6. You'll notice that the piston on the right has a smaller diameter dish than our old piston. This is because we'll be running this engine on race fuel now. The higher octane fuel is necessary when using a large hit of nitrous, and we figured we might as well gain some compression and horsepower by making the dish smaller since we were going to have to buy expensive race fuel anyway. The smaller dish will up the compression ratio from 12.29:1 to 13.7:1.