Summarize

BMW’s next-generation 2020 BMW M3 and M4 will receive a significantly upgraded six-cylinder engine good for up to 375kW. Not long ago the domain of the M5, the lower level M cars will now also flirt with that the magic 500 horsepower mark with a new flagship M4 Gran Coupé  joined by two-door coupé and cabriolet M4s and the M3 saloon. 

The S58 engine evolves out of firm’s standard 340i’s B58 lump unit with changes including longer 90mm stroke and the 84mm bore for a slightly higher capacity, while a biturbo set-up comprising a pair pf mono-scroll turbochargers in place of a single twin-scroll unit along with latest-spec BMW M Valvetronic and Double Vanos tech and a drop in compression ratio from 10.2:1 to 9.3:1. 

Those changes will see the engine rev beyond 7000rpm to deliver far higher specific outputs than today’s S55 engine. M engineers have managed to raise power by more than 11% to 380kW and 600Nm in the standard M4 and 13% to 375kW and 600Nm in the forthcoming AWD M4 Coupé Competition with a flat torque curve from 2600 to 5600rpm. 

The new S58 lump will meet latest emissions regulations with likely less than 200g/km, thanks to measures including adoption of twin Otto particulate filters. Secrecy surrounds the rest of the M4’s spec, but insiders suggest an eight-speed torque converter autobox turning xDrive all-wheel drive similar to M5 alongside a manual gearbox and rear-wheel drive for the less powerful model. Now that’s welcome news