Thermal Management, Function - GF07.10-P-1012MNF
Engine 176.9 in model 463
as of model year 2016 up to model year 2019
Function requirements for thermal management, general points
- Circuit 87M (Engine management ON)
- Engine runs
Circuit 87M (F58kN) is activated for circuit 15 ON.
Thermal management, general
The engine coolant temperature is regulated via the heat management controlled by the ME-SFI [ME] control unit (N3/10). The following advantages arise from this:
- Rapid reaching of the optimal operating temperature
- Reduction of the exhaust emissions
- Fuel savings (up to about 4 %)
- Improved heating comfort
The ME-SFI [ME] control unit reads in the following signals to the control the heat management:
- Engine oil temperature from engine oil temperature sensor (B1)
- Coolant temperature from coolant temperature sensor (B11/4)
- Charge air temperature from left charge air temperature sensor (B17/14) and right charge air temperature sensor (B17/15)
- Engine load from pressure sensor downstream of left throttle valve (B28/22) and pressure sensor downstream of right throttle valve (B28/23)
- Accelerator pedal actuation from accelerator pedal sensor (B37)
- Engine speed from crankshaft Hall sensor (B70)
- Control unit temperature from temperature sensor in ME-SFI control unit
- Status of air conditioning
The control and operating unit of the climate control (N22/7) transmits the status of the air conditioning system via the interior CAN (CAN B), electronic ignition lock control unit (N73), suspension CAN 1 (CAN E1), powertrain control unit (N127) and drive CAN (CAN C) to the ME-SFI [ME] control unit.
- Vehicle speed
The instrument cluster (A1) transmits the vehicle speed via the interior CAN, electronic ignition lock control unit, suspension CAN 1, powertrain control unit and drive CAN to the ME-SFI [ME] control unit.
- Wheel speeds
The Electronic Stability Program control unit (N30/4) transmits the wheel speeds via the suspension CAN 1, powertrain control unit and drive CAN to the ME-SFI [ME] control unit.
- Transmission oil temperature
The transmission oil temperature sensor records the transmission oil temperature. The fully integrated transmission control unit (Y3/8n4) transmits the signals via the drive CAN to the ME-SFI [ME] control unit.
Schematic diagram of coolant circuit
Function sequence for thermal management
The thermal management function encompasses the following subfunctions:
- Function sequence for heating the two-slide thermostat
- Function sequence for fan control
- Function sequence for overheating protection
- Function sequence for heating system switch-off
- Function sequence for air flap control
Function sequence for heating the two-slide thermostat
The temperature of the coolant can be controlled variably by the heatable two-slide thermostat. For this purpose, there is a coolant thermostat heating element in the two-valve thermostat that is actuated by the ME-SFI [ME] control unit in a demand-dependent manner using a ground signal.
The two-slide thermostat can assume five positions:
- Stationary coolant
- Bypass mode
- Mixed mode
- Radiator operation
- Fail-safe position
Stationary coolant
At a coolant temperature < 80 °C and an engine speed < 3000 rpm, both valves on the two-valve thermostat are closed completely.
Shortening of the engine warm-up phase by stationary coolant leads to fuel saving and therefore reduction of the CO2
output.
Bypass mode
- De-energized heating element (coolant temperature 80 to 105 °C)
- Energized heating element (coolant temperature 40 to 65 °C)
In partial-load range, the coolant temperature can be raised to approx. 105 °C (heating element de-energized). Therefore the friction power can be improved due to a higher engine oil temperature and the mixture formation improved due to less fuel condensation on the cylinder barrels.
Mixed mode
- De-energized heating element (coolant temperature 105 to 120 °C)
- Energized heating element (coolant temperature 65 to 90 °C)
Radiator operation
- De-energized heating element (coolant temperature>120 °C)
- Energized heating element (coolant temperature>90 °C)
Through heating the two-slide thermostat (heating element energized) this opens and the coolant is led through the engine radiator. For wide open throttle the two-slide thermostat is very quickly opened. The coolant temperature can be lowered whereby the best possible engine cooling and knock-free combustion are achieved.
