That Popping sound

[Jon172]

How can I get that popping sound like on the rally cars, when there changing down gears? ..If ya know what I mean!!



Ta

 

[Bryan]

dont know, but ive got it and all i have done is added an induction kit and exhaust if that elps at all

 

[clean16v]

have you got a straight through exhaust and performance filter? if so, when the exhaust is hot, i mean really HOT, cane it (2nd gear is best for me) then nearing the redline back off and tap the throttle very slightly and repeatedly and you might even get some flames!

 

[Dust]

Buy a TVR.

 

[Bryan]

nah ive only got a cat-back system and induction kit

 

[STICKER TWONK]

All Ive done is got a K&N induction kit and peco BB backbox and it pops like crazy when the revs are high with engine braking

 

[Carlouk]

The popping sound on rally cars is the als (anti lag system)

 

[clean16v]

will work wih cat but you wont get flames!! need cat-replacement pipe for that. My old RT would pop like crazy and get some mad flames through the gears.....the advantages of carbs eh? (before i get flamed i mean single point injection, as opposed to multi on the valver!)

 

[Matblack]

I remember some maniac on the net who used to sell what was in essence a spark plug which fitted to the end of the exhaust, when triggered it supposedly ignigted any remaining petrol in the exhaust gases and sent out flames!

MB

 

[Louise]

my Williams has decat and filter, and it pops. Mate was following me on the M25 the other day, and reported I had flames popping out the back a few times.

 

[Tom]

mine does it but im driveing around with no back box at the moment

 

[RobFenn]

lol. Im not entirely sure how the popping is created, and what is actually popping...anybody?

 

[Dust]

back pressure i think.......

 

[Dust]

.....suppose that doesnt help!

 

[clean16v]

unburnt fuel which enters the back box(a cat will stop the fuel) and if the exhaust is hot it will ignite it. This is why Force inducted cars always have flames out of exhaust because they expel LOADS of unburnt fuel

 

[RobFenn]

I didnt realise it would be the same answer to flames coming out as my dads Aston doesnt always pop and let out a sheet of flames at the same time.

I guess it cant be backpressure as it seems the less resistance in peoples systems is helping..

I dont think its neccessarily turbos as it sounds more like overfuelling, most race cars supply more fuel which would probably give a lot of excess??

 

[Jon172]

Thanks for you replys Guys!

 

[clean16v]

Quote: Originally posted by RobFenn on 04 March 2003




I dont think its neccessarily turbos as it sounds more like overfuelling...

Overfuellin would also cause it but on the whole, Force inducted cars do overfuel when being booted.

 

[RobFenn]

but dont turbos only use unused gas which provide the boost?

 

[Dust]

Quote: Originally posted by clean16v on 04 March 2003

unburnt fuel which enters the back box(a cat will stop the fuel) and if the exhaust is hot it will ignite it. This is why Force inducted cars always have flames out of exhaust because they expel LOADS of unburnt fuel

If a cat stops the un-burnt fuel, how come TVRs pop? They have Cats. Would it be the build up of pressure in the mid or back box? Smaller box = more pressure?

 

[clean16v]

Not sure what you mean.....a turbo spins up on exhaust gases, when compressed air is forced into inlet manifold so is LOADS of fuel, they must overfuel to avoid detonation. I am only going off this whole S/C,turbo thing cos all cars that have them spit flames out like there is no 2moro, so i can only guess that this is the reason

 

[CooperS-Boy]

My Cooper S exhaust pops and burbles loads after a quick run out. A nice little feature on the car I think.

 

[clean16v]

Quote: Originally posted by Dust on 04 March 2003

Quote: Originally posted by clean16v on 04 March 2003

unburnt fuel which enters the back box(a cat will stop the fuel) and if the exhaust is hot it will ignite it. This is why Force inducted cars always have flames out of exhaust because they expel LOADS of unburnt fuel

If a cat stops the un-burnt fuel, how come TVRs pop? They have Cats. Would it be the build up of pressure in the mid or back box? Smaller box = more pressure?

