2015 BMW M3 Sedan, M4 Coupe are officially revealed

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BMW has announced the 2015 M3 Sedan and M4 Coupe, high-performance versions of the new 3 Series and 4 Series that launched this year. The new Ms have stirred controversy in a variety of ways, but one must remember that the M cars traditionally don’t follow a specific mold.

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Back in 1988, BMW launched the M3 with a high-revving four-cylinder engine even though the top non-M 3 Series model was equipped with an inline-six. The reason: the little four-banger weighed less. The power-dense 2.3-liter four produced 197 horsepower, which was enough to make the original M3 one of the most sought after performance BMWs of all time. Two successive generations of M3 stepped up the cylinder count to six and provided a nice bump in power, and the M3 that came after them was equipped with a screaming V8. The M3’s history dictates that M cars aren’t about staying the same – they’re meant to push limits – and M Motorsport engineers decided that the new M3 Sedan and M4 Coupe would push limits best with a twin-turbocharged inline-six.

For those of you worried that the new mill will underwhelm, on paper it outperforms the last M3’s 4.0-liter V8 in a number of areas, including weighing 22 pounds less. The new 3.0-liter inline-six makes 425 turbocharged horsepower from 5,500 rpm all the way up to 7,300 rpm – just 300 rpm before the redline is reached. That’s five more horsepower than the V8, but more importantly, the 1800-rpm powerband is very broad. Torque from the turbo six is even more impressive: peak torque of 406 pound-feet starts at 1850 rpm and doesn’t start falling off until 5,500 rpm, right when the engine starts to make peak horsepower. That compares very favorably to the V8’s oft-bemoaned max torque of just 295 lb-ft.

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The broad power and torque bands can be attributed to the two fast-spooling, single-scroll turbochargers, Valvetronic variable valve timing and Double VANOS variable camshaft timing, the latter two working together to control intake valve lift. You could say that engine downsizing, turbocharging and controlling the valve timing are politically correct moves on BMW’s part, too. The automaker claims that the 3.0-liter six consumes nearly 25 percent less fuel than the V8 and produces nearly 25 percent less emissions.

Score one for the turbo M.

The M4 Coupe, weighing in at 3,300 pounds, is 176 pounds lighter than the outgoing M3, too. So all that additional power and torque translate to a manufacturer-estimated 0-60 time of 4.1 seconds with the six-speed manual, or 3.9 seconds with the M dual-clutch transmission for the lighter cars. Those numbers compare favorably to 4.5 seconds (DCT) and 4.7 seconds (6MT) for the outgoing model. BMW is mum on the new M3 sedan’s weight, however, but claims that it does 0-60 mph in the same amount of time. Both the M3 and M4 can reach an electronically limited top speed of 155 mph.

BMW learned its lesson from the cooling problems its turbo sixes experienced when the last generation 335i launched. The new engine gets a track-optimised cooling system complete with a main radiator with a water cooler postitioned to the side, an engine air intake with an indirect intercooler, an engine oil cooler, a baffled magnesium oil pan and an oil extraction pump with a sophisticated oil return system. All should help the new Ms stay frosty during the heat of battle.

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Both the M3 and M4 come standard with a six-speed manual transmission, connected to a carbon-fiber reinforced plastic (CFRP) driveshaft, connected to a mechanical limited-slip differential. À la Nissan 370Z, the new six-speed manual features an automatic throttle blip setting to rev-match downshifts. If buyers opt for the seven-speed dual-clutch transmission, the multi-plate limited slip diff is controlled electronically and can disengaged the diff’s clutch plates completely or lock them up 100 percent. DCT-equipped cars also get launch control.

In addition to using CFRP in certain components to save weight – for example, both M3 and M4 get a carbon roof – the suspension components have been redesigned and are made in aluminum. The front suspension of each model gets aluminum control arms, wheel carriers and axle subframe, which is bolted directly to the chassis with no bushings to reduce suspension elasticity and improve handling precision. Ball joints are used instead of rubber bushings to further improve suspension rigidity and maintain handling precision. Additionally, each model gets an aluminum stiffening plate and a CFRP front strut-tower brace to keep the front end stiff.

The rear, five-link suspension gets similar treatment. Each model gets control arms and wheel carriers made of forged aluminum that together weigh 6.5-pounds less than the previous M3’s setup. The rear subframe is also bolted directly to the chassis with no rubber bushings; again to improve rigidity and handling.

All that horsepower and performance-oriented suspension would be for naught at high speeds if the aerodynamics hadn’t been carefully honed to produce equal downforce at the front and rear. The front apron and gaping intakes move air around and through the car to produce downforce (and component cooling) at the front, while the rear lip spoiler adds an equal amount of dowforce at the rear. In particular, the intake air that passes over the oil cooler “creates a Venturi effect, which reduces front axle lift and, in doing so, improves the steering,” according to Albert Biermann, head of development at BMW. An air curtain and the side M gills with integrated Air Breather aft of the front wheels keeps air moving out of the wheel wells, which increases stability. And while the widened rear wheel arches detract from the cars’ aerodynamic efficiency, they were deemed necessary to fit the wheel and tire setup needed to handle the additional horsepower. They also look cool.

Standard wheels are 18-inchs (19-inchers are optional), with 255-section tires in front and 275-section at the back end. The wheels cover brakes with steel rotors, though optional carbon-ceramic units with gold-painted calipers can be had, as well.

The interior is spruced up with M-style touches, including door sills, the driver’s footrest, a gearshift lever, circular instruments with white graphics and the all-important, leather-clad steering wheel. M sport seats with a one-piece back panel (electronic adjustment optional) and color-contrast stitching, look grippy and good to use, too. The rear seats feature a 60/40 split, just in case you ever need to haul more than ass.

The new M3 and M4 are departures from previous M3s, but if the specifications point to anything, it’s that BMW and its M division are still pushing boundaries, just as they always have. Look for the M3 and M4’s world debut at next month’s Detroit Auto Show. The pair will go on sale in early summer as 2015 models.

Head below for the press release, which includes all of the available information on the M3 and M4, and for a short video on the new cars that Autobild has gotten together early.

Source: BMW, Autobild via YouTube

 

Saurabh Shukla

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