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[h=1]BMW TIS - Engine control for N46 Introduction >E46 >E87, E90[/h]Engine control for N46 E46, E85, E87, E90
Introduction >E46 The new generation of 4-cylinder spark-ignition engines (NG4) are continued and developed further.The 4-cylinder spark-ignition engines N40 and N42 have been redesigned. The modified N40 engine is now called N45. The modified N42 engine is now called N46.As with its predecessor, there are 2 engine-capacity versions of the N46: N46B18 (1.8 l) and N46B20 (2.0 l). The available power output remains unchanged at (85 and 105 kW). As on the predecessor version N42, the new N46 is available as a version for various southern and eastern European markets. The N45B16 (1.6 l) has the same rated output as the N46B18. The N45B16 has no Valvetronic system and no differential air intake control (DISA). Engine-specific data: [more ...] >E87, E90 On the E87, the N45 is the basic engine for all countries (EURO 4, without Valvetronic and DISA). The N46 is available with lower power output (N46B20uL) and a higher power output (N46B20oL). The differential air intake control (DISA) is not used on the N46B20uL.For both output ratings, the N46 makes do without the signal from the air mass meter (on vehicles with catalytic converter). The air mass is derived from the signal for Lambda control and other input factors from the DME. The spark-ignition engines on the E87 and E90 no longer have an oil dipstick. The electronic oil level check can be performed via a menu in the instrument cluster (alternative: Central Information Display). The N46B20oL from the E87 is installed on the E90. > E85 The N46 with the higher power rating (N46B20oL) will also be installed in the Z4 from mid-2005. The vehicle electrical system in the E85 is based on the vehicle electrical system in the E46. Like the E46, the N46 on the E85 is equipped with a secondary air system. There are 2 different versions of the exhaust system: - Left-hand drive: Air-gap-insulated exhaust manifold with 2 oxygen sensors - Right-hand drive: Split exhaust manifold with 4 oxygen sensors The engines which have been further developed also include redesigned digital engine electronics (DME). In the N46, the control for the Valvetronic system has been integrated into the DME control unit. The DME control unit now has 2 connector chambers. On the E87 and E90, the N46 engine no longer has a secondary air system (catalytic converter fitted close to the engine). For the first time on a 4-cylinder engine, bus communications are routed through the Electrical System 2000. Electrical System 2000: All control units are addressed at the same time with Key Word Protocol 2000. This SI Technology bulletin (SBT) describes the engine control system for the following model series: - E46, E85[system overview ...] - E87, E90[system overview ...] Brief description of components The engine control system is described on the basis of the N46. Differences for the E87 or E90 are marked "> E87, E90". For the digital engine electronics (DME) on the N46, the following sensors supply signals to the DME control unit: - Eccentric shaft sensor The eccentric shaft sensor records the position of the eccentric shaft for the Valvetronic. The eccentric shaft adjusts the camshaft so that the optimum valve lift for the inlet valve is achieved regardless of operating condition (infinitely adjustable valve lift at intake). The eccentric shaft is adjusted by the Valvetronic actuator. The eccentric shaft sensor is equipped with 2 angle sensors which operate independently of one another. The DME control unit adjusts the position of the eccentric shaft via the Valvetronic actuator until the actual and the nominal position correspond. - Intake camshaft sensor and exhaust camshaft sensor The valve gear is equipped with variable camshaft control (double VANOS) for the intake and exhaust camshaft. Both camshaft sensors record camshaft adjustment. - Alternator The alternator exchanges data with the DME control unit using a bit-serial data interface. The alternator sends the DME control unit information on type and manufacturer, for example. This enables the DME control unit to modify the alternator control to suit the alternator model which has been installed. - EWS control unit or CAS control unit The electronic immobiliser is an anti-theft system which prevents the engine from starting. The engine can only be started if the electronic immobiliser enables this. >E46, E85 The immobiliser control unit sends an encoded release signal to the DME control unit via the EWS data line. The engine can only be started after this. > E87, E90 The E87 and E90 do not have an EWS control unit. The immobiliser functions are assumed by the Car Access System (CAS). In addition, the CAS control unit also assumes the convenient-start system. - Crankshaft sensor The crankshaft sensor records the position of the crankshaft with the aid of a sensor gear which is screwed to the crankshaft. The crankshaft sensor is required in order to achieve fully sequential fuel injection (individual fuel injection for each cylinder at optimum firing point). - Accelerator pedal module The accelerator pedal module identifies the position of the accelerator pedal. Using