S85B50 Engine M5, M6
S85B50 engine
E60, E61 M5 E63, E64 M6
Introduction
The S85B50 is the first BMW 10-cylinder gasoline engine to be used in a production vehicle.
The power output is 507 HP (373 kW) with a cylinder capacity of 5 liters. The maximum torque is around 520 Nm.
The V10 engine, with a speed range of up to 8250 rpm, guarantees exceptionally high dynamics. The lightweight construction of this engine means that it achieves a power/weight ratio of only 3.5 kg/HP (relative to an unladen weight of 1755 kg).
In terms of dynamics therefore, it is comparable with a sports car.
The design of the engine and the engine electronics have their origins in Formula 1.
The most important innovations in the S85B50 are:
- Ionic current measurement for the knock control and misfire detection
- Torque feedback control operation using electrically-activated individual throttle butterflies
- Oil supply with 4 oil pumps to cater for all driving situations
- Demand-oriented fuel delivery with variable fuel pressure
- Double VANOS with approximately 70 bar high pressure for rapid camshaft adjustment
- Cooling according to the crossflow principle with split radiator
- Engine output selectable in 2 stages with "POWER button"
Brief description of components
The following components which are activated mechanically and electrically are described:
- Engine block
The S85B50, a 90° V engine, is extremely compact. The 90° angle produces a vibration- and comfort-oriented balancing of masses.
The very high maximum speed of 8,250 rpm means that an extremely rigid engine block is required.
The necessary torsional strength is provided by a bedplate construction.
With the bedplate construction, the crankcase is split. In a split crankcase, the crankshaft bearings are part of a separate stable frame: the "bedplate".
A liquid sealing compound which is injected into a groove forms a seal to the crankcase.
- Light alloy crankcase without cylinder bushes
The crankcase is made from an alloy containing aluminium and silicon.
The cylinder barrel is formed using exposed, hard silicon crystals. This means that additional cylinder bushes are not required. The iron-coated pistons run directly into this unlined bore hole.
- Single-part light alloy cylinder head
The cylinder head has been made from one piece.
The idle air and secondary air channels are integrated into the cylinder head.
This reduces sealing surfaces and also increases rigidity.
- Weight-optimized crankshaft drive
The crankshaft is relatively short due to the cylinder spacing of 98 mm. This achieves a high bending resistance and torsional strength combined with low weight. Both inlet camshaft drive sprockets are integrated into the crankshaft.
The weight of the cracked connecting rods made of high high-tensile steel has been optimized which further reduces the masses to be displaced.
The pistons are made of aluminium alloy and are coated with iron. One piston including piston pins and rings weighs only around 480 grammes.
- Weight-optimized valve gear
The camshaft is hollow-cast. The camshaft sensor gear for each camshaft sensor is integrated into the camshaft.
The inlet valves are extremely light. The valve shaft is only 5 mm thick to achieve an optimum flow cross section.
The bucket tappets with hydraulic valve clearance adjustment are box-shaped and spherical. Reason: less weight and reduced friction.
Anti-twist locks are mounted on the bucket tappets.
- Collector for intake air
The S85B50 has an intake manifold on each cylinder bank. The intake manifolds are connected to the air intake filters by short hoses. The intake manifold is mounted on the throttle valve assembly with anti-twist hose clamps.
The air is drawn in via 2 air inlets in the grille and bumper (a total of 4 air inlets to air intake filter).
A cyclone filter is integrated into each intake manifold. The oil from the crankcase ventilation system is separated then drained off into the oil sump.
The condensation which forms in the intake manifold is drained off via a line in the crankcase.
- 2 throttle valve positioners and 2 throttle valve sensors
The S85B50 has 10 individual throttle butterflies.
One electric throttle valve positioner activates 5 individual throttle butterflies which are mechanically coupled. The throttle valve position for each cylinder bank is adjusted via the throttle valve sensor.
A local CAN bus (Local CAN) is used for communication between the DME and the throttle valve positioner.
- 2 idle actuators
One electric idle actuator on each cylinder bank controls the air supply at idling speed and when engine loads are low. Both idle actuators are accommodated in the V formed by the two cylinder banks. The idle actuator contains a throttle valve. The DME controls the idle actuator via a local CAN bus (Local CAN). The SMG control unit is also connected to this Local-CAN.
