Originally Posted by
DP-buggyboy
Stroke will be the same as a "long stroke" .21 buggy engine.
So, when I got out of the shower last night after coming home from a race, I had a little flash of an idea of how to use the crankcase to supercharge a 4 stroke engine. You could simply valve it with reed-valves. The intake charge would get sucked into the crankcase when the piston goes up, then pushed back out into a the intake manifold as the piston goes back down. This would happen twice as often as the intake stroke, so I'm guessing it could give a significant boost without adding more rotating parts. Of course, other types of valves could be used, but it's just a generic and random idea at this point.
Has anyone ever seen this used in any type of 4 stroke engine?
I haven't seen an engine using it, but again, the reason is likely based on energy loss. The problem with that system is given by the actual lower crankcase compression. Since the case's compresion is so low relatively speaking, there is not enough energy to supply the combustion chamber with enough fuel/air at the higher flow/rpms.
When the valve opens in the usual combustion chamber in a high compression 4 stroke, there is so little space in the chamber at TDC that the pulses that the piston produces as it moves up and down are reflected with very high efficiency so there's a lot of energy to move the gases to and from the chamber to fill it up. Actualy the higher the compression, the easier it is for the engineto breath at high rpms.
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