this information, the DME control unit calculates the required position of the Valvetronic or the throttle valve while taking other criteria into account (for N45: only position of throttle valve). - Air mass meter The air mass meter records the air mass which is drawn in. The DME control unit calculates the required load conditions using this information (base value for fuel injection period). > E87, E90 The air mass meter in the N46B20 engine is not used for recording a signal. As on previous models, the intake air temperature sensor is installed in the housing of the air mass meter (exception: no catalytic converter is fitted). The DME calculates the air mass using a model. The most important input factor is the Lambda control signal. To this end, the oxygen sensor (control sensor) is located close to the engine. - Coolant temperature sensor The coolant temperature sensor records the coolant temperature in the engine cooling circuit. The coolant temperature is the measured variable used in these calculations, for example: injection quantity and nominal idle speed. - Temperature sensor on radiator outlet The temperature sensor on the radiator outlet records the coolant temperature downstream of the radiator. The DME control unit requires information on the coolant temperature at the radiator outlet to activate the radiator fan, for example. - Thermal oil level sensor The thermal oil level sensor delivers 2 signals to the DME control unit: engine oil temperature and oil level (for N45 on the E46: oil level only). The oil level is required for checking the level of oil in the engine. > E87, E90 The spark-ignition engines on the E87 and E90 no longer have a dipstick. The oil-level sensor supplies a signal for the electronic engine oil level control to the DME control unit. The engine oil level is displayed electronically on the instrument cluster through the on-board computer functions (bars). If the vehicle is equipped with a Central Information Display (CID), the engine oil level is displayed under "Service requirements" in the "Service" menu [more ...] - Suction pipe pressure sensor The suction pipe pressure sensor measures low pressure in the suction unit (N46 only). In engines with Valvetronic, for example, a partial vacuum of approximately 50 millibars is set in idle speed. The inlet pipe vacuum acts as a substitute value for the load signal. - 2 knock sensors Both knock sensors detect combustion knock. Knock sensor 1 monitors cylinders 1 and 2. The other knock sensor monitors cylinders 3 and 4. The DME control unit performs cylinder-selective knock detection. - Oxygen sensors > N46 / N46oL: For every 2 cylinders, an oxygen sensor is installed upstream of the catalytic converter and downstream of the catalytic converter (cylinders 1 and 4, cylinders 2 and 3). Exception: Left-hand drive vehicles with manual transmission have only 2 oxygen sensors and one air-gap insulated exhaust manifold [for further information, please refer to SI Technology (SBT) 18 01 03 060] > N45 / N46uL: This engine has 2 oxygen sensors. The oxygen sensors upstream of the catalytic converter (control sensors) record the composition of the exhaust gas. The oxygen sensors downstream of the catalytic converter (monitoring sensors) monitor the function of the catalytic converter. The oxygen sensors are heated by the DME control unit so that they reach their operating temperature more quickly. - Clutch module In vehicles with manual transmission, the clutch module records the clutch position at the clutch pedal (clutch depressed: clutch switch open; clutch not depressed: clutch switch closed). The clutch module comprises the clutch switch and electronic evaluation unit. - Brake light switch Two switches are fitted in the brake light switch: the brake-light switch and the brake light test switch (duplicated as a safety measure). The signals enable the DME control unit to determine whether or not the brake pedal is depressed. - Oil-pressure switch The oil-pressure switch provides the DME control unit with an indication of whether or not there is sufficient oil pressure in the engine. >E46: The oil pressure switch is connected to the instrument cluster. The signal is delivered by the instrument cluster via the K-CAN. > E87, E85, E90: The oil pressure switch is directly connected to the DME control unit. - DSC control unit The DSC control unit sends the signal containing information on the vehicle's road speed via a separate line (redundant to PT-CAN) to the DME control unit. This signal is required for several functions e.g. the idle speed control. - Multi-function steering wheel or cruise control On vehicles with N46, there is no separate control unit for the cruise-control system. >E46 The multi-function steering wheel (MFL) has an MFL button pad on its right-hand side for operating cruise control. The signals for cruise control are evaluated by the DME control unit. >E85 The signals are transferred via a separate wire from the steering-column stalk to the DME. > E87, E90: The signals for controlling the cruise-control system are transmitted onto the bus system from the steering column switch cluster (SZL). - DME control unit 2 additional sensors are located on the board in the DME control unit: a temperature sensor