The next-generation BMW M3 is continuing to shed its disguise in these latest spy pictures.

The four-door performance saloon, known under the internal codename F80, will be the first M3 to receive a turbocharged six-cylinder petrol engine.

These latest spy shots show the M3 saloon for the first time with a lightweight camoflagued roof. In previous spy shots the roof hasn't been camoflagued, hinting that BMW may have made some late changes to the design. Other BMW prototypes, including the M4, have also been seen with the same roof design.

The new M3 is set to receive a heavily reworked 450bhp version of BMW’s N55 turbocharged 3.0-litre straight six engine, seen most recently in the 640i and the M135i. Details remain scarce, but it's unlikely that much of the standard direct-injection petrol unit will remain for its application in the new M3.

In a bid to match the performance levels of the Audi RS4 and RS5 and Mercedes-Benz's C63 AMG saloon and coupé models, the new engine is expected to deliver in the region of 450bhp and around 480lb ft of torque. That’s 36bhp and 80lb ft more than the fourth-generation M3’s naturally aspirated 4.0-litre V8 engine.

By comparison, the naturally aspirated 4.2-litre V8 used by the Audi RS4 and RS5 kicks out 444bhp and 317lb ft of torque, while the C63’s naturally aspirated 6.2-litre V8 provides 451bhp and 443lb ft.

The new M3 engine will be allied to a standard seven-speed, dual-clutch gearbox. It’s essentially the same unit used in the M5, albeit with altered ratios. As has become tradition, drive will be sent to the rear wheels via an electronically controlled variable M differential offering 100 per cent lock-up. For the first time since the M3’s inception in 1986, there will be no manual gearbox option.

Despite BMW’s increasing commitment to carbonfibre construction with its upcoming i brand, the M3 will retain a unitary steel platform structure. However, in a move aimed at getting it to hit the scales below the 1605kg kerb weight of the current M3 saloon, certain parts of the new M3's bodyshell, including its bonnet and doors, will be fashioned from aluminium.

The new car will also offer dynamic damping control, with three stages of stiffness. Further changes centre around the steering, which adopts electro-mechanical operation for the first time.

The M3 will feature a series of functional but visually subdued styling changes over the standard 3-series saloon, and these latest spy pictures of the car on test in Death Valley give the best clues yet to the look of the new M3, particuarly at the front end.

Previous pictures revealed new styling changes - including a deeper front bumper with large cooling ducts for its new forced-induction engine, a lightly altered kidney grille, unique door mirrors, wider sills, a subtle boot lip spoiler, BMW M’s traditional quad exhausts and a deeper rear bumper that incorporates a fully functioning diffuser to help cool the rear differential more efficiently.