It would seem BMW has been caught lying, but in the best possible way. In typical German automaker fashion, there are signs the Bavarians have intentionally underrated the twin-turbo, inline-six engine powering the new M3 and M4. Illinois-based aftermarket specialist IND Distribution got a hold of a completely stock coupe and conducted an independent dyno test.
BMW may say its S58 engine produces 473 horsepower (353 kilowatts) at the crank for the non-Competition models, but in reality, the six-cylinder mill generates nearly as much power at the wheels. IND Distribution says the rear-wheel-drive M4 they tested produced 464.92 hp (346.7 kW) at the wheels. As for torque, the engine is officially rated at 406 pound-feet (550 Newton-meters) at the crank, but it pushed out 408.55 lb-ft (553.9 Nm) at the wheels during the dyno run.
Factoring in the typical 15 percent drivetrain loss, IND Distribution estimates the engine generates somewhere in the region of 547 hp (408 kW) and 480 lb-ft (651 Nm) at the crank. To put those numbers into perspective, BMW says the hotter M4 Competition has 503 hp (375 kW) and 479 lb-ft (650 Nm) at the crank.
The "15 percent" rule is debatable as some would argue newer cars only lose about 10 percent from the crankshaft to the wheels, but even so, the lower output figures would still put the base model quite close to the official rating provided by BMW for the M4 Coupe Competition. It's also important to mention the car tested by IND Distribution was still in the break-in period, so the engine should push out more power once it racks up some miles.
Dyno tests typically show different results for the same car, so it's best to be cautious and wait for subsequent evaluations of the S58 in these new M models to get a better understanding of the output ratings. If this first test (done with a Dynojet 424) is any indication, the new M4 appears to have way more power than advertised.
There are already signs a hotter M4 will be launched in 2022, possibly with the CSL suffix, which could come with a bump in power. Meanwhile, BMW is putting the finishing touches on the M4 Convertible for a summer launch, with the first-ever M3 Touring expected sometime next year. The next-generation M2 Coupe might inherit the same engine, albeit detuned to avoid clashing with its big-brother M4.