For the M3/M4's full specs, photos, and videos, see our
Tech Guide Thread.
Examining M3 and M4 technology
By Jens Meiners
Thanks, BMW, for the earth-hugging i3 and the i8, but what enthusiasts really care about is the next M3 - and its two-door variation, the M4. Production of the current one has ended in July, while the next models won't go into production before Spring. Why the gap? We hear that BMW has essentially run out of parts to build them.
It means the end of an era: The E90 M3 was fitted with the last naturally aspirated BMW M engine - and it was also the last BMW M to use a dedicated M engine developed from scratch. No more. Despite the attention that BMW's performance division dedicated to the new S55 engine, it is still derived from the ubiquitous N55 3.0-liter straight-six. Moreover, the next M3 and the M4 will be fitted with electric power steering. Is the world coming to an end?
Hardly. We just spent a day at BMW's driving dynamics center in Maisach near Munich, examining prototypes and discussing the car with M GmbH's top brass, including CEO Friedrich Nitschke and M GmbH's engineering chief Albert Biermann. There was no opportunity to get behind the wheel of the M3 or M4, but a "taxi drive" in a prototype with DTM pilot Bruno Spengler easily managed to whet our appetite.
What to expect
As part of BMW's renaming policy, the legendary M3 moniker will henceforth be reserved for the four-door variant; the two-door version, based on what is now called the 4-series, will come as the M4. Both the M3 and the M4 coupe will be launched at the Detroit auto show next January; later next year, there will be an M4 Cabriolet. Despite the industry-wide trend to revert to fabric tops on premium cars, the 4-series convertible gets a heavy and complex hard-top roof, tailored to "lantern parkers" - not least because this roof design can essentially be carried over from its predecessor.
The M3/M4 is brimming with dedicated parts - Albert Biermann says that the content of standalone components amounts to roughly 50 per cent. This includes body, chassis and powertrain components. BMW's goal was not only higher performance, but also less weight. The new model weighs about 175 lbs less than its predecessor and comes in at just below 3300 lbs (with a 90 per cent full tank of gas, but no driver). That's on par with an E46 M3. Somewhat surprisingly, the switch from the V-8 to the turbocharged i-6 contributes only about 20 lbs to the savings.
A veritable powerhouse
The i-6, internally called S55, is the heart of the new car; Norbert Siegl, who was responsible for the development of the all-aluminum powerhouse, maintains that it is essentially a new unit - even though he started out with the BMW AG's N55. The 3.0-liter inline-six will make slightly over 420 horsepower and "far beyond 369 lb-ft," BMW says. Our educated guess is that it will make around 390 lb-ft. The engine is boosted by two relatively small Mitsubishi turbochargers which provide up to 18.1 PSI. (BMW disingeniously sticks to the "Twin Power" designation, which signifies little. The same moniker is stuck to the single-turbo N55 engine.). There is an electromechanical wastegate and a large intercooler, which sits atop the engine - and which is the reason for the massive bulge on the M3/M4's aluminum hood.
The S55 redlines slightly beyond 7500 rpm; peak power is available from around 5000 rpm until 7300 rpm. Maximum torque is produced from under 2000 rpm to over 5000 rpm; there are no spikes in the torque and power curves, and the power rush is absolutely seamless. The S55 uses BMW's Valvetronic variable valve timing and Double-VANOS variable camshaft timing system; it comes with a closed-deck crankcase, LDS-coated cylinder walls and a forged crankshaft. The magnesium oil sump is extra-light, while double-flow recirculation pumps are designed to ensure lubrication of the engine and the turbochargers even on the racetrack.
In "Sport" and "Sport Plus" settings, the turbochargers are "pre-tensioned," which means that they keep spinning at a high rate of speed even after you have taken your foot off the throttle. This trick ensures ultra-quick response times fully comparable to those of a naturally aspirated engine. To bring engine revs down, cylinders are deactivated. The system doesn't work for extended time, but it operates under racetrack conditions and whenever the car senses quick bursts of acceleration and deceleration.
BMW will continue to offer both a six-speed manual and a "wet" seven-speed dual-clutch automatic. The ZF-supplied six-speed manual is 26.5 lbs lighter than the previously used box; the weight difference to the Getrag DCT is even more significant, and on top of that, the manual box doesn't need the oil cooler required by the automatic. But it isn't gimmick-free: Like a Nissan 370Z (whose balky transmission needs it), it automatically blips the throttle during downshifting. Forget about your mastery of heel-and-toe technique.
Thankfully, the straight-six sound in the M3/M4, familiar to E36 and E46 drivers, is all natural; no artificial sound actors (read: no Active Sound) are fitted.
Note about Active Sound: we asked and were told by one of the engineers that there was absolutely no artificial sound feature, but others have written today that the M3/M4 will use the speakers to amplify the sound. A request for clarification is in at BMW and we should have an answer by tomorrow morning.