- Secondary air pump and secondary air valve
The secondary air pump mixes fresh air with the exhaust gas following engine start-up.
The fresh air causes the combustible hydrocarbons in the exhaust gas to oxidise.
This reduces the proportion of hydrocarbons in the exhaust gas and also enables the operating temperature of the main catalytic converters near the engine to be reached more quickly.
In order to monitor the system, a small mass air flow sensor measures the secondary air supply. The secondary air valve is a mechanical valve. The secondary air pump generates pressure which in turn opens the secondary air valve.
- 2 VANOS adjustment units and VANOS accumulator
A VANOS adjustment unit on each cylinder bank facilitates camshaft adjustment (double VANOS). A separate oil pump supplies oil with a maximum pressure of 90 bar to the VANOS adjustment unit.
In the S85B50, the VANOS solenoid valves on the VANOS adjustment unit operate proportionally. The crankshaft drives the high-pressure pump for the VANOS adjustment unit via gear teeth.
The nitrogen in the VANOS accumulator is precompressed at 40 bar. The oil chamber is separated from the gas chamber by a piston. When the engine is switched off, the pressure accumulator valve on the VANOS accumulator is closed.
- 2 fuel pumps and fuel-pressure sensor
There are 2 fuel pumps (vane-cell pumps) in the fuel tank. Both fuel pumps are integrated into the right half of the tank. The fuel pumps are activated by the DME via a separate fuel pump output stage according to demand. The fuel-pressure sensor is located in the front left wheel well. In order to supply fuel according to demand, the fuel delivery pressure must be measured. The measured fuel delivery pressure is sent to the DME.
- 4 oil pumps
A total of 4 oil pumps are responsible for the oil supply.
The oil pump housing contains 2 oil pumps. The duocentric pump pumps the oil from the front oil sump to the rear oil sump.
A controllable pendulum slide cell pump draws the oil from the rear sump and pumps it into the oil filter.
2 electric oil pumps draw oil from the cylinder head on the outside during extreme cornering manoeuvres and pump it into the rear oil sump.
- Oil pressure switch
The oil pressure switch signals to the DME that the critical oil pressure threshold has been reached. If the pressure falls below the threshold, the DME generates a Check-Control message.
- Electric vacuum pump and low-pressure sensor
The electric vacuum pump generates low air pressure for the brake power assistance.
The electric vacuum pump replaces the suction jet pump used previously.
The electric vacuum pump is a vane-cell pump.
The low air pressure generated is measured by a low air pressure sensor.
- Radiator with coolant thermostat
Coolant flows in a crosswise direction through the cylinder head as well as the engine block according to the familiar method.
New: The S85B50 radiator has two parts.
Each cylinder head therefore has its own radiator feed.
This arrangement reduces the pressure drop in the radiator from approximately 3 bar to approximately 1.4 bar.
Due to the two-part cooling concept, the coolant thermostat is positioned in the return flow.
- 2 exhaust gas temperature sensors
The S85B50 has 2 exhaust lines made of stainless steel.
An exhaust-gas temperature sensor on each cylinder bank measures the exhaust-gas temperature. The DME requires this signal for protection of the catalytic converter.
Note: From 03/06, the signals from the exhaust gas temperature sensors are not used.
From 03/06, the signals from the exhaust gas temperature sensors in DME are not used. However, the exhaust gas temperature sensors were still fitted until 09/06.
The signals were replaced by calculated exhaust gas temperatures. The exhaust gas temperatures are also no longed diagnosed in the DME.
- POWER button
The POWER button is mounted in the selector lever cover and is used to select the engine power output: P500 = 500 HP, P400 = 400 HP.
- 2 ionic current control units
Each cylinder bank has one ionic current control unit.
The ionic current control unit is positioned between the DME control module and the ignition coils. The igniter output stages are in the ionic current control unit. The ionic current control unit records and amplifies the signals from the spark plugs. This operation is known as ionic current measurement. The signal is transmitted to the DME via a separate line for each cylinder bank.
- DME: Digital engine electronics
The newly developed MSS65 engine control is responsible for this engine's outstanding output and low exhaust emission.
The engine control has more than 1000 individual components. The DME control module coordinates all engine operations. Also included are interfaces for other control modules, e.g. sequential manual gearbox.
The DME control module is extremely efficient. The 3 microprocessors can perform 200 million computer operations per second.
The DME control module calculates the following for each individual cylinder from more than 50 input signals:
- Firing point
- Charge
- Injection quantity
- Injection start
Adjustment of the variable camshaft control and positioning of the 10 individual throttle butterflies is synchronised with this.
System functions
The following system functions are described:
- Knock control and misfire detection with ionic current measurement
- Torque feedback control operation
- Double VANOS variable camshaft control
- Vacuum supply
- Oil supply
- Fuel supply system
- Exhaust system
Knock control and misfire detection with ionic current measurement
Due to the extremely high engine speeds, the S85B50 places very special demands on components and system functions. One example of this is the knock control.
Conventional knock sensors would be unsuitable as they cannot deliver adequate signals at these high engine speeds.
Ionic current measurement is used instead and is carried out by 2 ionic current control units. One of these control units is positioned at the front of each cylinder bank on the cylinder head cover. The ionic current control unit is connected to the DME control module and the ignition coils. The DME control module and the ignition coils are not directly connected.
The ionic current measurement is carried out as follows:
- The DME control module triggers the ignition sparks at the spark plug. This ignites the fuel-air mixture which starts to burn.
- The resulting heat energy creates positively and negatively charged molecules (= ions). The number of ions produced increases according to the combustion temperature. The more efficient the combustion, the more ions are produced.
- A DC voltage is applied at the spark plug by the ionic current control unit immediately following ignition. If free ions are present in the mixture, current flows. The ionic current control unit measures and evaluates this "ionic current".
The ionic current control unit measures and amplifies this ionic current. The DME evaluates this ionic current.
- The DME control module detects ionic current which is too low during ignition and combustion (no ignition sparks or poor combustion), as well as combustion knock.
- If discrepancies are detected, the DME control module makes adjustments.
The ionic current measurement detects:
- Combustion knock
- Misfiring
The ionic current measurement is also capable of analysing each individual combustion process through all engine speed ranges.
The misfire detection can determine whether misfiring is caused by a missing ignition spark or is due to failed combustion.
Torque feedback control operation
The air volume is the most important variable in the torque feedback control operation. 2 throttle valve positioners for the 10 individual throttle butterflies and 2 idle speed actuators modify the air volume. All 4 actuators are activated by the Digital Motor Electronics (DME).
The DME is connected by a local CAN bus to each throttle valve positioner and idle actuator.
The DME evaluates the nominal value for the load using input variables such as:
- Driver's desired load via accelerator-pedal module
- Coolant temperature
- Intervention by other control units such as SMG or DSC
The DME uses this nominal value to determine a nominal position for the throttle valves.
At idle speed and low engine loads, the throttle valves in the idle actuators are activated first. The individual throttle butterflies are opened if a larger air volume is required.
To adjust the engine output, the actuators are provided with the nominal throttle valve angle value by the DME.
2 Hall sensors are incorporated into each throttle valve sensor. Hall sensor 1 reports the throttle valve position back to the throttle valve positioner. The throttle valve positioner forwards the signal via the Local-CAN to the DME.
Hall sensor 2 is supplied and read out directly by the DME. This Hall sensor only serves to monitor the control operation.
If the throttle valve positioner fails, a return spring closes each individual throttle butterfly.
Both idle actuators are equipped with an angle sensor to facilitate adjustment of the throttle valve angle. The angle sensor value is reported back to the DME via the local CAN bus.
The DME determines the actual value of the load signal in order to check the setting of the throttle valves. The load signal is determined using the signals from the throttle valve sensors and the idle actuators.
The plausibility of the load signal is also checked using the signals from both mass air flow sensors. If the deviations between the nominal value and actual value are too great, a plausibility check is carried out using the signal from the oxygen sensor.
Double VANOS variable camshaft control
The variable camshaft control improves torque in the low and medium engine speed range.
Due to a larger valve overlap, the volume of residual fumes at idle speed is reduced. A recirculation of internal exhaust gas in the part-load range reduces the volume of nitrogen oxide.
The following is also achieved:
- Faster heating of catalytic converters
- Reduced exhaust emissions following a cold start
- Reduced fuel consumption
A controlled VANOS adjustment unit is mounted at both intake and exhaust camshafts.