Fail-safe position
To prevent damage, the fail/safe position is adopted in the case of stationary coolant and an engine speed > 3000 rpm. The coolant is passed back over the differential pressure disc to the engine (short circuit).
Above a coolant temperature of approx. 120 °C, the two-valve thermostat is always fully opened (limp-home function) irrespective of the energization of the heating element).
Function sequence for fan control
The powertrain control unit directly actuates the fan motor (M4/7). The ME-SFI control unit transmits the fan nominal speed via drive CAN to the powertrain control unit. If the powertrain control unit does not receive a valid fan request, the fan motor is actuated at maximum rpm. In the case of a fault in the signal line (loss of frequency) by the powertrain control unit, the fan motor switches itself to the maximum rpm (fan emergency mode).
The climate control unit transmits the status of the air conditioning system and a fan request via the interior CAN, electronic ignition lock control unit and suspension CAN 1 to the powertrain control unit.
Delayed fan switch off:
If the coolant temperature, the ME-SFI [ME] control unit temperature or a heat input integral calculated from the engine load, coolant temperature, vehicle speed and outside temperature (averaged over the last 6 min) exceeds a specified threshold value, the fan motor will run-on in case of ignition OFF for up to 5 min. If the battery voltage drops down a lot, the delayed fan switch off is suppressed.
The delayed fan switch off is not broken off by "ignition ON". When starting the engine in delayed fan switch off the fan regulation for normal operation is suppressed until the delayed fan switch off is completed.
Function sequence for overheating protection
In a case of thermal overload the overheating protection protects the catalytic converters against engine damage and overheating damage. To this the ME-SFI [ME] control unit reads in the signals of the coolant temperature sensor and the engine oil temperature sensor.
The following measures should be taken to avoid overheating of the engine:
- A characteristics map-dependent ignition angle setting in the direction "retarded", dependent on the engine load and-engine speed, as of a coolant temperature of approx. 90 °C and a charge air temperature of approx. 20 °C
- Characteristics map-dependent reduction of the injection quantity for a coolant temperature of more than 106 °C
- Regulation of the injection period through actuation of:
- Left quantity control valve (Y94/1)
- Right quantity control valve (Y94/2)
- Fuel injector for cylinder 1 (Y76/1)
- Fuel injector for cylinder 2 (Y76/2)
- Fuel injector for cylinder 3 (Y76/3)
- Fuel injector for cylinder 4 (Y76/4)
- Fuel injector for cylinder 5 (Y76/5)
- Fuel injector for cylinder 6 (Y76/6)
- Fuel injector for cylinder 7 (Y76/7)
- Fuel injector for cylinder 8 (Y76/8)
- Reduced opening of left throttle valve actuator (M16/60) and right throttle valve actuator (M16/61), depending on engine load and engine speed
- Actuation of coolant thermostat heating element by ME-SFI [ME] control unit
If the engine oil or coolant temperature is too high, a warning message in instrument cluster is shown. The ME-SFI [ME] control unit transmits the warning message output request via the drive CAN, powertrain control unit, suspension CAN 1, electronic ignition lock control unit and interior CAN to the instrument cluster.
Function sequence for heating system switch-off
To heat up the engine more quickly, the ME-SFI [ME] control unit deactivates the coolant circuit of the heating system via the heating system shutoff valve (Y16/2).
Function sequence for air flap control
The air flowing through the engine compartment is routed via an air duct (passive duct) at the hood in a targeted manner into the area between the cylinder banks in order to be able to accordingly flow into the component parts positioned there (exhaust gas turbocharger and catalytic converters).
In certain operating statuses, the air cross-section of the air duct must be closed in order to prevent a recirculation of the radiator exhaust air via the air duct, e. g. in the case of engine fan operation at low vehicle speeds. This cross-section is released or closed off by the air flap. Air flap is actuated via the engine cooling air flap actuator motor (M107). The powertrain control unit actuates the engine cooling air flap actuator motor via the Drivetrain LIN (LIN C3).
| Electrical function schematic for heat management | PE07.10-P-2712-97ZGD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNF |