BMW UK has announced details of the third M3 derivative, the new BMW M3 Convertible. The fourth generation of BMW's open-topped M3 becomes the first M car to feature a Retractable Hard-Top.

The launch of the new M3 Convertible also represents another first with the introduction of BMW's new seven-speed M Double Clutch Transmission (M DCT) as an option to the standard six-speed manual gearbox. Offering the highest levels of performance and driving dynamics with instantaneous gear shifts, the new BMW M3 Convertible offers a unique recipe for drivers who enjoy open-topped motoring accompanied by an eight-cylinder symphony.

Engine and Drivetrain

The first generation of M3 Convertible, launched in 1988, delivered 200hp from BMW's first 16-valve 2.3-litre four-cylinder engine. Subsequent generations of M3 engines have taken top category honours on a record six successive occasions in the Engine of the Year awards.

Wind the clock forward twenty years to the introduction of today's E93-generation M3 Convertible. The new M3 Convertible's engine develops more than twice the power of the original, delivering 420hp at 8,300rpm and 400Nm of torque at 3,900rpm from its 3,999cc V8-power unit. Like the previous three generations, the engine in the new M3 Convertible easily breaks through the magical 100hp per litre barrier, offering 105hp per litre. The new car also offers a 10 per cent improvement in the power-to-weight ratio when compared to its predecessor E46 M3 Convertible.

The V8 engine powers the car from zero to 62mph in 5.3 seconds and on to an electronically-limited top speed of 155mph. However, even with these supercar levels of performance, BMW's EfficientDynamics programme ensures that economy is not compromised with the car delivering 21.9mpg on the combined cycle.

In standard specification, power is transferred to the road by BMW M's six-speed manual gearbox and variable M differential. This conveys up to 100 per cent of available power to the wheel with most grip.

Purchasers of the new M3 Convertible, along with M3 Coupé and M3 Saloon buyers, can now also specify BMW's new seven-speed M DCT Double Clutch Transmission with Drivelogic. Changing gear using either paddles on the steering wheel or the gear lever, the new M DCT gearbox uses two oil-cooled wet clutches, one controlling gears 1, 3, 5 and 7 and the other controlling gears 2, 4 and 6. With gear changes made in only a few milliseconds and the next gear selected in readiness, the M DCT-equipped car outperforms the manual gearbox car in outright performance, economy and emissions. The zero to 62mph sprint is reduced by 0.2 seconds to 5.1 seconds while the combined consumption improves by 1.1mpg and the CO2 emissions decrease by 16g/km to 293g/km.

In common with the Sequential Manual Gearbox on the M5 and M6 models, the new M DCT gearbox also features Drivelogic to allow the driver the ability to fine tune the shift characteristics of the transmission. With six shift speeds available in the manual mode and five available when the gearbox is pre-selecting its own ratio, the driver can fine-tune the gear change. And to ensure that the gear changes are perfectly tuned to the engine output, the new M DCT gearbox employs eight LED shift lights, located in the rev counter, to warn the driver of the need to upshift.

Finally, to guarantee ease of use in around-town driving situations, the new M DCT gearbox uses a gradient detection system and Low Speed Assistant. These combine to ensure that the car won't roll back on hill-starts and that the engine's high levels of output don't corrupt the driving experience at slower speeds.

BMW EfficientDynamics

Power and performance head the wish-list for most M car buyers, but BMW's EfficientDynamics programme now also guarantees that efficiencies are optimised. Brake Energy Regeneration is featured as standard on all M3 derivatives, plus M5 Saloon and Touring, and M6 Coupé and Convertible. This standard-fit technology uses an Intelligent Alternator Control and Absorbent Glass Mat battery to recognise when the engine is on over-run. It activates the alternator to charge the battery with what would previously have been wasted energy.

A reduction in weight is another EfficientDynamics facet adopted on the new M3 Convertible, especially in the drivetrain. Using an engine block manufactured alongside the BMW Sauber F1 engines at BMW's light-alloy foundry at Landshut, Germany, the new V8 powerplant weighs a mere 202kgs; 15kgs less than the six-cylinder engine it replaces. To further highlight the weight advantages, the crankshaft in the new engine is made from one complete forging and weighs only 20kgs.

A bespoke driving experience

In common with the M3 Coupé, the new M3 Convertible features an MDrive button that brings together numerous personalised functions of the car. The settings for the optional Electronic Damper Control (Normal, Comfort and Sport), three DSC+ traction control settings and three specific engine control maps that govern throttle response can be controlled with one button on the steering wheel. As can the response rate of the Servotronic power steering. If the car is equipped with the new M DCT gearbox, the Drivelogic preference can also be saved. Once the desired settings are created in the iDrive menu, part of the standard Professional navigation system, one push of the MDrive button can transform the M3's driving experience.

Hard-top or open-top?

The new BMW M3 Convertible is the first M3 to feature an electro-hydraulic Retractable Hard-Top as standard. It's also the first M3 to feature BMW's innovative Sun Reflective leather technology, allowing the driver the opportunity to leave the roof down for prolonged periods without the seat leather overheating. The M3 Convertible combines the elegance of the 'standard' 3 Series Convertible with the athleticism of the M3 Coupé. A striking powerdome and two air intakes in the aluminium bonnet cover the new V8-engine and help engine cooling. Primarily, the design of the front of the car is defined by the significant volumes of air required for the induction system. As a result, three large air ducts in the front lower apron keep the engine breathing. The flared wheel arches house the standard 18-inch double-spoke light-alloy wheels, with a striking 19-inch wheel available as an option. Another BMW M trait, a side gill in the front wing, also includes the side direction indicator and the M3 logo. Aerodynamically-efficient door mirrors channel air flow and reduce drag, as does the rear diffuser, which houses BMW M's trademark twin double exhaust pipes.