Press Release
High-pressure double-VANOS for an optimum cylinder charge.
Variable double-VANOS camshaft management ensures an optimum charge cycle within the ten-cylinder. This, in turn, helps to keep valve timing extremely short and fast – which in practice means more power, an even better torque curve, optimum responsiveness, greater fuel economy, and cleaner emissions.
Running at low loads and engine speeds, the engine therefore operates with a greater valve overlap and, as a result, a higher level of internal exhaust gas recirculation. This, in turn, reduces charge cycle losses and improves fuel economy accordingly. As a function of the gas pedal position and engine speed – the parameters crucial to the power and performance required of the engine – valve increments are adjusted infinitely and by way of map control.
To ensure such efficient management, the sprocket connected with the crankshaft by a single chain is linked to the camshaft by a two-stage helical gearing. With the adjustment piston being moved along its axis, the helical gear pattern turns the camshaft relative to the sprocket, allowing variation of the intake camshaft angle by up to 66° and the outlet camshaft angle by up to 37°.
M double-VANOS requires a high level of oil pressure in order to adjust the camshaft at maximum speed and with maximum precision. Accordingly, engine oil is compressed to an operating pressure of 80 bar by a radial piston pump fitted in the crankcase. This map-controlled high-pressure adjustment guarantees short adjustment times and provides the optimum spread angle synchronized to ignition timing and the amount of fuel injected as a function of engine load and speed at all operating points.
Reliable oil supply even in extremely fast bends.
The oil required for lubrication is delivered to the engine by a total of four oil pumps. The reasons for such an unusually elaborate and sophisticated oil supply system are the high standard of dynamic performance and the extreme acceleration of the BMW M6. In bends, for example, BMW’s large Coupe is easily able to achieve lateral acceleration of well over 1g. The centrifugal forces generated in such a process press the engine oil into the outer row of cylinders to such an extent that the oil is no longer able to flow back in the usual process from the cylinder head, possibly leading to a lack of oil in the sump. And should worst really come to worst, the oil pump might then draw in air instead of oil.
To rule out such an eventuality, the engine comes with lateral force-controlled oil supply where, starting at lateral acceleration of approximately 0.6 g, one of two electrically driven duocentric pumps draws oil out of the outer cylinder head in a bend and conveys it to the main oil sump. A lateral acceleration sensor serves as the actuator for initiating pump action. The oil pump itself is a volume-flow controlled pendulum slide cell pump delivering exactly the amount of engine oil actually required by the engine. This is made possible by the inner rotor of the pump adjustable in its eccentricity versus the pump housing as a function of current oil pressure in the main oil duct.
A lubrication film which does not break when applying the brakes.
When applying the brakes to the extreme, the BMW M6 builds up negative acceleration up to a staggering 1.3 g. Under such extreme conditions, it is quite possible that the flow of oil back to the oil sump serving as an intermediate storage reservoir will no longer be sufficient, especially as the oil sump for reasons of space is fitted beneath the front axle subframe. So if worst came to worst, lubrication might be entirely interrupted. To reliably prevent this eventuality, the engine of the BMW M6 comes with a so-called “quasi-dry sump system” incorporating two oil reservoirs: one in front of the front axle subframe, another behind the subframe.
A reflow pump integrated in the compressed oil pump housing draws oil out of the small oil sump at the front and pumps it into the large oil sump at the back. Both the reflow openings and the compressed oil pump extraction point are precisely matched to the car’s acceleration and driving forces.
Ten individual throttle butterflies controlled electronically.
Again reflecting the supreme standard of motorsport, each of the ten cylinders comes with its own throttle butterfly, each row of cylinders being controlled by a separate adjuster. While this system is extremely demanding and sophisticated in mechanical terms, there is no better way to achieve engine response within split-seconds. To give the engine a particularly sensitive response at low engine speeds while building up power just as fast wherever necessary for dynamic performance of the highest standard, the throttle butterflies are masterminded electronically by two contact-free Hall potentiometers scanning and evaluating the position of the gas pedal 200 times a second.
