The Czech guys from DieselPower.cz have taken the BMW F10 M550d to the Dyno. The 2012 M550d tri-turbo is the most powerful Diesel car ever to be produced by BMW, having a power output of 381 HP and 740 NM of torque, and features a all-wheel xDrive tracntion . Usually, BMW performance models produce more power at the crank compared to the the actual BMW factory specifications.
The 3 liters inline six-cylinder got three turbochargers – 2 small ones for low and high revs range and one large for high output at high revs. The first small turbo starts working from the lowest speed (1000 – 1500 RPM), then follows the big turbo for high speed (1500 – 2600 RPM) and high speeds are involved second small turbine. The system is fairly well explained on the official M550d video that BMW made public at the beginning of this year.
Throughout some series of measurements, the maximum measured power was 352 HP at 4066 RPM and maximum torque of 736 NM at 2443 RPM, 29 HP and 4 NM less than specified by BMW.
What is also worth attention, was the collapse of power and torque around 2800 RPM. As seen above, this is precisely the moment when the large turbo starts to kick in. BMW should tweak this for better liniar acceleration.
Major problem of the M550d, in my opinion is the immense weight of almost 2 tons (1970kg), 250 kg more than an E60 535d. Lower actual power plus the increased weight, is the reason why the new Audi A6 BiTdi (First audi 3.0 bi-turbo diesel) with 313 HP have quite similar acceleration performance up to 200 KPH.