Well Dayumn...
https://www.roadandtrack.com/news/a4...w-m4-csl-dyno/
Just as the sun rises and sets, BMW publishes conservative horsepower and torque figures. The German owner of a new M4 CSL put their car on the dyno and got an astonishing result—596 hp and 531 lb-ft of torque. BMW, for reference, advertises the M4 CSL at 543 hp and 479 lb-ft.
It's better for automakers to under, rather than overrate horsepower to avoid false advertising, but we can't help but wonder how BMW arrives at its power and torque figures. Is its dyno on the top of the mountain? Do engineers turn the heat to 120 degrees? Does whoever is responsible for publishing final figures just subtract 10 percent? Who knows. What we do know is that it is routine for BMWs to make far more power than advertised. Dyno tests from last year on the standard 473-hp M3 suggested that the car probably makes more like 547 hp at the crankshaft, so it's no surprise the CSL—which ups the boost pressure on the M4's straight-six to over 30 psi—makes damn near 600 hp.