What Exactly Causes the Jake Brake on Decel Sound? (with side pipes open)

[GottaBoss]

Is it something about the design of the motor or is it the catalytic converters, the resonators or something else?

I'd like to reduce or eliminate it but first I need to know what causes it.

 

[Fordman9870]

If it is while using the red key. it is due to engine braking designed to help out on the road course. if it is all the time. It was designed that way to sound like the old days. Im sure you can have it tuned for less.

 

[cosm3os]

It's not a red key thing. My GT does it--and it's glooorious!

 

[steveespo]

Excess fuel burning in the headers and down pipes when the throttle closes, Car goes from full rich at 80%+ throttle to stochiometric (14.7:1) when throttle closes. You should hear it with long tube headers and a tune, glorious sound. The side pipes give a more direct sound path for you to hear it.
Steve

 

[cosm3os]

I was told there would be no math.

 

[Grant 302]

Nothing 'causes' it per se. It's more that there's nothing to eliminate it from the side pipe exits. Pretty sure it's a function of the size/overlap in our cams and the architecture of our engine. Since some of that is tunable, the tune might be a way to reduce it, but I suspect it wouldn't be able to be completely dialed out with cam timing and A/F adjustments.

You might be able to reduce it with mufflers or resonators in the side pipes, but I don't really see a practical way to do that which won't kill your ground clearance since J tubes and glass pack types take up space.

I'm sure it's not what you're looking for, but removing the sidepipes would be the cheapest and easiest way.

 

[GottaBoss]

If it is while using the red key. it is due to engine braking designed to help out on the road course. if it is all the time. It was designed that way to sound like the old days. Im sure you can have it tuned for less.

I haven't loaded the Trackey tune yet so it's not that. I've actually seen some mention here that it's less noticeable with the Trackey but I don't know that first hand.

I have QTP cutouts on the side pipes and the more open they are the more noticeable it is. Up to about half open it sounds okay to me but I like them open further except for the decel sound.

 

[F.D. Sako]

I can assure you, j-brake decel. sound is more prominent with the track key, especially with open side pipes. And I like it

 

[ArizonaBOSS]

Why would you want to eliminate that????

 

[cosm3os]

OP, I'll give you a good deal on my GT H pipe. That'll fix it!

 

[boss man]

You may want to check out the Kooks side pipes. I hear good things about them. I also heard that they are loud. But if you have the QTP it may be the perfect setup for you.

 

[WinterSucks]

If I engine brake for 5+ seconds at low rpms on the street I can reliably get a loud bang the instant I touch the gas again. Sometimes it's as loud as a backfire or tire blow out...depends how long I coast in gear. Track key and Kooks make it VERY loud on a friends Boss I drove.

 

[Mad Hatter]

Truly mechanical music! Must not be altered! Would pay extra for it.....poor GT's.

Sent from my GT-I9100 using Tapatalk 2

 

[Fiddler49]

Sounds deeper and less poppy with the Kooks shorty headers. And with the Trackey, you get a whole symphony of badass backfires, growls, and deceleration madness!

Does it show I like my Kooks shorty headers? ;D

 

[racered302]

If I engine brake for 5+ seconds at low rpms on the street I can reliably get a loud bang the instant I touch the gas again. Sometimes it's as loud as a backfire or tire blow out...depends how long I coast in gear. Track key and Kooks make it VERY loud on a friends Boss I drove.

 

[four-walling]

Sounds like we are talking about 2 different issues here?

One is the annoying jake brake ( big rig diesel truck) sound the Boss makes using engine braking on a big downhill.

The other sound is the wonderful snap, crackle and pop of a quick downshift to a stop.

 

[four-walling]

I was told there would be no math.

You register for an account on the forum and you have to take your lumps.

 

[aircare84]

Okay guys, looks like I'm not going to do anything to eliminate it with the side pipes and I'm not getting rid of them - that would be Boss sacrilege.

Guess I'd better just learn to like it. 8)

The only way I've found to reduce it, it to limit the side pipes opening. I tried running the side pipes with the baffles removed, & also did not care for the 'Jake Brake' sound on decal. Went with 3/4" side pipe baffles & found a good balance.
Have to just adjust your cutouts to a tone you want.

 

[VoodooBoss]

The only way I've found to reduce it, it to limit the side pipes opening. I tried running the side pipes with the baffles removed, & also did not care for the 'Jake Brake' sound on decal. Went with 3/4" side pipe baffles & found a good balance.
Have to just adjust your cutouts to a tone you want.

Smaller discs will cut down the jake brake effect. The smallest I have available are 1/2".

 

[BLAZN BOSS]

Valid ideas..............but what he is experiencing is back pressure............or the lack there of coupled with high compression and valve overlap. I'm sure I will take a beating on this cause just like oil choice there are always opinions.................sooooooooooo........I did some looking and found one explanation: An exhaust burble, or throaty popping noise which could be likened to a babbling brook, is has a different cause if it only occurs when suddenly backing off on a vehicle's throttle. Essentially, the sudden easing off the throttle causes an immediate decrease in exhaust emissions to the degree that atmospheric pressure surrounding the exhaust pipe pushes cool air up into the exhaust system. This air collides with the warm exhaust gasses and creates a rumbling not unlike thunder. Normally this will only happen if the tailpipe has too wide a diameter to maintain equalized air pressure, or there is a seam in the exhaust pipes which is not air tight.