BMW has added 60 horsepower to the twin turbo engine under the bonnet of the new M3 Saloon and M4 Coupe, now boasting 503bhp and capable of hitting 62mph in a scant 3.9 seconds.

The two newcomers, due for launch in March next year, continue a line of medium-sized and usable-every-day BMW models that made their debut 35 years ago with performance that lifted them well above their more mundane stablemates.

The latest in the line both have new 3.0 litre straight-six petrol engines, producing a massive 650Nm of torque, an electronically limited 155mph top speed and official fuel economy of 27.7mpg, with 234g/km of CO2 emissions.

The M3 Competition Saloon will cost £74,755 and the M4 Competition Coupe will be £76,055.

Both models use a specially tuned eight-speed M Steptronic transmission with Drivelogic. The M Steptronic transmission enables both fully automatic gear changes and manual shifts with sequential gear selection.

Fitted as standard along with the newly designed selector lever are carbon gearshift paddles on the steering wheel. With a simple tap of a paddle the driver can switch from automatic to manual mode.

The electronically controlled shock absorbers in the standard adaptive M suspension optimise road contact and traction in every situation with the use of electromagnetically controlled valves that act in just a few milliseconds to generate the required damping force.

Both models come as standard with parking assistant, cruise control with braking function and front collision warning with brake intervention, the lane departure warning system including lane return with steering assistance, the attentiveness assistant and the speed limit info system.

Also standard is driving assistant, which brings the lane change warning, rear crossing traffic warning and rear collision prevention into play. Customers can also add the driving assistant professional as part of the optional technology plus pack, which includes the steering and lane control assistant with new active navigation function. The new emergency lane Assistant, meanwhile, guides the car automatically to the most appropriate side of its lane in tailbacks on the motorway..

Also included in this package is the BMW drive recorder which uses the driver assistance systems' cameras to record video sequences outside the car of up to 40 seconds in length.

The BMW M3 Competition Saloon and new BMW M4 Competition Coupe add 122mm to the length of their predecessors and are 26mm and 17mm wider respectively.

Both models have a deep, frameless and all-black BMW kidney grille - likely to be the first thing a viewer of the newcomers will notice.