Would it be safer on the motor to have less compression with a turbo? If so is there anyway to space the head from the block to decrease compression? Another question, with adding a turbo, should the timing be retarded? Any help please.....

Yes, its safer with low compression, it gives you more leeway in your tuning. No, don't use headgaskets, or head spacer type things to lower your compression, it will put a lot of stress on your timing chain.

The timing should be retarded usually, but its something only a dyno can tell. Some people have actually advanced the timing.





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depends.... if you want to run ridiculous boost, drop the compression, but if you want a really responsive turbo car, run more static compression with a smaller turbo and less boost. Big turbo with lowered compression is more what you're looking for on a drag setup. Safety is all in the tuning.




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i can't really post the chart because my scanner doesn't work. But there's a nice graph in Maximum Boost that shows correlation between compression ratio, PSI level, and octane level necessary for maximum performance and safety. If you don't have that book you might want it.




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Jersey Jay 1.8T wrote:depends.... if you want to run ridiculous boost, drop the compression, but if you want a really responsive turbo car, run more static compression with a smaller turbo and less boost. Big turbo with lowered compression is more what you're looking for on a drag setup. Safety is all in the tuning.

My theory on boosting J-s as well......




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