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M6 Cabrio - E64 (2006 - ...) - V10: Effortless Muscle

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Effortless Muscle
Formula 1 technology for the road.
The V10 power unit developed by BMW M GmbH is one of the most fascinating engines ever offered in a four-seater production convertible. And this is no surprise, considering that this supreme engine is based on BMW’s world-famous ten-cylinder Formula 1 power unit acknowledged as the most powerful engine in the highest category of motorsport until the change in rules and regulations in 2006. The V10 proudly boasted in the BMW M6 Convertible shares not only the number of cylinders and their configuration, but also the high-speed engine concept with this supreme F1 power unit. The result is enormous power and pulling force from high engine speeds, a quality characteristic of all highperformance naturally aspirated engines from BMW M GmbH. The facts and figures alone are more than impressive, ten cylinders, five litres engine capacity, 373 kW/507 hp, maximum torque of 520 Newton-metres or 383 lb-ft, and top engine speed of 8,250 rpm telling a clear story. As impressive as all this is on paper, the qualities of the engine are even more thrilling on the road: Just merely touching the gas pedal, the driver will enjoy all the qualities of a typical high-performance sports engine in the BMW M6 Convertible reminiscent even in its sound of the marque’s former Formula 1 power unit.


Formula 1 technology for the road.
BMW M has always regarded the high speed engine concept – more power from higher engine speeds – as the best and most appropriate strategy. And truly reflecting this philosophy, the V10 power unit reaches engine speeds formerly regarded as quite impossible in a production engine due to the enormous forces acting on the materials and components alone: At 8, 000 rpm, each of the ten pistons covers approximately 20 metres or 66 feet a second – almost twice as much as the pistons in a Formula 1 power unit. But while long-lasting driving qualities are a relative factor in motorsport, an M power unit will last the long life of a car built for many years of driving pleasure – in every climate, under all driving conditions, and with every style of motoring. The high-speed engine concept offers decisive benefits: First, output per litre of 101 horsepower generally experienced only in motorsport, with the engine’s maximum power of 507 hp or 373 kW coming from relatively small engine capacity of 4,999 cc. Second, the compact design and dimensions of the engine serve to reduce the overall weight of this high-performance power unit to just 240 kg or 529 lb. Contrary to similarly powerful engines based on a different concept, the M high-speed concept allows use of a lighter powertrain and shorter transmission ratios, reducing the weight and masses to be accelerated in the car. This again directly benefits the driving dynamics of the BMW M6 Convertible, particularly the car’s acceleration resulting from superior torque at high engine speeds and an appropriate overall transmission ratio. Outperforming other concepts, the fast-revving V10 power unit allows optimum gearbox and final drive transmission ratios, conveying impressive power and performance to the drive wheels at all times. Developing peak torque of 520 Newton-metres or 383 lb-ft at 6,100 rpm, the V10 guarantees supreme power at all times, especially as 450 Newtonmetres or 332 lb-ft comes from just 3,500 rpm and 80 per cent of the engine’s maximum torque is maintained consistently throughout a wide speed range of 5,500 rpm. As unusual as this is for a sports engine, the driver enjoys the full benefit at all times: The BMW M6 Convertible offers the very best in sporting performance and in relaxed cruising on a country road. Acceleration from 0–100 km/h, for example, comes in just 4.8 seconds and the BMW M6 Convertible completes the standing-start kilometre in 22.9 seconds. Acceleration from 80–120 km/h or 50–75 mph in fourth gear, in turn, takes just 4.7 seconds as yet further proof of the car’s supreme performance.

Ten cylinders – the ideal concept for sports motoring.
Looking at the engine’s dimensions and the number of components, ten cylinders are the optimum engine concept. A further advantage is that capacity of 500 cubic centimetres in each cylinder is ideal for a highly efficient combustion process, the M power unit combining two rows of five cylinders each in a 90° V-angle and with 17 millimetres or 0.67´´ cylinder bank displacement to form an extremely compact engine in ideal configuration. The 90° angle was chosen on account of its superior mass balance for minimum vibration and maximum comfort, offering the ideal combination of smoothness and component strength. With high engine speeds, combustion pressures and temperatures subjecting the crankcase to extreme loads, the engineers at BMW M have opted for an exceptionally compact and torsionally stiff bedplate structure. Conceived for superior stiffness and finely balanced, the crankshaft is made of forged, high-strength steel, runs in six bearings, and weighs just 21.8 kilos or 48.1 lb. The weight-optimised box pistons, in turn, are cast out of a high temperatureresistant aluminium alloy and come with special iron surface coating. Piston weight is just 481.7 grams including the piston pins and rings. And the weight of the trapezoidal conrods made of high-strength steel has also been optimised to the last gram. The single-piece aluminium cylinder heads boast four valves per cylinder, again typical of a BMW engine, and are operated by spherical cup tappets featuring hydraulic valve play compensation. Measuring 5 millimetres or 0.20´´ in diameter, the intake valves are particularly slender and therefore hardly impair flow conditions in the intake manifold. The crossflow cooling concept minimises any loss of pressure in the cooling system, maintains consistent temperature distribution in the cylinder head, and reduces peak temperatures at all critical points. To ensure an optimum flow of coolant around each cylinder, the coolant flows from the crankcase via the outlet side through the cylinder head and across the collector rail on the intake side to the thermostat and the radiator.


Reliable supply of oil even in extremely fast bends.
Clearly, the V10 power unit in the BMW M6 Convertible guarantees exceptional performance at all times. And since this also means truly outstanding straight-ahead and lateral acceleration, the lubricant in the engine is sometimes forced so hard into the outer row of cylinders in a bend that as a result there might even be a shortage of oil in the sump. Starting at lateral acceleration of approximately 0.6 g, therefore, oil is drawn from the outer cylinder head in a bend and pumped back to the main oil sump. Since extreme braking manoeuvres might also interrupt the reflow of oil, the quasi-dry sump lubrication system with one oil reservoir up front and one behind the front axle subframe provides the desired counter-effect, a reflow pump extracting oil from the front oil sump and pumping it to the rear sump wherever required.

Last Updated on Monday, 12 April 2010 14:37  

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