how high of comp ratio can you have when you turbo a engine

Depends on the chamber design and octane of your fuel and how good of a tune.

Street car with aluminum heads up to maybe 15psi, 93 octane, no higher than 9 to 1 i'd say but I havent tried any higher than 12 psi yet on mine. So maybe 15 is too much.

8.5-8.8 can handle abit more.

If you run meth/water injection probly could see 15-20 psi depending. race gas even higher. All depends