I would like to compile some data as to what compression can be expected from different rebuilds and engine mods.

Please list:
1) engine model (13BT, REW etc.)
2) rotor compression
3) porting
4) use of lapped vs. new irons
5) rotor housing condition (new, used etc.)
6) use of new or used side and corner seals
7) brand/style of apex seal

If any of you engine builders just want to comment of more general trends, that would be great too.

Thanks,
Justin

 

1. No difference! The compression ratios are the same.
2. not sure what %
3. more overlap lowers the engines ability to make the most compression due to the loss of some of the intake mixture out of the exhaust.
4. not sure %
5. new housings and new apex seals have the best chance at making the most compression since everything wears more evenly.
6. not much difference as these seals hardly wear much due to low spring tension.
7. 3 piece was said to be the best seals for the most compression. Though I feel it's difference compared to a 2 piece seal isn't much to factor.

Lastly a tight minimum .002 side seal to corner seal clearance will make the most difference in determining how well an engine makes compression.