Coming this summer to a BMW dealer near you: the all-new 2015 BMW M4 convertible. BMW has selected the 2014 New York International Auto Show to debut the M3 sedan and M4 coupe’s new sibling—the M4 convertible. All three share the same three-liter inline six, developing 425 horsepower and 406 pound-feet of torque, mated to either a six-speed manual (yay!) or a seven-speed M DCT transmission.
At a glance:
Engine: BMW M TwinPower Turbo three-liter inline six
Transmission: Six-speed manual (standard); seven speed DCT (optional)
Power: 425 horsepower; 406 pound feet of torque
0–60 mph: 4.4 seconds (six-speed); 4.2 seconds (seven-speed DCT)
Tope speed: 155 mph (electronically limited)
Curb weight: 4,055 pounds
Hardtop retraction: 20 seconds
Availability: Summer 2014
The new inline-six M engine: High-revving, turbocharged unit combines the best of both worlds.
All the new 3 Series M cars are returning to an inline-six motor, harkening back to the days of the E36 and E46 M3s. This new six is turbocharged, however, and packs a lot more power. It revs higher than most turbo engines—up to 7,600 rpm—delivering power over a broader engine speed range. Fuel consumption figures are not yet available, but a fair assumption is that the convertible’s extra 500 pounds will cause it to burn a bit more fuel than the fixed-roofed versions.
The new inline turbo six’s 425 horsepower is more than the previous version’s V8. So is its torque, peaking at 406 pound-feet—over a 1,850–5,500 rpm band—which is about a 40 percent increase. All this takes the new M3 Convertible from zero to 60 mph in 4.4 seconds with the six-speed manual, and 4.2 seconds if you opt for the seven-speed M Double Clutch Transmission. The electronic top-speed limiter kicks in at 155 miles per hour.
The M TwinPower Turbo technology uses two fast-responding mono-scroll turbochargers, High Precision Direct 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 objective is smooth power delivery, sharp throttle response, and reduced fuel consumption and emissions.
The six-cylinder engine has a closed-deck crankcase design that is very rigid and allows for higher cylinder pressures that can lead to more power. And here’s an interesting bit of news. Instead of liners, the cylinder bores receive a twin-wire arc-sprayed coating, which turns out to be much lighter in weight than conventional liners. The forged, torsionally rigid crankshaft also saves weight while providing increased torque-carrying capacity. This reduces rotating mass which, as most performance seekers know, results in better throttle response and faster acceleration.
Innovative technologies delivering top-level performance.
The standard BMW M4 Convertible gearbox is a six-speed manual. Drivers who want slightly better acceleration and paddle shifters will opt for the seven-speed Double Clutch Transmission. The M DCT transmission basically combines two gearboxes, each with its own clutch. Gear changes are quicker and are executed with no interruption in the power flow. When not using the gear shift lever or paddle shifters, Drivelogic provides the driver a choice of comfort-oriented, economy-focused, or ultra-sporty automatic shift modes. The M DCT also has a Launch Control function.
The electromechanical steering system in recent BMWs has been somewhat controversial among drivers who want the most direct road feel. BMW M GmbH claims this system does offer a direct steering feel and precise feedback. The integrated Servotronic function electronically adjusts the level of steering assistance according to the car’s speed. Three steering settings (Comfort, Sport, and Sport+) can be selected at the touch of a button to adjust the desired level of steering assistance.
The optional Adaptive M suspension also has Comfort, Sport, and Sport+ modes. The standard M compound brakes are excellent, but even lighter and more effective M carbon ceramic brakes are optional, plus they have gold-painted calipers.
Lightweight design across the board: Shedding weight in all the right places.
BMW has incorporated their extensive experience in lightweight design into the M4 Convertible. The end result is a car that—at 4,055 pounds—is about 90 pounds lighter than its predecessor. This was achieved with aluminum front fenders and hood and lightweight aluminum construction in the chassis. BMW also made extensive use of a material to which it is committed for the material’s light weight, strength, and durability—carbon-fiber-reinforced plastic (CFRP). For example, the M4 Convertible has a CFRP drive shaft. The high rigidity and low weight of the CFRP tube mean that the drive shaft can be produced as a single-piece component without a center bearing, resulting an a 40 percent weight savings over the previous model. Less weight means less mass and in this case, less rotating mass that in turn results in better powertrain response.
