I am under the impression that the B230F and the B230FT are the same engine with a difference of a turbo and slightly different head gasket. If that's the case, the engines being exactly the same, how is there a difference in compression? My manual lists the turbo at being 8.7:1 and (I think) the N/A being 9.1:1 (maybe 9.7?).
If the displacement, pistons, head gasket size are the same, the only thing I can think of is that the valves on the turbo are opening earlier or something like that.
This originally stemmed from my learning about stroker motors and thinking it would be easy to make a "stroker" by swapping a B230 for a B230FT and moving the turbo to the N/A engine. Then I realized I had no idea how the two could have different compression.
I realize the problem with the higher compression in the presence of a turbo is pinging, but the EGR system on CA cars and the knock sensor would "take care" of that. Granted the knock sensor retards the timing and would essentially reduce power and the EGR introduces non-combustible gases and also takes some of the engine's power, I would think the higher compression would be better.

Could someone please explain this?

-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond