BMW 'reinvents the 3-series'

BMW is poised to completely reinvent the 3-series family for the low-carbon age.

Talking exclusively to Autocar, a senior BMW source revealed that a ground-up rethink of the company’s biggest-selling model will ensure that the next-generation 3-series will “remain relevant even when it goes off sale in 12 years’ time”.

The new 3-series is expected to make its public debut at the 2011 Paris motor show. In its first incarnation, the new model is expected to offer class-leading aerodynamics, with a Cd figure of 0.24, as well as pioneering the use of three-cylinder engines in premium vehicles.

Engine
The 2011 3-series should get the option of turbocharged three-cylinder petrol and diesel engines. In effect half of one of the new-generation six-cylinder units, a 1.5-litre, three-pot diesel should be good for 150bhp and 220lb ft of torque.

The petrol version should deliver 150bhp and 170lb ft but will be cheaper to build because it won’t need the emissions kit demanded of a Euro 6-compliant diesel engine.

These units should be less expensive to make than a four-pot, as well as offering unparalleled weight distribution, since they will sit virtually in the rear of the engine bay. The 2016 engines may have electric motors to spin the turbochargers up to operating speed.

Drag reduction
Insiders say BMW cannot — as a premium car maker — contemplate using ‘pure’ aerodynamic solutions for the car’s upper body. It wants enough flexibility to style the car and knows that faired-in wheels, for example, would not appeal to most buyers.

BMW engineers say about 40 per cent of overall air resistance comes from the proportions and shape of the vehicle. So it’s the remaining 60 per cent that it will concentrate on reducing.

Broken down, 30 per cent of drag is attributed to the wheels and wheel arches, 20 per cent to the underfloor shape and 10 per cent to the flow of the cooling air around the brakes and engine bay.

Air curtain
The big aerodynamic step forward for the 2011 3-series is the ‘Air Curtain’. This uses narrow, upright intakes in the lower bumper which channel air through the bumper and out of a slot inside the front of the wheel well.

As it exits the wheel well, this high-speed airflow runs across the face of the wheel, creating what is in effect a ‘curtain’ over the wheel face.

Smoothing the turbulent flow across this part of the car helps reduce the Cd of a 5-series from 0.28 to 0.27.

Running gear
BMW’s front-engined, rear-drive layout remains, but changes will be needed if the 3-series is to “remain relevant” for the 10 years it will be on sale.

To that end, provision has to be made for some kind of electric hybrid assist on the rear axle (which could be combined with the differential) and space needs to be found for the battery pack and electronic control units.

Engineers will also be challenged by the lightweight three-cylinder engines, which will demand very specific suspension settings.

Electrical architecture
The 2011 3-series will be fully integrated with the internet (the 5-series GT will be the first BMW to be launched with the system).
Although the move will open the way for the car to receive a huge amount of information (including from local traffic management systems), for the 2016 model the basic electrical architecture will be transformed to take into account new systems such as the low-energy lighting, electric engine ancillaries and various types of hybrid power assistance.

Climate control
The 2016 3-series could be the first BMW to be fitted with a new type of heating system. Current systems use twice the power needed to heat a 250m2 room, so the future version is expected to reclaim heat from the exhaust system.

A heat store is also possible. An insider said it will use far less power because the cabin will be “de-humidified”. Air-con, he said, overcools to prevent condensation from forming inside the car.

Eight-speed auto
BMW is betting on its new eight-speed automatic transmission being more widely adopted in the future. Rather than using dual-clutch automated manual gearboxes (which will be reserved for performance models), BMW thinks a super-efficient auto will be a hit with premium buyers.

It will sell 150,000 six-cylinder diesel autos this year. The current version is eight per cent more efficient than the previous six-speed auto. By 2011 this transmission will also have been fitted with automatic stop-start.