ME-SFI thermal management, function - GF07.61-P-4012G
ENGINE 273 in MODEL 463.202/222/236/237 up to 31.5.12 as of model year 2009/YoM 08
Function requirements for thermal management for the ME-SFI gasoline injection and ignition system (engine electronic) (ME), general points
- Circuit 87M ON (engine control ON)
- Engine running
ME-SFI thermal management, general points
The coolant temperature of the engine is regulated by the controlled thermal management from ME-SFI [ME] control unit.
This has the following advantages:
- Operating temperature is reached faster
- Reduction of exhaust gas emissions
- Fuel savings (up to around 4%)
- Improved heat comfort.
Thermal management is performed according to the following sensors and signals:
- Hot film MAF sensor, engine load
- Intake air temperature sensor
- Coolant temperature sensor
- Accelerator pedal sensor, accelerator pedal operation (how fast and how far → driver type calm or sporty)
- Crankshaft Hall sensor, engine speed
- AAC [KLA] control and operating unit, outside air temperature and status of the air conditioning via the interior CAN and drive train CAN
- ESP control unit, vehicle speed via the drive train CAN
ME-SFI thermal management, function sequence
Thermal management consists of the following subfunctions:
- Heating the three-disk thermostat
- Fan control
Heating the three-disk thermostat
Depending on the operating conditions (performance map), the ME-SFI [ME] control unit actuates the heating element in the three-disk thermostat valve with a ground signal. The voltage is supplied through "circuit 87 M2".
When heated, the three-disk thermostat opens in the coolant thermostat. In this way the coolant temperature of 80 to 100°C is regulated via the duty cycle.
The three-disk thermostat can be set in four positions:
- Full throttling
- Bypass mode
- Mixed mode
- Cooler mode
Position of the three-disk thermostat
Full throttling
For a cold start the three-disk thermostat is not heated. The engine oil is warmed up via the heat exchanger at the front on the engine.
The closing plate on the three-disk thermostat opens but dependent on the pressure (by the rotating coolant pump) from about 3500 rpm (short circuit operation).
Bypass mode
From an outside temperature >12°C and a coolant temperature of 45°C or from a coolant temperature of about 70°C, switching to short-circuit operation takes place.
For short-circuit operation the three-disk thermostat is heated less and part of the coolant flows back into the engine circuit. Short-circuit operation can be 'choked', so that the heater responds more quickly.
Mixed-fuel mode
The mixed-fuel operation is enabled if the coolant temperature reaches 98°C for the first time after the start.
For mixed-fuel operation the three-disk thermostat is heated in such a way that the coolant flows through the engine radiator and the engine circuit.
At partial load, the three-disk thermostat regulates at an increased coolant temperature of around 100°C.
In order to prevent critical coolant temperatures from occurring, the range of increased coolant temperature is lowered under the following conditions:
- Intake air temperature >38°C
- Engine speed >3000 rpm
- Engine load > 30%
- Sporty driver
The coolant temperature is thus lowered according to outside air temperature. If outside air temperature is below 12°C, the temperature is lowered to about 90 °C and if outside air temperature is above 12°C, it is lowered to about 80°C.
Cooler mode
The three-disk thermostat is heated constantly during radiator operation. The coolant only flows through the engine radiator. If coolant temperature is above about 110°C, the three-disk thermostat is open continuously, irrespective of heating (limp-home function).
If the coolant temperature is too high, a warning message is shown on the multifunction display (A1p13) of the instrument cluster. The ME-SFI [ME] control unit sends an appropriate signal via the engine compartment CAN to the instrument cluster to do this.
Fan control
The ME-SFI [ME] control unit actuates the electrical radiator fan. The specified fan speed is set by the ME-SFI [ME] control unit in this way using a pulse width modulated signal (PWM signal).
The duty cycle of the PWM signal is 10 to 90%.
Meaning:
10%: Fan motor "OFF"
20%: Fan motor "ON", minimal rpm
90%: Fan motor "ON", maximum rpm
If the actuation is faulty, the electric suction fan rotates with maximum rotational speed (fan emergency mode).
The AAC [KLA] control and operating unit sends the air conditioning status to the ME-SFI [ME] control unit via the interior and engine compartment CAN.
Delayed fan switch off
For "ignition OFF", the radiator fan runs on for up to 5 min if the coolant temperature or engine oil temperature (calculated from the temperature model) exceed the specified maximum values.
The PWM signal duty cycle is 40% maximum while the delayed fan switch-off is active.
If the battery voltage is dropping too much, the delayed fan switch-off is stopped.
| Instrument cluster, component description | A1 | GF54.30-P-6000G | |
| Component description for ME-SFI [ME] control unit | N3/10 | GF07.61-P-6000G | |
| Component description for automatic air conditioning control and operating unit | N22 | GF83.40-P-3000G | |
| Component description for ESP control unit | N30/4 | GF42.45-P-5118G | |
| Component description for electronic ignition/starter switch control unit (EIS) | N73 | GF80.57-P-6000G |