Comp cams uses a 110 deg lobe seperation compared to others. I've talked to a few companys about this (Reed,Crane,crap can't remember) And they feel that a turbo should have 112deg lobe seperation for better power. Now if you start talking about a 9 sec or faster car the rules change...
What happens, is that with the overlap and the high
exhaust back pressure caused by driving the turbo,
exhaust re-enters the combustion chamber past the exhaust
valve. Thus it acts like an EGR valve and the end result is quenched
combustion.
