The 2013 F10 M5 with its 4.4L V8 S63Tu turbo engine has previously been shown to be underrated from the factory, which is BMW’s habit with its official quote power figures.
The latest results showing this come from iND who have just begun performance testing on their F10 M5. The result was 527 RWHP (rear wheel horsepower) on a totally stock F10 M5 running on pump gas and dyno’d on a dynojet. This represents just a 6% drivetrain loss.
The M5’s S63tu V8 runs a higher compression at 10.0:1 (@ 22 PSI), compared to the X5M/X6M S63 engine’s 9.3:1 (@ 17 PSI).