Exhaust backfiring?!

[LAZZEE RARSE]

Call me a noob im not assed.

But on my way home from work i saw another veccy burn passed me. As i caught it up at the traffic lights, it started reved its engine and the exhaust started backfiring.

Seen this before on tv and other highly tuned cars.

But got me wondering how do you get your echaust to backfire. And why does it backfire??

[John IS3]

Backfiring is caused by unburnt fuel igniting in the exhaust normally ;)

[keefy*2010]

Call me a noob im not assed.

But on my way home from work i saw another veccy burn passed me. As i caught it up at the traffic lights, it started reved its engine and the exhaust started backfiring.

Seen this before on tv and other highly tuned cars.

But got me wondering how do you get your echaust to backfire. And why does it backfire??

Must have been petrol head and able to adjust the electronic timing or perhaps they turn ignition off momentarily, mainly boy racers around here do it

[Grumpy1954]

It's possible to advance/retard (can't remember which) the timing to make it backfire, but John likely got the reason in this case.

[rushy]

De cat.......or flamer kit.

[DasArab]

or flamer kit.

I go with that, it would be difficult to get a "normal" car to do that these days due to the lambda sensors and the cat. Used to be able to get my MKII escort to do teh popping and banging on over run years ago, that was fun.

[LAZZEE RARSE]

Fail mot if you decat exhaust though dont it?

[John IS3]

Not if you re-fit it before the MOT :)

[rushy]

Fail mot if you decat exhaust though dont it?
You can get a de cat pipe made so you just bolt the cat back in when needed, although on more modern petrol's you need to play the the management as well so the EML doesn't come on and put you into limp.

[sxi-dean]

My 3.0 V6 406 coupe used to pop following heavy accelaration and then subsequent quick lift off. Only did it after I had a stainless system fitted though, and it sounded great!

[GSiFan]

If the driver was revving the nuts off it, it might have been hitting the rev limiter, which cuts ignition to a random cylinder every revolution or two to keep the revs down to prevent the engine from grenading itself.

Paul :)

[wayne10244]

My old mk 3 astra used to do it and spit out flames when the car got hot that was a 2.0 red 230 bhp

[kamar]

unless it was a turbo with anti lag on it like subaru and evos

[wayne10244]

The astra had a race spec engine blue printed it cost me £4500 just for the engine

[LAZZEE RARSE]

If the driver was revving the nuts off it, it might have been hitting the rev limiter, which cuts ignition to a random cylinder every revolution or two to keep the revs down to prevent the engine from grenading itself.

Paul :)

So what your saying is thT with no modifications my car will spit fire if i hit the rev limiter?

[GSiFan]

Not necessarily. But some cars do. It's not a great example but once, about 18 1/2 years ago, I was alongside a TVR Griffith at the front of a queue for a roundabout. I was in my first car - a knackered and ancient BMW 735i. The Griff revved like crazy and shot off the line, belching a huge ball of flame from its exhausts. Amazing noise too! :D

Anyway, don't blame me if you go and over-rev your engine! :sweat: No liability accepted! :faint2:

Paul :)