After Burner

[Dave Haller]

Anyone out there know what causes afterburning in a header? I run zoomies on my alcohol buring BBC and experienced what others called afterburning in the pipes. It looks like that may have happened by the color on the pipes from the flange to the bend. We were fat on the tune and were dialing it in when the weather turned on us at WOS. I got to thinking, dangerous, alcolhol burns cooler so if raw fuel is getting into the exhaust header how does that cause afterburing if the pipe is cooler as well?

[Dean Los Angeles]

The amount of air available to burn with fuel is limited to the stochiometric ratio of the fuel and the amount that can get mixed and burned.

You always run above stochiometric just for that reason. The amount that can burn is a very complex subject.

So to get the maximum power you are always on the rich side, and that leaves unburned fuel in the exhaust.

At some point the fuel reaches the air boundary and there is always something hot enough to ignite it.

[SPARKY]

spark retarded to much CAN contribute to more unburned fuel in exhaust