The guys from G-Power have come up with some incredible kits for the latest M models in BMW’s range. The BMW M8, for example, can get upgraded to create monster power figures, as is the case with the G8M Bi-Turbo, a car that is supposed to offer 770 horsepower, according to the German tuner. However, a trip down to the local dyno can show different numbers, as one would expect.

Usually, when you dyno a car, your readout shows vastly different numbers compared to the ones listed by your car’s manufacturer. A number of factors play into this outcome, from the car’s age (internal combustion engines lose power over time) to the efficiency of your transmission. Most of the time you can expect to see a difference of around 10 to 20 percent between the power developed by the engine and what actually reaches the ground via your wheels.

The video below goes against the stream though. The guys from G-Power popped a BMW M8 on the dyno after it was fitted with their GP-770 kit. As the name suggests, the power output was supposed to go up from the stock 625 horsepower to 770 horsepower, a drastic increase no matter how you look at it. Instead, the dyno showed an even better outcome, with a readout of over 806 horsepower and 924 Nm  (681 lb-ft) of torque.

Those are truly amazing figures, and turn the M8 (or M5 as they use the same engines) into a proper supercar killer. As a matter of fact, we’ve already seen drag races with 800 HP F9x M models against certified supercars and the results spoke for themselves. At the moment, it’s hard to find a better deal if you’re looking to upgrade your current-generation S63 4.4-liter twin-turbo V8. Admittedly, some hardware changes are needed too, apart from an ECU re-map but all-in all, it’s not that hard to squeeze 800 HP out of that mill.