Exhaust popping on overrun

[Dracoro]

Anyone care to explain what it's all about please

All I know it's unburnt fuel being burnt in the exhaust.

Why does it tend to only happen on certain cars. Why not on 1.0l fiestas? Or it's it just inaudible on a 1.0l with straw exhaust?

Sounds great but curious to why it happens. The Exhaust on my westie is fine, not blowing/leaking at all etc. but does pop sometimes when slowing down and hot.

[S8ight]

un burnt fuel or an air leak

[steppenwolf]

If you have TB's ( although in fairness, this could apply equally to carbs. too) the following may be of interest:-

Popping on the Overrun

[Dracoro]

Is there anything wrong with it doing it though? any damage that it might cause?

[Mark Purves]

I know of one C******m that has had this feature mapped into its ECU so that when the throttle is opened again a 3 - 4 foot flame appears from the exhaust. Great at night not so good for anything along side at the time.

     

[steppenwolf]

Is there anything wrong with it doing it though? any damage that it might cause?

Not really - unless you have a carbon fibre can and then it might shatter if the car really rumbles ....

[chumley-warner]

It will eventually burn out / blow out the silencing material in your silencer, but if you have a repackable exhaust, you can repack it too. Now it is getting warmer try driving at twilight and have a look at the flamey goodness coming out of them........turn your wing mirrors down if you don't want to look away from the road, but the whole side of your car should light up if you're lucky!

 

[Matt Seabrook]

[Blatman]

Is there anything wrong with it doing it though? any damage that it might cause?

With a carbon silencer, YES. It could catch fire, and the carbon SBD boxes don't like backfiring much at all. It says so on their web site.

Have a search for what can be done to help this situation by lining the silencer with a heat blanket, and while you're in the search, look for NickM's (I think) burnt can. Not a pretty site, although it wasn't done by backfiring/flamethrowing, IIRC.......

[felters]

I actually got pulled over by Plod in January for this very thing. He seemed almost amused by it... suggested that I avoid gearchanges near small dogs (and their owners) waiting to cross the road. He said that barbecuing live animals would render me liable to prosecution on a number of different charges outside of the Road Traffic Acts...

[chumley-warner]

Shoe-poib!

Nothing they can do about it on a Q plate, but perhaps a case of disturbing the peace might be something your could frame and place above your fireplace?

   

[the bear]

I was told it was to do with the race cam and twin carb setup on my car. The cam momentarily allows the inlet and outlet valves to be open at the same time and any unburnt fuel because of the sudden lift off the throttle means the fuel is passed out of the hot end. The mechanic who explianed it although now running an independant Beemer service centre is time served and reckons it's just the character of the set up and leave it as is.

[Matt Seabrook]

The lean mixture will not burn completely inside the engine if it is too weak and is chucked into the exhaust. When enough of it gets in to the exhaust it will ignite and result in a popping noise of in the case of a Westy with a short exhaust and straight through silencer shoot flames out of the exhaust.  With a fuel injected car the injectors shut the fuel of completely so there is no fuel to get into the exhaust system so no popping or shooting flames. If there is an air leak in to the exhaust this could make the matter worse but is still stems down to a lean mixture.

Could not be   ed to type it all agian.