Does a car consume fuel under engine braking?

[Vic]

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

No no no. The brakes stop the car, not the engine. The ONLY reason to downshift is to make sure that the car is always in the proper gear.

 

[randay]

this should be on mythbusters!

 

[randay]

Originally posted by: Vic

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

No no no. The brakes stop the car, not the engine. The ONLY reason to downshift is to make sure that the car is always in the proper gear.

I mean "to engine brake, or not to engine brake, that is the question".

 

[Serp86]

so true

 

[Toastedlightly]

Originally posted by: Vic

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

No no no. The brakes stop the car, not the engine. The ONLY reason to downshift is to make sure that the car is always in the proper gear.

I thought the whole point of "engine braking" was that the compression of the engine (force needed to compress the air inside the piston) was more than the fuel being put in, thus the engine is turned by the driveline, reducing overall speed (or something like that)

 

[JulesMaximus]

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

 

[FoBoT]

Downshifting
The first thing to understand is the purpose of the downshift. It is not to slow the car, that is the job of the brakes. The purpose of downshifting is to have the car in the correct gear to accelerate through and out of the corner.

Here is the process:

As you enter the braking zone, apply the brakes, but do not immediately downshift. The downshift should be done after the RPM?s have dropped, but must be complete before you begin the turn-in. Downshifting too early can over-rev the motor, waiting too long means you will be rolling the car through the corner entry, giving up the ability to use the throttle to balance the car.

http://www.nasaproracing.com/hpde/heelandtoe.html

 

[MercenaryForHire]

This should be a goddamn sticky.

- M4H

 

[mattpegher]

I agree that less fuel is used during coasting in neutral then highgear without throttle but I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0. And a few times I have run out of gas going downhill and the engine stalls and you loose power steering and poser brakes.

 

[BD2003]

Originally posted by: DivideBYZero
MAKE IT STOP! NOT AGAIN! :|

Seriously...we beat this question to death a few months ago, and the ignorance is back in all its glory.

 

[DivideBYZero]

Originally posted by: mattpegher
I agree that less fuel is used during coasting in neutral then highgear without throttle but I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0. And a few times I have run out of gas going downhill and the engine stalls and you loose power steering and poser brakes.

ARRRRRRRRRRRRRGHHH!!!!!! :|


Look at the GODDAMMNED PDF I linked above. I think fugging BOSCH knew what they were doing when they designed their FI system better than a Sebum farmer with a 'nagging doubt'.

 

[randay]

Originally posted by: JulesMaximus

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

What I mean is purposely engine braking, ie. downshifting and using your engine to slow down your car, vs just braking(regular) all the way, vs coasting in neutral and only disc/drum braking. The first way you lessen wear on your brakes, the second other way is just normal wear, and the third way you lessen engine wear. In the end, would there be a noticable difference on any of the parts, where you could say I got x miles out of y because I drive like z.

 

[DivideBYZero]

Pads and Discs are relatively cheap, randay.

 

[mattpegher]

Ok I beleive you but why do I lose power steering and power brakes if I run out of gas, when coasting down hill?

 

[Nyati13]

Originally posted by: Serp86
OK - for example when going down a hill - which is more efficient? Letting the car in e.g. 3rd or pressing the clutch/selecting neutral?

It depends entirely on which car, and how it's engine management is built. "Car" is just far too generic in this case.

Cars (manual tranny) with modern fuel injection systems can completely shut off the flow of fuel (and shut off the spark also) when engine braking. ("can" does not mean that all manufacturers build their cars this way, it simply means they could do so if they wished. *for the pedants out there*)
Cars with carburators always consume some fuel. Automatics will always burn a bit of fuel, even when engine braking. etc....

 

[DivideBYZero]

Originally posted by: mattpegher
Ok I beleive you but why do I lose power steering and power brakes if I run out of gas, when coasting down hill?

No vacuum.

http://en.wikipedia.org/wiki/Manifold_vacuum#Uses_of_manifold_vacuum

 

[BD2003]

Originally posted by: randay

Originally posted by: JulesMaximus

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

What I mean is purposely engine braking, ie. downshifting and using your engine to slow down your car, vs just braking(regular) all the way, vs coasting in neutral and only disc/drum braking. The first way you lessen wear on your brakes, the second other way is just normal wear, and the third way you lessen engine wear. In the end, would there be a noticable difference on any of the parts, where you could say I got x miles out of y because I drive like z.

But unless you perfectly rev-match (which requires fuel, mind you), youre increasing wear on your clutch, and I don't know about you, but I find it a hell of a lot cheaper and easier to replace my brake pads.

 

[JulesMaximus]

Originally posted by: randay

Originally posted by: JulesMaximus

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

What I mean is purposely engine braking, ie. downshifting and using your engine to slow down your car, vs just braking(regular) all the way, vs coasting in neutral and only disc/drum braking. The first way you lessen wear on your brakes, the second other way is just normal wear, and the third way you lessen engine wear. In the end, would there be a noticable difference on any of the parts, where you could say I got x miles out of y because I drive like z.