and an ambient-pressure sensor. The thermal monitoring of components in the DME control unit is carried out by the temperature sensor. The ambient pressure is required to calculate the mixture composition. The ambient pressure reduces as the height above sea level increases. In the N46, the DME control unit is connected to the vehicle's system via the engine wiring harness and vehicle wiring harness (2 connector chambers). [more ...] The DME control unit is connected to the rest of the bus system by the PT-CAN (Powertrain CAN) via the following gateway: · E46: E85: Instrument cluster (KOMBI) · E87, E90 - Junction box electronics (JBE)The digital engine electronics (DME) in the N46 control the following actuators: - Valvetronic actuator The air flow to the engine during throttle-free operation is adjusted by the variable valve lift and not the throttle valve. Valvetronic is driven by an electric motor. The Valvetronic actuator is mounted on the cylinder head. The Valvetronic actuator uses a worm gear to drive the eccentric shaft in the cylinder head oil chamber. The eccentric shaft sensor provides the DME control unit with an indication of the position of the eccentric shaft. - Actuator for variable suction unit The N46B20 has a differential air intake control (DISA). The DISA actuator drives one sliding sleeve per cylinder. The sliding sleeves lengthen or shorten the intake port. This means that a more ample torque curve is reached at low engine speeds without a loss of engine output at higher engine speeds. - Electric throttle-valve actuator The DME control unit calculates the position of the throttle valve using the position of the accelerator pedal amongst other variables. In the electric throttle-valve actuator, the position of the throttle valve is monitored by 2 potentiometers. The electric throttle-valve actuator is electrically opened or closed by the DME control unit. With Valvetronic, the throttle-valve actuator is activated for the following functions: · Engine start (warm-up) · Idle speed control · Full load operation · Emergency operation - 2 VANOS solenoid valves The purpose of the variable camshaft control is to increase torque in the low and medium engine speed ranges. A VANOS solenoid valve controls a VANOS adjustment unit on the intake end and the exhaust end. The VANOS solenoid valves are controlled by the DME control unit. - Fuel pump relay The fuel pump relay controls the electric fuel pump. The DME control unit monitors the activation of the fuel pump relay. The fuel pump relay is controlled via a safety circuit only when the engine is running and shortly after terminal 15 ON for pressure build-up (delivery line for fuel pump).>E87, E90: The fuel-pump relay is in the junction box. - 4 injection valves During fully sequential fuel injection, each injection valve is controlled by the DME control unit via its own final stage. During this process, the fuel injection time of the specific cylinder is adjusted to suit the operating conditions (engine speed, load and engine temperature). - Fuel evaporation control valve The fuel evaporation control valve regenerates the activated carbon filter using scavenging air. The scavenging air which is drawn through the activated carbon filter is then enriched with hydrocarbons and fed to the combustion engine. In a current-free state, the fuel evaporation control valve is closed. This prevents the ingress of fuel vapour from the activated carbon filter into the suction pipe when the engine is switched off. - 4 ignition coils with overload-protection relay The ignition coils are activated by the DME control unit. From ignition overload-protection relay receive the ignition coils terminal 30. - Map thermostat The opening and closing of the map thermostat (N46 only) is controlled by a characteristic map. The map thermostat ensures that within its control range a constant coolant temperature is maintained at the engine inlet. For driving conditions with low loads, the map thermostat sets a high coolant temperature (efficient consumption). For full loads or higher engine speeds, the coolant temperature is reduced to protect the components. - Secondary air pump relay and secondary air pump (for EURO 4 exhaust emission regulations) >E46, E85 The secondary air pump relay activates the secondary air pump shortly after the engine has been switched on. The switch-on period depends on the following criteria: engine temperature, load and engine speed. The purpose of air injection via the secondary air system is to carry out exhaust re-treatment during the engine warm-up phase. - Radiator fan The radiator fan is controlled by the DME control unit via a pulse-width-modulated signal (evaluation by electronic circuitry in the fan). The DME control unit controls the various radiator fan speeds by means of a pulse-width-modulated signal (between 10 and 90 %). Cycle ratios which are less than 5 % and greater than 95 % will not trigger the control device and are used for the purposes of fault recognition. The speed of the radiator fan is dependent on the coolant temperature at the radiator outlet (radiator) and the pressure in the air-conditioning system. When the car's road speed increases, the speed of the radiator fan decreases. - A/C compressor >E46 