It’s quite hard to argue that the BMW M850i either in Coupe or Convertible guise is a slow car. Having tested both, I can wholeheartedly say that I find it hard to imagine just how fast the full-on M8 will be if these two are already this quick. They basically defy the laws of physics and it’s all down to the 4.4-liter twin-turbo V8 under the hood. Reworked for the new generation of cars made by BMW, the N63 engine is now at an all-time high in terms of power.

While previous iterations of the mill had anything from 400 to 450 HP, the latest version now develops 530 HP and 750 Nm (553 lb-ft) of torque. If on the horsepower meter it falls a bit shy of the S63 mill, the torque numbers are on par with the latest version of the M-developed engine found on the F90 M5. And that’s how the eye-watering speeds the M850i xDrive models are capable of.

And yet, for some people, that’s not enough. Therefore, tuners can have a blast creating upgrades for the 4.4-liter mill that can even top the S63 in terms of figures. The guys from BR-Performance have published a video featuring their Stage 1 upgrade for the M850i. The company claims the upgrade will take the power output up to 680 HP and 850 Nm (627 lb-ft) of torque, an increase of 150 HP and 100 Nm of torque over the standard car.

Considering the M850i xDrive can do 0-62 mph (100 km/h) in 3.6 seconds we’re rather curious to see how this monster performs. It will probably turn the M Performance car into an M5 rival, at least in a straight line. Unfortunately, all we have in the video is the car on the dyno but at least we can hear that V8 roar.