I wonder how much boost they're running . I'm genuinely surprised they brought the compression down that much! The Effective Compression for the B58 in the Z4 at 11:1 comp and roughly 12psi of boost is just about 20:1 ECR. The S58 would have to run 17psi at minimum to match that 20:1 ECR, but most likely is running something like 24psi peak to get to roughly 25:1 ECR to make its 500+ hp. I know in this day and age, manufacturers (especially the Germans) are leaning on fairly substantial boost levels to make power (look at the Merc CLA45, 26+psi!), but it seems largely unnecessary with the generally good DI systems they have. I really would really like to know the rationale behind it. The S58 could hit the same ECR target at 21psi with 10:1 static CR, and with 11:1, it could do it at 18psi. I have no doubt that the motor would be able to handle it because a 350bar DI system should provide plenty of atomization and control as well. Plus with the electronic wastegate, Dual Vanos, advanced ignition timing, etc, knock control is probably really robust. And a higher static CR would provide a far more responsive setup, with better off boost performance, better efficiency, and more headroom going forward. Not to mention less stress on the head and turbos, which is always a bonus for reliability. Idk, very odd choice in my opinion, but I'm sure they did their research and testing with a variety of static CRs.