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Originally Posted by G_R5GTT
How would that work then?  The flame created in the cylinder is used in the power stroke so if you had the exhaust valve open then, you would have serious problems. |
basically, in an engine running at high rpms the combustion cycle is forced to happen so fast that the fuel is still burning when the exhaust valves open. this is why when you watch a top fuel dragster at night you can clearly see the flames pouring out of the exhaust stack at full throttle.
as for 1979-300d's question....its fairly complex, but long story short, cars shoot flames in three situations.
-they have a kit designed for flame throwing for show...something that sprays fuel at a point near the end of the exhaust, and then a spark plug at the very tip. light the spark up, start dumping fuel, and you get a nice flame.
-anti lag system. these systems are similar to a flame thrower kit, but much farther up the exhaust near the exhaust manifold. they are used on turbo cars to increase turbo spool time. basically fuel is dumped in behind the turbo and the ensuing explosion creates a shock wave that slams the turbo exhaust wheel and gets it spinning quickly. the "bang bang bang" sound and flames popping out is the mini-explosions happening in rapid fire way up in the exhaust and flowing out.
-running very rich on any engine type, be it N/A or turbo. you'll see flames shoot out during shifts or under very fast throttle lifts. this is because when the throttle closes very fast at high rpm, the engine recieves very little air in relation to engine speed because the throttle plate is closed, so you run rich and excess fuel particles are pumped into the burning hot exhaust, where it ignites and blows out. also, the injectors try to react very fast to sensor readings, but at high rpms, and under very fast throttle closings, they cant react fast enough to not dump a little excess fuel in initially, further causing the rich condition. if you own a newer car.....start it up on a cold morning, and blip the throttle a bit. notice how your car "holds onto" the revs, and wont let them drop fast. this is to prevent that rich condition under a throttle closing (also because catalytic converters are destroyed in rich conditions), which as an side effect causes high emissions from the unburned/half burned fuel.
sorry for the super long post. i'm no expert, but thats the basics. hope that helped.