GF07.15-W-3016A | Quantity control when idling, function | 4.7.07 |
ENGINE 904.9 in MODEL 375.1 with BODY 375.830
ENGINE 904.9 in MODEL 970, 972, 975, 976 with BODY 972.899
ENGINE 906.9 in MODEL 970, 972, 974, 975, 976 with BODY 972.899
ENGINE 906.9 in MODEL 375.3 with BODY 375.810
ENGINE 906.9, 926.9 in MODEL 950, 952, 953, 954 with BODY 940.899
The delivery quantity must be constantly adapted to the operating state of the engine when idling:
If the load take-up from the engine changes or if there is a higher demand for fuel (due to lower outside temperatures), the MR/PLD control unit adjusts the fuel quantity (over the delivery angle) within the prescribed limits.
The delivery angle is dependent on the performance maps in the MR/PLD control unit and is always influenced by the following input parameters:
Engine speed
Air mass
Engine temperature
Fuel temperature
Smoke limitation, the smooth running control and the altitude correction in the engine control (MR) can also effect the delivery angle, however:
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Smoke limit
The fuel quantity is limited via the smoke limitation characteristics so that virtually no output of smoke occurs.
Smooth running control
Smooth running control balances out differences in the fuel quantities achieved by the individual unit pumps:
Development of torque on the various cylinders can differ due to tolerances and wear on the individual unit pumps. This leads to rough running of the engine,
which means that the rotational speed of the crankshaft will always be slightly faster and slower. One particularly feels this when idling. The smooth running control on the engine control (MR) can react to rough running since it actuates every unit pump individually. It balances out fluctuations in engine speed through arranging slightly different injected amounts for each individual cylinder until all cylinders are developing the same torque.
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Altitude correction
Within the MR/PLD control unit there is an atmospheric pressure sensor. It determines the air pressure of the ambient air from which the engine control (MR) deduces an altitude correction.
The altitude correction prevents too much fuel being injected at high altitudes.