Thermal management, function - GF07.10-P-1012MMA

ENGINE 157.9 in MODEL 212, 218 up to model year 2014 

ENGINE 278.9 in MODEL 207, 212, 218 up to model year 2014 

Function requirements for thermal management, general points 

• Circuit 87M (engine timing ON)
• Engine running

Thermal management, general 

The coolant temperature of the engine is regulated by the thermal management controlled by the ME-SFI [ME] control unit (N3/10). This has the following advantages:

• Optimum operating temperature is reached faster
• Reduction of the exhaust emissions
• Fuel savings (up to approx. 4%)
• Improved heat comfort.

Thermal management is performed based on the following sensors and signals:

• Coolant temperature sensor (B11/4) (model 207, 212), coolant temperature sensor (B11/4) (model 218)
• Charge air temperature sensor (B17/8)
• Pressure sensor downstream of throttle valve (B28/7), engine load
• Accelerator pedal sensor (B37), accelerator pedal operation (how fast and how far driver type calm or sporty)
• Oil sensor (oil level, temperature and quality) (B40) (for engine 157)
• Crankshaft Hall sensor (B70), engine speed
• Temperature sensor in the ME-SFI [ME] control unit
• Front SAM control unit with fuse and relay module (N10/1), outside air temperature via the chassis CAN (CAN E)
• Automatic air conditioning control and operating unit (N22/7), air conditioning system status via the interior CAN (CAN B) and chassis CAN
• Instrument cluster (A1), vehicle speed via chassis CAN
• Electronic Stability Program control unit (N30/4) (except code (233) DISTRONIC PLUS) or Electronic Stability Program Premium control unit (N30/7) (for code (233) DISTRONIC PLUS), wheel speed signal via the chassis CAN
• Fully integrated transmission control controller unit (Y3/8), status of transmission oil temperature via drive train CAN (CAN C)

Function sequence for thermal management 

The thermal management system is described in the following steps:

• Function sequence for two-disk thermostat heating 
• Function sequence for fan control 
• Function sequence for overheating protection 

Function sequence for two-disk thermostat heating 

The coolant temperature can be varied by the heatable two-disk thermostat. For this purpose, the two-disk thermostat contains the coolant thermostat heating element (R48), which the ME-SFI control unit actuates with a ground signal as required.

The two-disk thermostat can be set to three positions:

• Bypass mode 
• Mixed-fuel mode 
• Cooler mode 

Two-disk thermostat positions 

Short-circuit mode position 

Heating element deenergized for coolant temperature <100°C Heating element energized for coolant temperature <65°C To optimize in-engine friction and thus save fuel, the coolant temperature can be raised to about 105°C in partial-load range (heating element is deenergized).

The friction power is reduced by the higher engine oil temperature and mixture formation is improved by reducing the fuel condensation in the cylinder barrels.

Mixed-fuel mode position 

Heating element deenergized for coolant temperature 100 to 115°C Heating element energized for coolant temperature 65 to 100°C

Radiator mode position 

Heating element deenergized for coolant temperature >115°C Heating element energized for coolant temperature >100°C

Heating the two-disk thermostat (heating element energized) causes it to open and the coolant passes through the engine radiator.

At wide open throttle, the two-disk thermostat can be opened very quickly. The coolant temperature can be lowered in the process to about 80°C whereby the best possible engine cooling and knock-free combustion is achieved.

When coolant temperature is above about 115°C, the two-disk thermostat is always fully open (limp-home function), whether the heating element is energized or not.

Function sequence for fan control 

The ME-SFI [ME] control unit actuates the internal combustion engine fan motor and air conditioning system with integrated control (M4/7). The specified fan speed is set by the ME-SFI [ME] control unit with a pulse width modulated signal (PWM signal).

The duty cycle of the PWM signal is 10 to 90%.

This means, for example:

10 % fan motor off "OFF"

20 % fan motor "ON", minimum rpm

90 % fan motor "ON", maximum rpm

If actuation is faulty, the air fan motor rotates at the maximum rotational speed (fan emergency mode).

The automatic air conditioning control and operating unit transmits the air conditioning status via the interior and chassis CAN to the ME-SFI [ME] control unit.

Delayed fan switch off 

After "ignition OFF", the fan motor continues to run for up to 6 min. if the coolant temperature or engine oil temperature is above the specified maximum value.

The PWM signal duty cycle is 40% maximum while the delayed fan switch off is active.

If the battery voltage drops too much during this time, delayed fan switch off is stopped.

Function sequence for overheating protection 

In case of thermal overload, the overheating protection protects against engine damage and overheating damage to the catalytic converter. If the coolant or charge air temperature is too high, the ME-SFI [ME] control unit no longer fully opens the boost pressure control flap depending on engine speed and load. Furthermore, the throttle valve of the throttle valve actuator (M16/6) can no longer be opened fully. The ME-SFI [ME] control unit shortens the injection time of the fuel injectors (Y76) according to the smaller air mass.

The ME-SFI [ME] control unit also actuates the coolant thermostat heating element so that the two-disk thermostat is fully open and all the coolant is cooled by the engine radiator.

If engine oil or coolant temperature is too high, a warning message is shown in the multifunction display (A1p13) on the instrument cluster. For this purpose, the ME-SFI [ME] control unit transmits the appropriate signal over the chassis CAN to the instrument cluster.

	Electrical function schematic for heat management	MODEL 207	PE07.10-P-2712-97EAI
		MODEL 212	PE07.10-P-2712-97DAK
		MODEL 218	PE07.10-P-2712-97XAC
	Overview of system components for gasoline injection and ignition system with direct injection	ENGINE 157.9 in MODEL 212, 218 up to model year 2014 ENGINE 278.9 in MODEL 207, 212, 218 up to model year 2014	GF07.70-P-9998MM