S/C compression ratio

nickb777

In my Cortenays s/c conversion they put double space head gasket to lower the compression from 9.5:1 to 8.5:1 I believe just wondering why on the 300 bhp 2.0 build they increase it from 9.5: to 10:1.

As I am looking at pistons at the moment I want to be certain which to get.

exmantaa

I believe it has to do with the ignition, or better knock prevention.
The US superchargerkit for the 2,2 uses the standard engine till around 240hp, so with standard compression ratio.. (10:1 I believe?) But the ECU is reflashed with a special SC program.

The Hitec SC conversion (similar to Courtenay?) uses a piggyback with extra injectors for additional fuelling, but the ignition timing is from the standard ECU.

(I personally dislike the idea of making an engine less efficient by lowering the comp. ratio and raising the boost...)

slindborg

the yanks love "normal" compression high boost applications.

With the Z22se's std peak torque being fairly low down the rev range, the A/C wont be at its max efficiency by then so the engines volumetic efficiency will dorp off after peak torque so you can pile in the boost to fill in the gap.

exmantaa

"Yank normal compression" is traditionally not spectacular. Our 10:1 is quite low for a modern n.a. engine.
I believe the old red top XE had 11,5:1??? But the 2,2 is not a high revving machine like a Honda K20A. More a multi purpose GM mule...

nickb777

exmantaa said:

The Hitec SC conversion (similar to Courtenay?) uses a piggyback with extra injectors for additional fuelling, but the ignition timing is from the standard ECU.

(I personally dislike the idea of making an engine less efficient by lowering the comp. ratio and raising the boost...)

Yes they do So I still need some info from Jon as to what mods he is planning on doing for the stage 3 S/C. I believe he is going stand alone ECU. With the £$ as it is I don't mind geting all the parts and building my spare block up ( Vocky's actually) Then letting Jon put it all together.

slindborg

the XE was/is 10.5:1... still nothing that fancy.