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The reason why my engine has worked with this high cr is bacause the cylinderhead has bad flowfigures and the exhaust manifold is original, the volumetric efficiance suffers from this... maybe it will be about 80-85%, according to my experiance this allows you to use a higher cr without detonation but hp and driveability also suffers from low VE so it would be better with a lower cr and a engine that breathes better!!

About dished pistons, In my new turboed A15 (pictures under my photos) I am using dished pistons with the dish offset, the cr is 7,8:1 and I am running 12-20psi boost without much problems, I belive that well designed pistons are a huge help, the squish are also very important..... exactly like Feral said!! Feral has a huge fanclub here in Finland

Cheers Marcus