BMW has been deliberately underrating its engines for as long as we can remember. To the surprise of no one, the S58 inside the M4 CSL is no exception. UK tuning shop Evolve Automotive strapped the Competition Sport Lightweight onto a dyno to find out how much power that inline-six really makes. From the factory, the twin-turbo 3.0-liter is rated at 543 hp and 479 lb-ft (650 Nm).

Limited to only 1,000 units, this M4 CSL painted in matte Frozen Brooklyn Grey is hiding considerably more power than what BMW claims. The six-cylinder engine managed to push out 582.3 hp and 517 lb-ft (701 Nm) at the crankshaft. That’s a significant bump of 39.3 hp and 38 lb-ft (51 Nm) compared to the official technical specifications.

Evolve Automotive also loaded up the data from a previous dyno run with an M3 Competition (G80), a stock car with rear-wheel drive like the M4 CSL (G81). That one was a pleasant surprise as well since it pushed out 529.6 hp and 517.6 lb-ft (701 Nm) or 26.6 hp and 38.6 lb-ft (52.3 Nm) more than BMW’s rating.

50 wealthy individuals were able to get an M4 with an even higher official power rating. We’re talking about the 3.0 CSL featuring the company’s most potent inline-six ever. It makes 553 hp according to BMW but we’d be interested in finding out how many horses it really has in a dyno test. Because the modern-day Batmobile has a six-speed manual instead of the CSL’s eight-speed automatic, torque is electronically governed at only 405 lb-ft (550 Nm) for reliability reasons.

If you’re thinking of buying a new M3 or an M4, there could be some good news on the way. The upcoming facelift is said to bring a bit more power to the Competition models fitted with xDrive. As it stands, these cars make 503 hp per BMW but their six-cylinder engines might be massaged to extract an additional 15 hp for a grand total of 518 hp. The updated models are going to be unveiled later this year.

Source: Evolve Automotive / YouTube