Quote Originally Posted by 81911SC
Reversion? Scavaging? Know anything about either of them?
This man hit it on the dot. You gotta have SOME length to the exhaust pipe. Open header is fine, but if you cannot Scavange your exhaust gases then you will have Reversion inside the combustion chamber. The valves will be workin against each other. This goes for NA and FI. That is the same principle behind adjustable cam gears. The amount of overlap affects reversion, which affects power. NA setups can make alot of power if they set up the exhaust cam to "venturi" the air into the intake.