Responding precisely to any change in running conditions, engine management sets the position of the ten individual throttle butterflies via the two adjusters. Naturally, it goes without saying that all this takes place within fractions of a second. Only 120 milliseconds being required to open the throttle butterflies in full – roughly the time a driver takes to press down the gas pedal.
The benefit for the driver is instantaneous engine response with the car “taking off” without the slightest delay and the driver being able to sensitively dose the engine power required. At the same time electronic operation of the throttle butterflies makes the transition from overrun to part load and vice versa absolutely smooth and harmonious.
The V10 draws in the air it needs through ten flow-optimized intake funnels extending into two air collectors. The funnels and collectors are all made of a light composite material containing 30 per cent glass fiber.
Twin-chamber stainless-steel exhaust system.
As important as the intake side may be for giving the power unit of the M6 maximum output and performance, the exhaust system may not be neglected in any respect. So here again, only the best meets the demanding standards of the engineers and other specialists at BMW M.The two five-in-one stainless-steel manifolds have been optimized in elaborate computer processes to provide exactly the same operating length.
To ensure exactly the right tube diameter, in turn, the stainless-steel pipes, produced as one unit without a seam in between, are formed from inside in an internal high-pressure molding process and under a production pressure of up to 800 bar. And last but not least, the exhaust manifolds come with walls measuring only about 0.8 millimeters in thickness – again a clear sign of the utmost care and diligence the engineers at BMW M have given to each and every detail of this masterpiece in engine construction.
A high-performance sports engine clean and compatible with the environment.
The exhaust system is designed consistently for minimum counterpressure, the dynamic gas flow is optimized for perfect power and torque. The exhaust system extends back to the silencers in two chambers, leading into the four striking tailpipes so typical of a BMW M Car. Compared to the M5, the sound of the exhaust on the M6 is even more muscular and aggressive.
As is to be expected of a BMW M Car, two trimetal-coated catalysts on each exhaust pipe clean emissions from the ten-cylinder in line with the demanding European EU4 and, respectively, the equally stringent US LEV2 standards. Two catalysts are fitted in the underfloor, one catalyst each in the exhaust pipe close to the engine. In conjunction with the thin-walled exhaust manifolds, these catalysts reach their optimum operating temperature as quickly as possible, a significant requirement particularly when starting the engine cold.
Particular fortes of the system are its low pressure loss and high level of mechanical stiffness.
Engine control unit unique the world over.
The MS S65 engine management unit is crucial to the outstanding performance and emission management of the V10. It ensures optimum coordination of all engine functions, on the one hand, and the car’s control units, on the other. It also controls interaction with the SMG transmission.
This engine management system is quite unique in production engine technology worldwide: Incorporating more than 1,000 components, it has by far the highest level of package density. The hardware and software, as well as the specific functions of the system, have all been developed by BMW M.
High engine speed demands extreme performance.
Given the high speed of the engine and the large number of management and control functions, the demands made of the engine management system are very significant indeed. To meet these demands, the MS S65 control unit comes with no less than three 32-bit processors able to handle more than 200 million operations per second. Working with absolute precision, they determine the optimum ignition timing from more than 50 incoming signals individually for each cylinder and operating cycle, at the same time calculating the ideal cylinder charge, injection volume and injection point. The system also determines and sets the optimum camshaft spread, just as it adjusts the individual throttle butterflies.
Pressing the Power button, the driver is able activate a high-performance program calling up all of the engine’s power and performance. This program uses a more progressive map control line relating gas pedal to the opening of the throttle butterflies and modifying the dynamic engine management functions for even greater responsiveness.
The more comfort-oriented of the two programs is called up automatically as soon as the engine is started. The driver has the option to configure the program switch-over function as a feature of the car’s MDrive control. MDrive also offers yet a further sports program for particularly dynamic motoring.
