Mike Paula

You would need to factor in the CC's of your dish to Calculate your compression ratio. Normally you use a dish pistion to lower Compression ratio in motor running forced induction. Also if you have any valve relief in the piston those will all so need to be factored in.

GPM

43 cc dish, 9.0 compression blower motor. I was wondering how much the dish effects the quench.

PatriYacht

There is a flat area on dish pistons also. On domed pistons the flat area is in the same place. Take a quick look at www.flatlanderracing.com. Look at pistons in their catalog. The flat area covers about 25% of the top of the piston opposite the dish or dome.

Whiteknuckle

Don't confuse quench with valve relief, valve clearance or compression ratio.

GPM

The only flat area on mine is a 1/4 inch ring around the outer edge.

Mike Paula

For you math boy's out there

Compression Ratio =( Displacement + Piston Volume + Deck Clearance Volume + Gasket Volume + Combustion Chamber Volume) / (Piston Volume + Deck Clearance Volume + Gasket Volume + Combustion Chamber Volume)

found this on the net
http://www.angelfire.com/fl/procrastination/motor.html

GPM

If, I'm understanding this right, the quench area is where the flat area of the piston almost touches the flat area of the head inside the cylinder. Is this correct?

Mike Paula

Quench area is the flat area on the top of the piston that will almost be level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.
The quench area also runs cooler than the rest of the chamber (hence the word quench)

PatriYacht

Yes. That piston is wild. I've never seen one completely dished before. It doesn't seem to have any quench at all.

GPM

Thanks, that's what I thought. I'm wondering what effect it has on my engine.