Originally Posted by
CCS86
It just doesn't make conceptual sense to me. I have no dyno testing to backup my intuition.
To my knowledge, overlap helps in both getting out the last bits of combusted charge (better scavenging), and helping to initiate cylinder filling for the next event, using inertia from the exhaust flow.
Better scavenging should improve power in any application, so I could see a small amount of overlap being helpful. But with positive MAP ready to fill the cylinders, even when cylinder pressure isn't very low, it's hard to picture overlap being much help there.