Exhaust-gas recirculation consists of three functions: • Setpoint calculation • Air-mass calculation • Open-loop or closed-loop control and monitoring Setpoint calculation provides the setpoint and air mass calculation provides the actual value for open-loop/closed-loop control. Setpoint calculation The EGR setpoint is a function of: • Engine speed • Injection quantity • Air temperature • Water… Read More »
High pressure control There are three subfunctions which make up high pressure control: • Setpoint generation • Rail-pressure control • Rail-pressure monitoring Setpoint generation The setpoint is generated as a function of the engine’s operating point. On the basis of the operating point, the setpoint is corrected by a value which depends on the following… Read More »
Injection-rate metering consists of the advance- main- and post-injection phases (known respectively as VE, HE and NE). The injection quantities for each individual injection process are computed as functions of total quantity setpoint, engine speed and other variables and are then used to calculate the start of activation and the activation duration. Advance injection (VE)… Read More »
The result of injection-rate calculation when the car is on the move is the total quantity of fuel to be injected into each individual cylinder. The required quantity is basically determined by the maximum from the driver’s request and the cruise control. Under certain circumstances, engine-speed-dependent injection-rate limitation can take effect at this stage. As… Read More »
Injection-rate control consists of the subfunctions • Injection-rate calculation • Injection-rate metering Injection-rate calculation computes the quantity of fuel to be injected on the basis of the current operating point of engine and car. A distinction is drawn between injection-rate calculation with the car on the move and injection-rate calculation during the start phase. The… Read More »
Synchronisation of the crankshaft and camshaft is necessary in order to ensure the engine start procedure functions correctly. The crankshaft sensor registers the crankshaft position. The control unit’s internal parameters correlate this information with the various top dead centre positions. The level of the signal from the camshaft sensor distinguishes between gas-expulsion TDC and injection… Read More »
Synchronisation of the crankshaft and camshaft is necessary in order to ensure the engine start procedure functions correctly. The crankshaft sensor registers the crankshaft position. The control unit’s internal parameters correlate this information with the various top dead centre positions. The level of the signal from the camshaft sensor distinguishes between gas-expulsion TDC and injection… Read More »
The speed of the camshaft is registered by the camshaft speed sensor. This phase sensor supplies a digital signal (square-wave signal). The DDE control unit can use this signal to synchronise the crankshaft and camshafts. The result of a defective rpm sensor is that the engine can no longer be started (see crankshaft/camshaft synchronisation).
The engine speed is registered by the crankshaft speed sensor. This inductive sensor supplies a sine-wave signal with speed dependent amplitude and frequency. In order to discharge speed-synchronous functions, the DDE control unit uses this signal to generate a number of pulses proportional to the cylinders (e.g. for advance/main injection). The speed-monitoring facility can also… Read More »
The vehicle-speed signal is transmitted along a direct line from the ABS/ASC control unit. Road speed is calculated on the basis of pulses per unit of time. Acceleration is calculated from the difference between the two most recently computed road-speed values. This acceleration value is limited to a maximum value. An error is reported if… Read More »