Synchronize Fuel Injection And Firing Order Function - GF07.10-P-1006MRA
Engine 274.9 in model 205 (except 205.047/053/054/147/247/253)
Engine 274.9 in model 253 (except 253.354/954)
Function requirements synchronization of fuel injection and firing order, general points
- Circuit 87M (Engine management ON)
- Engine runs
Synchronization of fuel injection and firing order, general points
Synchronization of the injection and firing order is achieved by the ME-SFI [ME] control unit (N3/10) for actuation of cylinder 1 ignition coil to cylinder 4 ignition coil (T1/1 to T1/4) and the cylinder 1 injection nozzle to cylinder 4 injection nozzle (Y76/1 to Y76/4).
Furthermore, synchronization is required for knock control and fuel shutoff on the individual cylinders. The ME-SFI [ME] control unit synchronizes the injection and firing order using the signals from the following sensors:
- intake camshaft Hall sensor (B6/15), intake camshaft setting
- Exhaust camshaft Hall sensor (B6/16), exhaust camshaft setting
- Crankshaft Hall sensor (B70), engine speed and crankshaft position
Function sequence for synchronization of the fuel injection and firing order
The function sequence is described in the following steps:
- Function sequence for synchronization
- Function sequence for engine speed signal
Function sequence for synchronization
When starting the engine, the injection sequence is specified to match the firing order. To do this the voltage signals are read in by the crankshaft position sensor and by the intake camshaft Hall sensor or exhaust camshaft Hall sensor. The ignition TDC (top dead center) of cylinder 1 is detected by the crankshaft Hall sensor.
Function sequence for engine speed signal "Using the signal from the crankshaft Hall sensor, the ME-SFI [ME] control unit generates the short circuit-proof engine speed signal (for example for cold testing and diagnosis) and outputs it over the powertrain CAN (CAN C1).
A multiple wheel on the crankshaft with magnetic pole fields with different polarity generates a digital signal with an idle signal level of 5 V and brief pulses of 0 V in the crankshaft Hall sensor when the crankshaft turns. In the process each individual pole field or every change in the magnetic field represents a change in angle of 6° CKA (C rankshaft A ngle).
To absolutely determine the position of the multiple wheel relative to the crank assembly, a single pole field is configured with a distance of 18°CKA.
direction recognition
If the engine rotates backwards, something which can only happen sporadically, briefly before standstill, after the engine has been stopped, then the pulse duration for the 0 V-pulse is altered. The ME-SFI [ME] control unit can thereby determine any change in direction of rotation and thus record the exact angular position of the crankshaft at any given time. This information is required, in particular, when quickly starting the engine in the ECO start/stop mode.
If the voltage signal fails from the crankshaft Hall sensor the voltage signals from the intake camshaft Hall sensor or from exhaust camshaft Hall sensor are used as a replacement for limp-home mode.
If the voltage signal from the intake camshaft Hall sensor is missing, the signal from the exhaust camshaft Hall sensor is used instead for detection of ignition TDC in cylinder 1.
If no voltage signal is available from any camshaft Hall sensor, ignition and injection take place after a 360° crank angle in order to allow an emergency start.
| Electrical function schematic, synchronization o the injection and firing order | PE07.10-P-2706-97FBA | ||
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