The A/C compressor relay switches the A/C compressor on or off. The A/C compressor relay is controlled by the DME control unit. >E85 The DME control unit is connected to the integrated automatic heating/air-conditioning system (IHKA). The IHKA switches the A/C compressor on or off. >E87, E90 The DME control unit supplies the signal to the junction box on the PT-CAN (Electrical System 2000). The junction box switches the A/C compressor on or off. - Suction-jet pump >N45 only: A suction-jet pump generates the low pressure required by the brake booster. The suction-jet pump is actuated by the DME control unit. [for further information, please refer to SI Technology (SBT) 11 02 05 130] System functions The following system functions are described: - Power supply and voltage monitoring - Electronic immobiliser - Air supply: differential air intake control "DISA" - Calculation of air mass (only N46B20 on E87, E90) - "Valvetronic" variable valve gear - "VANOS" variable camshaft control - Fuel injection - Ignition-circuit monitoring - Control of alternator - Engine cooling - Knock control - Tank ventilation - Lambda control system - Secondary air system - Evaluation of road speed signal - Monitoring of oil level and oil pressure - A/C compressor activationPower supply and voltage monitoring Power is supplied to the DME control unit as follows: The ignition starter switch sends a signal via terminal 15 ON to the DME control unit (separate Pin). The DME control unit then activates the DME master relay. This enables the DME master relay to supply power to other inputs on the DME control unit. The DME master relay also ensures that power is also supplied to other control units and components. For memory functions, the DME control unit also requires an uninterrupted power supply via terminal 30. The earth connection for the DME control unit is provided by several pins which are connected inside the control unit. The battery voltage is regularly monitored by the DME control unit. If the battery voltage falls below 2.5 volts or exceeds 24 volts, a fault is registered. The diagnosis become active 3 minutes after the engine has started. This ensures that the effects of the starting operation or starting assistance on the battery voltage will not be registered as a fault.Electronic immobiliser The electronic immobiliser is an anti-theft and start-enabling device. On the E46, the electronic immobiliser is controlled by the EWS control unit. On the E87, the electronic immobiliser is controlled by the CAS control unit. Every ignition key contains a transponder chip. The ignition lock is surrounded by a ring antenna. Power is supplied from the EWS or CAS control unit to the transponder chip via this coil (key does not require a battery). The power supply and data transfer function is performed according to the transformer principle. For this, the key sends identification data to the EWS or CAS control unit. If the identification data are correct, the EWS or CAS control unit activates the starter via a relay which is located in the control unit. At the same time, the EWS or CAS control unit sends the DME control unit an encoded release signal (rolling code) to start the engine. The DME control unit only enables the start if a correct release signal has been received from the EWS or CAS control unit. These operations may result in a slight delay in starting (up to half a second). The following faults are stored in the DME control unit: · missing or disturbed release signal from the EWS control unit · Rolling code from the EWS or CAS control unit does not tally with the rolling code computed by the DME control unit. If a fault is detected, the engine start is blocked.Air supply: differential air intake control "DISA" The intake strokes of the pistons generate cyclic pressure waves in the suction pipe. These pressure waves travel along the suction pipe and are reflected by the closed inlet valves. A precise matching of the suction pipe length with the valve response time produces the following effect: Shortly before the inlet valve is closed, a pressure maximum of the reflected air wave reaches the inlet valve. This has a supercharging effect which pumps a higher proportion of fresh air into the cylinder. The differentiated suction unit also makes use of the inherent benefits of both short and long suction pipes. · The effect of short suction pipes or suction pipes with a large diameter is a high efficiency in the upper engine speed range (and also low torque in the medium engine speed range). · Long suction pipes or suction pipes with a small diameter make high torque in the medium engine speed range possible. A front intake pipe is installed upstream of each resonating pipe. When the sliding sleeves are closed, the combined effect of the front intake pipe and resonating pipe is similar to that of a long suction pipe. The pulsating air column inside it increases torque in the medium engine speed range considerably. To increase performance in the higher engine speed range, the sliding sleeves are opened. This largely reduces the dynamics in the front intake pipes. The short resonating pipes which are now effective can make high performance figures in the upper engine speed range possible. The DME control unit