What causes flames with meth?

[dsm1gb]

I'm curious, I've seen a few peoples exhaust flaming for 5 seconds or so using meth, is this a good or bad thing, and what causes this? I haven't noticed this on my own car.

[Richard L]

This is quite normal for a PPS (progressive pump speed) system without an inline valve to shut off the flow instantly when running high percentage of methanol.

The inertia of the pump and pressurised delivery line keeps the methanol flowing after lift-off, causing over-run or dribble (http://www.youtube.com/watch?feature=endscreen&NR=1&v=KZRI7WZHggQ). When the throttle snaps shut, methanol is leaking pass the throttle plate into the plenum, continue to fuel the engine at a very rich afr.

During the intake stroke, the methanol is re-ignited by the exiting exhaust gas, continue to burn along the exhaust pipe. In most cases, it is harmless. But under some circumstances, it can cause two very serious conditions:

1. Pre-igniton: intake air is set alight can continue to burnt during the compression stroke before the spark occurs.

2. If the excess methanol and charge air in the plenum forms an ideal afr, it can be quite explosive, especially engine with large valve overlap period.

I read blown manifolds once to twice a year.

[Aldis1]

Look in your preferred tuner mag and there should be a ad for devices that will do that in the back. Usually they need a spark plug in the exhaust tube and a way to supply a flammable fluid into the exhaust after the muffler.