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Message: <blockquote data-quote="rollakid" data-source="post: 415647" data-attributes="member: 6588">cam lobes.. hmm.. some sifoo please verify this for me, dunno correct or not my understanding:degree of the cam lobes determine the duration of the opening of the valvethe higher the degree, the longer the valve will openif the engine runs very slow, the best time for the valve to open is when the piston hits the top end and start to move down. and the best time to close is when the piston hits the bottom end and start to move up. Its because the air manage to go in fast enough and open and close like that can suck in the most air.but in reality engine move very fast. and like what acoustic said sometime ago, forget when, that air is "stupid" it will keep on rushing in because of the air velocity.if the engine moves fast, closing the valve sooner (short duration cam) will cause the engine to suck in less air, cuz the air tak sempat masuk.thats why high reving engine use high duration cam to get more power. opening the valve for a longer period of time and close much later, so that more air can be suck in because of the air velocity/vacuum in combustion chamber (cuz air tak sempat masuk, so even if the piston hit bottom end there's still vacumm inside).high duration cam makes more power than retarding cam timing because retard timing makes valve close later, but also make it open later. high duration cam can open earlier and close later, so more air come in.reason why racing cam with high duration don't make power at low rev is because it close so late, the air manage to fill the combustion chamber, but the valve don't close, which result in the air pushed back into the intake manifold..turbo make power at low rev or high rev, as long as the turbo's size is correct. this is why most (if not all) force induction user uses low duration high lift cam. this is because the air is pumped inside, not suck in by the vacuum. so with a cam that make the valve close nearly after the piston hit the bottom end, the turbine can pump in most air into the chamber. The high lift cam is to let more air come in easier.----------------------disclaimer------------------------i'm not trying to say anything or give info... before i get flame for nothing.. i wan to say i just want verification on what i understand so far... :ph34r: and hope can correct what i misunderstood... only do some reading on intake cam so far.. haven't understand exhaust cam much yet :(</blockquote>

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