What causes the bubble/pop

[Someone²]

Hi all
Just a quick question what causes the bubbling sound when a car is decelerating my mate has a 93 lancer with a cannon on it and when he lets off the gas it just bubbles away, i have the same sort of exhaust on the civic but the noise it completely different so im guessing it is not the muffler that makes this noise.
Any info would be appreciated.

[James The Wog]

back fire?

[Someone²]

Isnt that more of a bang noise??? I have a friend who's skyline sumtimes backfires after building boost and then letting of the gas and then giving it another quick burst :) then get a nice blue flame... i thought that was backfire... the noise i am refering to is more like the wrx bubbly rumble.

[V73C]

isnt it just how advanced or retarted u set ur car

[95civic]

I thought it had something to do with back pressure....

[dsp26]

it's the catalyst doing it's job in igniting unburnt mixtures in the exhaust... you just can hear it on stock mufflers...

[Klayemore]

No back pressure.

[Someone²]

Ok so there seems to be no definitive answer here, so mayb not knowing what makes the noise, how about how to cause it?

[doggys_fan]

its backfire i have it all the time
basically when ever i take my foot off the accelerator
its got a popping sound to it
it happens to every car but wif a cannon its louder dont know y but

[rayb3na_]

isnt backfiring when u get a flame out of your exhaust? i get the burble noise too.. when it hits extreme like from 7k revs dropping it makes a BANG just what happens in my car lol

[Someone²]

ok so its back fire or back pressure, what do i change to cause it coz i just luv that sound.

[aaronng]

Excess fuel being ignited in your exhaust causes the burble sound.

[NightKids]

If you love the sound you should be go-karting!

[JohnL]

Excess fuel being ignited in your exhaust causes the burble sound.

Agreed. 'Burbling' and 'popping' are caused by a small ignition or series of ignitions inside the pipe, typically on the overun when more unburned oxygen finds it's way into the pipe through the induction (as opposed to a large external ignition that can occur at the end of the pipe when hot but unburned fuel is exposed to atmospheric oxygen).

[aaronng]

And the reason why you hear it more with a cannon muffler is because the cannon has less muffling capacity than a stock muffler. So you can hear the ignitions happening in the exhaust.

[xntrik]

sounds horrible.
cant be good for your car.

[aaronng]

sounds horrible.
cant be good for your car.

Probably happens even with stock cars are coming off heavy throttle. You just can't hear it.

[Feverpitched]

sounds horrible.
cant be good for your car.

I personally like the sound of overrun.

I can't see it being very hard on your exhaust pipes either.

[JohnL]

sounds horrible.
cant be good for your car.

It does no harm whatsoever, except in very rare circumstance. I have heard of a muffler (or maybe it was a resonator) being split open by an internal 'backfire', but my best guess is that the exhaust probably had a leak and on the overun sucked air into the muffler due to exhaust pressure momentarily dropping below atmospheric, enough to cause a larger than usual internal explosion. An exhaust leak is often associated with an increase in backfire type behaviour, due to oxygen being sucked in through the leak.

[JohnL]

I personally like the sound of overrun.

I can't see it being very hard on your exhaust pipes either.

I like it too, so long as it's not embarrasingly loud, i.e. I like the burble and pop, not actual backfires.

Once with my old clubman style sports car half the exhaust system fell off, leaving about three feet of unmuffled pipe. I had no choice but to drive it home in that state, and christ was it loud, but also on the overun the exhaust backfired with extreme enthusiasm, complete with rather large sheets of blue flames (rather spectacular considering it was night time).

This was terrific fun for a brief while, but considering the end of the exhaust was only about three feet from my right ear (with no real bodywork or windows between), and that it made me prime police bait, I was more than relieved to refit the (retrieved) exhaust system.

[beeza]

Snap,crackle,pop :)

[Feverpitched]

I like it too, so long as it's not embarrasingly loud, i.e. I like the burble and pop, not actual backfires.

Once with my old clubman style sports car half the exhaust system fell off, leaving about three feet of unmuffled pipe. I had no choice but to drive it home in that state, and christ was it loud, but also on the overun the exhaust backfired with extreme enthusiasm, complete with rather large sheets of blue flames (rather spectacular considering it was night time).

This was terrific fun for a brief while, but considering the end of the exhaust was only about three feet from my right ear (with no real bodywork or windows between), and that it made me prime police bait, I was more than relieved to refit the (retrieved) exhaust system.

Reminds me of my first car, a 76 Toyota Celica. I fitted a set of extractors with a mid mounted muffler in the afternoon but ran out of time to get the rest of the exhaust made up. So I did what any young bloke with an obnoxiously loud 70's coupe would do - I drove it around for the night. By the end of it I stank, I had a headache and I was slightly giddy, but by god it sounded good :cool:

Completely open pipes in an open wheeler would be something else entirely though!

[Someone²]

I like it too, so long as it's not embarrasingly loud, i.e. I like the burble and pop, not actual backfires.why

Yep thats what i like so how do i obtain this burble and pop, will extractors and pipes do it, or will a high flow cat, my friends car does it heaps but then his is a carby engine where mine is fuel injected and mine is newer so mayb that is why.

I dont like exhausts that are really loud i mean the ultimate would be almost silent untill i give it a squeese then give i nice roar but what im really trying to obtain is that burble sound when decelerating.,

Currently the exhaust is stock bar the read muffler which is a cannon, gets a bit droany when driving at 110km/h but the note it gives is pretty ok, but hardly any burble want to get rid of the droan and add some burble

[JohnL]

Completely open pipes in an open wheeler would be something else entirely though!

