Thermal Management, Function - GF07.10-D-1012TSB

Engine 274 in model 907 

Block diagram 

Function requirements for thermal management, general points 

• Circuit 87M ON (Engine management ON)
• Engine running (3).

Thermal management, general 

The coolant temperature of the engine (3) is regulated by the heat management that is controlled by the ME-SFI [ME] control unit (N3/36)

This is dependent on the following sensors and signals:

• Coolant temperature sensor (B11/21), via direct line
• Charge air temperature sensor upstream of throttle valve (B17), via direct line
• Charge air temperature sensor downstream of throttle valve (B17/16), via direct line
• Intake manifold pressure sensor (B28/24), via direct line
• Crankshaft Hall sensor (B70/2), via direct line
• Accelerator pedal module (A68), via powertrain control unit (N127) and drive CAN (CAN C)
• SAM control unit (N10), outside temperature via the interior CAN (CAN B), electronic ignition lock control unit (EZS) (N73/8), suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C)
• Automatic climate control control and operating unit (N22/2), air conditioning system status via climate control LIN (LIN B8) and SAM control unit (N10)
• ESP control unit® (N30/4), wheel speed via the suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C)
• Fully integrated transmission control (VGS) electric controller unit (N15/15), transmission oil temperature via the drive CAN (CAN C)

Coolant circuit, shown schematically 

Heat management 

The thermal management is described in the following points:

• Coolant thermostat regulation
• Overheating protection
• Fan control

Coolant thermostat regulation 

The ball rotary valve (48b) in the coolant thermostat (48) is opened and closed by the temperature-influenced expansion and contraction of the wax expansion element (48a) in a temperature range of approx.

98 to 108 °C.

In addition, actuation of the coolant thermostat heating element (R48/4) can be used to perform the opening and closing of the coolant thermostat (48) variably and depending on the engine requirements. For this purpose, the ME-SFI [ME] control unit (N3/36) actuates, depending on the operating conditions, the thermostat heating element (R48/4) with a ground signal.

The coolant thermostat (48) can adopt the following positions depending on the coolant temperature and the actuation by the ME-SFI [ME] control unit (N3/36):

• Closed 
• Open (mixed-fuel mode) 
• Open (radiator operation) 

View of coolant thermostat (48) closed 

Closed 

The ball rotary slide (48b) of the coolant thermostat (48) is closed if the following conditions are fulfilled:

• Coolant temperature < approx. 98 °C
• Thermostat heating element (R48/4) deenergized
• No wide open throttle request

In this position the coolant flows through the engine circuit and the heater heat exchanger as required (4). The engine radiator (1) is not flowed through.

Open (mixed-fuel mode) 

The ball rotary slide (48b) begins to open if one of the following conditions is fulfilled:

• Reaching a coolant temperature of approx. 98 °C for the first time after starting (no full-load request).
• Thermostat heating element (R48/4) is energized.

In a coolant temperature range of approx. 98 to 108 °C or depending on the energization of the thermostat heating element (R48/4), the wax expansion element (48a) starts the expand and actuates the ball rotary valve (48b). This releases the connection to the engine radiator (1).

The opening cross-section of the ball rotary slide (48) is adapted according to the temperature of the expanding wax element (48a). The coolant flow to the engine radiator (1) is varied in this way.

Open (radiator operation) 

Where a coolant temperature of approx. 108 °C is exceeded, the ball rotary valve (48b) is fully opened and the coolant can flow into the radiator (1) in an unrestricted manner.

For a coolant temperature > 85 °C and a full load request, the ball rotary valve (48b) also opens fully by heating the wax expansion element (48a).

In order to avoid reaching critical temperature ranges the coolant temperature is lowered under the following conditions:

• Intake air temperature > 38 °C
• Engine speed > 3000 RPM
• Engine load > 30 %

The coolant temperature is lowered here dependent on the air outside temperature the heating of the expanding wax element (48a):

• Outside temperature ≤ 12 °C to approx. 90 °C
• Outside temperature > 12 °C to approx. 80 °C

Overheating protection 

In the event of thermal overload, the overheating protection protects against engine damage and overheating damage to the near-engine mounted catalytic converter. For this purpose, the following measures are implemented:

• 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
• Less opening of the throttle valve actuator (M16/50), dependent on the engine load and rotational speed
• Shortening of the injection period of the fuel injectors (Y62) according to the lower air mass
• Energization of thermostat heating element (R48/4) by the ME-SFI [ME] control unit (N3/36) for the full opening of the ball rotary valve (48b)

A warning message in the instrument cluster is shown for an excessively high coolant temperature. For this purpose, the ME-SFI [ME] control unit (N3/36) transmits a corresponding signal via the drive CAN (CAN C) to the powertrain control unit (N127) and on via the suspension FlexRay (Flex E), EZS control unit (N73/8) and user interface CAN (CAN HMI) to the instrument cluster (A1).

Fan control 

The powertrain control unit (N127) actuates the cooler fan (M4/14). In this connection, the actuation is realized via the drivetrain LIN (LIN C3) and all rotational speeds between 0 and 100 % can be set. In the case of an incorrect actuation, the cooler fan (M4/14) runs at max. rotational speed (fan emergency operation).

The automatic climate control control and operating unit (N22/2) (with code HH4 (THERMOTRONIC automatic climate control)) transmits the air conditioning system status to the ME-SFI [ME] control unit (N3/36) via the climate control LIN (LIN B8), SAM control unit (N10), interior CAN (CAN B), EZS control unit (N73/8), suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C).

Delayed fan switch off 

The cooler fan (M4/14) runs on for up to 5 min after "ignition OFF" if the coolant temperature or the engine oil temperature have exceeded the specified maximum values.

If the battery voltage drops down a lot, the delayed fan switch off is suppressed.

Electrical function schematic for heat management	PE07.10-D-2712-97TSB
Overview of system components for gasoline injection and ignition system with direct injection	GF07.70-D-9998TSB