First of all, I generally don't come flying up to a stop light at high speed braking only at the last possible second so really what I'm doing is ensuring that I'm in the proper gear for the speed I'm going. As I slow I will downshift into the appropriate gear and brake when I reach a point where I need to begin coming to a stop.

There's no mathematical formula. It's just the correct way to drive and the most rewarding. Jesus, this stuff is like trying to explain how to pleasure a woman to Spock...:roll:

 

[DivideBYZero]

Originally posted by: JulesMaximus

There's no mathematical formula. It's just the correct way to drive and the most rewarding. Jesus, this stuff is like trying to explain how to pleasure a woman to Spock...:roll;

That is Sig material right there.

 

[JulesMaximus]

Originally posted by: BD2003

Originally posted by: randay

Originally posted by: JulesMaximus

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

What I mean is purposely engine braking, ie. downshifting and using your engine to slow down your car, vs just braking(regular) all the way, vs coasting in neutral and only disc/drum braking. The first way you lessen wear on your brakes, the second other way is just normal wear, and the third way you lessen engine wear. In the end, would there be a noticable difference on any of the parts, where you could say I got x miles out of y because I drive like z.

But unless you perfectly rev-match (which requires fuel, mind you), youre increasing wear on your clutch, and I don't know about you, but I find it a hell of a lot cheaper and easier to replace my brake pads.

You know, if you don't drive your car at all you'll inflict almost no wear on it.

 

[JulesMaximus]

Originally posted by: DivideBYZero

Originally posted by: JulesMaximus

There's no mathematical formula. It's just the correct way to drive and the most rewarding. Jesus, this stuff is like trying to explain how to pleasure a woman to Spock...:roll;

That is Sig material right there.

Feel free to use it. :laugh:

 

[Nyati13]

Originally posted by: mattpegher
Ok I beleive you but why do I lose power steering and power brakes if I run out of gas, when coasting down hill?

Do You drive an automatic, or a manual? Old car? New Car? Fuel Injected? Carburated? No specifics=no valid answer.

 

[randay]

Originally posted by: DivideBYZero
Pads and Discs are relatively cheap, randay.

Rotors arent stupid volvos. Don't ask me why but I can see it with my own two eyes plain as day my brake pads eat my rotors. But lets look at it from another stand point then, would shifting wear from the brakes to your engine/clutch/whatever be more economical since your engine and clutch and whatever are gonna last a whole lot longer then your pads(and in my case, rotors)? Would it greatly accelerate my engine and clutch wear? By the time my engine and clutch go, I would probably be buying a new car anyway? Would it be worth getting thousands of miles extra out of your pads and instead wear your engine by engine braking? I guess it would depend on the car huh.

 

[BD2003]

Originally posted by: JulesMaximus

Originally posted by: BD2003

Originally posted by: randay

Originally posted by: JulesMaximus

Originally posted by: randay
Also on a related note, would it be more economical to engine brake more then regular brake, or regular brake more then engine brake. Meaning would coasting in neutral offset engine wear, gas vs maintenance? cost wise.

Coasting in gear doesn't cause any more wear on the engine than coasting in neutral.

I don't understand your question, you should really do both at the same time. Whether you do it all the was down to first gear is a matter of personal preference and how smooth you can do it (first gear is one of the harder ones to rev match and generally less forgiving if you misjudge).

If you really want to learn to do it you need to practice. Don't worry about the cost...you are going to wear out your car regardless and things will need to be replaced especially if you drive it hard. I'd rather learn proper driving techniques than sit there worrying about how many miles you'll get out of your clutch or throwout bearing. What's a clutch and throwout bearing cost? $500-600? Unless you really don't know how to drive you should get at least 100k miles out of one. That's about $.006/mile. BFD.

What I mean is purposely engine braking, ie. downshifting and using your engine to slow down your car, vs just braking(regular) all the way, vs coasting in neutral and only disc/drum braking. The first way you lessen wear on your brakes, the second other way is just normal wear, and the third way you lessen engine wear. In the end, would there be a noticable difference on any of the parts, where you could say I got x miles out of y because I drive like z.

But unless you perfectly rev-match (which requires fuel, mind you), youre increasing wear on your clutch, and I don't know about you, but I find it a hell of a lot cheaper and easier to replace my brake pads.

You know, if you don't drive your car at all you'll inflict almost no wear on it.

But of course.

In general I leave it in the highest gear I reached while slowing to a stop or light. Zero gas is used while coasting whatever gear it is. If it's slowing down for another reason, I'll rev-match and shift. But I'm not going to go down through all the gears while slowing down for the hell of it.

 

[JS80]

how about automatics?