BMW has announced the introduction of the new 630i with the world’s lightest six-cylinder engine under the bonnet.

Powered by an all-new 3.0-litre straight-six engine featuring VALVETRONIC technology and made from magnesium and aluminium composite, the 630i goes on sale in September 2004.

Available in both Coupé and Convertible guises from launch, the 630i develops 258bhp at 6,600rpm, increased by 12 per cent compared to the current 3.0-litre petrol unit. Maximum torque is 300Nm (221lb/ft) and is available from 2,500rpm up to 4,000rpm with the redline starting at a 7,000rpm.

On the road this translates into a zero to 62mph time of 6.5 seconds (6.7 seconds for an automatic) in the Coupé and 6.9 seconds (7.2 seconds) in the Convertible. Top speed on all versions is limited to 155mph. Fuel consumption figures are 31.4mpg (29.7mpg) for the Coupé and 29.4mpg (28.5mpg) for the Convertible, and this represents a 12 per cent increase over the current 3.0-litre engine.

This EU4 compliant 3.0-litre engine, which features the world’s first electric water pump to keep the block cool for increased efficiency, will appear in future BMW models.

Full specification details are yet to be finalised, but expect the choice of either six-speed manual, automatic or BMW’s Sequential Manual Gearbox and the car will sit on 17-inch light alloy wheels fitted with 245/50 R17 tyres.

The 630i will also feature Dynamic Stability Control + Dynamic Traction Control, Dynamic Brake Control and ABS as standard among a host of other safety features. Meanwhile, the list of optional equipment will include Active Steering and Dynamic Drive.

Visually little distinguishes the 630i from the 645Ci. However, badging aside, the 630i’s chrome-plated exhaust pipes are round rather than oval, while the radiator grille slats have been de-chromed. Inside, there’s a full leather interior.

Prices for the 630i Coupé and Convertible will be announced at a later date.