New BMW M6 - In Depth (Part I)

Press Release

The new V10 Power Unit in the BMW M6: A Masterpiece in Engine Construction

The ten-cylinder power unit featured in the BMW M6 may rightly be regarded as the most fascinating engine you can imagine in a production car. Launched just half a year ago in the BMW M5, this unique power unit has been thrilling enthusiasts all over the world ever since, offering a seemingly never-ending surge of power and performance. Many people see this engine as the “civilian derivative” of the BMW WilliamsF1 racing unit.

The V10 is reminiscent of BMW’s Formula1 racing engine also in terms of its sound: A bit deeper and more muscular than even in the M5, the V10 featured in the BMW M6 clearly “shouts out” its dedication to motorsport.

Inspired by the Formula1 power unit.

The V10 featured in the BMW M6 shares both the number of cylinders as well as its high-speed concept with BMW’s Formula1 power unit. This alone guarantees enormous thrust and muscle from high engine speeds, a feature characteristic of all high-performance normal-aspiration power units developed and built by BMW M GmbH.

Reflecting this exclusive standard, this top-of-the-range engine is equally impressive in all its specifications: ten cylinders, five liter capacity, 507 horsepower maximum output, 383 lb-ft maximum torque, engine speeds up to 8,250 rpm – a power pack in its purest form.

But at the same time this engine is far more than the sum total of outstanding performance data: Barely touching the gas pedal, you will immediately appreciate this high-speed normally-aspirated engine as a typical sports power unit. And at the same time it is perfectly civilized in everyday traffic: Sometimes a luxurious coupe, sometimes a thoroughbred sports car. The M6 offers you the best of both worlds, setting the benchmark in both categories.

Brand-new and offering the best of the best.

The V10 power unit created by the engineers at BMW M GmbH for the M5 and M6 is brand-new from the ground up. In the process of developing this engine, they were inspired by the BMW WilliamsF1 power unit, one of the most powerful engines in the highest category of motorsport. As their second consideration, they focused on M-specific features in standard production such as double-VANOS, individual throttle butterflies, top-performance engine electronics, and oil supply with centrifugal force control.

In principle there are three options to achieve optimum power and performance in engine construction: To make the engine larger, obtaining higher torque in the process, to boost engine output by means of a turbocharger or compressor, or to increase engine speed by means of the high-speed engine philosophy.

Power is more than just a number.

This means that on the road, power and performance is more than just an impressive horsepower rating. Rather, what really counts is a car’s behavior when accelerating and its driving dynamics. And this depends on the thrust and muscle actually generated by the drivetrain as well as the weight of the car. The thrust going to the drive wheels, in turn, is a result of engine torque and the overall transmission ratio. The high-speed engine concept, therefore, allows the right transmission and final drive ratios, guaranteeing impressive performance also in everyday motoring.

Given these basic laws of physics, we find huge differences between various engines, even when on paper they have the same output. A large-volume engine, for example, has the disadvantage of both extra weight and larger dimensions leading to higher fuel consumption. A turbocharged engine likewise consumes more fuel and lacks spontaneity that is the instantaneous response of the engine to the driver’s wishes.

The high-revving concept – the perfect answer.

This leaves the third option: the compact, fast-revving normal-aspiration power unit. For traditional reasons alone the engineers at BMW M acknowledge this concept as the ideal solution, increasing engine output and performance by an appropriate increase in engine speed. The fact remains, however, that the high-speed engine concept is far more demanding in technological terms, making it a greater challenge requiring more sophisticated solutions. Reaching engine speeds of 8,250 rpm, the V10 enters a speed range until recently reserved to thoroughbred racing cars alone.

Formula 1 technology for the road.

Featuring qualities of this kind, the new V10 raises the limits to technology in series engine production to a higher standard never seen before. A comparison clearly shows what this means in terms the loads and forces acting on the various materials: At a speed of 8,000 rpm, each of the 10 pistons covers a distance of some 20 meters a second. Revving at 18,000 rpm in the BMW WilliamsF1, piston travel is actually 25 meters per second. But while durability is merely a relative factor in motorsport, a BMW M engine must last the same long life as the car itself – in all kinds of weather, under all traffic conditions, and with that typical M style of motoring.

507 horsepower for a new world of driving dynamics

The fast-revving ten-cylinder develops maximum output of 507 horsepower at 7,750 rpm. But compared with its output and performance it remains a lightweight athlete weighing just 240 kg or 529 lb. When it comes to output per liter, on the other hand, this engine is definitely a “heavy” player. The ten-cylinder easily achieves the magical limit of 100 hp per liter, with specific output comparable to that of a racing machine.

Only engine speed can really bring out power and torque.

Maximum torque of 383 lb-ft comes at 6,100 rpm. But the ten-cylinder develops 332 lb-ft from just 3,500 rpm, with 80 per cent of the engine’s maximum torque offered consistently throughout a wide range of 5,500 rpm.

This alone places the BMW M6 with its high-speed engine far above the competition, with virtually all other models focusing on torque alone provided by larger engine capacity and/or turbocharging. A further drawback with other models is that they require a significantly reinforced and, as a result, very heavy drivetrain to convey their extremely high torque, thus suffering from extra weight and mass which consistently has to be accelerated and slowed down. By contrast, BMW’s compact V10 with its high-speed concept benefits from a far lighter drivetrain with a much faster gearshift.

