Even since the BMW X3 M Competition and X4 M Competition models first came out we’ve been hearing how fast they are. For cars this big to be this fast using 3-liter engines, something just didn’t add up. The spec sheet did show impressive numbers but even so, a lot of us have been secretly suspecting that the S58 engine is making more power than advertised. Luckily for us, this suspicion is set straight in the video below.

The guys from DSC Off in Russia brought the two models together to have a proper comparison for a change. While the traditional drag race was included in the mix, they also decided to put the cars on the dyno, something that should settle the debate regarding horsepower once and for all. The results showed numbers pretty close to the claims of both manufacturers. If Google translate was correct, the graphs in the video show the estimated power developed at the crank, not at the wheels.

The BMW apparently develops up to 560 PS and 621 Nm of torque. Applying a 10% transmission loss, we should see about 510 PS at the wheels which is a good estimate. On the other side of things, the GLC 63 AMG S is even closer to the manufacturer claims. The 4-liter twin turbo V8 showed 517 PS at the crank and 686 Nm of torque. While the torque figure is slightly under the 700 Nm claimed by Mercedes, the horsepower is also a bit higher. The variation is smaller though.

What we can notice though is what the extra 2 cylinders and displacement bring to the table. If you take a look at the graphs you’ll notice that the Mercedes-AMG is already reaching peak torque at 2,500 RPM while the X4 M Competition does the same at 3,500 RPM. Nevertheless, the extra horsepower of the BMW is impressive and shows why in the drag races. In both standing start and rolling race versions the X4 M Competition pulls away at over 200 km/h (124 mph). However, the Mercedes has the – very small – edge on the 1/4 mile. The dyno runs start at the 17-minute mark, in case you don’t want to see the entire video.