AN entire book could be written on this subject. BAsically anytime you creat more power, you create more heat, (heat is energy) , more heat means you need more gap to compansate for the expansion on the top piston ring, this goes for any engine weather it be N/A or boosted, the appropriate amount is determined by bore size, type of piston, type of piston material, boost psi, fuel type, heat exchangers, rpm, load, manifold pressure, and more, more than what can be coverd on this page. There are alot of good books on boosted applications, study them.
