Important points on fitting Pistons

[Mike Wienandt]

Mike

Great info.

Total Tapped CR? Do you mean Total Trapped CR? Which I know as cylinder volume above the top of the exhaust port to TDC and is much lower than based on total cylinder volume from TDC to BDC.

Thanks
Pete

Effective Compression Ratio is the same as Trapped compression ratio. ECR or TCR. It is when the exhaust port closes. If you raise the E port you are compressing less, so you can make the head tighter to make up for higher ports. A little math required.

Geometric compression ratio is also call four stroke compression ratio. That takes into account the entire cylinder displacement compared to head volume. This is useless in my mind. I need to know what is it really. as so I work with so many different engines and port duration s.

Great question.