EJ22T hybrid Compression question

[Imprezive]

My brother is gathering parts to swap some 20G heads onto his 2.2T block. And I know that puts the CR down to 7:1, I was wondering if this was low enough to sort of let the engine "bog down" at low RPM since the turbo won't be producing much boost?

I am guessing the answer is no since people have and are doing this swap. But could someone clear it up for me?

[professor]

yes it will produce somewhat less power when off boost or when boost is low, due to the lower compression ratio

but this effect is often over-estimated, the function of power versus compression ratio is a weak one

lower compression ratio is a godsend when you have relatively poor engine management, so unless you have a stand-alone, perfectly tuned ecu then you may be better off overall.

historically almost all turbo cars have been between 7:1 and 8:1, with higher compression becoming more common as engine management improves. Most of the outrageous power racing engines of the 80's were in the low 7's.

[Matt Monson]

And the Porshce 930's and 935's of the 70's were around 6.5:1

The EJ22T with Ej20g heads combination is 6.7:1, assuming we are talking about the 89-94 Legacy EJ20G heads. If they are WRX heads, the compression will be marginally higher since the combustion chamber was a little smaller once they went to direct actuation on the valves...