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M3 Sedan - E90 (2007 - ...) - The V8 Power Unit

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The BMW M3 featuring an eight-cylinder power unit for the first time.
After 15 years the straight-six power unit in the two preceding model generations of the BMW M3 lauded several times as the Engine of the Year, has now given way to an even more superior successor, the two model variants of the new BMW M3 featuring an eight-cylinder for the first time. Through its specifications alone, this brand-new high-performance power unit offers clear proof of the outstanding skills of the engine specialists at BMW M GmbH gained also in motorsport. Displacing 3,999 cc, the new V8 develops maximum output of 309 kW/420 hp and peak torque of 400 Newton-metres/295 lb-ft at an engine speed of 3,900 rpm. Perhaps an even more impressive point is that some 85 per cent of this maximum torque is available consistently all the way throughout the huge speed range of 6,500 rpm. The most striking highlight of the eight-cylinder is certainly the high-speed engine concept again so typical of BMW M: With the engine revving up all the way to 8,400 rpm, it obviously offers immense power and torque at all speeds. This power is fed to the rear wheels by a six-speed manual gearbox as well as brand-new final drive, a combination offering a standard of acceleration quite comparable in its spontaneity and endurance to the dynamic potential of a fully-fledged racing car. Apart from specific output of 105 hp per litre, average fuel consumption determined in the EU test cycle of just 12.4 litres/100 km, equal to 22.8 mpg imp, clearly expresses the supreme engineering skills of the engine development specialists at BMW M GmbH. Indeed, this kind of economy confirms the remarkable efficiency of the new BMW M3 Saloon in the world of high-performance sports cars, particularly when also considering the space available in the car. The V8 power unit featured in the new BMW M3 is a genuine lightweight weighing only 202 kg or 445 lb. In fact, it is even some 15 kg or 33 lb lighter than the six-cylinder in the former model.

Production of components with know-how from Formula 1.
The engine block of the new eight-cylinder comes from BMW’s light-alloy foundry in Landshut, which also makes the engine block for the BMW Sauber F1 racing cars. The crankcase is made of a special aluminium-silicon alloy, eliminating the need for conventional cylinder liners. Instead, the appropriate cylinder surface is provided by releasing and exposing the hard silicon crystals, the iron-coated pistons running directly in the honed cylinder bores without any additional surface coating.
High engine speeds and high combustion pressure obviously cause extreme loads acting on the crankcase, which is therefore particularly compact and torsionally rigid in its bedplate design, ensuring very precise and smooth balance of the crankshaft. A further point is that the forged crankshaft is very stiff and highly resistant to both flexural and torsional forces, but nevertheless weighs only about 20 kg or 44 lb.


Valve management by double- VANOS operating at low oil pressure.
The V8 power unit within the engine compartment of the new BMW M3 Saloon boasts BMW’s variable double-VANOS camshaft management. Offering extremely fast and responsive valve timing, this technology reduces charge cycle losses and improves the output, torque and response of the engine in the process, with a positive influence also on fuel economy and emission management. Focusing especially on the new eight-cylinder, the engineers at BMW M GmbH have indeed developed a low-pressure version of double-VANOS ensuring extremely quick valve timing even under normal engine oil pressure. A separate throttle butterfly for each cylinder is a feature quite unique not only with racing engines when it comes to achieving highly spontaneous and direct performance with immediate reaction to the gas pedal at all times. The new power unit features eight individual throttle butterflies, one on each cylinder. In each case two step motors operate the four throttle butterflies on each row of cylinders, giving the engine a particularly sensitive response at low speeds together with an immediate reaction whenever the driver presses down the accelerator for extra power and performance. A volume flow-controlled pendulum slide cell pump supplies the eight cylinders with lubricating oil, delivering exactly the quantity required by the engine. Wet sump oil lubrication optimised for dynamic performance, in turn, ensures a consistent lubricating process also in extreme braking manoeuvres, the system as such featuring two oil sumps: a small oil sump in front of the front axle subframe and a large oil sump further back. A separate duocentric reflow pump, finally, extracts oil from the front oil sump and pumps it to the oil sump further back.

New engine management and Brake Energy Regeneration.
The electronic management of the V8 power unit coordinating all engine functions with optimum efficiency is likewise a new, even more sophisticated development. This electronic “brain” also supports the M-specific functions of the clutch, the gearbox, the steering and brakes, and last but not least the engine control unit performs a wide range of on-board diagnosis functions and masterminds the ancillary engine units.
A particular highlight in engine management is the use of ion current technology serving to determine engine knocking as well as misfiring and miscombustion in the cylinders. Contrary to conventional methods, this monitoring and control function is performed precisely where the phenomena involved may occur, that is within the combustion chambers. To do this the spark plug in each cylinder senses and controls the risk of knocking, at the same time monitoring the correct ignition and recognising any misfiring. In other words, the spark plug acts as an actuator for the ignition and as a sensor monitoring the combustion process, and is therefore able to distinguish between misfiring and miscombustion. This dual function of the spark plugs obviously facilitates the diagnostic procedures required in service and maintenance. Intelligent energy management with Brake Energy Regeneration enhances the efficiency of the V8 power unit in the new M3 Saloon to an even higher level, concentrating the generation of electric power for the on-board network on periods of overrun and application of the brakes. This serves to charge the car’s battery without directly using the energy contained in the fuel. As long as the engine is pulling the car, on the other hand, the generator is usually disengaged. Which means that apart from the particularly efficient generation of electric power, the driver also benefits from even more engine power when accelerating.


Last Updated on Monday, 12 April 2010 14:37  

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