IN DETAIL: BMW M4 GT4
Engine
The M4 GT4 retains the 2993cc, twin-turbocharged straight-six ‘S58B30’ engine from the road-going M4, with up to 542bhp and 479lb ft of torque available, as per the M4 CSL. However, the GT4’S ECU can be manipulated to comply with Balance of Performance requirements at different championships. This isn’t a simple reduction in boost, and hence power, in every gear; instead the restriction might just be in gears one to four, for example.
Gearbox
Some GT4 cars now run full race sequential gearboxes with pneumatic shift, but the M4 GT4 sticks with the road car’s ZF auto, albeit with seven ratios instead of eight and a new motorsport program for faster shifts. It can still be used as a full automatic or operated with the paddles. In place of the fully variable M Differential there’s a Drexler limited-slip diff. There’s also a launch control function but this won’t be any use in the N24, which has a rolling start.
Driver aids
Many of the features of the M4 road cars remain in the GT4, although with unique programming for the higher forces delivered by race suspension and slick tyres. There’s a full DSC mode (good for wet weather but also useable in the dry), plus MDM mode, which still utilises the stability control. The driver can also elect to disable ESC and instead use the variable traction control system, which has ten settings. On a very cold test day, MDM felt very good indeed.
Lightweighting
BMW has collaborated with sustainable lightweighting experts Bcomp on the GT4, replacing carbonfibre components with new items incorporating natural flax fibres. Bcomp’s Amplitex and Powerribs products are used extensively for the interior, plus externally in the front splitter, bonnet, doors, bootlid and adjustable rear wing. The weaves look more like early carbon-kevlar and F40 geeks would be pleased to see the patterns beneath the paint and decals. Safety is also improved as the flaxfibre fabrics don’t splinter upon impact.
Suspension
KW supplies the two-wayadjustable motorsport dampers for the M4 GT4, with three options for springs from H&R. The dampers’ solid-piston design enables greater control of the hydraulic forces than a conventional damper. Anti-roll bars front and rear have five positions to help further tailor the balance and body control.