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 optimized 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 degrees 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 "semi-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 motorsports. 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-optimized 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 optimized for equal length by using complicated calculating methods. For exact pipe diameters, the seamless stainless steel pipes are formed from the inside using the so-called interior high-pressure forming technique 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 a button, the driver can activate two sportier control maps for the throttle system, which offer an even more progressive response of the throttle butterflies to the actuation of the accelerator pedal. If the driver selects one of these settings, the dynamic transient functions of the electronic engine management system switch 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.
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 ??????????????????????????????????????????????????????????C 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.
