Hartge has developed an aftermarket program for the BMW 6-Series GranCoupe 640i and 640d models. In its standard configuration, the inline-six 3.0-liter turbocharged engine of the 640i produces 320 HP (235 kW) and 450 Nm (332 lb-ft), but with Hartge's modifications it outputs 367 HP (270 kW) at 5,900 rpm and 520 Nm (383 lb-ft) reached at 2,950 rpm.
The 640d makes use of a 3.0-liter diesel generating 313 HP (230 kW) and 630 Nm (465 lb-ft). After making the necessary tweaks, Hartge was able to raise its output to 362 HP (266 kW) at 4,400 rpm and 730 Nm (538 lb-ft) at 1,800 rpm.
The additional power was possible by increasing the airflow by using an in-house stainless steel exhaust system with Hartge's stainless steel middle and rear silencers with dual 80mm round tailpipes.
Aside from the power boost, the 640i can be fitted with sports springs lowering the four-door coupe by 25 mm and 20 mm (front/rear). The 640d can also be lowered by 30 mm and 25 mm, respectively. The exterior packs the tuner's emblem on the hood and boot lid, while inside the car receives bespoke floor mats, aluminum emblem on the steering wheel and aluminum pedals. Various wheels are available in different styles and sizes.