The exhaust system operates in two stages, with the flaps located before the rear silencer. It can be bypassed as a function of load and engine speed. Engineers are still toying with approaches to alleviate the harshness of the switch; one possibility is sequential bypassing - first left, then right, or vice versa.
The engine's impressive power is channeled to the rear wheels through an innovative carbon-fiber propshaft, which is 40 per cent lighter than a conventional driveshaft, reacts more directly, but also costs BMW about twice as much. It is tested for velocities up to 205 mph: "We don't know what the tuners will do to this car," says an engineer. Getting up there will require extensive engine work: In series production trim, the M3/M4 would theoretically top out at around 185 mph. It will, however, be governed to 155 mph or 174 mph, depending on customer specification. No zero-to-sixty times are communicated, but the M3/M4 will significantly better the current M3. Fuel consumption is expected to drop by 25 per cent, which is very good news, considering the thirst of the outgoing V-8.
Handling the tarmac
For the first time, the rear differential is electronically controlled - and while the regular settings play it safe, M Dynamic mode is configured to allow wheelslip and "encourage drifting." There still is the safety net of the stability control system, but it can be switched off entirely.
The chassis has been massively tweaked to achieve superior stiffness and performance. The front suspension gets aluminum control arms, wheel carriers and subframes; there is a carbon-fiber strut brace up front. In the rear, there is a five-link axle with forged aluminum control arms; the rear subframe is bolted directly onto the body, a motorsports solution which is shared with the M5 and the M6. Forged aluminum wheels are standard; BMW offers both 18-inch and 19-inch versions, while the 20-inch wheels of the M4 Concept won't make it into series production. With either 18- and 19-inch wheels, the M3 and M4 will come with 255/35 ZR rubber up front and 275/35 ZR tires in the rear. The prototypes were fitted with Michelin Pilot Sport tires, but other tire brands will be certified as well.
Compound brakes with four pistons up front and two in the rear are standard; the optional carbon-ceramic brakes come with six pistons in the front and four pistons abaft. An adjustable, adaptive suspension is optional, but the regular suspension represents a "good compromise," according to chief engineer Albert Biermann.
BMW did not shy away from the dreaded move to electric power steering, but engineers solemnly declare they have outdone themselves to achieve a sensitive and direct feel. The EPS system of the regular 3 series was deemed insufficient, and M GmbH developed an entirely new electric power steering unit, which is built by ZF. Late in the development process, feedback from Nürburgring laps conducted by BMW's DTM racers led to subtle recalibrations. Three levels of assistance can be selected. We need to spend time behind the wheel ourselves, but the effort put in by M GmbH is a very positive indicator.
Why it looks like it does
The prototypes we drove were still covered with tape, and a few stylistic elements were concealed - such as the (obviously non-functional) rear diffuser. The real car will look very much like the
M4 Concept unveiled at the Pebble Beach Concours d'Elegance in August, although neither the 20-inch wheels nor the wild yellow paint will be offered to customers. Virtually everything else, however, will be on the production cars, including the wider body and those massive front air intakes which channel the air to the "track-ready" cooling system. It includes separate radiators for the turbochargers, the high-temperature and low-temperature water system, and the dual-clutch transmission.
On the M3 and M4, the front fenders and the front hood are made from aluminum instead of steel; the roof, now on both models, is made from carbon fiber. A sunroof is available, but it means a carbon roof delete. Functional "air breathers" and "air curtains" are included, and they feature more prominently than on the regular 4-series. The M4 gets a carbon fiber shield-molded trunk lid with an integrated rear spoiler that recalls the M3 CSL - and continues the distinct contour of the roof. The M3 keeps the trunk lid of the regular 3-series, but it is accentuated by a Gurney flap.
Both the M3 and the M4 retain the headlights of the regular 4-series. Xenon lights will be standard and LEDs optional, even though halogens would have brought the weight further down. But "we didn't want to cheat by offering a standard version that nobody wants," an engineer said. BMW is weighing another option: The M3/M4 could be fitted with a lithium-ion starter battery, such as offered as an option by Porsche, and standard equipment on the Mercedes-Benz S 63 AMG. There is no decision yet.
Today, BMW doesn't talk about the interior; we expect to see a relatively mild variation of the regular interior, a 200-mph speedometer, and the usual array of M-specific buttons around the gear shifter. The seats will be significantly lighter than those on a regular 3- and 4-series.
It will deliver
Could the M3 and M4 have become any lighter or more sporty? Only if the car moves towards a racing specification and by means of decontenting. As it is, it is probably the most extreme offering in a pack of competitors than includes the Audi RS5, the Mercedes-Benz C63 AMG, and soon the Cadillac ATS-V. We can't wait to get behind the wheel.
For the M3/M4's full specs, photos, and videos, see our
Tech Guide Thread.