adjusts the sliding sleeves via the DISA actuator (12 volts) with integrated transmission. The information as to whether a downwards or upwards gearshift was made is saved by the DME control unit. When the value falls below 4400 rpm, the DME control unit closes the sliding sleeve with the assistance of the DISA actuator. When the value of 4500 rpm is exceeded, the sliding sleeves are opened again. At changeover, these engine speeds are displaced reciprocally (hysteresis) to prevent the sleeves opening and closing in rapid succession. In the event of system failure, the sliding sleeves remain in their respective positions. The driver will be aware of system failure through a loss of power and reduction in the final speed. Once the engine has been switched off (terminal 15 OFF), the sliding sleeves are run once to their limit position. This prevents deposits accumulating and blockage of the sliding sleeve during longer journeys at low engine speeds.Calculation of air mass (only N46B20 on E87 and E90) The air mass drawn in is no longer measured directly by the air mass meter, but is rather calculated by the DME. For this calculation, a charge calculation (charge model) is programmed in the DME. The following signals are input into this calculation: · Inlet valve lift (load identification) · VANOS setting (load identification) · Throttle valve setting (choke action) · Intake-air temperature (air density correction) · Engine speed (cylinder fill levels) · Inlet pipe vacuum (correction for choke action) · Ambient pressure (air density due to altitude correction) The air mass so calculated is compared to: · Signal from oxygen sensor (fuel-air ratio) · Injection time (fuel quantity) The calculated air mass is corrected as necessary. In the event of the oxygen sensor failing, a fault will be entered in the DME fault memory (air mass plausibility check). In such cases, the calculated air mass is no longer compared."Valvetronic" variable valve gear Valvetronic was developed to reduce fuel consumption. The control device for Valvetronic is now integrated into the DME control unit. The quantity of air supplied to the engine when Valvetronic is active is adjusted by the variable valve lift on the inlet valve and not the throttle-valve actuator. An electrically-adjustable eccentric shaft changes the action of the camshaft on the roller cam follower via an intermediate lever. The result of this is variable valve lift. With Valvetronic, the throttle-valve actuator is activated for the following functions: · Engine start (warm-up) · Idle speed control · Full load operation · Emergency operation In all other operating conditions, the throttle valve only remains open far enough to induce a slight low pressure. This low pressure is required to ventilate the tank, for example. The DME control unit calculates the associated setting of Valvetronic using the position of the accelerator pedal and other variables. The DME control unit controls the Valvetronic actuator on the cylinder head. The Valvetronic actuator uses a worm gear to drive the eccentric shaft in the cylinder head oil chamber. The eccentric shaft sensor records the current position of the eccentric shaft. The eccentric shaft sensor is equipped with 2 angle sensors. The DME control unit adjusts the current position of the eccentric shaft via the Valvetronic actuator until the nominal position is reached. For safety reasons, 2 angle sensors are used with characteristic curves which have opposing directions. Both signals are digitally transmitted to the DME control unit. The DME control unit supplies 5 volts to both angle sensors. Both signals from the eccentric shaft sensors are continuously monitored by the DME control unit. Checks are made as to whether the signals are plausible in their own right and also in relation to one another. The signals may not differ. Where a short circuit or fault develops, the signals lie outside the measuring range. The DME control unit continuously checks whether the actual position of the eccentric shaft corresponds with its nominal position. This makes it possible to detect any stiff movements in the mechanics. In the event of a fault, the valves are opened as wide as possible. The air supply is controlled by the throttle valve. If the actual position of the eccentric shaft cannot be detected, the valves are opened to the maximum extent without regulation (controlled emergency operation). In order to achieve the correct valve opening, an adaptation must be made to balance all tolerances in the valve gear. During this adaptation process, the mechanical stops on the eccentric shaft are adjusted. The positions registered are subsequently saved. These positions are used as the basis for calculating the actual valve lift at any point during operation. The adaptation process is automatic: each time the engine is restarted, the position of the eccentric shaft is compared with the values registered. If following a repair, for example, a different position of the eccentric shaft is detected, the adaptation process is carried out. In addition, the adaptation can be initiated via the BMW diagnosis system."