This is one for you mechanical engineer types

[scoll911]

I'm watching racing on the speed channel and I'm curious -- what causes flaming out of the exhaust pipes

[Randy Webb]

hot, unburned fuel meeting O2 -- tuning for max power doesn't mean all the fuel gets burned.

[Doug Zielke]

Unburned fuel igniting in the (hot) exhaust pipes.
This usually happens on the overrun. Motors with large amounts of cam overlap contribute to this phenomenon.

[Wayne 962]

They have cool flame-throwers installed just for the cameras!

-Wayne

[A Quiet Boom]

Dougs got it right in the case of Gasoline powered cars, Randy would be partially correct on NitroMethane and some Methanol cars. Actually the NitroMethane is still burning as it exits the pipes.

[Kevin Stewart]

Running a msd will do this the msd's spak stays lite a bunch longer, and will happen when there is a Y pipe in the system, Kevin

[Jack Olsen]

It's most common on Turbos, but even an ordinary rev limiter will do it sometimes.

[Kevin Stewart]

Running a msd will do this the msd's spak stays lite a bunch longer, and will happen when there is a Y pipe in the system, Kevin

[Milu]

fitting a sparkplug to your tailpipe connected to the battery with a switch in the cabin also helps flaming from the exhaust

[widebody911]

I'm told that when I lift at the end of the straight @ Thunderhill, my car shoots about 5' of flame out of each pipe. It also shoots flames on the dyno at the end of each test, when the tech lets up.

[stlrj]

The reason it's most common on turbos is because the K-jetronic is not equiped with the fuel shut off on decel feature that motronic incorporates to prevent this from happening.

Cheers,

Joe