We have the first technical details of the new BMW M3 sedan and M4 coupe ahead of their Detroit show debut in January – both will be powered by a 3.0 litre S55B30 twin-turbo straight-six that develops around 430 hp at 7,300 rpm and more than 500 Nm of torque from 1,800 to 5,200 rpm, bettering the outgoing V8-powered M3’s figures by over 30%.
Being smaller than the previous naturally-aspirated V8, the engine can be placed further back in the bay. BMWBlog points out that as the TwinPower Turbo assembly is mounted at the bottom and rearward of the motor, mated to the exhaust manifold, the recirculating exhaust gases have a very short distance to travel before they are sucked into the turbocharger.
The engine is mated to either a ZF six-speed manual or an optional seven-speed M DCT with DriveLogic and launch control. The manual ‘box is 12 kg lighter than its Getrag predecessor and auto-blips on downshifts – like Nissan’s Synchro Rev Match. The Active M diff is now electrically-actuated, constantly varying the locking effect. Of course, M Dynamic Mode is present as well.
Boasting direct injection, Valvetronic and Double Vanos tech, the EU6-compliant motor can rev up to 7,500 rpm. It features a closed-deck crankcase design, allowing increased rigidity and cylinder pressures. The cylinder bores feature a twin-wire arc-sprayed coating instead of liners, saving weight. The prop shaft is made out of CFRP – the material’s high rigidity and low weight allow the shaft to be produced as a single piece without a centre bearing.
A forged, torsionally-rigid crankshaft provides increased torque-carrying capacity, and its reduced rotating masses improve throttle response and acceleration. Fuel consumption and emissions are down by about 25%, while the vehicles themselves weigh under 1,500 kg – in the case of the M4, an 80 kg reduction over its M3 coupe predecessor. Weight distribution for both cars are virtually 50:50.
Keeping things cool, apart from the main radiator, are radiators for the high- and low-temperature circuits, turbocharger and gearbox, plus a temperature-stabilising electric water pump and an indirect intercooler, mounted on top of the engine to ensure the air going in stays as cool as possible.
Under strong lateral acceleration, a magnesium oil sump with a special cover limits oil movement, while an oil extraction pump and a sophisticated oil return system ensure circulation is uninterrupted. Electrically-controlled flaps in the twin tailpipes provide the soundtrack, while minimising back pressure and giving feedback on engine load.
Suspension is handled by a double-joint spring strut front axle and a five-link rear axle. The control arms, wheel carriers and axle subframes are made out of aluminium, while an aluminium stiffening plate, CFRP front strut brace (weighing only 1.5 kg) and extra bolted joints between the axle subframe and body sills all help to increase rigidity.
The electromechanical steering and optional Adaptive M suspension both offer Comfort, Sport and Sport+ settings. M compound brakes are standard; for even greater stopping power, carbon ceramic brakes are available as an option.
Large front air intakes, exposed CFRP components and the rear diffuser are as much about function as form. Reducing lift are the front apron, smooth underbody and ‘Gurney’ rear spoiler lip (integrated spoiler lip on the M4), while the Air Curtain and M gills with Air Breather minimise front wheel arch turbulence.
Along with those already mentioned, CFRP is used in the roof (for both sedan and coupe this time, yielding savings of 5 kg and more than 6 kg respectively), front and rear fascias, and boot liner. BMW works drivers Bruno Spengler and Timo Glock have extensively tested the BMW M3 and M4 on the Nurburgring.
Spengler had this to say: “The suspension has a very sporty set-up, the feedback from the front axle is extremely direct and the grip at the rear axle is phenomenal. The power is right there, even at low rpm, and you can sense that you’ll be able to access the output and torque over an extremely wide rev band.” Verily, we’re salivating.