The new V10 engine in the BMW M5: A masterpiece in engine construction.
The heart of every BMW is its powerful engine. It is more than obvious that this particularly applies to the models made by BMW M GmbH.
This description alone, however, would not do justice to the new engine in the M5: modestly put, this ten-cylinder power unit is a milestone in modern
engine construction. It is one of the most fascinating engines the world over ever to be used in a series-production vehicle.
Some automobile aficionados also attach great importance to the sound of
the engine. This is also the case with the V10: this technological masterpiece is to the sports vehicle aficionado what a symphony is to the ears of music lovers. Similarities to the sound of the BMW WilliamsF1 racing engine won’t go unnoticed. The M5’s V10 engine not only has got the same number of cylinders as its Formula 1 counterpart. Both engines also have the high-revving concept in common, a principle which generates enormous forward thrust from high engine speeds and is a characteristic of all high-performance, naturally aspirated BMW M GmbH engines. All this, in conjunction with the ten cylinders, results in an orchestra-like staccato, something that is normally only heard on the race track.
First high-revving V10 engine to be featured in
a regular-production saloon.
The new M5’s high-revving V10, which has so far been reserved for racing cars and exotic low-volume cars, is the first engine of its kind to be used in a series-production saloon. In order to do justice to the exclusivity of the M family, this high-performance power unit offers a performance which is truly impressive: it has ten cylinders, displaces five litres and produces a
maximum output of 507 bhp and a maximum torque of 520 Newton metres. Engine speed peaks at 8,250 rpm – a road-going athlete par excellence.
But there is more to the engine than just impressive performance data.
At the slightest movement of the gas pedal, the high-revving normally aspirated engine reveals itself to be a typical sports engine. At the same time, it is perfectly suited for use in daily traffic. The M5 is a saloon for everyday use with the heart of an athlete – in other words, a roadworthy sports saloon. The M5 fully lives up to these two demands, opening up a new dimension of effortlessness. 20 years after the presentation of the first M5 marked the introduction of the segment of powerful sports saloons, this new engine once again points the way forward in this particular class.
Inspired by the Formula 1 engine.
The engine was redesigned from scratch by the BMW M GmbH engineers. When constructing the power unit, the engineers drew inspiration
from the BMW WilliamsF1 engine, which is generally regarded as the most powerful engine on the starting grid of the top echelon of motor sport.
On the other hand, they transferred all M specific features from series-production automobiles, such as bi-VANOS, individual throttle butterflies and the most powerful engine electronics system currently available, an in-house development, as well as a traverse force regulated oil supply system.
In order to create a worthy successor of the previous M5, which features a 400 bhp V8 engine, it was essential to do one thing: to increase performance even further. In engine construction there are three possibilities for boosting performance: increase the cubic capacity and raise maximum torque in the process, boost performance by using a turbocharger or a compressor or use a high-revving concept to increase torque.
Power is more than increased horsepower.
There is more to it than pure output. Acceleration behaviour and driving dynamics are further important aspects, which are greatly dependent on the actual forward thrust and the vehicle weight. The forward thrust at the
driven wheels is a result of both torque and the total ratio. The high-revving concept contributes greatly to an optimum transmission and rear-axle ratio, which, in turn, helps to unleash impressive drive forces.
When it comes to the laws of physics, the wheat is separated from the chaff, even if the engines under comparison are identical in output. If an engine’s cubic capacity is increased, one has to put up with – for the benefit of high performance and torque – the problem of additional weight, more space required and higher fuel consumption. Supercharged engines also have drawbacks. Only rarely do they excel due to fuel economy and their spontaneity, i.e. the engine’s ultra-fast response to the driver’s inputs, fails to meet the high demands made of an M overall concept.
High-revving concept is the perfect solution.