The CFRP strut brace in the engine compartment is another example of how weight-saving measures can also improve driving dynamics. Weighing 3.3 pounds, the strut brace is more rigid and lighter than a comparable aluminum component and it also helps improve steering response and precision.
BMW is proving itself as a global leader in high-strength, lightweight CFRP construction. For proof, look no further than the first mass-production vehicle with a body consisting entirely of CFRP—the BMW i3.
Design: the powerfully expressive face of BMW M.
BMW has designed a distinct M persona into the front of its M cars that is so naturally aggressive and representative of a strong, purpose-built performance car that they have started introducing derivational M styling packages for many of its other vehicles series. And while the 5 Series or X5 looks good with an M Sport style line, the face of a real M car looks better. It’s the whole package. The traditional twin-headlight arrangement and kidney grilles look good, just like the rest of the 4 Series. From there, however, it gets mean with three seriously large air intakes and a hood bump that screams BMW M power. The intakes feed air to the brakes and engine while the power dome on the hood makes room for the M TwinPower Turbo engine’s intercooler. The exterior mirrors with their twin-stalk mounts are aerodynamic and fresh while still reminiscent of the mirrors on the classic E36 M3.
View from the side: low-slung silhouette and dynamic lines.
The profile of the M4 Convertible carries the dynamic impression created by the front end to the rest of the car. The traditional BMW proportions of a long hood, long wheelbase, set-back greenhouse, and short front overhang are enhanced by M design elements such as the newly designed M gills, which are stylistic and functional. Integrated into them are Air Breathers, which combine with the Air Curtains in the front apron to improve aerodynamics by moving the airflow around the wheel arches.
The interior design: ergonomics with a sporting ambience.
Traditional BMW M equipment details welcome the driver to the interior of the M4 Convertible: M door sill finishers; an M driver’s footrest; M gearshift lever; M-design circular instruments with white graphics; M leather steering wheel with chrome trim, color contrast stitching, and electroplated-look shift paddles (if the car has the optional M-DCT gearbox). Once inside, the driver-focused ergonomics are evident.
The front seats feature a full-size single-piece back panel. Seat construction is flat, with high, width-adjustable side bolsters and low-set seat surfaces that make for excellent support and a great seating position. Electric adjustment and heating, an illuminated BMW M logo on the backrest, and optional three-temperature neck warmers for comfortable open-air driving at high speeds and low temperatures remind owners that this is a luxury performance car.
Three-piece retractable hardtop. Form and function.
The BMW M4 Convertible follows the previous 3 Series M cars with the next generation of retractable hardtop. It works. With the top up, it almost wants to make you buy it just because it looks so good. With the top down, it’s the sun-on-your face convertible you wanted. The new BMW M4 Convertible’s hardtop features design improvements that reduce noise levels for a much quieter interior experience. The sound-absorbing headliner reduces wind noise by up to 2 dB in comparison to its predecessor model.
When the top is up, the luggage compartment has a volume of thirteen cubic feet—0.7 cubic feet more than was available in the BMW M3 Convertible. All trunk volumes are based on ECE measures. Bulky items can be transported by using the flat and level storage area available when the backrest of the rear seat is folded down. The standard load-through feature makes even more space available: Either a wide opening between the rear passenger compartment and the trunk, or a smaller opening, for skis for example, when four people are seated in the vehicle.
Transforming the M4 from a coupe into a convertible takes 20 seconds. The top can also be lowered when the vehicle is travelling at speeds of up to 11 mph.
