Originally Posted by Jafro

I get knock on pump gas above 19 PSI. My pistons are 9:1. I have a front-mount intercooler. Forget that it's a Mitsubishi for a second and realize that pump gas has it's limitations. You make power by flowing air, not by pressurizing it. All that does is make the intake charge hotter. Raising the compression will add power, sure... but it's more likely to pre-ignite with pump gas unless the whole front of your car is an intercooler or you're running water injection.

If you're not building that rotating assembly like a brick shithouse, don't raise the compression. Forged pistons will give you a little more durability when you get knock from pre-ignition, but that won't save your rods or crank.