The third option, a compact, high-revving naturally aspirated engine,
is the perfect answer. If only for the sake of tradition, for the BMW M engineers the following solution was the ideal choice: boosting performance by increasing torque. In this context it must be said that, from a technological viewpoint, the high-revving concept is far more sophisticated, so that it is much more difficult to put this concept into practice. After all, it is no coincidence that BMW’s introduction of the new M5 has made them the first manufacturer worldwide to position a high-rpm V10 engine in the segment of powerful final production sports saloons.
Offering a maximum speed of 8,250 rpm, the ten-cylinder engine has ventured into terrain which has up to now been reserved for thoroughbred racing cars. By way of comparison: the previous M5’s engine speed is electronically limited to 7,000 rpm. The new ten-cylinder powerplant has broken the 8,000 rpm barrier.
Formula 1 technology takes to the roads.
With this new engine beneath the bonnet, the M5 redefines what is technologically feasible in the manufacture of series-production engines.
The higher the torque, the closer the engine gets to the physical limits.
The following comparison gives you an idea of the immense stress acting on the material: at 8,000 crankshaft revolutions per minute, each of the
ten pistons covers a distance of approximately 20 metres per second. Coming back to the ten-cylinder engine in the BMW WilliamsF1: at 18,000 rpm, the pistons move as much as 25 metres per second. The difference is, however, that a Formula 1 racing engine only has to travel 800 kilometres in one racing weekend, whilst the M engine must last the lifetime of the
vehicle, regardless of the climate, traffic situation and style of motoring.
It is evident that the M5 engine has various basic technological principles, production methods and materials in common with the Formula 1 engine and that it is based on technological transfer.
A 25 percent plus in performance – a new dimension
of driving dynamics.
The completely redesigned V10 engine, a high-revving ten-cylinder powerplant, is superior to its predecessor, which features 8 cylinders and the same cubic capacity, in all disciplines. Proof of this is provided by its performance which is up by more than 25 percent. The new V10 engine produces a maximum output of 507 bhp (373 kW) at 7,750 rpm (maximum output of the V8 is 400 bhp – 294 kW – at 6,600 rpm). Weighing in at just
240 kilograms, the new ten-cylinder engine is almost identical in weight with its eight-cylinder forebear. Given its awe-inspiring performance, the new ten-cylinder engine is a real lightweight. However, the engine is a heavyweight when it comes to its output per litre: the ten-cylinder M5 exceeds the magical mark of 100 bhp per litre of cubic capacity, its specific output being on par with that of racing cars.
Engine speed has a major influence on performance and torque.
As far as maximum torque (520 Newton metres) is concerned, the ten-cylinder matches the eight-cylinder power unit. Nevertheless, the new M5 beats its predecessor in all disciplines relating to driving dynamics. This phenomenon is also connected to the engine speed. A case in point: if a cyclist changes down when going uphill, he must pedal faster but he will master almost every gradient no matter how steep. If he does not change gears or if he even changes up, he needs a lot more energy or he has to get off the bike.
If there are two cyclists with the same amount of stamina, it is always the cyclist who pedals faster that wins the race.
The logical consequence is that the new M5 with its high-revving engine also effortlessly outdoes all direct competitors who exclusively rely on the
“torque concept” of an eight-cylinder engine with an increased cubic capacity. In addition, this engine’s superiority can be put down to the fact that the concept-related extremely high torque of competing engines has to be transferred via a massively reinforced and heavy drive train – added weight and mass that must also be accelerated. Thanks to the V10’s high-revving concept, a considerably lighter drive train can be used and closer gear ratios can be achieved.
By the way, the new M5 also outdoes its competition when it comes to
torque: peak torque of 520 Newton metres is reached at 6,100 rpm, a torque of 450 Newton metres is already obtained at 3,500 rpm. And 80 percent of maximum torque is available at up to 5,500 rpm, which is a wide speed range for an engine of this calibre.
Ten cylinders – the sports engine concept.
Its dimensions, number of components and filling quantities make the ten-cylinder engine the perfect choice for a high-performance sports powerplant. The new V10 therefore represents the perfect solution for a car such as the M5. In addition, the ten cylinders with a displacement of 500 cc each, fully live up to the ideals of the most discerning engineers.
