One of the best ways to increase the efficiency of any internal combustion engine is to raise the compression ratio. As long as fuel with a high enough octane rating is available (so it will burn without detonation), raising the compression ratio can be a very effective performance boost.

The amount of material which must be milled from heads (or cylinders) to change compression ratios may be easily determined. Although the formula listed in the next column may look strange (or too simple) it is correct and it does work!

Only the stroke length, the original and new compression ratios need to be known. As an example, how much must be milled off EV80 heads to raise the compression ratio from 8.5 to 9.73? Stroke length=4.25 for a stock EV80. With this formula, T=.080 (see table in next column). All of the values in the following table were calculated with this formula. This formula also assumes that combustion chamber volumes and cylinder bores are not changed for this calculation.