SFI SYSTEM


  1. CONSTRUCTION


    1. Magneto-Resistance Element (MRE) type cam position sensors (No. 2 crank position sensors) (intake and exhaust) are used. To detect each camshaft position, a timing rotor that is secured to the camshaft is used to generate 3 pulses for every 2 revolutions of the crankshaft. The timing rotor for each camshaft is part of the respective camshaft.

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    2. An MRE type cam position sensor (No. 2 crank position sensor) consists of an MRE, a magnet and a sensor. 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 high or low. The ECM detects the camshaft position based on this output voltage.

    3. The differences between a MRE type sensor and the pick-up coil type sensor used on the conventional models are as follows:


      • The MRE type sensor outputs a constant level of high and low digital signals regardless of the engine speed. Therefore, the MRE type sensor can detect the positions of the camshaft at an early stage of cranking.

      • The pick-up coil type sensor outputs analog signals with levels that change with the engine speed.

      Figure 1. MRE Type and Pick-up Coil Type Output Waveform Image Comparison

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