Compact design for increased robustness and comfort.
BMW, one of the leaders in engine construction, has made a name for itself primarily as a manufacturer of inline engines. When constructing the new ten-cylinder engine, the engineers arranged the two five-cylinder banks at an angle of 90° (V-configuration) with a 17 mm offset to create a compact aggregate. The 90° angle has been chosen due to its low-vibration and comfort-oriented mass balancing properties. In its geometry the engine solves the conflict between minimum vibrations and maximum component robustness.
The cylinder crankcases are cast utilising the low-pressure gravity die casting method and are made of hypereutectic aluminium-silicon alloy. This special alloy contains at least 17 percent silicon. The cylinder liners are created by precipitation of the hard silicon crystals. Additional liners are not necessary – the iron-coated pistons run up and down in the uncoated bores. Stroke is 75.2 mm, bore is 92 mm, overall cubic capacity amounts to 4,999 cc.
By the way, the blocks for the M5 engines are cast at the same place as the Formula 1 engines: at the BMW light alloy foundry in Landshut.
Bedplate derived from racing technology.
High engine speeds, high combustion pressures and high temperatures put an enormous strain on the crankcase. Therefore the engineers have chosen the so-called bedplate design, a compact and extremely stiff configuration which is derived from car racing. The new engine in the BMW M5 is the first series-production V engine to feature such a bedplate design. The aluminium bedplate with integral grey-cast iron inserts ensures high-precision crankshaft alignment, keeping the main bearing clearance over the entire operating temperature range at a minimum. The grey-cast iron inserts help to reduce the thermal expansion of the aluminium casing. To ensure positive coupling with the adjoining aluminium frame, the inserts have been provided with openings. At the same time, this architecture contributes to fulfilling the demands made of the M5’s engine acoustics.
The extremely stiff and finely balanced crankshaft made of forged, high-
tensile steel is supported by six bearings and weighs a mere 21.8 kilograms.
It balances inertia forces and is designed for maximum torsional stiffness.
The main bearing diameter measures 60 mm at a bearing width of 28.2 mm. Two conrods connect to each of the five crank pins, which are offset at an angle of 72 degrees. A reduced cylinder spacing of only 98 mm enables the use of a short crankshaft, thus resulting in high flexural strength and torsional stiffness, as well as a very low weight.
Every gram counts in lightweight construction.
The weight-optimised pistons are made of high temperature resistant aluminium alloy and are provided with an iron coating. They weigh a mere
481.7 grams, including piston pins and rings. The compression height is 27.4 mm at a compression ratio of 12.0:1. The pistons are cooled using oil spray jets which are directly connected to the main oil duct. The 140.7 millimetres long, weight-optimised, fracture-split trapezoidal connecting rods are also made of high-strength steel and effectively reduce the oscillating masses. Each of the connecting rods forged from 70MnVS4 has a weight of only 623 grams, including the bearing shells.
The single-piece aluminium cylinder heads of the V10 engine are also produced at the BMW light alloy foundry in Landshut. The cylinder heads feature integrated air ducts for air injection which is important for rapid catalytic converter warm-up. The cylinder heads incorporate four valves per cylinder, a BMW specific engine architecture. The valves are actuated by spherical tappets featuring hydraulic valve play compensation. The tappet diameter has been reduced to 28 millimetres and its weight is down to 31 grams.
Through optimisation of all parts and components of the valve train, the moving mass has been reduced by 17.5 percent in comparison with
the predecessor model. The diameter of the intake valve is 35 millimetres,
the exhaust valve measures 30.5 millimetres in diameter.
Innovations with attention to the smallest detail reduce
The intake valves are exclusively manufactured for the M5 engine.
With a reduced shaft measuring only 5 mm in diameter, there is hardly any impedance of the flow in the intake tract. Hydraulic valve play compensation units automatically provide for the optimum valve adjustment at all times, which is beneficial to the customer as it lowers maintenance costs.
