Thermal Management, Function - GF07.10-P-1012MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects the engine running by evaluating the signals of the crankshaft Hall sensor (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Heat management
The ME-SFI [ME] control unit regulates the coolant temperature of the engine via the thermal management.
The following advantages arise from this:
- Rapid attainment of the optimum 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 signals of the following sensors for controlling the thermal management:
- Engine oil temperature sensor (B1)
- Coolant temperature sensor (B11/4)
- Left charge air temperature sensor (B17/14)
- Right charge air temperature sensor (B17/15)
- Pressure sensor downstream of left throttle valve (B28/22)
- Pressure sensor downstream of right throttle valve (B28/23)
- Accelerator pedal sensor (B37) (model 205, 253)
With model 213, the powertrain control unit (N127) reads in the signals from the accelerator pedal sensor directly and sends these via the drive train CAN (CAN C1) to the ME-SFI [ME] control unit.
- Crankshaft Hall sensor
- Temperature sensor in the ME-SFI [ME] control unit
The ME-SFI [ME] control unit also evaluates the following variables:
- Requirements of the air conditioning system
The climate control unit (N22/1) transmits the requests for RPM and torque increase via the interior CAN (CAN B), the electronic ignition lock control unit (N73), the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drive train CAN (CAN C1) to the ME-SFI [ME] control unit.
- Vehicle speed
The instrument cluster (A1) transmits the vehicle speed via the user interface CAN (CAN HMI), the electronic ignition lock control unit, the chassis FlexRay, the powertrain control unit and the drive train CAN to the ME-SFI [ME] control unit.
- Wheel speed
The Electronic Stability Program control unit (N30/4) transmits the wheel speeds via the chassis FlexRay, the powertrain control unit and the drive train CAN to the ME-SFI [ME] control unit.
- Transmission oil temperature
The fully integrated transmission control unit (Y3/8n4) transmits the transmission oil temperature via the drive train CAN to the ME-SFI [ME] control unit.
High temperature circuit and oil cooling system, shown in diagram form in model 205
The thermal management monitors the following statuses:
- Heating the two-valve thermostat
- Fan control
- Overheating protection
Heating the two-valve thermostat
The temperature of the coolant can be controlled variably by the heatable two-slide thermostat. There is a coolant thermostat heating element in the two-slide thermostat which is actuated as required by the ME-SFI [ME] control unit 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
With a coolant temperature of below 80°C and an engine RPM of less than 3000, the valves of the two-valve thermostat close off the flow of coolant to and from the engine and to the engine cooler.
The shorter engine warm-up phase thanks to stationary coolant leads to fuel savings and therefore reduction of the CO 2
output.
Bypass mode
In short-circuit mode, the flow of coolant to and from the engine is enabled. The coolant temperature is raised in partial-load range to approx. 105°C (heating element de-energized). Due to the higher engine oil temperature, the lubricity of the engine oil increases. There is less friction. The mixture formation improves thanks to less fuel condensation at the cylinder barrels.
- Coolant temperature 40 to 65°C, heating element energized
- Coolant temperature 80 to 105°C, heating element de-energized
Mixed mode
In mixed mode, the flow of coolant to and from the engine and to the engine cooler is enabled.
- Coolant temperature 65 to 90°C, heating element is energized
- Coolant temperature 105 to 120°C, heating element is de-energized
Radiator operation
In radiator mode, the flow of coolant from the engine to the engine cooler is enabled.
- Coolant temperature over 120°C, heating element is de-energized
- Coolant temperature over 90°C, heating element is energized
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
The fail-safe position prevents engine damage if the coolant is stationary and the engine RPM is above 3000 RPM. With the opening of the differential pressure disc, the flow of coolant is directed back from the engine to the engine (short circuit).
With coolant temperatures above 120°C, the two-slide thermostat is always completely open (limp-home function).
Fan control
The powertrain control unit actuates the fan motor (M4/7) via the drive train LIN (LIN C3).
In the event of interference in the signal line the fan motor automatically switches to maximum RPM (emergency running of the fan).
If the air conditioning system is operating, the fan motor is also actuated. The climate control unit sends the fan nominal speed via the interior CAN, the electronic ignition lock control unit and the chassis FlexRay to the powertrain control unit. The powertrain control unit then actuates the fan motor via the drive train LIN accordingly. If the powertrain control unit does not receive a valid fan request, the fan motor is actuated at maximum RPM.
Delayed fan switch off
After switching the engine off (circuit 15 OFF), the fan motor runs on for up to 5 minutes if the coolant temperature, the temperature of the ME-SFI [ME] control unit or a thermal input integral calculated on the basis of the engine load, the coolant temperature, the vehicle speed and the outside temperature (averaged over the last 6 minutes) has exceeded specified threshold values. If the on-board electrical system voltage drops down excessively, the delayed fan switch off is suppressed.
The delayed fan switch-off is not aborted when circuit 15 is switched 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.
Overheating protection
In a case of thermal overload the overheating protection protects the catalytic converters against engine damage and overheating damage. The ME-SFI [ME] control unit reads in the signals of the coolant temperature sensor and the engine oil temperature sensor for this.
The following measures are taken for overheating protection:
- Ignition angle setting in the direction of "retarded", depending on engine load and engine speed, from a coolant temperature of approx. 90°C and a charge air temperature of approx. 20°C
- Reduction of the injection quantity at a coolant temperature above 106°C
- Controlling the injection duration
- Reducing the opening cross-section of the throttle valves, depending on the engine load and the engine RPM
- Actuation of the coolant thermostat heating element by the ME-SFI [ME] control unit
If the engine oil or coolant temperature is too high, a warning message in the instrument cluster is shown. The ME-SFI [ME] control unit transmits the request for output of the warning via the drive train CAN, the powertrain control unit, the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster.
| Electrical function schematic for heat management | Engine 177.9 in model 205, 253 | PE07.10-P-2712-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2712-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 | GF07.70-P-9998MNE |