2 VANOS solenoid valves activate each VANOS adjustment unit. The required position of the intake and exhaust camshaft is calculated using the engine speed and load signal (dependent on intake temperature and engine temperature). The DME control unit activates the VANOS solenoid valves accordingly.
To perform the adjustment, the variable camshaft control requires an information signal on the current position of the camshaft. Camshaft sensors on the intake and exhaust end record the position of the camshafts.
Further information about the double VANOS can be found in a separate enclosure.
Vacuum supply
In some operating situations the low air pressure required for the brake power assistance is insufficient. This particularly applies if the catalytic converter is heated up when the engine is cold. An electric vacuum pump generates the low air pressure which is required. The DME switches the vacuum pump on or off as required. The switching thresholds depend on the speed.
Oil supply
4 oil pumps are responsible for the oil supply.
Owing to the engine's dynamism and extreme acceleration performance, an unusually complex oil supply system is required.
The oil pump housing contains 2 oil pumps.
The pendulum slide cell pump delivers the exact volume of oil which is required by the engine. The inner rotor (pendulum slide) is mounted on sliding bearings. The volumetric flow control is dependent on the oil pressure in the main oil gallery.
The oil sump is split into two parts. During heavy braking, the oil will possibly not run out of the front oil sump back into the rear oil sump.
The second oil pump in the oil pump housing draws the oil from the front oil sump into the rear oil sump. This ensures that the oil supply will be maintained during heavy braking.
During extreme cornering, a high lateral acceleration is produced which forces the engine oil into the cylinder head on the outside of the curve. 2 electric oil pumps ensure that the oil supply is maintained. The oil pump on the outside of the curve draws the engine oil from the cylinder head into the rear oil sump.
The DSC sensor reports the lateral acceleration to the DME via the PT-CAN.
Fuel supply system
The following specific demands are placed on the S85B50 fuel system:
- Fuel delivery with high dynamics
- Lower level of fuel vapour in the tank due to reduced heating of fuel
- Minimised current consumption of fuel pumps with improved charge balance and subsequent reduced fuel consumption
A demand-oriented fuel supply with a variable fuel delivery pressure meets these requirements.
The fuel delivery pressure is adjusted as a function of the engine load. A fuel-pressure sensor measures the fuel delivery pressure. The signal is sent to the DME.
The fuel delivery pressure varies between approximately 2.5 and 6 bar.
The 2 fuel pumps are connected hydraulically in parallel.
The fuel pumps are activated by a separate fuel pump output stage. The DME control module activates the fuel pump output stage.
To do this, the DME control module sends a pulse-modulated signal to the fuel pump output stage. The fuel pump output stage controls the first fuel pump according to demand (also by means of PWM signal).
The maximum permissible deviation for the cycle ratio between the incoming and outgoing PWM signals is 3%. This tolerance applies throughout the entire service life of the electric fuel pumps.
If a cycle ratio of 98% is achieved at the input for the fuel pump output stage, the second fuel pump is also connected without regulation (higher load range).
During this process, the system pressure is restricted to 6 bar by the mechanical fuel-pressure regulator in the fuel tank.
Exhaust system
The double-flow exhaust system is made of stainless steel.
The fan-type manifolds ("5 in 1") provide each cylinder with exactly the same length. The manifold pipes have a wall thickness of approximately 0.8 mm.
There are 2 catalytic converters on the floorpan. One catalytic converter is positioned on each exhaust line near the engine.
An exhaust gas temperature sensor on each cylinder bank mainly serves to protect the catalytic converter.
The S85B50 is equipped with 2 control sensors (LSU 4.9) and 2 monitoring sensors (LSH 25) for the oxygen-sensor control.
The exhaust system complies with the following exhaust emission regulations:
- EURO 4
- US LEV 2
- Japan LEV 2000
Note: From 03/06, the signals from the exhaust gas temperature sensors are not used.
From 03/06, the signals from the exhaust gas temperature sensors in DME are not used. However, the exhaust gas temperature sensors were still fitted until 09/06.
The signals were replaced by calculated exhaust gas temperatures. The exhaust gas temperatures are also no longed diagnosed in the DME.
Notes for service staff
The following information is available for service staff:
- General notes:
- Diagnosis:
- Encoding/programming: ---
Subject to change.