The lighter, more powerful two-door M hero now kicks off from $189,900 before on-road costs, sitting above the existing M4 Pure ($139,900) and M4 Competition ($156,710) in the range.
Otherwise unchanged, power in the CS comes from a twin-turbo inline-six with 338kW and 600Nm on tap, up 7kW and 50Nm compared to the rest of the range.
The 100km/h sprint takes just 3.9 seconds and, thanks to targeted weight savings, the car uses 8.4L/100km on the New European Drive Cycle (NEDC) – 0.4L/100km less than the Pure and Competition.
If you manage to match those figures in the real world, please let us know in the comments. We'd love to give you a prize.
Power is sent to the rear wheels through a seven-speed dual-clutch transmission in the CS, with no manual option. Carbon-fibre reinforced plastic has been used for the front splitter, bonnet, roof, spoiler and diffuser, helping shave between 10 and 32kg from lower-spec models.
Working in tandem with a unique suspension tune and the extra power, the CS lapped the Nurburgring Nordschleife in 7:38 – 22 seconds faster than the regular M4 could manage.
Inside, the pared-back M4 trades proper door trims for lightweight cards with fabric pulls, while dual-zone climate control has been turfed in favour of a single-zone system. BMW says the 12-speaker audio system has been specially modified for the CS, too. A head-up display is standard, along with BMW ConnectedDrive services, DAB+ radio, parking sensors, speed limit information and rain-sensing wipers.
Options on the CS include special paint options (Lime Rock Grey and Frozen Dark Blue II, $4400), a rear roller sunblind ($600), sun protection glazing ($800), headlight washers ($500), a TV tuner ($2250) and Apple CarPlay ($623). Sorry Android acolytes, you're going to have to run with iDrive 6.0, no Android Auto will be offered. You'll also pay more for carbon-ceramic brakes, to the tune of $15,000.