I'm old enough to remember watching Formula 5000 at Oran Park, which sounded fantastic (till they broke!). Even V8 Sports Sedans just aren't the same!

It is however just a wonderfully loud induction and exhaust noise, not subtle and multi layered with mechanical sounds underlayed. I actually prefer the sound of something like a Porsche, Ferrari, Maserati, Bugatti etc for something a bit more sonically 'interesting', if not quite so bloody LOUD!

What was that, my ears are ringing!

[JohnL]

why
Because while it's entertaining for 10 or 20 minutes, it wears you out, gives you a headache, attracts unwanted police attention and is just plain embarrasing.

I'm not talking an occassional bang from the exhaust and the exhaust otherwise being somewhat anti-social, I'm talking a major sonic overload with a very loud 'gunshot' at each gearchange and the overun sounding (and looking) a bit like two gangs shooting it out in an echoing side street.

I have to say though, it did sound absolutely glorious accelerating hard then backing off when driving through the King's Cross tunnel! (rooooaaAAAARRR, BANG, rooooaaAAAARRR, BANG, rooooaaAAAARRR, BANG BAng bang bang bang bang....bang). That tunnel has amazing acoustics!


Yep thats what i like so how do i obtain this burble and pop, will extractors and pipes do it, or will a high flow cat, my friends car does it heaps but then his is a carby engine where mine is fuel injected and mine is newer so mayb that is why.

The 'trouble' with injection is that on the overun the ECU cuts the injectors, so while some fuel will get dumped into the exhaust it won't be all that much. If you really want this affect, then you can't go past a couple of DCOE Weber carbs and some cams with tons of overlap.

You might have a better chance if you can figure out how to disable the overun fuel cut-off, but really don't know how well this would work (I also suspect it would be illegal so I'm not recommending you try it).


I dont like exhausts that are really loud i mean the ultimate would be almost silent untill i give it a squeese then give i nice roar but what im really trying to obtain is that burble sound when decelerating.,

You might have some luck with a bypass valve placed somewhere in front of the CAT, but I don't know if it would give you what you want and I'd bet it would be illegal...

[Someone²]

ok so it seems that having EFI is stopping extra fuel being dumped in my exhaust and thus i cant obtain the burble, well what about flamer kit dont they dump fuel into the exhaust then i just dont install the sparking bit and then ill get the burble???

If so where can i get one of them?

or should i just give up?

[xntrik]

cabramatta shit.
i hear it all the time with cannons. so annoying.

[JohnL]

or should i just give up?

That would be my advice.

[mclovin]

when you let off the accelerator the exhaust sucks in fresh air this in turn goes back through the exhaust and causes some unburnt gases to reburn causing ur noise. how old is ur mates exhaust, im betting that it has some small holes close to the engine pipe that is letting air through.

[Someone²]

when you let off the accelerator the exhaust sucks in fresh air this in turn goes back through the exhaust and causes some unburnt gases to reburn causing ur noise. how old is ur mates exhaust, im betting that it has some small holes close to the engine pipe that is letting air through.

Car is a 93 lancer, so i suppose it is possable that he has some small holes near the headers/cat.

[Limbo]

Its most likely backpressure. If it was backfire its alot louder and its a sharp cracking noise like a fire cracker.

Seen it on alot of canons, Its when you have small piping and then opens to a larger outlet. Try putting the sliencer on it and it will reduce it.
That's part of the reason why i run a tip the same size as the exhaust

[Someone²]

Its most likely backpressure. If it was backfire its alot louder and its a sharp cracking noise like a fire cracker.

Seen it on alot of canons, Its when you have small piping and then opens to a larger outlet. Try putting the sliencer on it and it will reduce it.
That's part of the reason why i run a tip the same size as the exhaust



Lol but i like the noise :P

[aaronng]

Lol but i like the noise :P

MP3 player set to repeat + really powerful speakers and amp.

[rpm boy]

Flamethrower kit dosnt work 2 well on efi cars cause it works on cutting the power to the car whilts still feeding through fuel... meaning when the powers cut to the car the ecu dosnt work and dosnt pump fuel through the injectors so dosnt work, works awsome ona carby motor with straight through exhaust... also if u want to make the burbling noise push the acc pedal really gently and itll work

[Someone²]

Flamethrower kit dosnt work 2 well on efi cars cause it works on cutting the power to the car whilts still feeding through fuel... meaning when the powers cut to the car the ecu dosnt work and dosnt pump fuel through the injectors so dosnt work, works awsome ona carby motor with straight through exhaust... also if u want to make the burbling noise push the acc pedal really gently and itll work


WooHoo go rpm boy... and it is such a simple answer by holding my foot slightly on the acclerator i get that lovely burble sound, still not as good as my mate, but i can now burble away all the way down great eastern highway from mundaring to midland :)

Thanks all for your input, im thinking that ill get a carby engine rwd as a weekend car when im out of uni, and do it up all nice. Then i can burble till the cows come home, only now i have a problem i now have 3 cars i want... I want a SV6 ute as a daily, and a accord euro as a weekend now i want somthing old as a project car, hrmm this is getting all too much. Why cant i have a cheap interest like um (insert cheap interest here)
Gah im going to sleep, thanks again everyone for the helpful info

[aowwllan]

No back pressure.

maybe?

my straight from a while back popped continually when i release the acceleration.

[steve88]

mine makes the noise all the time if i rev upto about 4000-5000 on 2nd gear and let go, its subtle but it sounds naice ;)