We knew the upgraded S63tu Twin Turbo 4.4 liter V8 in the F10 M5 would be stronger than the standard S63 Twin Turbo V8 4.4 liter units in the X5M and X6M even accusing BMW of sandbagging. We just did not think it would be this much stronger. We first reported on the differences between the S63 V8's in the M SUV's and the F10 M5 in June of last year and the M5 S63tu V8 has higher compression at 10.0:1 versus 9.3:1 and runs more boost at 22 psi versus 17 psi for the SUV's.
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