ECO Start/Stop Function Energy Management, Function - GF54.10-P-1040RR

Model 190 

The function "Energy management for ECO start/stop function" is considered from an energy management viewpoint. Detailed information about the function "Engine management for start/stop function" is contained in the function description "Gasoline injection and ignition system with direct injection, function".

Function requirements, general 

• Engine running and at operating temperature
• System diagnosis completed without errors
• Outside temperature T = -10 to 40°C
• On-board electrical system battery temperature (G1) T = 0 to 60°C
• On-board electrical system battery charged sufficiently

Energy management for ECO start/stop function in general 

Switching of the engine during standstill periods of the vehicle reduces the fuel consumption and therefore the carbon dioxide emissions. The master control unit of the ECO start/stop function is the ME-SFI control unit (N3/10) which records and evaluates all influencing factors. For a stationary vehicle, the ECO 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.

By using the voltage dip limiter (R62) (series resistor) at the positive terminal of the on-board electrical system battery, the tolerable voltage dip for the vehicle occupants when starting the engine (e.g. during operation of the radio or ventilation mode) is reduced. The voltage dip limiter reacts to the dip in voltage when starting the engine.

The voltage dip limiter is an electronically switchable series resistor that is used to reduce the high power consumption of the starter (M1) when starting the engine; it is connected via circuit 87 to the circuit 50 starter relay (N10/1kM). When starting the engine, the voltage dip limiter is exposed to voltage. It thereby detects the starting procedure and switches in the series resistor. If the on-board electrical system voltage reduces too much due to the high power consumption of the starter, the voltage dip limiter switches the series resistor out again.

The ECO start/stop function encompasses the following subfunctions:

• Function sequence for engine stop 
• Function sequence for engine start 
• Function sequence for forced engine start 

Additional function requirement for engine stop 

• Stop enable issued by ME-SFI [ME] control unit

Function sequence for engine stop 

As the master control unit for the ECO start/stop function, the ME-SFI control unit checks 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 on-board electrical system.

While the engine is running, the ME-SFI control unit assesses the operating rate of the alternator (G2). The alternator and the ME-SFI control unit communicate with each other over drivetrain LIN (LIN C1). The ME-SFI control unit then sends the "engine running" signal and information about the operating rate of the alternator via the drive train CAN (CAN C1), powertrain control unit (N127), chassis CAN 1 (CAN E1), front SAM control unit with fuse and relay module (N10/1) and interior CAN (CAN B) to the rear SAM control unit with fuse and relay module (N10/2).

The rear SAM control unit receives this, reads in the data from the electronics in the on-board electrical system battery via the battery sensor LIN (LIN B15), evaluates this data and sends information that describes the on-board electrical system status or the requirements for the on-board electrical system, via the interior CAN, front SAM control unit, chassis CAN 1, powertrain control unit and engine CAN (CAN C) to the ME-SFI control unit.

The following information is included in it:

• State of on-board electrical system battery
• Load on on-board electrical system

The ME-SFI control unit evaluates all relevant variables, issues the stop release accordingly and switches off the engine. The ME-SFI control unit then sends the "drivetrain operational" signal to the rear SAM control unit via the drive train CAN, powertrain control unit, chassis CAN 1, the front SAM control unit and interior CAN. This prevents the energy management system from reducing or switching off consumers if the "Engine running" signal is not sent.

The blower output is reduced when the automatic blower speed function of the air conditioning is active. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted.

After the engine has been switched off a maximum of three engine starts within a period of t = 1 minute (maximum idle time t = 180 s) with exceeding the speed threshold of v = 8 km/h are permitted.

Function sequence for engine start 

The engine starts by pressing down the accelerator pedal.

By using the voltage dip limiter (series resistor) at the positive terminal of the onboard electrical system battery, the tolerable voltage dip for the vehicle occupants when starting the engine (e.g. during operation of the radio or ventilation mode) is reduced.

The ME-SFI control unit evaluates all relevant variables and starts the engine. As soon as the ME-SFI control unit detects an engine speed of n = 400 to 700 RPM, it stops the starting procedure and sends the "engine running" signal via the drive train CAN, powertrain control unit and chassis CAN 1 to the rear SAM control unit.

Function sequence for forced engine start 

To ensure that the on-board electrical system stability is also available during engine OFF, 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 air conditioning system.

As soon as the energy management is no longer able to ensure the stability of the on-board electrical system, the rear SAM control unit sends the "start engine" request to the ME-SFI control unit via the interior CAN, front SAM control unit, chassis CAN 1, powertrain control unit and engine CAN. The ME-SFI 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 ECO start/stop function is switched off.

On the basis of the data from the electronics in the on-board electrical system battery, the rear SAM control unit calculates the required alternator specified voltage and sends it to the ME-SFI control unit via the interior CAN, front SAM control unit, chassis CAN 1, powertrain control unit and engine CAN. The ME-SFI control unit then starts the alternator regulation (alternator management). For this purpose, the ME-SFI control unit evaluates the operating rate of the alternator and requests the corresponding specified voltage (excitation voltage). The alternator and the ME-SFI control unit communicate with each other via the drivetrain LIN. The ME-SFI control unit then sends information about the operating rate of the alternator to the rear SAM control unit via the drive train CAN, powertrain control unit, chassis CAN 1, the front SAM control unit and interior CAN.

Detailed information about the alternator regulation can be found in the subfunction "engine ON energy management function".

	Electrical function schematic for energy management for engine start/stop		PE54.10-P-2070-97HBA
	Overview of energy management system components		GF54.10-P-9990RR