Automotive Intelligence - the web for automotive professionals and car enthusiasts
July 11, 2007
Making its debut in the BMW M3: eight-cylinder power unit with 420 hp: The truly impressive "heart" of the new BMW M3 is the car's brand-new eight-cylinder power unit in V-arrangement combining outstanding power and performance with unique dynamism. Displacing 3,999 cc, the new V8 develops maximum output of 309 kW/420 hp. Maximum torque, in turn, is 400 Newton-metres or 295 lb-ft at an engine speed of 3,900 rpm. And perhaps an even more impressive fact is that some 85 per cent of this maximum torque is available consistently throughout the enormous speed range of 6,500 rpm.
The new BMW M3 accelerates from 0-100 km/h in 4.8 seconds and has a top speed limited electronically of 250 km/h or 155 mph.
The eight-cylinder power unit owes its perhaps most striking feature to the high-speed engine concept again typical of BMW M: Maximum engine speed of 8,400 rpm gives the engine supreme thrust and torque at all times. This power is transmitted to the rear wheels via a six-speed manual gearbox in conjunction with brand-new final drive featuring BMW's Variable M Limited-Slip Differential.
Over and above the engine's specific output of 105 hp per litre, average fuel consumption in the EU test cycle of just 12.4 litres/100 kilometres (equal to 22.8 mpg imp) bears clear testimony to the supreme engineering that has gone into this equally supreme car.
Know-how carried over from Formula 1 in production, construction, and the choice of materials: The engine block of the new eight-cylinder comes from BMW's light-alloy foundry in Landshut north of Munich, which also builds the engine blocks for the Grand Prix cars raced by the BMW Sauber F1 Team. The crankcase is made of a special aluminium-silicon alloy. It is both compact and extremely strong and torsionally resistant in its bedplate design.
Despite the two extra cylinders, the entire power unit is approximately 15 kg or 33 lb lighter than the six-cylinder engine featured on the former model.
The V8 power unit of the new BMW M3 is equipped with variable double-VANOS camshaft control, a unique technology reducing losses in the charge cycle and thus improving power and torque in the process. Responding extremely quickly to the driver's commands, double-VANOS improves the spontaneity of the engine at all times, thus also helping to reduce fuel consumption and exhaust emissions.
The engineers at BMW M have developed a low-pressure version of double-VANOS specifically for the new eight-cylinder, operating at the regular operating pressure of the engine's oil circuit.
A further feature of the new power unit is the use of eight individual throttle butterflies giving the engine a particularly smooth and sensitive response throughout the entire speed range and enabling the driver to call up the superior power of the engine directly and smoothly at all times. A volume flow-controlled pendulum-slide vane pump supplies the eight-cylinder with lubricating oil, the amount of oil delivered to the engine always being geared precisely to what the engine needs at the given point in time.
Wet sump lubrication optimised for driving dynamics, finally, ensures an adequate supply of oil to the power unit even in extreme braking manoeuvres and under high centrifugal forces in a fast bend.
New engine management and Brake Energy Regeneration: Yet another new development is the electronic management of the V8 power unit integrating the clutch, gearbox, steering and brake functions tailored specifically to the requirements of a BMW M Car. And then, as a further highlight of engine management, ion flow technology serves to detect any tendency of the engine to knock as well as misfiring and mis-combustion.
Intelligent energy management featuring Brake Energy Regeneration enhances the efficiency of the power unit to an even higher standard: This new system generates electricity for the car's on-board network only in overrun and while applying the brakes, with the alternator generally being disconnected as long as the engine is in traction, "pulling" the car.
Apart from particularly efficient generation of electric power, this process also helps to provide extra drive power when accelerating.
July 6, 2007