Thermal Management, Function - GF07.10-D-1012HD
ENGINES 651.955/956/957 in MODEL 906
with CODE (XZ1) Model generation 1
with CODE (MZ0) Blue EFFICIENCY
Function requirements
- Circuit 87M On
- Circuit 61 ON
General
The coolant temperature of the engine is regulated by the thermal management system which is governed by the CDI control unit (N3/28). This has the following advantages:
- Operating temperature is reached faster
- Reducing exhaust gas emissions
- Fuel savings (up to around 4%)
- Improved heat comfort.
Thermal management is performed according to the following sensors and signals:
- Boost pressure sensor (B5/6), engine load
- Coolant temperature sensor (B11/17)
- Intake air temperature sensor (B2/12b1) (for model 906)
- Charge air temperature sensor (B17/13)
- Accelerator pedal module (B37/3) (for model 906), accelerator pedal actuation
- Fuel temperature sensor (B50/5)
- Engine oil temperature sensor (B40/9)
- Crankshaft sensor (L5/10), engine speed
- Temperature sensor in CDI control unit
- AAC [KLA] control and operating unit (S98), with code (HH9) Regulated air conditioning, (Tempmatic), outside air temperature and status of the A/C via the interior CAN (CAN B)
- ESP control unit (N30/4), vehicle speed
Function sequence
The thermal management system is described in the following steps:
- Function sequence for post-start phase
- Function sequence for heating the coolant thermostat
- Function sequence for maximum heating combustion
- Function sequence for tank protection
- Function sequence for overheating protection
Function sequence for post-start phase
In the post-start phase, the following measures are employed to warm up the engine rapidly, thereby reducing exhaust emissions:
- Interruption of piston cooling by cutting off the engine oil supply to the oil spray nozzles by means of the oil spray nozzles valve (Y127/1)
The oil spray nozzles are switched off in the post-start phase if one of the following conditions is met:
- Engine oil temperature > -10°C
- The max. shutoff time (depending on the engine model and performance, intake air and engine oil temperature) is not yet reached
- The engine speed or injection quantity has not reached an established limit value
At high engine oil temperatures, activation of the oil spray nozzles can be interrupted depending on the engine speed.
Function sequence for heating the coolant thermostat
Depending on the operating conditions (as a function of a characteristic map) the CDI control unit actuates the heating element in the thermostat (R48/2) using a ground signal.
The power is supplied through "circuit 87". The heating opens the coolant thermostat. In this way the coolant temperature of 55 to 106°C is regulated via the duty cycle.
Function sequence for maximum heating combustion
For the "hot burning process" more heat is conducted into the coolant system on the engine side due to a new combustion strategy.
The following function conditions must be met simultaneously:
- Accelerator pedal position from the accelerator pedal module is below 80% (partial throttle)
- No regeneration operation of diesel particulate filter (DPF)
- At least a 90% heat output is required from the AAC [KLA] control and operating unit with code (HH9) Regulated air conditioning, (Tempmatic)
- Outside air temperature from the outside air temperature sensor (B14) below 7°C (a renewed cut-in occurs at 4°C)
- Coolant temperature from coolant temperature sensor is below 82°C (renewed cut-in takes place at 74°C)
During the hot burning process a higher exhaust temperature is achieved through 2 preinjections with a significantly increased fuel quantity and a later main injection. In combination with the exhaust gas recirculation (EGR), more heat is released to the coolant inside the engine which leads to improved vehicle interior heating.
Function sequence for tank protection
Increasing the fuel pressure via the high-pressure pump (M41/3) from 4.5 bar up to 1800 bar also increases the temperature of the fuel.
To protect the fuel tank from overheating, the CDI control unit reads in the fuel temperature sensor and thus monitors the temperature of the fuel delivered to the high-pressure pump.
If the temperature of the fuel delivered to the common rail high-pressure pump goes above 90°C, the injection quantity and rail pressure are automatically reduced. This causes less fuel to be compressed.
The quantity control valve (Y94/3) diverts excess fuel back into the tank.
If the temperature of the fuel delivered to the high-pressure pump drops below 90°C, the tank protection function is deactivated by the CDI control unit.
Function sequence for overheating protection
In the case of a thermal overload, the overheating protection protects against engine damage and overheating damage. At a coolant temperature above 106°C the injection quantity is reduced based on the characteristic maps stored in the CDI control unit. Reduction occurs depending on the coolant temperature and oil temperature. To this end, the CDI control unit reads in the coolant temperature sensor, engine oil temperature sensor and the temperature sensor upstream of the turbocharger (B16/13) (turbocharger protection). After evaluation of the input signals, the CDI control unit, via the quantity control valve and the pressure regulator valve (Y74/5) regulates the fuel pressure in the rail and controls injection timing via actuation of the following injectors.
- Cylinder 1 injector (Y76/14)
- Cylinder 2 injector (Y76/15)
- Cylinder 3 injector (Y76/16)
| Component description for CDI control unit | N3/28 | GF07.16-D-6000HD |
| Component description for rail pressure sensor | B4/16 | GF07.04-D-6210HD |
| Component description for coolant temperature sensor | B11/17 | GF07.04-D-6040HD |
| Component description for oil temperature sensor | B40/9 | GF18.30-D-2011HD |
| Component description for coolant thermostat heating element | R48/2 | GF20.10-D-3163HD |
| Component description for exhaust gas recirculation controller | Y27/15 | GF14.20-D-4007HD |
| Component description for pressure regulating valve | Y74/5 | GF07.05-D-6020HD |
| Component description for fuel injectors | Y76/14, Y76/15, Y76/16, Y76/17 | GF07.03-D-6120HD |
| Component description for quantity control valve | Y94/3 | GF07.05-D-6010HD |
| Component description for oil spray nozzle shutoff valve | Y127/1 | GF18.30-D-2012HD |
| Oil circuit - as-built configuration | - | GF18.00-D-0800HD |