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Compression Ratio

This is a difficult one to pinpoint for absolute power and torque gains. A low compression ratio will be of benefit when you are planning to run high boost, if the boost is to high for the compression ratio this will lead to "Detonation" or "Pinging" when under load. A low compression ratio – say 7.5:1 will be of benefit for big horsepower but again the trade off is the response or lag (gas speed again). It is very important that we get back to application and decide what the car is used for and what you are trying to achieve.

In our experience a compression ratio of 8.5:1 is around the mark for the best compromise between response and power, it is also important to remember that you can always cheat a little here and use different fuels (super unleaded/ octane booster) to over come the problems of detonation associated with higher boost levels. The main manufacturers are actually going higher and higher with compression ratios to reduce lag and increase torque, this is mainly due to the really sophisticated management systems now available and the general improvement in the fuel we get from the pump.

There are many more factors that come into play when choosing a compression ratio and one type of engine can be quite different to another.