The higher the engine output, the higher the need for cooling the engine, particularly in the vicinity of the combustion chamber. Compared to conventional systems, the cross flow cooling concept of the M5 engine considerably minimises pressure losses in the cooling system. It ensures
an even temperature distribution in the cylinder head and the reduction of peak temperatures in critical areas of the cylinder head. Every single
cylinder is evenly supplied with the optimum amount of coolant which flows from the crankcase at the outlet side through the cylinder head
and via the manifold strip at the intake side to the thermostat or cooler.
High-pressure bi-VANOS for an optimum charge cycle.
The bi-VANOS variable camshaft control, which celebrated its world
premiere in the M3 back in 1995 and has been further optimised for use in the current M3 model, is also featured in the new M5 engine. It ensures an optimum charge cycle, thus helping to achieve extremely short adjustment times. This means in practice: increased performance, an improved torque curve, optimum responsiveness, lower consumption and fewer emissions.
For example, at the lower end of the load and engine-speed scale the car can be driven with an increased valve overlap, boosting internal exhaust gas recirculation. This, in turn, leads to a reduction in charge cycle losses and fuel consumption.
The adjustment of the angles as a function of the accelerator pedal position and the engine speed is infinite and map-controlled. For this purpose, the sprocket, which connects to the crankshaft via a simplex chain, is linked to the camshaft via a two-speed, helical gearbox. In the event of an axial displacement of the adjusting piston, the helical set of teeth turns the cam relative to the sprocket, which allows for the variation of the angle of the intake camshaft by up to 66° and that of the outlet camshaft by a maximum of 37° in relation to the crankshaft.
The M bi-VANOS technology requires very high oil pressures for ultra-precise, high-speed camshaft adjustment. This is why a radial piston pump in the crank chamber increases engine oil pressure to an operating pressure of 80 bar.
The map-controlled high-pressure adjustment ensures reduced adjustment times, allowing for the optimum angle, precisely the right ignition point and injection quantity under all conditions and in accordance with load and engine speed.
Constant lubrication even in hard cornering situations.
Four oil pumps provide the engine with lubricating oil. The reason behind this unusually elaborate oil supply system is the M5’s exceptional driving dynamics with extreme acceleration rates. The sports saloon has a cornering capability of over 1 g. During extreme cornering centrifugal forces force the engine oil to the cylinder bank facing the outside of the bend, thereby preventing the natural return of oil from the cylinder head, which might lead to inadequate oil supply in the oil sump. Should the worst come to the worst, the oil pump sucks air. In order to reliably prevent this situation, the engine features a traverse force regulated oil supply system. This system incorporates two electrically-operated duo-centric pumps which pick up oil from the outer cylinder head and transport it to the main oil sump if lateral acceleration rates exceed 0.6 g. A lateral-g sensor transmits signals to the pumps. The oil pump itself is a continuously variable pump with volume control which delivers exactly the amount of engine oil needed by the engine. This is achieved by the variable eccentricity of the pump’s rotor in relation to the pump casing, depending on the oil pressure in the main oil duct.
Proper oil circulation in all conditions.
In extreme braking manoeuvres the M5 might even reach negative acceleration rates of up to 1.3 g. If deceleration rates are that high, it might well be that the amount of oil flowing back to the oil sump, which functions as an intermediate buffer, is not sufficient, particularly since the oil sump is located behind the front-axle support in order to save space. The worst-case scenario is that lubrication is interrupted. In order to prevent this situation, the M5 engine has been fitted with a so-called “quasi-dry sump oil system” which incorporates two oil sumps: a smaller one in front of the crossmember and a bigger one behind. A recirculating pump has been integrated into the housing of the oil pressure pump, which picks up oil from the small front oil sump to convey it to the big rear oil sump, which has been carefully shielded. The return passages and the pickup point of the oil pressure pump are perfectly tuned to ensure proper oil circulation in all conditions.
Ten individual throttle valves are electronically actuated.
