Jake Brake !?

[voodoo chile]

I'm just curious, I can't remember if my car did this when the stock exhaust was on the vehicle or not. I have a 00 SS M6 with pacesetter LT, ORY and a LM 2. When down shifting, after my foot is off the accelerator the vehicle slows normally, then makes this sound like a jake brake and begins to slow quite quickly. Is this a problem or an exhaust leak or something, the car doesn't make any ticking noises or have anything else moded on it except the exhaust. Does this happen on everyones cars?? Thanks.

VooDoo.

[Smittro]

I'm just curious, I can't remember if my car did this when the stock exhaust was on the vehicle or not. I have a 00 SS M6 with pacesetter LT, ORY and a LM 2. When down shifting, after my foot is off the accelerator the vehicle slows normally, then makes this sound like a jake brake and begins to slow quite quickly. Is this a problem or an exhaust leak or something, the car doesn't make any ticking noises or have anything else moded on it except the exhaust. Does this happen on everyones cars?? Thanks.

VooDoo.

Not sure what you're talking about. I know what a "jake brake" is but yes if it's m6 and in gear and you let off the gas it will slow the car down.. The sound it makes is the sound of an engine being used to slow the vehicle..

[voodoo chile]

Yeah, I got that part, thanks. The sound happens a few seconds after my foot comes completely off of the throttle, it may be nothing, just wondering if this is something that is unique to the LS1 or is it a byproduct of the exhaust setup?

VooDoo

[justinmc978]

I'm just curious, I can't remember if my car did this when the stock exhaust was on the vehicle or not. I have a 00 SS M6 with pacesetter LT, ORY and a LM 2. When down shifting, after my foot is off the accelerator the vehicle slows normally, then makes this sound like a jake brake and begins to slow quite quickly. Is this a problem or an exhaust leak or something, the car doesn't make any ticking noises or have anything else moded on it except the exhaust. Does this happen on everyones cars?? Thanks.

VooDoo.

whats 'jake brake'? exhaust wouldnt have anything to do with the car slowing down unless it was rubbing on a tire or something..

JusTin

[Smittro]

whats 'jake brake'? exhaust wouldnt have anything to do with the car slowing down unless it was rubbing on a tire or something..

JusTin

A "jake brake" is an electric engine brake (some use solenoids to control valve timing). Usually associated with heavy road use tri-axles/tractor trailers..

[justinmc978]

A "jake brake" is an electric engine brake (some use solenoids to control valve timing). Usually associated with heavy road use tri-axles/tractor trailers..

ahh i didnt know that was an option on maros, i'm jealous

[Hi-Po]

Jake Brake and Exhaust brake are two completely different devices used.

Jake braked equipped engines cylinder heads have another exhuast valve which is activated by a solenoid usually when pedal is released/JB activated. Its opened near TDC to help release pressure and not pushing the piston back down. In turn, that slows the truck down.

Exhaust brake shuts off the exhaust after the exhaust manifold.

Neither of these is happening on your car, I can assure you

[Smittro]

ahh i didnt know that was an option on maros, i'm jealous

The term is a trucker term such as:

Commaparts = Cummins
Frateshacker = Freitliner(sp)
jake brake = engine brake
4 wheeler = cars/pickups etc,etc....

[Smittro]

Jake Brake and Exhaust brake are two completely different devices used.

Jake braked equipped engines cylinder heads have another exhuast valve which is activated by a solenoid usually when pedal is released/JB activated. Its opened near TDC to help release pressure and not pushing the piston back down. In turn, that slows the truck down.

Exhaust brake shuts off the exhaust after the exhaust manifold.

Neither of these is happening on your car, I can assure you

Thank you, our resident cattlepiler tech..

[Hi-Po]

Thank you, our resident cattlepiler tech..

Ex Cat

[mph476]

i know exactly what you're talking about. it did it when I had the gmmg. its just backpressure. totally normal.

