Digiplex trigger for TDC (3x8i) | FerrariChat
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Digiplex trigger for TDC (3x8i)

Discussion in 'Technical Q&A' started by waymar, Aug 24, 2016.

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  1. waymar

    waymar Formula 3

    Sep 2, 2008
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    Wayne Martin
    #1 waymar, Aug 24, 2016
    How does the digiplex know if it is firing on TDC compression stroke? There is a TDC sensor for each bank and unit. It will trigger the unit each time around. Does the digiplex fire on all four strokes? There is no cam sensor to tell it is on TDC compression stroke. Just saying ....
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    #2 Steve Magnusson, Aug 24, 2016
    The DigiPlex ECU fires its corresponding coil every time a pin on the flywheel passes the TDC sensor (there are two pins 180 deg apart) -- it's the distributor's job to send the spark to the cylinder in that bank that is at end of the compression stroke (and since the distributor rotor-to-intake cam relationship and the dist cap-to-engine relationship are fixed, it is never wrong ;)).
     
  3. waymar

    waymar Formula 3

    Sep 2, 2008
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    Wayne Martin
    #3 waymar, Aug 25, 2016
    Steve, that makes sense with two pins 180 apart. It fires each time it crosses a pin and with a flat plane crank that makes perfect sense. I was not aware of the two pins. Many thanks.
     
  4. fastradio

    fastradio F1 Rookie
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    Apr 26, 2006
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    David Feinberg
    #4 fastradio, Aug 25, 2016
    Taking this a bit further, the third signal comes from the teeth on the ring gear, via a third sensor. That signal feeds both Digiplex boxes and tell them when and how fast the engine is turning. Unlike the signals from the individual bank pins (as Steve described), if the "engine rpm" signal is lost, neither bank will fire. If one of the pin signal is lost, the corresponding bank will be lost.

    As the speed of signal processing improved over time, the Microplex system only needed one box and two triggers to operate.
     
  5. waymar

    waymar Formula 3

    Sep 2, 2008
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    #5 waymar, Aug 25, 2016
    Last edited: Aug 25, 2016
    I have read here that some 308i have run with Haltech E6X unit (nla) The new Haltech 550 unit would appear to work.
     
  6. waymar

    waymar Formula 3

    Sep 2, 2008
    1,354
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    Wayne Martin
    #6 waymar, Aug 27, 2016
    Does anyone have any experience using the stock crank sensors with a Haltech unit?
     

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