F13 640d grand tourer — 380hp stage 1 remap, the best kept secret
The F13 640d with the N57 3.0L diesel engine is one of the most underrated BMWs you can buy. Stock it makes 313hp and 630Nm. With a stage 1 ECU remap it pushes to 380hp and 750Nm. That is serious torque in a beautiful grand tourer.
I bought mine with 95k km for 18k EUR. After the remap, the car is transformed. The midrange pull is incredible — overtaking on the highway requires zero effort. The 8-speed ZF gearbox shifts smoothly and a TCU tune makes it even better.
Fuel economy is surprisingly good for a car this size — 7-8L per 100km on the highway at 130 km/h. The N57 diesel is efficient and the tall gearing helps.
The F13 6 Series is depreciating heavily which makes it a bargain. You get a beautiful GT car with a fantastic engine for the price of a new Golf GTI. The only downside is maintenance costs — it is still a big BMW with complex systems.
Common issues to watch: air suspension compressor failure, N57 timing chain wear at high mileage, and the usual diesel emissions system maintenance (DPF, EGR).