Idle speed control, function

GF07.16-W-2021MDF

Idle speed control, function

24.10.2019

Engine	936.9 in model 963
	with code V2B (Actros model generation 5)
Engine	936.9 in model 963
	with code V2F (Actros S/M cab, model generation 5)
Engine	936.9 in model 964
	with code V2J (Arocs model generation 5)
Engine	936.9 in model 964
	with code V3L (Actros BM964 model generation 5)

W07.16-A013-79

A3a	Drive control control unit (CPC5)		B622	Rail pressure sensor		Y616	Fan clutch solenoid valve
A4	Engine management control unit (MCM)		B624	Oxygen sensor		Y616 b1	Fan rpm sensor
A22	SAM with additional functions (XMC)		B625	Fuel pressure sensor (outlet)		Y621	Exhaust gas recirculation positioner
B600	Crankshaft position sensor		B626	Fuel pressure sensor (inlet)		Y627	AdBlue® heater coolant solenoid valve
B601	Camshaft position sensor		CAN 3	Frame CAN		Y628	Fuel metering valve
B602	Fuel temperature sensor		CAN 4	Drive train CAN		Y629	Fuel shutoff valve
B604	Oil pressure sensor		Y608	Cylinder 1 fuel injector		Y634	Pressure regulator valve
B606	Exhaust coolant temperature sensor		Y609	Cylinder 2 fuel injector		Y635	Camshaft positioner solenoid
B613	Fresh air differential pressure sensor		Y610	Cylinder 3 fuel injector		Y643	Quantity control valve
B614	Charge air temperature sensor in compressor housing (engine 936.916)		Y611	Cylinder 4 fuel injector		A	Input signals
B616	Charge air pressure and temperature sensor		Y612	Cylinder 5 fuel injector		B	Output signals
B617	Charge air temperature sensor in charge air distributor		Y613	Cylinder 6 fuel injector

General

The idle speed has been parameterized in the engine management control unit. In order to operate ancillaries at their working speed, the drive control control unit can transmit its own request via the drive train CAN, e.g. if the idle speed is to be higher. Essentially, the higher engine speed is always regulated. In other words, if the idle speed required by the drive control control unit is higher than the idle speed parameterized in the engine management control unit, then the engine speed required by the drive control control unit is regulated and vice versa.

Regulation of the idle speed takes place immediately after the starting procedure. A pre-requisite for this is that the drive control control unit does not detect any activation of the accelerator pedal. Depending on the engine's operating state, the engine management control unit calculates the injection timing point and quantity. The fuel injector of the cylinder in question is activated and fuel is injected into the combustion chamber. In order to guarantee the fuel supply to the high-pressure pump, the quantity control valve is activated. The pressure in the rail is regulated to around 900 bar by the pressure regulating valve. This ensures smooth engine running.

Throughout idling, the injection quantity is constantly adapted to the engine operating status, e.g. if the engine load condition changes or there is an increased fuel requirement (due to low outside temperatures).

To calculate the injection quantity, the engine management control unit mainly takes account of the following input factors:

 Engine speed

 Coolant temperature

 Fuel temperature

 Load request (specified torque)

Smoke limitation, smooth running control and altitude correction in the engine management control unit can also influence the injection quantity (period of actuation) as well as the start of actuation for the fuel injectors.

Smoke limit

The fuel quantity is limited via the smoke limitation characteristics so that virtually no output of smoke occurs.

Smooth running control

The smooth running control compensates for all of the differences in injection quantity in the individual fuel injectors.

Development of torque on the various cylinders can differ due to tolerances and wear on the individual fuel injectors. This leads to uneven running of the engine. The rotational speed of the crankshaft will always be slightly faster and slower. One particularly feels this when idling. The smooth running control can respond to rough running because it actuates every injection nozzle individually. It balances out the rotational speed fluctuations through slightly different injection quantities for the individual cylinder until all cylinders develop the same torque.

