Thermal Management, Function - GF07.10-P-1012MRD
Engine 274.9 in model 213, 238
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Thermal management, general
The ME-SFI [ME] control unit regulates the engine coolant temperature via the heat management.
The following advantages arise from this:
- Rapid reaching of the optimal operating temperature
- Reduction of the exhaust emissions
- Fuel savings
- Rapid heating of the vehicle interior
The ME-SFI [ME] control unit reads in the signals of the following sensors for controlling the thermal management:
- Coolant temperature
Coolant temperature sensor (B11/4)
- Charge air temperature
Charge air temperature sensor upstream of throttle valve (B17/7)
Charge air temperature sensor downstream of throttle valve (B17/9)
- Engine load
Pressure sensor downstream of throttle valve (B28/7)
- Accelerator pedal sensor (B37)
The powertrain control unit (N127) directly reads in the signals of the accelerator pedal sensor and transmits these via the drive CAN (CAN C1) to the ME-SFI [ME] control unit.
- Crankshaft Hall sensor
The ME-SFI [ME] control unit also evaluates the following variables:
- Air conditioning system requests
The climate control unit (N22/1) transmits the speed and torque increase requests via the interior CAN (CAN B), electronic ignition lock control unit (N73), suspension FlexRay (Flex E), powertrain control unit and drive CAN 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 (automatic transmission)
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.
- Outside temperature
The front SAM control unit (N10/6) transmits information on the outside temperature via the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and drive CAN to the ME-SFI [ME] control unit.
Schematic diagram of coolant circuit (transmission 725 with code M014 (Up-rated engine) and code 494 (USA version))
The thermal management is described in the following points:
- Coolant thermostat closed-loop control
- Post-start phase with electric coolant pump (M75/11)
- Deactivation of heating system (with code M014 (Up-rated engine) and code 494 (USA version))
- Overheating protection
- Fan control
- Radiator trim flaps (model 213 with code 5U3 (AIRPANEL))
Coolant thermostat closed-loop control
Mechanically influenced opening and closing of the ball rotary slide in the coolant thermostat occurs through the temperature-influenced elongation or contraction of the expansion wax element in a temperature range of about 102°C to 118°C. The target temperature is about 105°C. For 118°C the ball rotary slide is fully opened. In addition, opening and closing of the coolant thermostat heating element can be electronically influenced through actuation of the coolant thermostat heating element (R48). This occurs fully variable and dependent on the motoric requests.
The ball rotary slide in the coolant thermostat can take the following positions:
- Closed
- Open (mixed-fuel mode)
- Open (radiator operation)
Closed
The ball rotary slide of the coolant thermostat is closed if the following conditions are fulfilled:
- Coolant temperature below about 102°C
- Coolant thermostat heating element de-energized
- No wide open throttle request. In this position the coolant flows through the engine circuit and the heater heat exchanger and the ATL and, as required, the heater heat exchanger for the passenger compartment heater. The engine radiator is not integrated in the coolant circuit. The coolant is heated more quickly in this way.
Through rapid warming the engine reaches its operating temperature quicker which is favorable for fuel consumption.
View of coolant thermostat closed
Open (mixed-fuel mode)
The ball rotary slide begins to open if one of the following conditions is fulfilled:
- Reaching a coolant temperature of approx. 102°C for the first time after starting (no full-load request)
- Coolant thermostat heating element is energized. The expanding wax element starts to expand, and actuates the rotary ball valve, in a coolant temperature range from approx. 102°C to 118°C or depending on coolant thermostat heating element energization. This opens the connection to the engine radiator. The opening cross-section of the ball rotary valve is proportional to the temperature of the wax expansion element and/or the coolant temperature. In this way the volumetric flow rate of coolant to the engine radiator can be varied as required.
Open (radiator operation)
For exceeding of a coolant temperature of about 118°C the ball rotary slide is opened completely and the coolant can flow unheeded over the engine radiator.
View of the coolant thermostat opened
Electronic regulation
A complete opening is also possible at lower temperatures, if the coolant thermostat heating element is actuated by the ME-SFI [ME] control unit depending on the operating conditions.
