Testarossa, how many teeth on the flywheel? | FerrariChat

Testarossa, how many teeth on the flywheel?

Discussion in 'Boxers/TR/M' started by alhbln, Nov 26, 2015.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. alhbln

    alhbln Formula 3
    Consultant Owner

    Mar 4, 2008
    1,749
    Berlin, Germany
    Full Name:
    Adrian
    #1 alhbln, Nov 26, 2015
    Does anyone know how many teeth the Testarossa flywheel has?
    The workshop manual has a "Z=146" label next to the flywheel, but given that the flywheel has three TDC teeth, the amount of teeth (RPM pulses) per TDC segment would result in a point number (48.66…) which is kind of unusual for an early mapped ECU setup.

    While reverse engineering the MED120B Microplex i found out that the number of teeth between the TDC pulses is hardwired to 48, so that would indicate that the flywheel actually has 3*48 = 144 teeth.

    I had a chance to measure the RPM pulses on a Ferrari 412 (equipped with the same MED120B ECU as the Testarossa), and got 144 teeth as expected.

    Thanks,
    Adrian
     
  2. OptimusPrime

    OptimusPrime Formula Junior

    May 10, 2011
    284
    Florida
    Full Name:
    Tom
    #2 OptimusPrime, Nov 26, 2015
    Starter has 11 teeth
     
  3. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,932
    southwest germany and thailand
    Full Name:
    romano schwabel
    #3 turbo-joe, Nov 26, 2015
    the sprocket on the flywheel has 146 teeth ( just counted here )
    and those teeth are only for the rpm
    for the ignition there are the 3 "negative" teeth with 120° distance because all 120° crankshaft each bank needs 1 spark, so 120° times 6 is 720°, 2 turns
     
  4. alhbln

    alhbln Formula 3
    Consultant Owner

    Mar 4, 2008
    1,749
    Berlin, Germany
    Full Name:
    Adrian
    #4 alhbln, Nov 27, 2015
    Romano, thanks! If possible could you post a close up photo of one of the TDC negative teeth shown with the flywheel teeth? I want to understand the phase relation between the two.
     
  5. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,932
    southwest germany and thailand
    Full Name:
    romano schwabel
    #5 turbo-joe, Nov 27, 2015
    Last edited by a moderator: Sep 7, 2017
  6. alhbln

    alhbln Formula 3
    Consultant Owner

    Mar 4, 2008
    1,749
    Berlin, Germany
    Full Name:
    Adrian
    #6 alhbln, Nov 27, 2015
    I think it does make a difference, as the Microplex calculates the start of the individual advance timing based on the RPM sensor pulses (internal clock) starting from the TDC pulse crossing zero.
     
  7. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,932
    southwest germany and thailand
    Full Name:
    romano schwabel
    #7 turbo-joe, Nov 27, 2015
    you are right adrian
    the RPM sensor gives signal to the ignition box, but only for rpm, nothing more, the 3 negative teeth are for each TDC, but remember, you have a distiributor and so it does not matter if cyl 1, 2, 3...or 6 is firing, important is only the 120° distance on the flywheel for the signal.

    I changed more than once the sprocket from the flywheel and never had any problems when I put it on other way than it was before.
     

Share This Page