton airports' expansion, the road will just accommodate the traffic and will keep it with all the " fluidity " that it already has !!...sigh !!
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I presume the cpu must be making thousands of calculations a second or is it just as simple as it being tied into the speedometer and not many decisions are being made at all ?
i don't know...do you ?
Cruise control predates the use of microprocessors in cars.
The only real decision the computer will have to make is whether to change gear - the speed is simply locked with the speedometer.
Thank you George for this... I did wonder as I recall seeing cars with cruise control during pre-cpu times !!
I thought that perhaps nowadays they might have found a way to over calculate and over complicate it !..
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I thought that perhaps nowadays they might have found a way to over calculate and over complicate it !..
The only other area where I suppose the CPU could get clever is in adjusting valve timings, and generally adjusting the torque of the engine. I suppose the CPU could anticipate that since you are driving on cruise control, you wold suddenly be demanding massive amounts of torque, so if can maybe limit the amount of available torque or general flexability of the engine. I don't say that it necessarily does this, but it is an area where I suppose it might make a difference.
As you say, when you have unnaturally low speed limits, cruise control is often an easy way to make sure you do not exceed those speed limits, but you have to make sure there is no other traffic on the road, otherwise it is all too easy just to switch your mind into cruise control also, and suddenly find you have rammed the car ahead of you.
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Fulham is now south of the Thames? [:o]
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Fulham is now south of the Thames? [:o]
LOL !!....try Wandsworth !!...serves me right for looking at the map upside down !! *excuse mode*
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My cruise control only works at higher speeds (I think only greater than 45 mph, but it might be as low as 35).
Dick
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My cruise control only works at higher speeds (I think only greater than 45 mph, but it might be as low as 35).
Dick
Do you drive a manual?
It sounds like the cruise control is only working in top gear.
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Mine's an auto...I think the slowest speed is also 35 !
I must say....I'm not particularly relaxed when using cruise control ?!..if anything..I am more tense !!
Always (as George referred to) keeping an eye on the car in front....which..is prudent anyway of course !.......for me..it just serves it's purpose during the control speeding zone............
I have six points on my license from driving 43 and 42 in a motorway 40 mph zone !!.......at 3am !!
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Is it more efficient to use it rather than using my foot ?
I don't know about more efficient, but I've always found that using an internal combustion engine is much less strenuous than pushing the car with my foot. But then again, I'm a sloth. [::)]
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LOL. I never read it that way! [:P] But nice one [;)]
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Is it more efficient to use it rather than using my foot ?
I don't know about more efficient, but I've always found that using an internal combustion engine is much less strenuous than pushing the car with my foot. But then again, I'm a sloth. [::)]
LOL !!me um Fred Flinstone !!..Willllllllllllllllllmaaaaaaaaaaaaaaaa !!!!
I deserved that !!.........well spotted BASS and thanks for the chuckles !!
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LOL [;D]
WIIIIIIIILLLLLLLLMAAAAAAAAAAAAAAAAAAAAAA!!!
That's awesome [;)]
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Fulham is now south of the Thames? I think what the engine sounds like a voice-controlled tension control valve.