jake brake 2002 camaro v6

**bipolar420** · 11-29-2012, 06:19 AM

I have recently worked on my exhaust. And i have noticed a engine brake, jake brake. I was wondering if my car came equiped with a engine brake or did i do something while i was modding my exhaust. Theres more questions to come.

**Smittro** · 11-29-2012, 06:25 AM

No your car does not have a Jake Brake. You likely have some sort of exhaust issue. Or some other type of engine issue. What are the mods you've done to the exhaust that leads you to believe there's a problem?

**bipolar420** · 11-29-2012, 06:57 AM

Ive cut the catlytic coverter out put a straight pipe, and just after where the cat was like 1 ft is a cherry bomb. While driving and at a coast over 30 mph my car makes a rumble like a jake brake and it slows the car down till bout 30 and then stops and goes into a normal coast. It only works after 30 mph once below nothin.

**jiveass** · 11-29-2012, 07:10 AM

sounds like transmission to me...

**Smittro** · 11-29-2012, 07:12 AM

I have done the same thing (without the cherry domb) to my 3800. I would suggest a trany programming issue rather than an exhaust issue.

- - - Updated - - -

Originally Posted by jiveass

sounds like transmission to me...

Beat me to it..

**bipolar420** · 11-29-2012, 07:24 AM

So what would you suggest? I know i need to get a tranny flush. But besides that what can i do?

**Smittro** · 11-29-2012, 07:27 AM

Originally Posted by bipolar420

So what would you suggest? I know i need to get a tranny flush. But besides that what can i do?

Yeah you can have the trany "tuned" I did for better shifts. Other than that you can't do much. I'd also have the torque converter lockup checked to be sure it's unlocking and locking as it should.

**bipolar420** · 11-29-2012, 08:49 AM

Well after driving it around for a lil bit. It dont feel like the tranny just feels like a backfire rumble like you would with a cherrybomb. From where the exhaust comes into 1 line theres only 4 foot of pipe with a straight tube where the cat goes thats like 2 1/2ft, then goes into a 90 degree bend, goes 3 to 4 inches then another 90 degree bend towards the back 4 to 6 inches then a cherry bomb and nothin after that. It stops like a foot before the rear axel.

**Firebirdjones** · 11-29-2012, 08:55 AM

Originally Posted by bipolar420

While driving and at a coast over 30 mph my car makes a rumble like a jake brake and it slows the car down till bout 30 and then stops and goes into a normal coast. It only works after 30 mph once below nothin.

That's in the tune, called DFCO (decelleration fuel cut off) It activates when off the accelerator for more than 2-3 seconds, and will stay activated until the disengage time that is commanded in the tune (usually around 1500 rpms).
They generally won't activate unless above a certain rpm as well (sometimes 1800 or more). In some tunes the activate/deactivate rpms are so extreme that most cars don't even see DFCO at all (both my 6.0 LQ4 and my wifes 2000 SS camaro were that way).

I've changed my DFCO tune to make it more active and pick up some MPG as a result. Anything above 1300 rpms it will activate, and won't shut off until 1100 rpms. When it kicks in you can definately feel more engine braking. I think that is what you are experiencing.

**Spikito** · 11-29-2012, 09:08 AM

this was my first thought ^^^^

**bipolar420** · 11-29-2012, 09:41 AM

Originally Posted by Firebirdjones

Originally Posted by bipolar420

While driving and at a coast over 30 mph my car makes a rumble like a jake brake and it slows the car down till bout 30 and then stops and goes into a normal coast. It only works after 30 mph once below nothin.

That's in the tune, called DFCO (decelleration fuel cut off) It activates when off the accelerator for more than 2-3 seconds, and will stay activated until the disengage time that is commanded in the tune (usually around 1500 rpms).
They generally won't activate unless above a certain rpm as well (sometimes 1800 or more). In some tunes the activate/deactivate rpms are so extreme that most cars don't even see DFCO at all (both my 6.0 LQ4 and my wifes 2000 SS camaro were that way).

I've changed my DFCO tune to make it more active and pick up some MPG as a result. Anything above 1300 rpms it will activate, and won't shut off until 1100 rpms. When it kicks in you can definately feel more engine braking. I think that is what you are experiencing.

A couple of things 1 how would i go about changing the dfco if need to? 2 is it a good thing my car does that? And last of all could changing my exhaust change the compression sound to where i do hear the engine brake more? Cause i had the original exhaust before i changed it.