[voodoo chile]

i know exactly what you're talking about. it did it when I had the gmmg. its just backpressure. totally normal.

Thanks, glad to see at least someone picked up on what I was talking about. The "jake brake" reference was used as an example to illustrate what the noise sounded like, amazing that everyone took it out of context so quickly.

VooDoo

[tatertot91]

Thanks, glad to see at least someone picked up on what I was talking about. The "jake brake" reference was used as an example to illustrate what the noise sounded like, amazing that everyone took it out of context so quickly.

VooDoo

some people on this forum tend to do that

[Smittro]

Okay I'm going to explain this the best I can since post #2 was overly simplistic.. You can not hear "back pressure".. If you have a loud exhaust what you are hearing is the compression of the engine being used to slow the momentum+weight of the vehicle. Combustion is still taking place, however when you let off of the gas, no more fuel is being applied to the engine except what it takes for the engine to achieve idle.. As the rotating mass begins to slow, so do the frequency of explosions in the combustion process, hence the change in pitch/sound you are hearing. Same process happens to a "free" spinning engine but @ a much faster rate, due to the fact that alone, an engine has much less mass being applied to its compression as it begins to slow down.

An engine is nothing more than a big air compressor. A shop air compressor has its exhaust pluged with an air tank. The sound its compressor makes is air being breathed in and forced into the tank, you do not hear the air in the tank pushing back. So what do you think happens with an open exhaust pipe on an engine with your foot off the gas? Answer, nothing.. The air just escapes.. The explosions are not strong enough to create "quote" back pressure, so the air just escapes with the sound of a weak explosion in it.. Oh yeah it's normal don't sweat it..

[Teknik_SS]

The term is a trucker term such as:

Commaparts = Cummins
Frateshacker = Freitliner(sp)
jake brake = engine brake
4 wheeler = cars/pickups etc,etc....

Don't forget the

Petercar = Peterbilt

And the all time bob and tom TRUCKER CLOCK! Who wants it!!

[Teknik_SS]

Oh and yes its normal! My car has done it since day 1

[Smittro]

Don't forget the

Petercar = Peterbilt

And the all time bob and tom TRUCKER CLOCK! Who wants it!!

[Too Fast]

Yeah, I got that part, thanks. The sound happens a few seconds after my foot comes completely off of the throttle, it may be nothing, just wondering if this is something that is unique to the LS1 or is it a byproduct of the exhaust setup?

VooDoo

A few people who posted are close to right, but the exact thing that is happening is given by the clue he describes that I highlighted.

What really happens after you let your foot all the way off the throttle, after a couple seconds, is that the PCM shuts off the fuel almost completely. The injector pulse goes to abour .5 ms, when idling the pulse is around 2 ms That's the different sound you hear. It also slows the car quicker since there is no fuel being supplied. When you first let off the gas, in gear, the PCM strategy still allows the idle fuel injector pulse, then it changes to the .5, and if you're paying attention, you can tell when it occurs. Then your engine is a big air compressor.

[voodoo chile]

A few people who posted are close to right, but the exact thing that is happening is given by the clue he describes that I highlighted.

What really happens after you let your foot all the way off the throttle, after a couple seconds, is that the PCM shuts off the fuel almost completely. The injector pulse goes to abour .5 ms, when idling the pulse is around 2 ms That's the different sound you hear. It also slows the car quicker since there is no fuel being supplied. When you first let off the gas, in gear, the PCM strategy still allows the idle fuel injector pulse, then it changes to the .5, and if you're paying attention, you can tell when it occurs. Then your engine is a big air compressor.

Thats what I was looking for, thanks. I think when you unrestrict the exhaust, the pitch change is more noticable, coupled with the feel of the additional drag when the fuel trimming is changed, thats very interesting, thanks again.

VooDoo

[Smittro]

An engine is always an air compressor. Only difference is combustion... Unsubscribing..................