A good example is that of a cyclist riding up a hill. Shifting down a gear, the cyclist will have to turn the pedals faster, but is able, in return, to take virtually every grade. Should the cyclist remain in the same gear or even shift up, on the other hand, the choices would be to either put more strength into the pedals or, quite simply, get off the bicycle. Taking two cyclists absolutely equal in their strength and stamina, the winner will always be the cyclist able to turn the pedals more quickly.

Ten cylinders – the sports concept.

Ten cylinders are the optimum concept for a high-performance sports engine: An engine of this kind has exactly the right dimensions, the right number of components and filling capacities. And displacing 500 cubic centimeters, each cylinder is of exactly the right size, as defined by the really demanding engine specialist.

Compact construction for extra strength and enhanced comfort.

As one of the world’s leading engine manufacturers, BMW has become famous above all for its in-line power units. Now, focusing on the ten-cylinder, the engineers at BMW M GmbH have placed two rows of five cylinders next to each other at a V angle of 90° and with displacement between the two cylinder banks of 17 millimeters or 0.67´´, thus forming a very compact and dynamic configuration. The 90° angle was chosen for its vibration-and comfort-oriented mass balance, perfectly solving the conflict of interests between maximum smoothness free of vibrations and a high level of component strength.

The cylinder crankcase is cast in a low-pressure die-casting process using an over-eutectic aluminum-silicon alloy, in this case with a share of silicon of at least 17 per cent. The cylinder liners are formed by exposing the hard silicon crystals, with the iron-coated pistons running directly in the uncoated bore. Cylinder stroke measures 75.2 millimeters or 2.96´´, cylinder bore is 92.0 millimeters or 3.62´´, adding up to an overall capacity of 4,999 cc. Like the engine blocks for Formula1, the M engine blocks are cast at BMW’s light-alloy foundry in Landshut just north of Munich.

Bedplate construction like in motorsport.

High engine speeds, high combustion pressure and temperatures subject the crankcase to extremely tough and demanding conditions. The engineers at BMW Motorsport have therefore made the crankcase very compact and unusually stiff in a so-called bedplate structure, a technology carried over from motorsport. The BMW ten-cylinder is the first production V engine to feature such a bedplate construction.

The aluminum bedplate with grey-cast-iron inlays guarantees very precise crankshaft bearing – in particular, it keeps main bearing tolerance within close limits throughout the entire range of operating temperature. The grey-cast-iron inlays reduce thermal expansion of the aluminum housing and feature special openings to provide a positive connection with the surrounding aluminum frame. At the same time this construction serves to fulfill the acoustic requirements made of the engine.

Specially designed for a high level of stiffness and finely balanced for optimum precision, the crankshaft made of forged, high-strength steel runs in six bearings and weighs just 21.8 kg or 48.1lb. Designed for minimum mass inertia, the crankshaft offers a very high standard of torsional stiffness. In each case two connecting rods interact with one of the five crank journals displaced from one another at an angle of 72°. The small distance between cylinders of just 98 millimeters or 3.86´´ and the short crankshaft made possible as a result interact with one another for a very high level of flexural and torsional stiffness on very low weight.

Lightweight engineering watching out for every gram.

The weight-optimized box-type pistons are cast out of a high temperature-resistant aluminum alloy and are iron-coated on the surface, weighing just 481.7 grams including their piston pins and rings. Compression height is 27.4 millimeters or 1.08´´, with a compression ratio of 12.0:1. The pistons are cooled by oil spray nozzles connected to the main oil duct. The trapezoidal connecting rods, in turn, measuring 140.7 millimeters or 5.54´´ in length, are weight-optimized, manufactured in cracked technology, and come in high-strength steel. This effectively reduces oscillating masses within the engine, each of the connecting rods forged from 70MnVS4 weighing just 623 grams including the bearing shell.

The single-piece aluminum cylinder heads on the V10 power unit are also cast by BMW at the light-alloy foundry in Landshut. As an important contribution to the appropriate temperature of the catalyst with the catalytic converter warming up quickly, the cylinder heads come with integrated air ducts for secondary air injection. A further feature is the typical configuration with four valves per cylinder characteristic of a BMW engine. The valves themselves are operated by ball-shaped cup tappets with hydraulic valve play compensation. Tappet diameter is just 28 millimeters or 1.10´´, tappet weight 31 grams. The intake valves, in turn, measure 35 millimeters or 1.38´´ in diameter, the outlet valves 30.5 millimeters or 1.20´´.

Special innovations reducing the cost of maintenance.

The intake valves are made exclusively for the V10. Measuring only 5.0 millimeters or 0.20´´ in diameter, they come with particularly thin shafts hardly impairing flow conditions in the intake duct. Valve clearance is automatically maintained at exactly the right point by hydraulic valve play compensation elements, helping to reduce the cost of ownership.

More power from the engine means a greater need for efficient cooling, particularly near the combustion chambers. With its crossflow cooling concept, the V10 power unit significantly reduces pressure losses in the cooling system compared with a conventional cooling configuration, guaranteeing a consistent distribution of temperatures in the cylinder head and reducing temperature peaks at all critical points.

Each cylinder is cooled consistently by an optimum amount of coolant flowing smoothly around the cylinders. To achieve this effect, the coolant flows from the crankcase via the outlet side of the engine through the cylinder head and over the collector rail on the intake side all the way to the thermostat and, respectively, the radiator itself.