Quote:
Originally Posted by Blue Thunder
Sure. Without getting too overly technical a 4 stroke engine does just that. Intake, compression, power, exhaust. When the piston was coming up for the compression stroke, it wasn't really compressing much, hence the 45 psi of compression referenced earlier in this thread. The spark plug fires within a few degrees of top dead center. When that fuel/air mixture ignited it would blast right by that huge crack in the intake valve and backfire out through the throttle body. I'm assuming the valve pictured is the intake. If it's the exhaust valve the same thing would happen but the backfire would go out the exhaust port...
BT
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Good explanation.
4 stroke:
1. Intake- Piston travels downward creating a vacuum in the cylinder and the fuel air mixture is drawn into the cylinder through the open intake valve.
2. Compression-Intake and exhaust valves are closed creating a sealed chamber where the fuel/air mixture is compressed by the upward traveling piston, almost to the point of igniting the fuel/air mixture on it's own. (How a diesel motor works)
3. Power-Both valves are still closed, The spark plug fires and the rapidly expanding combustion drives the piston downward creating power.
(In my motor all the power that was supposed to be generated in this cylinder was lost through the broken valve and forced back up into the intake mainifold)
4. Exhaust-Piston traveling back up in the cylinder forces the spent gases back out through the open exhaust valve.
(Some of the hot exhaust gases would pass through the broken intake valve during this stroke as well possibly igniting more fuel in the intake manifold)
Then the process starts all over again
Each cylinder in a 4 stroke motor only makes power during one of the 4 strokes (power stroke). In a V8, V6, etc, the power stroke is happening at different times in different cylinders thus the motor is producing power all the time. In a 1 cylinder "lawn mower" motor they need a weighted mass (flywheel) to rotate/carry the piston through the other 3 strokes