Each of the ten cylinders has its own throttle valve, each cylinder bank, in turn, is served by its own actuator, a concept we are familiar with from motor sport. Although this system is very complex from a mechanical viewpoint, there is no better way to achieve spontaneous engine response. In order to attain maximum engine responsiveness in the lower speed range, and to achieve an immediate vehicle response at the high end of the performance spectrum, all throttle valves are controlled fully electronically. Two contactless Hall potentiometers determine and evaluate the position of the accelerator pedal 200 times per second. The engine management reacts to changes and causes the two actuators to adjust the ten throttle valves. It goes without saying that this process is performed at a lightning-fast speed: it takes just 120 milliseconds to completely open the throttle valves, this is about the time an experienced driver needs to fully depress the accelerator pedal.
This gives the driver a feeling of instantaneous response and allows him to “dose” the gas pedal even more precisely. At the same time, the electronic throttle valve actuation keeps transitions from overrun to part load and vice versa smooth and harmonious.
The V10 engine uses ten flow-optimised intake trumpets to “breathe in”
air from two intake plenums. The intake plenums and the trumpets are made of a lightweight compound material that contains 30 percent fibreglass.
Dual exhaust system made of stainless steel.
Although the intake system contributes considerably to the remarkable performance of the new M5 engine, the importance of the exhaust system must not be underestimated. Also with respect to the exhaust system,
only the best was good enough for the BMW M engineers. The two stainless steel 5-in-1 high-performance tubular headers have been optimised for equal length by using complicated calculating methods. For exact pipe diameters, the seamless stainless steel pipes are formed from the inside using an interior high-pressure forming technique (hydroforming) with a pressure of up to 800 bar. The manifold pipes have a wall thickness of just about 0.8 mm, which is also a sign of the M engineers’ incredible attention to detail when designing this masterpiece in engine construction.
Even a sports engine can be a paragon of cleanliness.
When designing the exhaust system, the engineers considered it most important to keep the counterpressure to a minimum and to optimise the gas-dynamic design for impeccable performance and torque behaviour.
The exhaust system has a dual-flow design all the way to the silencers.
The exhaust gases finally leave the system through four tailpipes which are what make the rear end of the M vehicles so unmistakable.
As you would expect from a BMW M automobile, two trimetal-coated catalytic converters per exhaust line clean the exhaust gases produced by the ten-cylinder engine in compliance with the demanding European EU4 standard and the American LEV 2 standard. There are two underfloor catalysts. The other two catalytic converters (one for each exhaust line) are located close to the engine.
In conjunction with the thin-walled exhaust manifolds, these catalysts quickly reach their optimum operating temperature, which means that they are fully operational quickly after a cold start. They excel due to their low pressure losses and high mechanical strength.
The engine control module: the first of its kind in the world.
The MS S65 engine management system is the central factor behind the V10’s outstanding performance and emission data. It enables the optimum coordination of all engine functions with the different vehicle control units, especially with that of the SMG. This innovative control unit is a world-first in a regular-production car: with more than 1,000 individual components, this engine management system is unparalleled in its package density. By the way, hardware, software and functioning are BMW M in-house developments.
High engine speeds call for high-level performance.
Due to the M5 engine’s high speeds and the large number of control and regulating tasks, the demands placed on the MS S65 control unit’s performance are extremely high. In order to meet these demands, the engine control module has been equipped with three 32-bit processors that perform more than 200 million individual calculations per second. Compared to the M3 control unit presented only four years ago, this represents a performance increase by factor eight. In terms of memory capacity, the latest control unit outdoes the previous one by as much as factor ten. Receiving more than 50 input signals, this system calculates for each individual cylinder and for each individual cycle the optimum ignition point, the ideal cylinder charge, the injection quantity and the injection point. At the same time this system calculates and makes the necessary adjustments for the optimum camshaft angle and the optimum position of the ten individual throttle butterflies.
