Compression Ratio / Boost


The compression ratio of your engine has a direct effect on the amount of boost that can be run safely. The compression ratio of your engine is known as “static”. When boost pressure is combined with your static ratio, the result is known as the effective compression ratio. High ratio engines in the range of 9.5:1 or 10:1 will only be able to run small amounts of boost. Although a high ratio engine can run on boost if set up properly, you will make more power with low ratio high boost application. The following chart will give you a rough idea where your application will be under boost. These are guidelines only, applications will vary.



Note :

Street applications running 92 octane fuel should limit effective ratio to 12:1 or lower.

Use of higher octane fuels will aid effective ratios higher than 12:1.