pistons and compression

Hello! I'm a young guy and don't know that much about engines and I was wondering how different pistons can get more compression. also, does the ratio mean the room in the cylinder with the piston at the bottom of its stroke compared to the piston at the top?

[smokinwrench]

You can buy pistons with a taller dome which gives less area in the combustion chamber. That gives you a higher compression ratio=more horse power. 10/1 compression is about as high as you want to go on pump gas.

Makes sense but if it has a dome on it, it is displacing that much less on the bottom of its stroke. Also, would a dome leave enough room for the valves. I've seen cases where a piston had grooves cut into it for the valves when the engine really heats up.

[Mobular]

Yes the taller dome will take up initial volume room at bdc, but when the piston is at tdc, the ratio between the two is increased...meaning the final area at tdc is less. The "grooves" on the top of a higher compression piston are valve reliefs, nothing to do with heat.