**Firebirdjones** · 11-29-2012, 09:52 AM

Originally Posted by bipolar420

A couple of things 1 how would i go about changing the dfco if need to? 2 is it a good thing my car does that? And last of all could changing my exhaust change the compression sound to where i do hear the engine brake more? Cause i had the original exhaust before i changed it.

You need tuning software to get in there and adjust it. Yes it's a good thing. No need for the engine to dump fuel with the throttle closed. It's a great way to pick up fuel mileage in city driving, or going down hills on the expressway. I picked up about 2 mpg adjusting mine to be more active.
It's why you get more engine braking with a carburator setup, once the throttle blades are closed it shuts down the main jet fuel flow. Same thing with fuel injection and DFCO, but you have to have settings in the tune to take advantage of it. Some have it and some don't.

Yes, changing the exhaust has allowed you to actually hear what's going on. It was always there, but with a stock system you'll never hear it. You have to have a very sensitive butt to even feel DFCO activate so you probably never noticed it before. Now you can hear it.

**Spikito** · 11-29-2012, 09:53 AM

yeah my car now has headers, no cat, and cherry bomb type exhaust, i hear it WAY more now that when I had a closer to factory exhaust.

Whats happening is that when you decelerate like that, instead of the engine running the rear wheels, the rear wheels are running the engine. since you're off the pedal, the intake butterfly is closed, but the RPMs are still up so the engine is chugging fuel, that's how you get that sound. After a few seconds in these conditions, the PCM automatically cuts the fuel supply, to save gas.

Also....jake brakes are only found on diesel engines...our spark plugs would make a jake brake irrelevant.

**Firebirdjones** · 11-29-2012, 10:01 AM

Just to give you an idea, my wifes 6 speed camaro with the factory 3.42 gears would never enter DFCO on the factory tune.

It wasn't commanded to activate until 1800 or 1900 rpms. If I never get above that rpm then it never comes on. The problem was that most of the time putting around town I was below that RPM so it never comes on (going through the gears won't activate it because you aren't off the gas long enough before shifting to next gear) And on the highway with 3.42's, even 80 mph wasn't fast enough to get above that rpm, so we never saw it on the highway at all.

I would suspect most of your 4th gen LS1 tunes are this way (all mine have been) so what I do is lower that activation rpm, and also lower the deactivation rpm. Now it enters DFCO easily and also stays in it longer.

**bipolar420** · 11-29-2012, 07:46 PM

Thanks for the info. I done thought i went and messed up something. Everything was fine and quiet (made it loud cause i wanted to be louder like a v8). Then did the exhaust mod and raised the air filter input up by 3/4 of a inch for better air flow cause the change in the exhaust. But if everything is fine thats great. Now this up and coming week i got to take the front break pad shims and grind them down or move them one of the 2 cause i got a bad squeek goin on and i just changed to racing roters and pads at the same time.

**Smittro** · 11-29-2012, 08:09 PM

Curious FBJ. Is this the same for the throttle by wire cars? Because that is what the 2002 3800 is? My 2001 throttle by wire never acted in this way.

**Smittro** · 11-29-2012, 08:13 PM

Originally Posted by Spikito

yeah my car now has headers, no cat, and cherry bomb type exhaust, i hear it WAY more now that when I had a closer to factory exhaust.

Whats happening is that when you decelerate like that, instead of the engine running the rear wheels, the rear wheels are running the engine. since you're off the pedal, the intake butterfly is closed, but the RPMs are still up so the engine is chugging fuel, that's how you get that sound. After a few seconds in these conditions, the PCM automatically cuts the fuel supply, to save gas.

Also....jake brakes are only found on diesel engines...our spark plugs would make a jake brake irrelevant.

A "jake brake" works by controling valve timing and has nothing to do with whether it has spark plugs or not.

**bipolar420** · 11-29-2012, 08:21 PM

Yes my camaro is a 3800 v6

**Smittro** · 11-29-2012, 08:32 PM

Originally Posted by bipolar420

Yes my camaro is a 3800 v6

Yes and yours is also a throttle by wire TB. The ls1 cars which FBJ is refering to are not.

**Spikito** · 11-30-2012, 03:07 AM

Originally Posted by Smittro

A "jake brake" works by controling valve timing and has nothing to do with whether it has spark plugs or not.

since diesels run on compression alone, the valve timing is adjusted so that compression is never allowed to build, resulting in no compression, if the same were done in a gasoline engine, the spark plug would still fire, and combustion would still occur, it would just all blow out the exhaust