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 · reduction in fuel consumption A controlled VANOS adjustment unit is mounted at both intake and exhaust camshafts. A VANOS solenoid valve is used to control the 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 adjustment unit accordingly. The control of the intake and exhaust camshaft is variable within their maximum adjustment range. Once the correct camshaft position has been reached, the VANOS solenoid valves ensure that the oil volume in the servo control cylinders in both chambers remains constant. This keeps the camshafts in this position. To perform the adjustment, the variable camshaft control requires information on the current position of the camshaft. Camshaft sensors on the intake and exhaust end record the position of the camshafts. When the engine is started, the inlet camshaft is in the end position ("retarded" position). When the engine is started, the exhaust camshaft is pretensioned by a spring and held in the "advanced" position.Fuel injection During fully sequential fuel injection, each injection valve is controlled by means of its own final stage. Fully sequential fuel injection has the following advantages: · improved fuel preparation for each individual cylinder · adaptation of the fuel injection timing to suit the engine's operating condition (engine speed, load, engine temperature) · cylinder-selective correction of injected fuel quantity for varying load (during a cycle, the fuel injection timing can be corrected by extending or shortening it) · cylinder-selective cutoff (e.g. when an ignition coil is defective) · diagnosis for each individual injection valve possible The control of each injection valve by means of its own individual final stage achieves a fuel build-up which is the same in all cylinders. This ensures a uniformly-effective fuel preparation throughout. The fuel build-up time is variable and depends on the load, engine speed and engine temperature. As it is only injected once per camshaft rotation, the spread of fuel due to tolerances in the components is reduced. In addition, the idle-running performance is improved as the response and dropout times at the injection valves are reduced. Moreover, a marginal reduction in fuel consumption is also achieved. When the vehicle is in motion and there is a sudden acceleration or the throttle is closed, the fuel injection period can be adjusted. If the injection valves are still open, the mixture at every valve can be adjusted by extending or shortening the fuel injection period. This achieves an improved engine response.Ignition-circuit monitoring The current in the primary coil for the ignition coil is used to monitor the ignition circuit. When the engine is switched on, the current must stay within specific values during certain time thresholds. The ignition diagnosis monitors the: · primary power circuit for the ignition coil · ignition wiring harness · secondary power circuit for the ignition coil with the spark plug The ignition-circuit monitoring can detect the following faults: · short circuit at the primary end of the ignition coil · short circuit at the secondary end of the ignition coil · Spark plug · break in line to control device · defective ignition output stage The following are not detected: · intermittent faults such as loose contacts in the line to the control device · spark-over in high-tension circuit parallel to spark gab where a short-circuit in the coil does not developControl of alternator (bit-serial data interface) The following functions have been implemented in the DME control unit for the alternator with bit-serial data interface: · switching the alternator on and off using defined parameters · specification of the alternator's maximum permissible power consumption · calculation of the input torque for the alternator based on the power consumption · control of the alternator's response when higher electrical loads are connected (Load-Response function) · diagnosis for the data line between alternator and DME control unit · storage of faults which develop in the alternator in the fault memory of the DME control unit · activation of the charge telltale light in the instrument cluster via bus connection The principal function of the alternator is also guaranteed when communication between the alternator and DME control unit is interrupted. The following fault causes can be distinguished in fault memory entries: · Overheating protection: The alternator is overloaded. For safety reasons, the alternator voltage is reduced until the alternator has cooled down (charge telltale light does not light up). · Mechanical fault: There is a mechanical block in the alternator. or: The belt drive is defective. · Electrical fault: Excitation diode defective, excitation coil has been interrupted, overvoltage due to defective governor. · Communication failure: Line between DME control unit and alternator defective. An interruption or short circuit in the alternator coils will not be detected.Engine cooling The opening and closing of the map thermostat (N46 only) is controlled by a characteristic map. This regulating operation can be split into 3 operating ranges: · Map thermostat closed: The coolant only flows through the engine and the coolant circuit is closed. · Map thermostat open: The entire coolant volume flows through the radiator. This results in maximum