The test car is also wearing a larger rear spoiler than the current production M4 and has gained new LED tail-lights, as well as LED headlight details to match the facelifted 3 Series, as has been seen on the standard 4 Series Gran Coupé during testing.
These changes match up with the 4 Series Gran Coupé test mule we spotted earlier this year, with the facelifted M4 due for release a few months after this.
No major mechanical upgrades are expected for the 2017 M4, so power will still come from the same twin-turbocharged straight-six engine as today’s production model, but output will be increased beyond the 425bhp and 406lb ft of torque produced by the current car.
The M4’s engine is proven to be able to produce substantially more power. The GTS, with its efficiency improving water injection system, outputs 493bhp. However, the regular 2017 M4 will likely offer a figure closer to that of the current 444bhp M4 Competition Pack.
Inside, little is expected to change from today’s M4. BMW’s range-topping 7 Series has demonstrated the level of autonomous technology the manufacturer has available, but the 4 Series and M4 are unlikely to inherit such systems until the next all-new model is launched later this decade.