Based on the B58 engine already used by the X3 and X4 M40i, the inline six-cylinder unit delivers 473bhp and 442lb ft in standard form and 503bhp and 442lb ft in the X3M and X4M Competition – the latter of which receives a louder M Sport exhaust as standard.
Power is channelled to all four wheels via an eight-speed torque-converter automatic gearbox and a variable M xDrive four-wheel-drive system, with an electronic rear differential and torque vectoring system. The Competition versions of the X3M and X4M are said to achieve 26.9mpg and 26.7mpg combined respectively.
There is no pure rear-wheel-drive mode, with maximum traction the priority. Base cars come with 20in wheels shod with 255/45 (front) and 265/45 (rear) tyres. Competition models feature 21in rims with 255/40 (front) and 265/40 (rear) tyres.
The standard X3 and X4’s MacPherson strut (front) and multi-link (rear) suspension has been heavily reworked, as have the variable ratio steering system and the brakes, which use 395mm steel discs and four-pot calipers up front and 370mm steel discs with floating calipers at the rear.
Beulke said a significant amount of engineering was focused on stiffening the front-end structure of the standard SUVs to improve agility and steering precision. To this end, the X3M and X4M receive a sturdy strut brace across the front suspension towers as well as additional bracing below the engine.
The fastest model – the 1970kg X4M Competition – is capable of 0-62mph in 4.1sec and reaching a governed top speed of 155mph, with an optional M Driver’s package allowing the limit to be raised to 177mph.
The X3M and X4M were not conceived for off-road driving, but Beulke said both perform “remarkably well” away from Tarmac, thanks to the locking effect of the rear differential. The new S58 engine comes with efficiency-boosting tech including brake energy recuperation. The most economical of the new M models, the 1970kg X3M, is rated at 26.9mpg combined and emits 239g/km of CO2.