By pressing the power button on the selector lever cover, the driver can activate a sportier program with full performance characteristics. The activation of this program results in a more progressive response of the throttle butterfly to the accelerator pedal with the dynamic transient functions of the electronic engine management system switching over to a more instantaneous response. In the M5, the more comfortable of the two settings is automatically applied as soon as the engine is restarted. The change-over can also be pre-configured and called up in MDrive. In MDrive, there is a further, very sporty program available.
Comprehensive ancillary tasks for the engine management system.
The electronic throttle valve control is based on a so-called power and torque structure which uses a potentiometer on the accelerator pedal to measure the driver’s wish for power and performance and converts this to the desired function. The power and torque manager adjusts this request function by adding the power signals from the auxiliary engine units, such as the conditioning compressor or the generator. Functions such as idle-speed control, emission control and knock control are also coordinated and aligned to the maximum and minimum output and torque curves permitted by the Dynamic Stability Control (DSC) and the Engine Drag Force Control (EDFC).
The target output and torque calculated in this way is then maintained at the desired level, while taking into account the current ignition angle. In addition, the engine management system carries out comprehensive tasks for onboard diagnosis with various diagnosis routines to be used by the workshops as well as other functions, and the control of peripheral aggregates.
Highlight in engine management: ionic current technology.
The ionic current technology featured by the engine management unit is
a technological highlight which serves to detect engine knock, misfiring and combustion misses. The uncontrolled ignition of the fuel in the cylinder is called engine knock. In order to prevent engine knock, engines without knock control generally feature a lower compression ratio. Furthermore, the ignition point is retarded to prevent the cylinders from reaching or even exceeding the knock limit, which might cause damage to the engine. The “safety distance” to the knock limit resulting from this measure always has an adverse effect on fuel economy, engine output and torque. Active knock control, however, is an efficiency-boosting measure as it ensures optimum ignition timing and protects the engine from damages at the points of operation that are prone to knock.
Conventional systems employ several detectors on the outside of the cylinder to send knock signals to the knock control. In BMW M vehicles, one sensor monitors two cylinders. As the BMW M ten-cylinder engine is based on a multi-cylinder and high-revving concept, the use of those detectors alone is not sufficient in order to reliably detect engine knock. Due to the high engine speeds, evaluation must be very precise for optimum combustion quality in the cylinders, a factor which strongly influences the components’ durability as well as the emission behaviour. This is where ionic current measurement comes into play.
The spark plug takes on additional control functions.
This technology utilises the spark plug in each cylinder to sense and control engine knock. It also helps to check for correct ignition and to identify possible ignition misses. Thus the spark plug has a dual function – as an actuator for the ignition and as a sensor for monitoring the combustion process. Here again, the difference to conventional knock and ignition sensors becomes evident: they are located outside the combustion chamber, whilst the ionic current measuring is done inside the combustion chamber as spark plug and sensor are combined into one.
Measurement in the heart of the combustion chamber.
Temperatures in a spark-ignition internal combustion engine’s combustion chamber can reach up to 2,500 degrees. These high temperatures and
the chemical reactions produced during combustion activity lead to a partial ionisation of the fuel-air mixture in the combustion chamber. Particularly in the flame front, the gas becomes conductive through the generation of ions by means of separation or accumulation of electrons (ionisation). The spark plug electrode, which is electrically isolated from the cylinder head and linked to a small control unit operating independently from the engine management system, the so-called ionic current satellite, is supplied with a DC voltage and measures the so-called ionic current between the electrodes, the measured value depending on the degree of ionisation of the gas flowing between the electrodes. The ionic current measurement technique retrieves information on the combustion process directly from where things are happening, the combustion chamber. The ionic current satellite receives signals from the five spark plugs assigned to each cylinder bank, amplifies them and sends the data to the engine management system for analysis, which then makes the necessary interventions (for each cylinder separately). For example,
cylinder engine knock and the ignition point are adjusted for each single cylinder in order to optimise the combustion process.
The spark plug, which is both an ignition source and a sensor,
facilitates diagnosis when performing service and maintenance.