We already know that the new BMW M3 and M4 will receive a significantly upgraded six-cylinder engine producing more than 500bhp in its top form. 

The flagship model to use this new engine will be a new M4 Gran Coupé (imagined by Autocar below), the first time the four-door coupé has featured a full-fat M variant. The coupé and convertible will also return beside the M3 saloon. 

The 3.0-litre powerplant, which carries the internal codename S58, is a development of the firm’s standard B58 unit, as used in the existing 440i and other BMW models. 

But as M division officials have revealed to Autocar, “it is for all intents and purposes an all-new drivetrain with significant changes to the base engine that allow it to rev beyond 7000rpm and deliver a much higher specific output” than today’s S55 engine. 

As well as being earmarked for the next M4 coupé and the M4 Gran Coupé, the new twin-turbocharged straight six is also planned to propel a new M4 Convertible, the upcoming sixth-generation M3 and, in a lesser-powered form, the second-generation M2. It will be launched in the new X3 M and X4 M SUVs. 

An increase in power provides the new S58 engine with a higher specific output in Competition guise than the old S55 with water injection, a set-up used by the 493bhp M4 GTS. 

That unit provides the outgoing M4 coupé with 425bhp in standard guise and 444bhp in Competition form. 

BMW’s M division engineers have managed to raise power by more than 11% in the standard M4 and 13% in the Competition, with claimed outputs of 473bhp and 502bhp respectively. 

These figures appear set to place the new model in direct competition with the 444bhp Audi RS5 and 503bhp Mercedes-Benz C63S Coupé.