BMW has now introduced its new M3 and M4 models—but Roundel readers will already be familiar with the territory, thanks to a pithy analysis in the current edition of the magazine. And we cut to the chase—far short of the 8,134 words the December press release took. Check out our report on page 42 of Roundel.
In brief, the new BMW M3 sedan and M4 coupe are lighter, more powerful, and more fuel-efficient than the old V8-powered M3—and even sharper to drive. Here’s Brit magazine CAR’s opinion (apparently space is at more of a premium than in the corporate world, and this is sharply succinct):
“The new M3’s twin-turbo (S55) straight six displaces 2,979cc, and develops 425 bhp and 406 lb ft. While horsepower is only up 11 bhp from the old V8 M3, torque has jumped a massive 111 pound-feet, and is on tap all the way from 1,800 to 5500 rpm. Peak power is available from 5,390–7,000rpm; the twin-turbo engine revs out to 7,600 rpm.
Downsizing also improves fuel economy by a claimed 25%; official stats herald 34 mpg. More important, the new M3 will hit 62 mph (that’s 100 kph) in 4.1 seconds (when fitted with the optional seven-speed dual-clutch gearbox) and tops out at a limited 155 mph. However, if you add on the M Driver’s pack, the limit goes to 174 mph. That’s in a 65–70-mph world, so be careful.
The flared air dams front and rear turn up the visual aggression to 11—although BMW does claim that the combination of vents, intakes, and wings decreases lift at the front and rear axles. BMW has increased the narrower M3 track to match that of the wider M4 coupe, too, necessitating a set of tasty blistered arches for that classic M car stance.
Track-spec cooling systems for the engine, brakes, and differential are standard. BMW says it’s worked hard to improve the car’s race-circuit performance to cater to track-day enthusiasts. Forged nineteen-inch alloys are standard, along with upgraded M Sport brakes. Lighter, larger carbon-ceramic stoppers with gold calipers will be on the options list, for when you park outside your favorite restaurant under the street lights—or for when you reach the end of the back straight at Circuit Of The Americas.
Carbon-fiber is all over the new M4 and M3. For the first time, the four-door gets a carbon roof, which saves 5 kg and lowers the car’s center of gravity. There’s also a one-piece carbon driveshaft, a carbon engine-bay strut brace, and carbon rings in the standard six-speed manual gearbox for smoother shifting (it’ll also auto-blip to rev-match downshifts).
That’s not the end of the weight-saving measures. The domed hood and front fenders are aluminum, and there are aluminum suspension control arms to save 3 kg of unsprung mass. At 1,520 kg, the F30 M3 weighs a huge 80 kg less than an equivalent E92 M3. There’s a retuned M Differential that BMW claims enhances traction by altering the amount of diff lock between zero and 100% in a fraction of a second. Spec the paddleshift gearbox and you get launch control and a “Smokey Burnout” function; stick with the manual, and it’s up to the driver to provide those feats yourself. One-piece sport seats, some M-branded footrest and steering wheel trinkets, and the usual tricolour stitching.”
Now for the nuts ’n’ bolts:
Aerodynamics has always been one of the key elements in BMW development. Engineers need to channel the air around the car to create the best possible platform for dynamic excellence, while also ensuring that the engine, powertrain, and brakes receive the requisite cooling under heavy loads on the race track. Details such as the front apron, smooth underbody, and Gurney spoiler at the rear of the M3 sedan (or integrated spoiler lip at the rear of the M4 coupe) reduce lift by an equal degree at the front and rear axles.
The exceptional performance of these cars places exacting demands on temperature management; in order to ensure optimum temperature, BMW engineers have developed an effective cooling system. Alongside the two turbochargers, the intake system includes an indirect intercooler, maximizing charge pressure and engine output. As well as a main radiator, there’s a water cooler for for the high- and low-temperature water circuits, and the engine and transmission oil (if the M Double Clutch Transmission is specified).
Power is transferred to the road via a standard six-speed manual gearbox, which is more compact than its predecessor and 26.4 pounds lighter. The manual gearbox uses innovative new carbon friction linings in its synchronizer rings. Dry-sump lubrication provides an efficient supply of oil to the engine. The gearbox blips the throttle on downshifts—previously a feature reserved for the M Double Clutch transmission—and this engagement speed control function improves the smoothness of the transmission.
The third generation of the M-DCT sees a benchmark in power and race track capability without compromising everyday usability. The optional seven-speed M Double Clutch Transmission with Drivelogic prompts the new turbocharged engine to new levels. As well as changing gear automatically, in manual mode the transmission enables ultra-fast gear changes. The integrated Launch Control function ensures optimum performance off the line. Stability Clutch Control opens the clutch when the car is understeering to bring it back into line. And M-DCT also includes functions like Drivelogic modes that can be selected by the driver to give the BMW M3 and BMW M4 more comfortable, thrifty, or sportier characteristics. The additional seventh gear over the manual gearbox also allows longer gear ratios.
The extremely light CFRP material allows engineers a new approach to the the driveshaft. It feeds the engine’s torque from the gearbox to the rear differential under extremely heavy loads, and it can be constructed as a single-piece unit with no center bearing. “As well as a weight saving of 40%, we have achieved a reduction in rotating masses,” explains BMW M GmbH chief engineer Albert Biermann.