use of the available cooling output. · Control range of the map thermostat: A proportion of the coolant flows through the radiator. The map thermostat maintains a constant coolant temperature within the control range at the engine inlet. In this operating range, the coolant temperature can now be selectively controlled with the assistance of the map thermostat. This means that a high coolant temperature can be set in the part-load range of the engine. High operating temperatures in the part-load range result in improved combustion. This in turn leads to reduced consumption and exhaust emission. During full load operation, certain disadvantages are associated with higher operating temperatures (retarding of ignition due to knock). A lower coolant temperature is therefore specifically set during full load operation with the assistance of the map thermostat.Knock control The engine is equipped with a cylinder-selective adaptive knock control. 2 knock sensors detect the combustion knock (cylinders 1 and 2, cylinders 3 and 4). The sensor signals are evaluated in the DME control unit. If the engine is operated with combustion knock for longer periods of time, this can cause serious damage. Knock is encouraged by: · an increased compression ratio · high cylinder fill levels · an inferior fuel grade (RM/MM) · a high intake air and engine temperature The value of the compression ratio can also become too high due to spread due to deposits or the manufacturing process. For engines without knock control, these unfavourable effects must be taken into consideration when designing the ignition system by applying a safety margin to the anti-knock limit. This makes reduced effectiveness in the upper load range unavoidable. The knock control prevents knock. The firing point of the relevant cylinder (cylinder-selective) is set as far as possible in the retarded direction only when a knocking risk is present. This means that the ignition control grid can be designed around ideal consumption values (without having to take the anti-knock limit into account). A safety margin is no longer necessary. The knock control performs all the necessary corrections to the firing point due to knock and also makes trouble-free driving with regular grade petrol (minimum RM 91) possible. The knock control provides: · protection from damage caused by knocking (also in unfavourable conditions) · reduced consumption and increased torque throughout the entire upper load range (according to the quality of fuel used) · high economic efficiency through optimum use of the available fuel quality and by taking the specific engine condition into account The knock control self-diagnosis performs the following checks: · check for disturbed signal, e.g. breaks in wiring or defective connector · self-test for evaluating circuit · check of engine noise level recorded by the knock sensor If a fault is identified during one of these checks, the knock control is switched off. Control of the ignition angle is adopted by an emergency program. A fault is simultaneously registered in the fault memory. The emergency program ensures damage-free operation from RM 91 as minimum. The emergency program is dependent on the load, engine speed and engine temperature.Tank ventilation The fuel evaporation control valve controls the regeneration of the activated carbon filter with scavenging air. Scavenging air drawn through the activated carbon filter is enriched with hydrocarbons (HC) depending on the loading of the activated carbon. The scavenging air is subsequently fed to the engine for combustion. The formation of hydrocarbons in the fuel tank is dependent on: · fuel temperature and ambient temperature · air pressure · fill level in the fuel tank In a current-free state, the fuel evaporation control valve is closed. This prevents the ingress of fuel vapour from the activated carbon filter into the suction pipe when the engine is switched off.Lambda control system Optimum efficiency of the catalytic converter can only be achieved if an ideal fuel/air ratio is used for combustion ( l = 1). To this end, oxygen sensors are used upstream and downstream of the catalytic converter. The oxygen sensors upstream of the catalytic converter have a steady characteristic output curve (measure oxygen content in rich and lean ranges.) The measurement method employed by this oxygen sensor is different to an oxygen sensor with an erratic characteristic output curve. The oxygen sensor is therefore connected using 6 pins instead of 4. · Oxygen sensors upstream of catalytic converter The oxygen sensors upstream of the catalytic converter (control sensors) are used to assess the composition of the exhaust gas. The control sensors are screwed into the exhaust manifold. The oxygen sensors measure the residual oxygen content in the exhaust fumes. The voltage values determined are relayed to the DME control unit. The DME control unit corrects the mixture composition by adjusting the injection period. Values which are greater or less than l =1 are aimed at depending on the operating condition. · Oxygen sensors downstream of catalytic converter The oxygen sensors downstream of the catalytic converter (monitoring sensors) are used to monitor the control sensors. In addition to