The M4 Coupe introduces a new model designation to the long-revered M-car lineup and several new driveline developments, including a new twin-turbocharged inline six-cylinder engine -- the S55, as M division insiders call it.
The new 3.0-liter engine began life as a development of BMW's widely used N55 engine. They share the 84.0 mm and 89.6 mm bore and stroke measurements, but changes are extensive. M division development boss Albert Biermann calls the S55 all new.
Peak power is 422 hp, 8 more than the 4.0-liter V8 it replaces. At 143 hp per liter, it's the highest specific output of any previous series production M engine. The power is also more accessible, delivered some 2800 rpm lower than before. The torque increase is more notable, up from 110 lb-ft to 405 lb-ft between 1850 rpm and 5500 rpm.
With aluminum (front fenders, hood, doors), carbon-fiber reinforced plastic (roof, trunk lid) and steel (rear fenders), the M4 weighs 3,300 pounds, 183 less than the outgoing car.
Power is sent to the rear wheels via a revised ZF-produced six-speed manual gearbox, which was originally developed for the M135i Coupe. It is 26 pounds lighter than the M3 Coupe's trans, and it now boasts dry-sump lubrication, a double-plate clutch, carbon-ceramic friction linings within the synchronizer rings, a blip function on downshifts and shorter individual ratios. A seven-speed M Double Clutch Transmission (M-DCT), as our test car had, is also available. It's essentially the same as the M5's. The Getrag-built trans has remote paddle shifters, launch control, a so-called smoky-burnout function and stability-clutch control. Beware, though: It adds 88 pounds to the car's weight over the manual. Both gearboxes have stop-start, brake-energy recuperation and optimum shift indicators. BMW says the car should get 26 mpg (manual) and 28 mpg (dual-clutch). Earlier talk that suggested the M4 Coupe would get optional four-wheel drive is just that – talk. Biermann says there are no plans to offer it, but he doesn't deny that it could be introduced later to boost appeal in potentially lucrative markets, such as the snowbelt states.
Suspension is MacPherson strut front and multi-link rear suspension, as well as a 62.2-inch front and 63.1-inch rear track – 1.3 inches and 0.7 inches wider than the 435i Coupe's. Wheelbase is 2 inches longer than the M3 Coupe at 110.7 inches. The heavily reworked suspension uses aluminum extensively to lower unsprung weight.
The standard 18-inch wheels are 9 inches wide in the front and 10 at the rear. They come with relatively conservative 225/40 and 275/40 profile Michelin Pilot Super Sport tires, developed specifically for the new M4. Our test car wore optional 19-inch rims (same width).
BMW
The 2015 M4 Coupe gets a twin-turbocharged 3.0-liter inline-six. It's more powerful than the outgoing V8.
On one hand, drivability and refinement are terrific. On the other, speed and dynamic proficiency are just as good. The key to its many talents is Drive Performance Control, allowing you to tailor the car's properties over a significantly wider range than its predecessor. Three buttons access it on the center console. Mode choices are Efficiency, Sport and Sport+ for engine mapping and Comfort, Sport and Sport+ modes for damping and electromechanical steering.
Importantly, you can mix and match each one. So, for example, you can call up differing properties for the engine, damping and steering rather than being stuck with one common mode for all like on standard BMWs. An M-mode also allows you to save preferred combinations, and they can then be easily accessed each time you enter the car via a pair of steering-wheel buttons.
In Comfort, there is nothing remotely demanding about the way it drives. You could cover loads of miles without ever feeling remotely challenged, all in a sumptuous environment offering outstanding levels of interior comfort and first rate ergonomics. In this sense, the M4 Coupe proves a convincing everyday car. It is more purposeful in feel compared to the 435i Coupe but no more taxing to drive.
Choose Sport and the car instantly becomes more purposeful in nature as driveline, chassis and electronic driving aids are altered for more engaging driving. The steering is more urgent, the throttle more aggressive, the ride stiffer and the electronic stability control more liberal, allowing you to be a hooligan when the conditions permit.
Moving to Sport+ further heightens the experience, although it is really only intended for the track work and ultimately proves wearing for any distance on the road.
BMW
It's hard to find fault with the M4 Coupe's performance cred, but its new engine is less engaging than the old V8. Can't complain about the comfortable interior, though.
Like all M-cars throughout the years, the engine moulds the M4's driving experience more than anything else. This is where the twin-turbo six both impresses and disappoints. At start-up, it sounds remarkably similar to the M5's twin-turbo V8, with an odd diesel-like chatter. It improves as you select first and move off.
Predictably, the biggest change over the M3 Coupe is power delivery; it couldn't be more different than before. With all the torque concentrated low, you get substantial shove from little more than idle. This results in outstanding flexibility across a much wider rev range, making it much better suited to stop/go city driving than its predecessor.
Don't count on the same razor-sharp throttle response as before when the road opens up and you put your foot down for the first time. The initial pick-up is a lot less rabid than with the old naturally aspirated engine – there's a fleeting moment of lag as the two turbos spool up to full boost. But once they do, the in-gear shove is uncompromising. There's no need to pile on the revs; just flex your right foot in a suitable gear and the engine obliges with truly muscular properties. The acceleration is spectacular, particularly between 3500 and 5500 rpm.
It lacks the aural intensity of the engine it replaces, though, despite Active Sound Design. It reproduces the six cylinder's sound through the audio speakers at various volumes and frequencies based on engine revs, throttle load and speed.
With two mono-scroll turbochargers, variable valve timing and continuously variable camshaft control, the engine revs freely, extending to 7600 rpm before the limiter. This is high for a turbo engine but 600 rpm less than the old naturally aspirated engine.
The optional dual clutch offers ease of use to match its fervent on-boost acceleration, leading to an impressive 4.1-second 0-62 time. The standing kilometer, now much accepted as the modern day acceleration yardstick for European car makers, happens in 21.9 seconds. This is 0.5 and 1 second faster than the M3 Coupe. BMW claims the M4 can accelerate from 50 mph to 75 mph in fourth gear in just 3.5 seconds. The M3 Coupe required 4.3 seconds. Top speed remains limited to 155 mph, though you can raise it to 174 mph with an optional M Driver's package.
Few cars anywhere near the M4's $65,125 starting price provide such dynamic finesse or engaging qualities. There is a perceptible completeness to the chassis, serving to provide the new car with a wonderfully fluid feel over challenging blacktop.
Directional stability is exceptional, there's a ton of grip and body control is superb.
BMW
Badges? Of course you get special M4 badges. And quad exhausts.
Well, there are a couple of shortfalls. It might be spectacularly powerful, but the new engine lacks engagement and sounds disappointingly flat at certain points in the rev range. For owners of the fourth-generation M3 Coupe, this will blunt its charm, but only until they discover the gains in driveability and stunning in-gear qualities brought on by its strapping torque. What it lacks in overall excitement, it more than makes up for in everyday driving appeal. Darn right, you want it . . .
2015 BMW M4 Coupe base price and specifications
On Sale: Summer 2014Base Price: $64,200
Drivetrain: 3.0-liter turbocharged inline-six; six-speed manual transmission; RWD
Output: 422 hp, 405 lb-ft
0-60: 4.1 seconds
Curb Weight: 3,300 lbs.
Fuel Economy: 26 mpg (combined, manufacturer)