The redesigned windblock is smaller, lighter, easier to use, easier to store behind the rear seat, and is standard equipment. The BMW M4 Convertible still has cargo space in the trunk, even when the retractable hardtop is lowered. It will be up to the owner to determine of 7.8 cubic feet is spacious enough. To help get to that space, an electro-hydraulic loading assistance system raises and positions the folded hardtop in the trunk as needed. This provides access to the trunk whether the top is up or down. When the hardtop is up, two storage compartments on the right and left of the main luggage area are accessible.
Optional equipment items provide comprehensive driver information.
This is a modern BMW, so you know it will be available with a wide range of driver assistance systems and mobility services, many of which have already been seen on the M3 and M4: The new generation Navigation System that offers extra capability, sharper graphics, and 3D elements for the map display; the Driving Assistant Plus that warns of imminent collisions with pedestrians or other vehicles; intelligent anti-dazzle LED High Beam Assistant; and Active Protection with Attention Assistant.
The BMW Head-Up Display is optional and on this car comes with additional, M-specific functions such as a gear display, rev counter, and Optimum Shift Indicator.
Hall of Fame: Open-top performance for over a quarter century
The new BMW M4 Convertible builds on 26 years of tradition. A 3 Series M Convertible has joined the two-door Coupe version in all four generations.
First generation: the racing car with the soft-top.
The launch of the first BMW M3—factory designation E30—in 1986 was needed to satisfy the homologation requirements for the German Touring Car Championship (DTM). In order to race it, BMW had one year to build 5,000 production road cars based on the competition car and offer them for sale to the public. The road-spec BMW M3 was created because the company had to and there were no plans for an open-top version—at first. But after about two years of pressure from the marketplace, BMW unveiled the new E30 M3 Convertible in 1988. Initially powered by four-cylinder motors cranking out 193 horsepower, BMW bumped that up to 215 horsepower in 1990, enabling a top speed of 148 mph and making it the world’s fastest four-seater series-produced convertible at the time. As was often the case then—and sometimes still today—the first generation BMW M3 Convertible was not offered for sale in the U.S.
Second generation: new advances in safety technology.
Unlike the E30 M3, BMW intended from the start to build a convertible version of the second generation M3 (E36). The M3 Coupe was introduced in 1992. The U.S. version of the E36 M3 was brought over in 1994 and that was also the year the world was introduced to the E36 M3 Convertible. It came with some significant safety improvements common on that generation of 3 Series. For example, the rollover bars of the standard rollover protection system—positioned behind the rear seat head restraints—would spring up instantly if onboard sensors indicated the car was close to turning over. Additionally, the car was built with an ultra-rigid windscreen frame to protect the occupants. The U.S. version of the second-generation M3 Convertible originally came with a 240-horsepower three-liter inline-six that was later bumped to 3.2-liters. The E36 M3 was also the first to be offered in a four-door version.
Third generation: shining an even brighter spotlight on the car’s sporting character.
Y2K saw the introduction of the BMW M3’s third generation. That round of the BMW 3 Series had the factory code E46. In spring 2001, M GmbH uncovered the latest M3 Convertible. It was identical to the M3 Coupe up to the A-pillar, but a striking beltline gave the open-top model an even broader, more powerful appearance. It seemed to present a more muscular, hunkered-down appearance than its ancestors. It was a heavier car, but it came with what it needed to handle it: a 333 horsepower high-revving naturally-aspirated M engine, artfully tuned M suspension, a variable M differential lock, and M high-performance brakes.
Fourth generation: giving the sporting character an even sharper edge.
Less than a year on from the debut of the fourth-generation BMW M3 Coupe (E92) and the four-door M3 Sedan (E90) that followed a little later, BMW launched the BMW M3 Convertible (E93) in spring 2008. A four-liter, eight-cylinder engine generating 414 horsepower gave the M3 Convertible’s drivers some impressive tools to satisfy their need for power, performance, and wind in their hair—or not. The E93 convertibles were the first 3 Series to have power retractable hard tops. They looked great and made for more comfort and less noise, but the car paid a penalty in additional weight. These were that last models for which the two-doors and four-doors shared the great M3 name together.
The new 2015 BMW M4 Convertible will arrive in US showrooms in summer 2014, in time for ideal top-down weather.
—Scott Blazey