this, the function of the catalytic converter is monitored. In the 4-cylinder engine, the monitoring sensors have a special arrangement: The monitoring sensor for cylinders 1 and 4 is positioned between the primary and main catalytic converter. The monitoring sensor for cylinders 2 and 3 is positioned downstream of the main catalytic converter. To ensure full operational reliability of the oxygen sensors upstream of the catalytic converter, a temperature of approximately 750 ° C is required (350 ° C for oxygen sensors downstream of the catalytic converter). For this reason, all oxygen sensors are heated. The oxygen sensor heating is controlled by the DME control unit. When the engine is cold, the oxygen sensor heating remains switched off, as the condensate which is present would otherwise destroy a hot oxygen sensor due to thermal strain. This means that the lambda control becomes active shortly after the engine is started. The oxygen sensor is initially warmed up using a reduced heating power, to avoid imposing unnecessary loads on it due to thermal strain.Secondary air system (not on E87, E90 as catalytic converter is located close to the engine) The purpose of the secondary air system is to perform exhaust re-treatment during the engine warm-up phase. During this process, fresh air is blown directly into the exhaust manifold thus increasing the rate at which the catalytic converter is heated (thermal post-combustion of exhaust fumes). The secondary air pump is activated by the DME control unit via the secondary air pump relay shortly after the engine has started. The switch-on period is dependent on the following marginal conditions: · Engine temperature · Load · Engine speed The pressure created by the secondary air pump opens the secondary air valve in the direction of the exhaust manifold. When closed, the secondary air valve protects the secondary air pump from deposits due to exhaust fumes. When the secondary air pump is activated, the oxygen-sensor voltage is monitored by the DME control unit. Providing the secondary air system is working correctly, the oxygen-sensor voltage generally falls within the lean range. The oxygen-sensor voltage is now registered by the DME control unit at regular intervals (every 20 ms). If an oxygen-sensor voltage measured falls in the lean range, an internal counter is increased. Once this counter exceeds a defined threshold value, the system is determined to be fully functional. If this threshold value is not reached, the DME control unit registers a fault in the secondary air system (fault memory entry).Evaluation of road speed signal The road-speed signal is required by the DME control unit in order to perform several functions: · Cruise control: Once the maximum road speed has been reached, the fuel preparation and ignition are adjusted. If required, individual ignition and injection signals are suppressed. A "soft" speed limiting function is thus carried out. · Control of A/C compressor: When the air-conditioning system is switched on, the A/C compressor is switched off during full-load acceleration: Condition: road speed is less than 13 km/h. · Idle speed control: When the vehicle is at a standstill, the idle speed is controlled around a fixed value (fixed slightly above engine speed at standstill). If the car's road speed is 0 km/h, the idle speed is adjusted (depends on A/C compressor ON, selected drive position for automatic transmission, light ON). · Poor-road-surface detection: At low road speeds, the check for smooth engine operation is switched off.Monitoring of oil level and engine oil pressure The thermal oil level sensor reports the engine oil level and engine oil temperature back to the DME control unit. A temperature sensor in the oil-level sensor indicates the engine oil temperature. The oil pressure is indicated by the oil-pressure switch. Calculation of oil level:The DME control unit works out the time required to heat up and cool the engine oil. The DME control unit activates the warning and indicator lamp in the instrument cluster via the PT-CAN (red: oil pressure low; yellow: oil level low). > E87, E90 with electronic oil level check: The dipstick, including the guide pipe, is discontinued on the N45 and N46 engines. The engine oil level is measured by a thermal oil level sensor. The measured value is displayed by means of a bar gauge in the instrument cluster. On vehicles with Central Information Display, the measured value is displayed on the CID. The signal from the thermal oil level sensor is evaluated by the DME. Besides the oil level, the thermal oil level sensor also indicates the engine oil temperature. The engine oil temperature is used together with the coolant temperature to calculate the engine temperature.A/C compressor activation The DME control unit supplies the signal to actuate the A/C compressor. The A/C compressor is switched off under the following conditions: · Full engine load · Road speed under 13 km/h >E87, E90 The junction box actuates the A/C compressor. The DME sends the signal on the bus system. Notes for service staff The following information is available for service staff: - General information: [more ...] - Diagnosis: [more ...] - Encoding/programming: --- - Car & Key Memory: ---
...right AB? hehe