The following data are read in directly by the ME-SFI [ME] control unit:
- Intake air temperature
- Outside temperature
- Engine speed
- Engine load
The compressor is actuated via a ground signal. The power supply takers place over "circuit 87 M2".
Dependent on the motoric requests, a higher or a lower coolant target temperature is adjusted.
For a high coolant target temperature (about 105°C) the manual regulation is supported by additional heating of the expanding wax element from 106°C. For 110°C the heating element is fully energized, which results in the full opening of the ball rotary slide. An increased coolant temperature produces in partial-load range a favorable performance level, which works very positively on the fuel consumption.
The low coolant target temperature lies around 85°C. In doing so the heating element is subject to a pre-control, which is variably adapted to the ambient conditions. In summer and at high outside temperatures, the heating element can already be fully energized at 80°C in order to avoid critical temperature ranges. In winter and for lower outside temperatures the heating element is energized at 30 to 50 % of the maximum output.
A low coolant temperature in the wide open throttle operation has a positive effect on the engine power, since the intake air is less warmed.
Post-start phase with electric coolant pump
In the post-start phase the coolant circulation stopped through cutting out of the electrical coolant pump. Due to missing cooling the engine warms quicker and the exhaust emission are reduced.
The electric coolant pump is switched off for a cold start if the following conditions are fulfilled:
- Coolant temperature less than 75°C
- No "heating" request from climate control unit
The electrical coolant pump switches on in response to the request "Heat'. In this way the FIR is heated quickly.
If the conditions for shutoff of the electric coolant pump are no longer fulfilled, the ME-SFI [ME] control unit stops actuation of the electric coolant pump. The coolant circulation is therefore achieved again.
Deactivation of heating system (with code M014 (Up-rated engine) and code 494 (USA version))
For a cold start and rapid heating up of the engine, the ME-SFI [ME] control unit switches off the heating system coolant flow by actuating the heating system shutoff valve (Y16/2) in the short term. If the engine or the coolant in the engine cooling circuit reaches a certain temperature, the feed flow to the heating system is freed up again.
Overheating protection
The overheating protection protects the engine and catalytic converter against damage due to thermal overload.
In the case of an imminent thermal overload, the ME-SFI [ME] control unit initiates the following measures:
- Ignition control in "retarded" direction depending on the engine load and engine speed from a coolant temperature of approx. 90°C and a charge air temperature of approx. 20°C.
- The opening of the throttle valve is reduced via the throttle valve actuator motor (M16/6m1) depending on the engine load and engine speed.
- The injection duration is adjusted to the lower air mass.
- The ball rotary valve in the coolant thermostat is fully opened by actuating the coolant thermostat heating element.
Fan control
The powertrain control unit actuates the fan motor (M4/7) via the drivetrain LIN (LIN C3) in an output controlled manner between 0 and 100 %. For faulty actuation the fan motor rotates at its maximum rotational speed (fan emergency mode).
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 has exceeded the specified maximum value. If the battery voltage drops down a lot, the delayed fan switch off is suppressed.
Radiator trim flaps (model 213 with code 5U3 (AIRPANEL))
The radiator trim flaps are close in order to lower the fuel consumption (thorough having a lower aerodynamic drag). This also causes reduced engine compartment cooling off and a dampening of engine external noise emissions to the outside. The radiator trim flaps are opened under the following preconditions:
- Coolant temperature > 105°C
- Charge air temperature > 34°C
- Vehicle speed > 180 km/h
- Fan output > 30 %
The radiator trim flap actuator motor (M2/37) is actuated by the powertrain control unit via the drivetrain-LIN. The radiator trim flaps are closed when the conditions are no longer fulfilled or the engine is off.
Through the spring preload of the actuator motor, the radiator trim flaps are opened suddenly with a noticeable noise if a malfunction occurs (emergency function).
Cleaning position
Turn the key in the ignition lock to position 2 (engine not have started).
The radiator trim flaps open automatically after approx. 120 seconds.
| Electrical function schematic for heat management | PE07.10-P-2712-97DBD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 274.9 in model 213 (except 213.050/053/153), 238 up to model year 2021 | GF07.70-P-9998MRD | |
| Engine 274.9 in model 213.050/053/153 up to model year 2021 | GF07.70-P-9998MRP |