[NPalacioM3]

Originally Posted by The Nebulizer

Thanks for the detailed explanation, Nick. I will NEVER engine brake again. (I did it for a little while and wondered if there was any issue with it.)

[AllwaysLow]

Originally Posted by NPalacioM3

NEVER.

I only said it's a strong word, because if your brakes don't work for whatever reason, your first reaction better be to attempt to use the engine speed to slow your car (at least enough where a possible e-brake won't endanger you any further).

i.e. not NEVER.

[trebm3]

hell with gas going up, no real reason to engine brake anymore. lol

[fuelthefire]

well no more engine braking for me then.

thanks Nick for disproving this misconception.

[altezzabob]

if you are engine braking (staying in a gear without blipping or giving gas) you are using less fuel then coasting in idle. If your foot is off the accelerator and the engine is 'braking' for you, it is not using ANY fuel until it hits the fuel cutoff point or you stall the car. Whichever comes first. You actually use more fuel coasting in idle in neutral then leaving it in whatever gear you are at and letting it decelerate near the idle point.

[Andrew 06M3Cab]

Originally Posted by NPalacioM3

It is true that you can do it and that a novice driver will most likely get away with it in a street car and not do any significant damage. There are two problems with this however, one is poor technique which will cause problems on the race track or during spirited driving once he/she gets faster and the other is mechanical. The technique problem is that when you engine brake at speed, you are suddenly adding engine speed to the drive shaft which upsets the rear mechanics (diff/driveshaft/axles/wheels and tires) of the car. In a high HP car, you can very easily loop it around by doing this and at best, you will get rear wheel hop because you are not slowing the car down enough to match engine speed. Either way, you are upsetting the contact patch of the rear tires and not allowing the suspension to do its job properly, not to mention possibly wrecking your car. Braking and downshifts should always be done in a straight line and trail braking at corner entry to rotate the car and point you into the corner, you should never be doing any downshifts at turn in. All downshifts should be done using the heel and toe method and if you are just tooling around town and not driving fast enough to need both brake and downshift, rev match. The mechanical problems here are that engine braking is thought to be, by professional engine builders, one of the main causes of cracked crank shafts in race car engines, bad thing. In addition, you are putting a tremendous amount of unnecessary stress on your very expensive transmission, why? The transmission and the engine in your car are not there to slow you down, that is what your brakes are for. I would much rather replace my brakes than my engine or transmission, so why be stubborn about it? Use the components of the car to do what they were intended to do, no reason to subject them to unnecessary stress or use.

Yes, that is my race car. It is an F2000 or Formula Continental here in the states.



It has nothing to do with the high revs. You ARE putting additional "force" (stress) on the engine and all transmission parts doing this because the drivetrain is under load. When you are slowing the car down this way, the inertia of the engine has no place to be dispersed since the car is not accelerating. You are "trapping" all of this energy between the crank shaft and the rear wheels with no place to go, this is a tremendous amount of strain on all of those components. Not a good thing. Again, use the brakes to slow your car down, that is what they are there for.



NEVER.

Very interesting and useful explanation. In theory I suppose so long as the engine is not at idle, if it is in gear with no gas applied it must be braking. While I don't expect a driving tutorial, I wonder at what point (ie what engine speed) should you downshift when you are merely slowing down in a straight line (corners, passing, hill climbs etc. aside)? In other words, at what point is the engine providing sufficiently little braking that it is not causing excess stress on the drive train)?

[rudeboiM3]

question slightly off-topic: do you recommend driving in high gears at low speeds... for example, would you rather be doing 70mph in 4th gear at 3500rpm, or 60mph in 6th gear but at 2000rpm (not exact numbers but you get the idea)? isn't there an optimal rpm level for each gear?

[TheWarrior]

Great explanation Nick, I will also never engine brake again, it makes perfect sense why not to do it around turns, from now it's normal braking for me or nothing, well maybe not nothing.....

Thanks for setting me straight mister!

[jldallover]

edit: Now that I'm looking at Nick's sig ... I see a F1 car in there .. it's quite possibly I am about to have my ass handed to me :-)[/QUOTE]

[nasrudin]

Originally Posted by Andrew 06M3Cab

....I wonder at what point (ie what engine speed) should you downshift when you are merely slowing down in a straight line (corners, passing, hill climbs etc. aside)? In other words, at what point is the engine providing sufficiently little braking that it is not causing excess stress on the drive train)?

I'm curious about this as well and would like to hear an expert opinion about this.

There is a big difference between shifting at 2000rpm from 3rd to 2nd gear at and letting yourself coast with minimal/feathered throttle input just to smooth out the shift, compared to doing the same thing in the upper half of the tach.

I mean technically the engine is braking in 2nd gear when you do the former, but how is that any different than just coasting in 2nd? And is the implication here that coasting in lower gears (which seems unavoidable to me in street driving) puts undue strain on the drivetrain?

And by undue, I mean a kind of activity that would really be damaging over the long term... when people throw out terms like "this puts more stress" or "less stress" on the drivetrain, that kind of vaugeness isn't very helpful. Of course every action is more or less stressful. I think many of us are wondering where the practical threshold lies, and are not interested in minimizing drivetrain stress at all costs.