Exhaust pops and bangs

[The Red Baron]

Followed a V8 Cerbera today that was cruising at 60 - 70mph and the pops and bangs from his exhaust sounded great.

I can sometimes get my 500 to do it but the engine has to be hot and only on the overrun through about 4000rpm.

How and why can you get this great sound? I have (as far as I know) a standard exhaust with the pre-cats removed.

[V8Bart]

You mean like this?
http://www.youtube.com/watch?v=bE0ViXI9caI

Only sounded that good in the heat so 25 deg plus for so much poping and the odd bang, pre cas removed, ACT Y piece and cherry bomb exhaust.
Like you say on the over run, though I found if you feather the throttle you could make is pop

[steve-V8s]

It happens because there is un-burnt fuel in the exhaust which would suggest a misfire. It can sometimes be because the mixture on a light throttle is too lean to ignite under compression but does ignite when it is released into the hot exhaust. It can also happen if you have a leak in the exhaust system which is letting air in. Some aftermarket ECU’s have a fuel cut mode on the overrun which may arguably reduce consumption very slightly which can cause the symptom. If you have a cat fitted un-burnt fuel in the exhaust is the very last thing it needs to deal with. To my mind if a car keeps backfiring without good reason it indicates a possibly damaging fault condition.

You could swap for a 1980s turbo charged rally car fitted with anti lag, they deliberately throw fuel in the exhaust on the over run to keep the turbo spinning.

[LordGrover]

Cerbs have AJP engines, completely different to Griffs.
You'll never get close to the same sound of a flat-plane crank V8.

... and that Granny, is how to suck eggs.


ETA: click

[MPoxon]

BB's old Griff had some epic cerb style pops and bangs on the overrun.

http://www.youtube.com/watch?v=caJ1IapV-xA

I would be very interested to know what you have to do to get it to sounds like that.

[clive f]

the cerb has a flat plane crank, pops and bangs are fantastic, especially when mapped in for fun

http://www.youtube.com/watch?v=j3MQLv7iDvg

[wargriff]

Mine popped and banged beautifully when I put diesel in it by mistake

May not be the best route for a successful outcome.

[The Red Baron]

Thanks for all the responses. I've learned something today then. Great link LordGrover, interesting reading for those with a mechanical bent!

I guess I'll have to put up with the cross-plane sound my Griff makes now - damn, what a shame!!!

Looking forward to meeting a few of you at the Growl.

2:1 it will rain!!!!!

[finestjammy]

My Chim pops and bangs a lot. Not under throttle but almost on every lift off and gear change. As far as I know it only has a sleeved silencer as a modification. I think a little air is leaking (possibly intentionally by the previous owner/s) into the exhaust as the MOT emissions numbers indicate this.

I always use super unleaded too plus a heaalthy dose of Millers petrol additive, so the fuel is probably at least 100 RON. This might help increase the intensity/frequency of the pops and bangs.

[Chris99]

LordGrover said:

Cerbs have AJP engines, completely different to Griffs.
You'll never get close to the same sound of a flat-plane crank V8.

... and that Granny, is how to suck eggs.


ETA: click

Excellent link - I understood the difference but not the reasons.

[Barkychoc]

I find if you are on overrun giving it a really tiny bit of throttle makes it pop and crackle

[peteA]

Barkychoc said:

I find if you are on overrun giving it a really tiny bit of throttle makes it pop and crackle

This!

I had a 4.2 Cerb and it had stright thro' decatted pipes and it popped and banged for England! Sounded great but my neighbours weren't so impressed!

The AJP engines have 'valve overlap'...the exhaust valves stay open a bit longer and as previously mentioned any excess fuel goes into the exhaust system and causes the pops and bangs. This is intentional and is not a fueling / timing / air leak problem - its just that the RV8 engines are different.

[DieselGriff]

wargriff said:

Mine popped and banged beautifully when I put diesel in it by mistake

May not be the best route for a successful outcome.

lol, glad I'm not the only one!

Mine pops when warm when feathering or on the overrun especially when using standard unleaded but it's also a pre-cat. There has been talk of her Spitting Flame by someone following us on a run, which is nice..

[Mr MoJo]

DieselGriff said:

wargriff said:

Mine popped and banged beautifully when I put diesel in it by mistake

May not be the best route for a successful outcome.

lol, glad I'm not the only one!

Mine pops when warm when feathering or on the overrun especially when using standard unleaded but it's also a pre-cat. There has been talk of her Spitting Flame by someone following us on a run, which is nice..

Will you be Growling this year DieselGriff ? Would be good to catch up again

[bananaface]

i had a straight thru cerb 4.5 before my griff. tbh, it gets on yer nerves after a while....dogs howling, people shaking fists, kids crying, parents cursing... and in the cerb you cant stop the thing doing it !!

[DieselGriff]

Mr MoJo said:

Will you be Growling this year DieselGriff ? Would be good to catch up again

Hi Simon,

Not likely this year unfortunately, although I haven't ruled out a day trip on the Saturday. I'm hoping next year will see normal service resume (Without the pre or post growl complications with any luck!)