Burble between gear changes or engine braking.. Mixture out??

[JA2Z]

Hi Guys,

Just a Q.

Since I've installed all the modifications on my car, during each gear change or when i'm engine braking i get a quite destinct *burble* sound through my exhaust.

Don't get me wrong it sounds kinda cool (like the rally cars), but i was wondering if that could be because my tune is out. It seems to happen when the TB butterfly is closed, so i'm guessing my mix is possibly too rich???

Any suggestions would be great.

Cheers

[maldotcom2]

It's normal. To most people it's desirable. On the VS when you are decelerating the injectors are shut off so i wouldnt worry about it.

[jokerflingo]

Excess fuel igniting, causing terrible fuel economy

[hako]

It's normal. To most people it's desirable. On the VS when you are decelerating the injectors are shut off so i wouldnt worry about it.

Just out of curiosity and interest, if the injectors are shut off, how come the exhaust still makes a noise when there is no fuel to burn ?
My old side valve V8 had this characteristic which was helped along by a few holes drilled in the exhaust down pipe....but she had a carby.
Maybe it's the mechanical pumping sound or something....a few backfires help!

[immortality]

the injectors are only shut off under certain circumstances during deceleration. the noise tends to be more noticable with aftermarket exausts, i figure even completly stock engines do it but the reverse flow factory style mufflers do a really good job of disquising it.

the noise may have something to do with flow reversion and exhaust presssure waves bouncing/colliding during deceleration? who knows. at the end of the day it's not hurting anything

[Steery]

Sounds good.

[eaton v8]

i used to get it as soon as i punched out the cats but with the new zorst and cats its gone

[immortality]

i used to get it as soon as i punched out the cats but with the new zorst and cats its gone

thats a good point, i don't run a cat, which would muffle sounds quite well

[JA2Z]

Excess fuel igniting, causing terrible fuel economy

Yeah, i think that might explain my fuel economy.

I have a functional cat installed. But when i replaced the original (hollowed) one i kept the original gaskets. i think they aren't doing their job properly and leaking slightly, hence the loud burble. i'll replace then and see if that makes a difference.

I'm definately gonna get a tune 'cause my economy is pretty pathetic.

Thanks guys

[M01ST]

i thought this was normal for an engine my mates vz ss ute when he idles down going down gears at night u can sometimes see flames coming out his exhaust, he has pacemakers into dual 2 1/2 inch with high flow cats into twin dumpers

[jokerflingo]

i thought this was normal for an engine my mates vz ss ute when he idles down going down gears at night u can sometimes see flames coming out his exhaust, he has pacemakers into dual 2 1/2 inch with high flow cats into twin dumpers

V8's are more known to do it then V6's

[rocco555]

is normal, nothing wrong, if you like the sound of it then just enjoy it

to get rid of it you'll have to make changes to your exhaust system (mufflers etc.)

[immortality]

V8's are more known to do it then V6's

it's to do with firing order and the pressure waves colliding in the exhaust. it's the same reason why LS1'a sound puss from the factory. they changed the firing order to smooth things out

[GTP 85]

I get the burble/ popping in my VN 5 speed. i love it haha

[M01ST]

I get it in my vs on some occasions only ever when Ive been driving longer then 30 minutes

[JA2Z]

Ok update.

I definately agree the burble sound is quite good, but something is not quite right, this is too loud.

So, I nipped up the Cat bolts quite hard let her idle to op temp then took her out for a hard drive....

Drove around for a bit and for the first bit good then, the same..... rev--- 3,500 - 2nd - rev--- hit about 3,000 and it started the load burble (aeroplane) sound again -- 5,000 - 3rd - Sh*t better slow down --- burble, burble, fart, burble - stop.

Drove home and left her and didn't think about it again for a while. took her out later that night.......

Fixed... Still had a beautiful rumble and burble when driving, but that aeroplane sounding note was gone. i guess it was the gaskets leaking, not tight enough, being nipped up tighter and heated up and cooled down must have set them in place. And that's all it needed.

Cheers

[maldotcom2]

I put a smear of muffler putty on both sides of my exhaust gaskets.