ECO Start/Stop Function Energy Management, Function - GF54.10-S-1040TRA
Model 447.6/7/8
With Code MJ8 (ECO start/stop function)
Model 448
With Code MJ8 (ECO start/stop function)
Function requirements, general
- System diagnosis completed without errors
- Outside temperature 0 to 40°C
- On-board electrical system battery temperature (G1) T = 0 to 60°C
- On-board electrical system battery and backup battery (G1/12) are sufficiently charged.
Energy management for engine start/stop, general
Switching of the engine during standstill periods of the vehicle reduces the fuel consumption and therefore the exhaust emissions. The master control unit for the engine start/stop function is the CDI control unit (N3/33) or the ME-SFI [ME] control unit (N3/34) (with engine 274) that records and evaluates all influencing factors.
For a stationary vehicle, the engine Start-Stop function switches the engine off automatically and starts it again, as soon as the driver wishes to drive off.
It is still possible to stop and start the engine in the conventional way.
The engine start/stop function encompasses the following subfunctions:
- Function sequence for engine stop
- Function sequence for engine start
- Function sequence for forced engine start
The function "Engine start/stop energy management, function" is viewed from an energy management point-of-view. Detailed information on the "Engine management for start/stop function" is contained in the function description "Common rail diesel injection (CDI), function".
Function sequence for engine stop
Additional function requirements for engine stop:
- Stop enable issued by CDI control unit or ME-SFI [ME] control unit
As the master control unit for the engine start/stop function, the CDI control unit or the ME-SFI [ME] control unit checks the various influencing factors for the stop enable. The energy management system provides information for this which describes the on-board electrical system status or the requirements for the onboard electrical system.
The signal acquisition and actuation module (SAM) control unit (N10/1) reads in the data from the battery sensor (B95) via the battery sensor LIN (LIN B15), evaluates this data and sends information about the on-board electrical system status or about the requirements placed on the on-board electrical system, via the interior CAN (CAN B), electronic ignition lock (EIS) control unit (N73), chassis CAN (CAN E) to the CDI control unit or the ME-SFI [ME] control unit.
The CDI control unit or the ME-SFI [ME] control unit evaluates all the relevant data, issues the stop enable and switches the engine off. The CDI control unit or the ME-SFI [ME] control unit then sends the "drive train operational" signal over the chassis CAN, electronic ignition lock (EIS) control unit and interior CAN to the signal acquisition and actuation module (SAM) control unit. This prevents the energy management system from reducing or switching off consumers if the "Engine running" signal is not sent.
Model 447.6/7/8
with code HH4 (THERMOTRONIC automatic climate control)
with code MJ8 (ECO start/stop function)
Model 447.6/7/8
with code HH9 (Air conditioner, automatic heater control)
with code MJ8 (ECO start/stop function)
Model 448
with code HH4 (THERMOTRONIC automatic climate control)
with code MJ8 (ECO start/stop function)
If the air conditioning system automatic mode is active, the blower output is reduced. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted.
Function sequence for engine start
As soon as the driver removes his/her foot from the brake pedal, the engine starts.
By using a backup battery, the voltage dip experienced by the vehicle occupants when the engine is started (e.g. during radio or ventilation operation) is not perceived.
The backup battery provides a constant (backed up) on-board electrical system voltage during restarting. The backup battery is monitored by the signal acquisition and actuation module (SAM) control unit and charges via the onboard electrical system backup battery relay (K120). For this purpose, the signal acquisition and actuation module (SAM) control unit sends a request directly to the on-board electrical system backup battery relay.
The CDI control unit or the ME-SFI [ME] control unit evaluates all relevant variables and starts the engine. As soon as the CDI control unit or the ME-SFI [ME] control unit detects an engine speed of 400 to 700 rpm, it terminates the starting procedure and sends the "engine running" signal via the chassis CAN, electronic ignition lock (EIS) control unit and interior CAN to the signal acquisition and actuation module (SAM) control unit.
Function sequence for forced engine start
To ensure that the on-board electrical system stability is also given during engine OFF, the CDI control unit or the ME-SFI [ME] control unit can also force the engine to start. A forced engine start is also conducted if, as a consequence of load-intensive consumers, the on-board electrical system stability can no longer be assured.
Load-intensive consumers can be requested by, for example, the following systems:
- Air conditioning
- Steering
- Sound system
- Comfort heater
As soon as the energy management is no longer able to ensure stability of the on-board electrical system, the signal acquisition and actuation module (SAM) control unit sends the "Start engine" request over the interior CAN, electronic ignition lock (EIS) control unit, chassis CAN to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit then starts the engine.
If, following this, the on-board electrical system stability can still not be assured, the engine is no longer switched off. The engine start/stop function is deactivated.
The signal acquisition and actuation module (SAM) control unit uses the data from the battery sensor to calculate the required alternator specified voltage and sends this over the interior CAN, electronic ignition lock (EIS) control unit and chassis CAN to the CDI control unit or the ME-SFI [ME] control unit. This makes the CDI control unit or the ME-SFI [ME] control unit start the alternator regulation (alternator management). For this purpose, the CDI control unit or the ME-SFI control unit evaluates the operating rate of the alternator (G2) and requests the corresponding specified voltage. The alternator and the CDI control unit or the ME-SFI [ME] control unit communicate with each other over the drive train LIN (LIN C3). The CDI control unit or the ME-SFI [ME] control unit sends information on the operating rate of the alternator over the chassis CAN, electronic ignition lock (EIS) control unit and interior CAN to the signal acquisition and actuation module (SAM) control unit.
Detailed information about the alternator regulation can be found in the separate subfunction "Engine ON energy management function".
| Electrical function schematic for energy management for engine start/stop | Model 448 with code MJ8 (ECO start/stop function) | PE54.10-S-2070-97VDA | |
| Model 447.6/7/8 with code MJ8 (ECO start/stop function) | PE54.10-S-2070-97TRA | ||
| Overview of energy management system components | Model 447.6 with code MJ8 (ECO start/stop function) Model 447.7 with code MJ8 (ECO start/stop function) except code ZH6 (Marco Polo ACTIVITY) Model 447.8 with code MJ8 (ECO start/stop function) except code ZK7 (Equipment line MARCO POLO) Model 448 with code MJ8 (ECO start/stop function) |
GF54.10-S-9990TRA |