Originally Posted by Back Road Runner
But this is what you want. You need that flow from the intake side to clear out the spent charge from the combustion chamber. This is the whole idea behind scavenging.
Backpressure is always bad. You're running a big air pump. You don't want restrictions. Restriction = inefficiency.
Yes the whole air pump thing....You know it's more complex than that. Engines that dont make Peak VE around 7K rpm normally show a torque increase from an engineered (Atleast to a certain extent) exhaust manifold and post exh. manifold exhaust system. You want the intake charge to 'push' some of the very last exh. gas out of the cylinder, but you dont want the air fuel charge to leave out the exhaust manifold.