Among other components that add to the dynamic repertoire of the M3 and M4 are hollow lightweight output shafts to the rear differential and the Active M Differential, which uses an electronically controlled multi-plate limited-slip differential. The multi-plate limited slip differential links up with the DSC (Dynamic Stability Control) system and takes into account the position of the accelerator pedal, the rotational speed of the wheels, and the car’s yaw rate. Every driving situation is analyzed, so an impending loss of traction can be identified early. The lock is adjusted as required within a fraction of a second, preventing wheelspin.
M Dynamic Mode improves the Dynamic Stability Control (DSC) system: While DSC counteracts understeer and oversteer, M Dynamic Mode allows greater wheel slip, and therefore easy drifting. The axles of the outgoing BMW M3 have also been redesigned. In the double-joint spring/strut front axle, aluminum construction for components such as control arms, wheel carriers and axle subframes saves 10 lbs over a steel design. Play-free ball joints and elastomeric bearings developed for the M3 and M4 ensure a direct transfer of forces. An aluminum stiffening plate, CFRP front strut brace, and additional bolted joints between the axle subframe and the body structure help to increase the rigidity of the front end.
Also lighter than the outgoing BMW M3 is the new five-link rear axle. All control arms and wheel carriers are manufactured using forged aluminum, which reduces the unsprung mass by six pounds compared with the previous generation. The rigid connection between the rear-axle subframe and the body—without the use of elastic rubber elements—further improves wheel location.
Development of tires was incorporated into the process from the outset to gain steering feel and precision, alongside lateral stability and braking forces. At the rear, traction, lateral stability, and directional stability take center stage. For this reason, both cars will leave the factory on low-weight eighteen-inch forged wheels (front axle: 9Jx18, rear axle: 10Jx18) with mixed-size tires (front axle: 255 mm, rear axle: 275 mm). Nineteen-inch wheels and tires are available as an option.
The electromechanical steering system in the new M3 and M4 offers direct steering and precise feedback. The integrated Servotronic function electronically adjusts the level of steering assistance according to the car’s speed, and the cars have three settings as standard, which can be selected at the touch of a button: COMFORT, SPORT, and SPORT PLUS modes. The optional Adaptive M suspension also comes with COMFORT, SPORT, and SPORT PLUS modes.
The BMW M3 and M4 come standard with BMW M compound brakes with outstanding stopping power and high resistance to fade. Far lighter than conventional equivalents, these brakes reduce unsprung mass and enhance dynamic performance. Even-lighter BMW M carbon-ceramic brakes can also be specified as an option. (Going to COTA? You want this option!)
The new M3 and M4 return to a six-in-line engine configuration, as used on the second and third generations of this iconic sports car. The new engine sees a slight power upgrade over the previous V8 to 425 horsepower, which is delivered between 5,500 and 7,300 rpm. Peak torque has been increased by roughly 40% to 406 pound feet—YES, YOU GOTTA LOVE THEM TURBOS!—and is maintained over a very wide rev band (1,850–5,500 rpm). The standard sprint from zero to 60 mph takes 4.1 seconds; with the seven-speed M Double Clutch Transmission, this number falls to 3.9 seconds. Top speed is 250 kph/155 mph (electronically limited).
The new engine also boasts excellent fuel efficiency: the M4 coupe achieves consumption nearly 25% better than the previous model’s figures. Regulated pollutant emissions are EU6-compliant. BMW M’s whoop-de-do “TwinPower Turbo” technology comprises two fast-responding mono-scroll turbochargers, high-precision direct fuel injection, Valvetronic variable valve timing, and double-VANOS continuously variable camshaft timing. Valvetronic and double-VANOS work in tandem to seamlessly control intake-valve lift; the result is smooth and efficient power delivery, very sharp response, and reduced fuel consumption and emissions. (You want multiple throttle bodies? How about NO throttle bodies?!)
The six-cylinder engine features a closed-deck crankcase design which is very rigid and allows cylinder pressures to be increased for improved power output. And instead of liners, the cylinder bores feature a twin-wire arc-sprayed coating, which results in a significant reduction in engine weight. A further technical highlight is the forged, torsionally rigid crankshaft, which, as well as providing increased torque-carrying capacity, is also lighter in weight. This significantly reduces rotating mass, resulting in improved throttle response and acceleration..
On the track, the exceptional driving dynamics of the M3 and M4 place extra demands on the engine’s oil-supply system. The low-weight magnesium oil sump features a special cover to limit movement of the oil under the effects of strong dynamic lateral acceleration. A zoomy engine sound—in keeping with the M3 and M4 mystique—is provided by a flap in the twin-pipe exhaust system.
Intelligent lightweight design was a top priority in the M3 and M4, and both models have shed weight. The BMW M4 weighs around 160 pounds less than a comparably equipped predecessor model. The M3 aedan also features a CFRP roof for the first time; on the E90/92 models, the CFRP roof was confined to the coupe version. Now the four-door M3 will get this striking design and functional feature as well.
The CFRP roof brings weight savings of eleven pounds in the case of the M3 sedan and thirteen pounds in the M4 coupe. It also lowers the vehicle’s center of gravity. Made from aluminum rather than steel, various body panels—including the hood—contribute to the models’ lightweight design. The use of carbon in these models is a reminder that BMW is a global leader in high-strength, lightweight CFRP construction, and that it was BMW who brought out the first mass-production vehicle with a body consisting entirely of this material: the innovative BMW i3.—Paul Duchene
