DANG! That's a good looking car!
Powertrain of the BMW Z4 M Coupé:
Powerful Passion.
The BMW Z4 M Coupé is certainly the most sporting and dynamic rendition of BMW’s new two-seater. And this is no surprise, considering that the car is powered by what is arguably the most well-known high-performance power unit proudly bearing the letter “M” acknowledged as truly outstanding by connoisseurs everywhere – the 3.2-litre straight-six also featured in the BMW M3. Interacting perfectly with the light and extremely stiff bodyshell, the excellent suspension and short overall transmission ratio, this high-speed, high-output engine guarantees optimum performance, supreme dynamics, and truly outstanding agility. And at the same time the M high-speed engine develops all its power smoothly but dynamically like a turbine: No other production engine of this size offers the same irresistible thrust and momentum as the six-cylinder featured in the BMW Z4 M Coupé.
The M high-speed engine concept – already the winner of five engine “Oscars”.
The M high-speed engine concept generates enormous power and thrust from high engine speeds. Indeed, it does this job so perfectly that BMW’s 3.2-litre six-cylinder has received the “Engine of the Year Award” as the best power unit in its class no less than five times in a row, thus proudly bringing home the engine “Oscar” in the automotive industry.
The car’s performance figures clearly prove that the M Coupé boasts a true super-athlete within its long and sleek engine compartment: Displacing 3,246 cc, the six-cylinder develops maximum output of 252 kW/343 hp at 7,900 rpm and revs up to a top speed of 8,000 rpm. A particularly important point is that the engine develops this irresistible power and performance throughout a wide useful speed range, with no less than 80 per cent of its maximum torque coming at just 2,000 rpm and the peak level of
365 Newton-metres or 269 lb-ft following at 4,900 rpm.
With its output per litre of 77.6 kW or 106 hp, the 3.2-litre straight-six also enters new dimensions in this respect, with three-digit output figures per litre so far being restricted almost exclusively to purebred racing engines.
Shattering performance.
Each of the 343 horses in the BMW Z4 M Coupé is required to move only 4.1 kilos or 9.0 lb. Obviously, this means truly outstanding performance on the road, with the BMW Z4 M Coupé accelerating from a standstill to 100 km/h
in just 5.0 seconds and completing the sprint from 80–120 km/h in fourth gear in the same ultra-fast time of five seconds flat. Top speed, finally, is limited electronically to 250 km/h or 155 mph.
The high-speed power unit – the perfect principle for supreme dynamics.
There are several ways to achieve optimum power and performance in engine technology: The first – obvious – option is to increase engine power simply by making the engine larger. But this also means extra weight, larger and bulkier dimensions, as well as limited agility of the car. A second possibility is to choose a turbocharger or compressor, the disadvantage in this case being that a turbocharged or supercharged engine generally leaves a lot to be desired in terms of spontaneity – that is a rapid response of the engine to movements of the gas pedal – not to mention the relatively high fuel consumption of such an engine.
This leaves the third option – the concept of a compact, high-speed normal-aspiration power unit. And indeed, this has always been the ideal solution for every BMW M engine with its highly sporting character: to increase engine output by running at higher engine speeds.
This concept meets the greatest demands in terms of spontaneity, maximum performance and engine effectiveness, and at the same time optimises
the agility of the entire car. The fact nevertheless remains that the high-speed engine concept is more demanding in technological terms and therefore more challenging in practice – considering that the engine pistons run at a speed of more than 24 metres or 79 feet per second when revving at 8,000 rpm. By comparison, while the crankshaft in a Formula 1 power unit rotates up to 18,000 times a minute or even faster, piston speed of approximately 25 metres or 82 feet per second is only slightly higher than on a BMW M series production engine. And an essential point to be considered in this context is that an M engine is required to offer a long service life, whereas a Formula 1 power unit only has to last two racing weekends – very little compared with the reliability required of an M power unit throughout a long running life on the road.
Power – more than just high output.
What really counts in determining a car’s performance is the power and thrust that actually goes to the drive wheels. This crucial factor follows from the combination of engine torque and the overall transmission ratio, where again a high-speed engine concept goes together perfectly with an optimum transmission and final drive ratio for impressive thrust and performance on the road.
Crankcase made of high-strength perlite casting.
Being required to run at high speeds and under high combustion pressure, the crankcase of the engine featured in the BMW Z4 M Coupé is made of high-strength perlite casting. The graphite-coated cast aluminium pistons with their machined piston crowns are cooled by oil spray nozzles, the connecting rods are forged-steel pre-cracked units.
