[asphaltgambler]

Really depends on the combination if running an aggressive camshaft where some cylinder pressure is bled off. The advertised mechanical compression ratio is just approximated with this piston. Also, very high cylinder pressures from forced induction and domes on a piston do not mix well. Crazy turbulence in the combustion chamber, hot spots, lots of quench areas.

Modern pump gas engines that are turbo'd have piston and combustion chambers that have more in common with a diesel design. Pistons are hanging out of the hole to minimize quench and deck height, usually dished concentrating the flame front dead center. The combustion chambers V-shaped, very shallow, perfect valve (stem) angles. The cam timing is variable, PLUS the fuel and ignition delivery is tightly controlled; per cylinder.

VW / Audi - somewhat 'old school' 1.8 turbo 4cyl engine ala early 2000's. Very basic but very good engine. 2-cams with somewhat crude variable timing on the intake cam only. The cranking compression was @210psi. The stock boost was @9lbs. Do the math. They can do this because of the total engineering that went into it