Altitude correction

Altitude correction is primarily designed in such a way that the exhaust gas turbocharger shaft speed, the compressor outlet temperature and the turbine inlet temperature of the exhaust gas turbocharger as well as the air/fuel ratio λ (lambda) do not exceed or fall below defined limits. To do this, the exhaust gas recirculation rate (EGR rate), the actuation start as well as the actuation period (injection quantity) of the fuel injectors are adjusted.

Exhaust gas recirculation (EGR)

To reduce the nitrogen oxides (NOx), the exhaust gas recirculation (EGR) is active for a specific time during idling. The exhaust gas recirculation (EGR) is switched off if idling lasts a relatively long time so that the exhaust gas recirculation cooler does not become contaminated.

In the case of the exhaust gas recirculation (EGR), the suctioned out or supercharged fresh air is mixed with exhaust gas. The oxygen content of the suctioned or supercharged air drops and its specific heat increases. This results in a decline in the combustion temperature and the output of nitrogen oxides (NOx), the proportion of which rises as the combustion temperature increases. The amount of exhaust gases produced is also reduced.

Fan control

During the whole operation of the engine, that is also in the idle phase, the fan speed is controlled dependent on the coolant temperature. The fan speed is determined based on input signals (A) from the fan rpm sensor. Control takes place through appropriate actuation of the fan clutch solenoid valve.

Exhaust aftertreatment

The EATS is active immediately after the engine start during the whole engine operation. It ensures that the emitted emissions in the exhaust are reduced to meet the limits established for the respective emissions standard. Different measures are instigated according to the emissions standard. In vehicles with Euro VI Standard, exhaust aftertreatment takes place via:

 Selective Catalytic Reduction (SCR) with an ammonia locking CAT

 Diesel oxidation catalytic converter (DOC)

 Diesel particulate filter (DPF)

Camshaft adjustment

Moving the timings of the exhaust camshaft at low engine speeds results in an increase in the exhaust temperature. This leads to improved regeneration of the DPF.

	Drive control (CPC) control unit, component description	A3a	GF30.35-W-4105H
	Engine management (MCM) control unit, component description	A4	GF07.08-W-4110MD
	SAM control unit with additional functions (XMC), component description	Vehicles with code E3W (PSM 2nd generation) A22	GF54.21-W-6006F
	Crankshaft position sensor, component description	B600	GF03.20-W-4100MD
	Camshaft position sensor component description	B601	GF05.20-W-4105MD
	Fuel temperature sensor component description	B602	GF47.50-W-4100MD
	Oil pressure switch component description	B604	GF18.40-W-2020MD
	Coolant outlet temperature sensor component description	B606	GF20.00-W-4100MD
	Component description for fresh air differential pressure sensor	B613	GF14.20-W-1003MD
	Charge air temperature sensor in compressor impeller housing, component description	Vehicles with engine 936.916 B614	GF09.41-W-4135MD
	Charge air pressure and temperature sensor, component description	B616	GF09.41-W-4110MD
	Charge air temperature sensor in charge air housing, component description	B617	GF09.41-W-4125MD
	Rail pressure sensor component description	B622	GF07.04-W-6253MD
	Component description for an oxygen sensor	B624	GF07.04-W-6101MD
	Diesel fuel metering device, component description	Vehicles with code M5Z(Engine version Euro VI) B625, B626, Y628, Y629	GF49.20-W-3011MD
	Component description for fuel injectors	Y608, Y609, Y610, Y611, Y612, Y613	GF07.03-W-6120MD
	Component description for the electromagnetic viscous coupling	Y616, Y616 b1	GF20.40-W-2002H
	Component description for exhaust gas recirculation actuator	Y621	GF14.20-W-4007MD
	AdBlue heater coolant solenoid valve, component description	Vehicles with code M5Z(Engine version Euro VI) Y627	GF14.40-W-3025MD
	Pressure regulator valve, component description	Y634	GF07.05-W-6020MD
	Camshaft positioner solenoid, component description	Y635	GF05.20-W-2110MD
	Component description for the quantity control valve	Y643	GF07.05-W-6010MD