SFI SYSTEM


  1. CONSTRUCTION


    1. A pick-up coil type crank position sensor is used. The timing rotor of the crankshaft consists of 34 teeth with 2 teeth missing. The crank position sensor outputs a crankshaft rotation signal every 10°, and the change in the signal due to the missing teeth is used to determine top-dead-center.

    2. A Magneto-Resistance Element (MRE) type cam position sensor is used. To detect the camshaft position, a timing rotor that is part of the camshaft is used to generate 3 pulses (3 high output, 3 low output) for every 2 revolutions of the crankshaft.

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      *1 Crank Position Sensor *2 Crankshaft Timing Sprocket
      *3 Cam Position Sensor *4 Timing Rotor

      Figure 1. Sensor Output Waveforms

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      *a Cam Position Sensor Signal
      *b Crank Position Sensor Signal
      *c 2 Teeth Missing

    3. The MRE type sensor consists of a magnet and a sensor with a built-in MRE. The direction of the magnetic field changes due to the profile (protruding and non-protruding portions) of the timing rotor, which passes by the sensor. As a result, the resistance of the MRE changes, and the output voltage to the ECM changes to either high or low. The ECM detects the cam position based on this output voltage.

    4. The differences between an MRE type sensor and a conventional pick-up coil type sensor are as follows.

      Sensor Type MRE Pick-up Coil
      Signal Output Constant digital output starts from low engine speeds. Analog output changes with the engine speeds.
      Crankshaft Position and Camshaft Position Detection

      • Detected by comparing the NE signals with the switching of the high/low output that results from the protruding and non-protruding portions of the timing rotor.

      • Can also be detected based on the number of NE signals input during high/low outputs.

      		 Detected by comparing the NE signals with the change of waveform that is output when the protruding portion of the timing rotor passes.
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