Cylinder head with roller-type followers.
The single-piece four-valve cylinder head is cast at BMW’s light-alloy foundry at the Landshut Plant in a steel die and features integrated air ducts for the injection of supplementary air required for quickly warming up the catalytic converter in the interest of optimum efficiency. Valve management, in turn,
is ensured by very precise roller-type rocker arms, with valve clearance having to be adjusted only on the occasion of a major inspection – which means service intervals, depending on driving conditions, of up to 40,000 kilometres or 25,000 miles.
Optimum engine management.
A specially developed engine control unit masterminds all functions within the high-performance engine featured in the BMW Z4 M Coupé.
This sophisticated system boasts a 32-bit micro-controller operating at high cycle frequency and two additional timing co-processors required to
handle the complex function data and, in particular, the high maximum rev speed of the engine. At the same time this sophisticated engine management also helps to improve emission control, offering an overall capacity of no less than 64 million instructions per second.
The unit controlling the camshaft adjustable infinitely on both the intake and outlet side (double-VANOS) is fully integrated into the overall system.
Further fully integrated features are the high-pressure oil supply, ongoing, permanent oil level control, an electronic immobiliser, electronic throttle butterfly management, as well as an elaborate diagnostic system for maintenance and service. The control unit calculates the ignition timing individually for each cylinder and operating stroke, the optimum injection volume, and the ideal injection point. The optimum cam spread is then calculated and set accordingly, synchronised to all other operating conditions.
High-pressure double-VANOS for an optimum charge cycle.
BMW’s variable double-VANOS camshaft management ensures an optimum gas cycle in the six-cylinder power unit, allowing extremely short adjustment times. In practice, this means more power, an even better torque curve, optimum engine response, greater fuel economy, and cleaner emissions.
Flow-optimised intake side.
Again reflecting racing technology, each cylinder comes with its own throttle butterfly. And to make sure the engine responds smoothly and sensitively at low speeds, while maintaining all of its spontaneity whenever the driver requires maximum power, the throttle butterflies are controlled fully electronically. This is done by scanning the position of the gas pedal and evaluating the data received no less than 200 times a second with the help of two potentiometers.
The engine management responds to any changes in running conditions and modifies the position of the throttle butterflies accordingly, taking only 120 milliseconds to open the butterflies to their maximum position. At the same time, electronic throttle butterfly control ensures perfect harmony in the transition from override to part load running conditions and vice versa.
Twin-chamber exhaust system.
The two fan-type manifolds on the exhaust system are designed for equal length and diameter, and serve to keep counter-pressure to a minimum.
The entire exhaust system extends in double-chamber arrangement through the silencers all the way to the four tailpipes so characteristic of a BMW M car.
A further essential point is that the BMW Z4 M Coupé develops the kind of sound you will expect from a car of this kind, especially with its four tailpipes at the rear: The exhaust system churns out that powerful and rough sound so typical of a genuine power unit from BMW M.
Each exhaust line comes with two tri-metal-coated, flow-optimised metal catalysts combining minimum pressure loss, a high level of mechanical strength and stiffness, as well as a short response time after starting the engine cold. The car’s exhaust emissions naturally fulfil the European EU4 standard, and the high overall level of engine efficiency guarantees not only supreme power and torque, but also superior fuel economy: Despite the car’s outstanding performance, fuel consumption in the EU test cycle is only 12.1 litres premium plus/100 km, equal to 23.3 mpg Imp.
Even more driving dynamics at the touch of a button.
Every time the driver starts the engine, the BMW Z4 M Coupé initially comes with a very smooth and finely adjustable setting on the gas pedal typical of a genuine sports car. Then, pressing the Sports button on the electronic butterfly control, the driver is able at any time to activate a more progressive control line for the ratio between gas pedal travel and throttle butterfly opening. This also switches over the dynamic transition functions on the electronic engine management for even greater spontaneity, the important benefit for the driver being that in this mode the BMW Z4 M Coupé responds even more spontaneously to his foot on the accelerator.
The pleasure of shifting gears six times over.
The high-speed engine concept offers particularly impressive and positive results whenever the engine is combined with an appropriate transmission. Indeed, this is the only way to convert the superior torque of the engine into optimum thrust and momentum by means of a short overall transmission ratio.
The six-speed manual gearbox meets all these requirements perfectly: Interacting with the final drive, the six-speed transmission ensures optimum performance throughout the engine’s entire gearshift and engine speed range. The typical features of this six-speed gearbox are short gearshift travel, precise shift lever control, close gear increments, and a high standard of running smoothness.
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