Does it pop flames though? doubt it would with a cat. Having said that, it depends on the cat doesnt it? I should have said most cats would stop the fuel. Doubt the cat on a TVR is similar to a clio! prob has performance cat

 

[RobFenn]

More investigation is needed. I also thought it might of been because of wild cams, as this might cause some backfiring which is the same noise. Looks like we need some one whos in the know

 

[clean16v]

YEAH, wild cams would also cause it. my theory is that anything that may cause a car to overfuel, i.e. big cams, S/C, turbo, carbs, T/Bs anything that will increase the volume of air in cylinders so the car overfuels to avoid detonation

 

[RobFenn]

And hence why race cars do it and road cars dont.

Ill go with that then.

 

[clean16v]

unless modified. BTW i meant a modified turbo or S/C ie upped boost. my mates G60 runs a shorter pulley has stage4 internals with a big straight through exhaust, when he changes gear you know about it!

 

[RobFenn]

ASFAIK my dads M3 does none of that though despite being a high revving motor.

 

[clean16v]

He has an E46 right? i heard one of them give it some today. Didnt know whether to laugh or cry, it certainly got my attention though!

 

[RobFenn]

Yeah. When we first got it though we thought it was pants, as youre not allowed to rev it above certain revs for a while but after about a month where we could cane it, it was a great sound, very similar to 355s, its that metallic kind of shreik, totally different to a vanquish and all the better for it.

 

[RobFenn]

Still far too quiet though

 

[Frosty]

The rally car pops, bangs, and flames are caused by the anti-lag system (as someone said earlier).

The road car pops and bangs are actually caused by a lean mixture which is the opposite to what most people believe.

TVRs pop because I dont think that they work on closed loop lambda mode unless they are at idle (if at all)!

 

[RobFenn]

Isnt lean bad for your car?

 

[clean16v]

HMMM, frosty? whats your theory on it then? not quite sure how flames can be produced when there is not enough fuel?

 

[RobFenn]

and whats the whole anti lag thing about as flames are caused on the overrun when your foot is off the pedal so why would you need antilag ???

 

[timrud]

Yeah I agree with the fact it is ALS that makes rally cars pop and flame...

Here is an excellent explanation of it.. http://bbs.rsownersclub.co.uk/showthread.php?s=&threadid=8634http://bbs.rsownersclub.co.uk/showthread.php?s=&threadid=8634

And heres some Videos, the first one has ALS and launch control, which imposes a temport limiter at around 4500rpm. http://ut.constantvibe.com/evo/antilag_vcd.mpghttp://ut.constantvibe.com/evo/antilag_vcd.mpg

This is a 3dr Cossie with a crazy WRC ALS system fitted, this thing is the bollox! His name on the RSOC is steve3drALS.... http://www.welshcosworth.co.uk/vids/stevealsflyby.wmvhttp://www.welshcosworth.co.uk/vids/stevealsflyby.wmv http://www.welshcosworth.co.uk/vids/stevealslaunch.wmvhttp://www.welshcosworth.co.uk/vids/stevealslaunch.wmv

Cheers, Tim

 

[clean16v]

is anti lag not just keeping the revs at a certain level? i.e. when the turbo comes on boost?

 

[Frosty]

Lean is bad under heavy load but when you are on overrun lean is fine.

While on overrun, the air/fuel mix is lean and the engine is reving around the 7,000rpm mark. Only a small percentage of each cylinder is full of mixture as the throttle body is firmly shut.

This small amount of air/fuel passes through the engine so quickly it doesnt actually burn and goes straight out the exhaust valve and within a very short period of time (because we are at 7k revs) a load of mixture is sitting in the exhaust. As soon as there is enough of it - boom! The mixture ignites on the hot exhaust. Theres your flame.

 

[RobFenn]

So how do road cars get all the popping and bangin when they have no ALS

 

[Dust]

Not sure if this helps but my mate put a supersprint exhaust on his car and added some octane boost, this made his car pop like fuk. So must be un-burnt fuel/octane.