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-   -   Saving fuel in a car by not using brakes (https://www.pprune.org/jet-blast/448931-saving-fuel-car-not-using-brakes.html)

ShyTorque 17th Apr 2011 07:01


Won't the money you save on fuel have to go on overhauling the brakes when they start sticking due to lack of use?
Good point, I noticed my car's brakes weren't quite as effective after the winter; obviously I'd been a bit easier on them in the extended slippery conditions we've had here. I gave them a bit of hard work to do and they're now back to normal.

Capetonian 17th Apr 2011 07:09

All Swiss citizens are, or think they are, Beamter with vague connections to the Polizei.

I remember driving into a nearly empty public car park, late one afternoon, in Luzern, and instead of zigging and zagging up and down the rows following the neatly painted arrows, wasting fuel, I cut across the end and parked. There was nobody, but nobody, on foot or in a car, who could have been incovenienced in any way. But as I was walking away from the car a little Schweizer busybody was there, pointing at the arrows on the ground and telling me that they had to be followed, 'obwohl Sie Polnisch sind' (even if you are Polish, because we were driving a Polish registered car).

I suspect that if we'd been driving a CH car he wouldn't have done it, he'd probably have called the Polizei who would have stripped me of my citizenship.

mike-wsm 17th Apr 2011 09:30

Best way to save fuel is to have a small car with a small engine and thrape the living daylights out of it. I used to run a SEAT Marbella and drove it with full wellie, either max throttle or max brake and used to get 50mpg. Quickest from A to B, too, never passed by anything except once on M4, he must have been doing 140, and not in km.

Sorry Ancient, being boring again, mea culpa.

corsair 17th Apr 2011 09:49

This is all very well and fine but using all these clever methods of slowing down without the use of brakes will inevitably result in someone slamming into the back of you because there was no warning from the brake lights as you slow down suddenly.

Windy Militant 17th Apr 2011 15:34

But That's the Point Corsair you're not slowing down suddenly. If done properly your using enough throttle to arrive at the bend at the best speed to get round it without having to scrub off speed with the brakes thereby saving energy by not converting fuel to heat. It also saves on pads and tyres! In the good old days of drum brakes it also avoided the dreaded brake fade and if our defensive driving assessor who is an ex Police instructor is to be believed puts the vehicle in a nicely balanced state to get around the bend safely and smoothly. ;)
Cacophonix ta for the video I can almost smell the Castrol R.:ok:

RJM 17th Apr 2011 16:10

This is interesting, especially about the Swiss.

I had a similarly interesting thread going a while ago about how different Europeans stack their firewood. The Swiss figured in that too, but even their appearance in the fascinating thread didn't save it from oblivion.

As to not using back brakes on motorcycles: get a Norton Commando - the back brake doesn't work at all.

Loose rivets 17th Apr 2011 16:46


Sorry Ancient, being boring again, mea culpa.

Well, Mike from WSM focused in on the answer about 4 posts in, but really, the issue hasn't been truly analyzed.

It's simply the point about the brakes being something special in the way they generate heat and consequently lose energy; something more than all the other heat generating parts of deceleration.

Mind you, the thread has raised some interesting points, like the one about planning cornering so that heat is not generated in the brakes, but this would still of course require the speed either not to have been built up in the first place, or have been washed off by some other means before the corner.


Cornering. A mass having its direction changed though 90 degrees, will have had its speed on one vector reduced to zero, and increased to 100% of whatever, on the new vector. This can't be a free lunch . . . erm, can it?

Dalex64 17th Apr 2011 17:31

The mathematician's savings don't come from not using the brakes.

They come from reducing engine power early (coasting) instead of maintaining power and speed until later.

Basically, all other things being equal (acceleration, top speed, distance), you save fuel by getting off of the gas sooner.

Loose rivets 17th Apr 2011 20:32

The few times I've experimented with that, I found I had to be so close - 20 feet, I'd agree with - that I was having to concentrate so hard on being ready to stop, that I was brain-:mad:'d before a mile was up.

spekesoftly 17th Apr 2011 20:48


what some call 'drafting' behind a truck.
And most call "suicidal stupidity" :rolleyes:

ShyTorque 17th Apr 2011 22:44


Cornering. A mass having its direction changed though 90 degrees, will have had its speed on one vector reduced to zero, and increased to 100% of whatever, on the new vector. This can't be a free lunch . . . erm, can it?
Think tyre temperatures....and what happens when cornering. They warm up on bends because the walls are flexing more than on the straight. That heat comes from the fuel tank.

G-CPTN 17th Apr 2011 23:22

Formula one tyres reach temperatures of 100 deg C, apparently (so I have heard).

Tyre use in Formula One - F1technical.net

BarbiesBoyfriend 17th Apr 2011 23:32

My Audi uses no fuel at all if you simply take your foot off and let it slow down.

On the other hand, if one slips it into neutral (it's an auto) the 'instant fuel' readout goes up to 120 mpg.

I like it when it does that as the bastard thing will only go 360 miles on 80 litres of 95 octane.

Thats 19mpg..

Still love her.:eek::ok::rolleyes:

Cacophonix 18th Apr 2011 05:25


That they would work to mitigate the energy required from the engine is obvious. If you slowed a car from, say 70mph to stop and put the energy into a reservoir and then accelerated to say 60mph before that energy was expended, (allowing for losses) you would only need to use the engine from 60mph back to 70mph and then a little power to maintain cruise. All the gas usually used from zero to 60mph would be saved.
The addition of the Kers system (plus storage/reservoir system - battery, flywheel or whatever) adds weight to the car and that weight takes energy (namely gas) to accelerate over the lifetime of driving the car.

This factor, coupled with energy storage (reservoir) and other inefficiencies means that that not all energy recouped can be put back into the system and therefore as you imply (allowing for losses) the system is not perfectly efficient so you don't get the one for one trade off implied by your last statement but I guess you didn't mean to say "all the gas".

Kers systems on road cars and buses have resulted in fuel savings of up to about 30% but the systems can be complicated and also add servicing costs etc.

Caco

Edited to say that those inefficiencies you noted have been the bane of all over unity machine visionaries since the day we started to look at machines.

mike-wsm 18th Apr 2011 06:14

Bandaide


That's inhumane and cruel to drive a big gas-guzzling muscle-car like that. If you got it, flaunt it. Owned several of the beasts, my favourite was this shape. Oh, wonderful vehicle, back in an era when we just went there and did it, no worries about the poor old planet.

Parapunter 18th Apr 2011 06:50


And most call "suicidal stupidity"
Likely a big difference between hunkering up behind a truck on some straight line 1000 mile long interstate and the M25 on a Monday morning in fairness to B.A. Still wouldn't do it though & flying formation only works if you can talk to the other guy...

RJM 18th Apr 2011 10:43

I just can't understand why we don't get more women on JB.


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