How do they make the flame come out of there exaust?

in the movie they used flamer kits that have a spark plug in your exhaust pipe and your ignition cuts for a second and sends unburn fuel down your exhaust piping, the spark plug sparks it and creates fire.

but in real life if you are running high boost with straight pipes you will shoot flame out of your exhaust.

Running unburn gas threw your engine is not good for it, but I saw them do a similar setup to the one explained above on the TV show TRUCKS and it was pretty cool.

How do they make the flame come out of there exaust?

This subject has been discussed at least a couple of times in the Street Racing forum alone.

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