Owners regard the factory 603 hp rating as conservative, citing dyno figures around 676 hp at the wheels that back-calculate to 750-800 hp at the crank, and quoting stock-tune claims near 687 hp. The exhaust note is described in reverent terms, and even owners consider the factory output more than enough without tuning.
The M177 4.0L twin-turbo V8 and its underrated output
Mercedes-Benz E63 AMG (W213) · mechanical