Engine management with a wide range of additional functions.
Electronic throttle butterfly control is based on a system of all-round output and torque management: The potentiometer on the gas pedal measures the driver’s demand for power and performance, translating this signal into the torque and output required at any given point in time. The output and torque manager then adjusts this power request by taking ancillaries and additional equipment such as the a/c compressor or alternator into account. Functions such as idle speed control, exhaust gas management and knock control are also coordinated and compared with the maximum and minimum forces required for Dynamic Stability Control as well as Engine Drag Force Management. The desired power and torque calculated in this way is then set within the engine, focusing in the process on the current ignition angle. And last but not least, engine management performs a wide range of additional on-board diagnostic functions with diagnostic routines for the workshop, additional operating functions, as well as the efficient management of peripheral units.
A new highlight in engine management: ionic current technology.
Ionic current technology serving to detect any risk of the engine knocking as well as misfiring and miscombustion is a new feature of the engine control unit. “Knocking” is unwanted self-ignition of fuel in the cylinders. Engines without knock control have a somewhat lower compression ratio and a somewhat later ignition point, to make sure that none of the cylinders ever reaches or let alone exceeds the knock limit. However, this “safety” distance from the knocking limit means a trade-off in terms of fuel economy, engine output, and torque.
Active knock control, by contrast, allows the engine to run at its optimum ignition point. Knock management protects the engine from damage at all points where knocking is monitored and limited. The result, obviously, is maximum efficiency on the road.
With conventional technology knock control receives its knock signal from various body sound sensors fitted on the outside of the cylinders. On a BMW M Car there is one sensor for each set of two cylinders. But as sophisticated and progressive as this technology may otherwise be, even this is not sufficient on a multi-cylinder, high-speed engine such as the new V10.
It is not able to reliably detect the risk of the engine knocking. And since at the same time a relatively high standard of monitoring accuracy is essential in the light of high engine speeds in order to guarantee appropriate combustion quality in the cylinders and, accordingly, a long service life of all components and appropriate emission control, the new technology now introduced is ionic current management.
Spark plugs with additional control functions.
Using this technology, the engine is able, via the spark plug in each cylinder, not only to sense and control the risk of knocking, but also to monitor the ignition process and recognize any tendency of the engine to misfire. In other words, the spark plug serves both as a sensor observing the combustion process and as an actuator for the ignition. This marks the big difference versus a conventional knocking and ignition sensor fitted outside of the combustion chamber. Ionic current measurement, by contrast, is conducted directly within the combustion chamber, the spark plug itself serving as the sensor.
Measurements right in the middle of the combustion process.
The temperatures generated in the combustion chambers of an internal combustion engine may well be up to 2,500 °C or 4,500 °F. As a result of these high temperatures and chemical reactions during the combustion process, the gasoline/air mixture in the combustion chambers is partially ionized. Particularly along the flame front, the gas becomes electrically conductive once ions are formed by the fission and accumulation of electrons (ionization). By means of the spark plug electrode electrically insulated from the cylinder head and connected to a control unit – the ionic current satellite – affiliated in turn to the engine management unit, the system is able to measure the ionic current flowing between the electrodes, with the spark plug electrode itself being kept under direct voltage. The level of such ionic current flow depends on the degree of gas ionization between the electrodes.
Ionic current measurement thus provides information on the combustion process directly where it counts, that is in the combustion chamber itself. The ionic current satellite receives signals from the five spark plugs in each row of cylinders, amplifies these signals and conveys the data to the engine management unit. The control unit then analyses the data received and, where necessary, intervenes on specific cylinders, adjusting the ignition timing ideally to the combustion process by way of knock control.
This dual function of the spark plugs serving, first, as the spark-generating unit and, second, as a sensor, helps additionally to facilitate diagnostic procedures in maintenance and service.
