What does 360's exhaust timing 652-672 bits mean? | FerrariChat

What does 360's exhaust timing 652-672 bits mean?

Discussion in 'Technical Q&A' started by 24000rpm, Feb 14, 2019.

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  1. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,649
    China and California
    #1 24000rpm, Feb 14, 2019
    so i have 3 questions concerning this exhaust timing.

    1. on the shop manual, it says, the phase angle should be between 652 to 672 bits.
    While I understand "degrees" , I don't understand what is 652-672 "bits"? can somebody chime in?

    2. If at idle. my exhaust phase angle is 670, when the timing variator is actuated, is it going to be more than 670? if so, how many "bits" are being variated?

    3. assuming there's no timing advance, Is it safe to say that if I can rotate the crankshaft by a 1/2 rachet by hand, the valves are not touching the pistons?
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    34,119
    Austin TX
    Full Name:
    Brian Crall
    #2 Rifledriver, Feb 14, 2019
    While talking to people at the factory back when it was new it was pretty clear they really didn't know what the scale was and any answer was to prevent them from admitting they didn't know. I have little doubt that is where the "Bits" came from. That was quite common. There is an institutional inability in Maranello to say "I don't know". It seems to cause loss of face. From my own experiments the number is equivalent to degrees on a 720 degree scale. I never bothered to find out 720 degrees starting where. The information is in the book as to how far the variator advances things. I do not recall from memory.

    I would add that on a street car the target number is 656-657
     
  3. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,649
    China and California
    #3 24000rpm, Feb 14, 2019
    Thank you so much for the reply, that was my guess too.

     
  4. RedNeck

    RedNeck F1 World Champ
    Silver Subscribed

    Jul 8, 2016
    10,017
    The CSA
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    Me
    #4 RedNeck, Feb 15, 2019
    That's the problem with Europeans, you never know if they are generalizing or talking digitally :D
     
  5. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,649
    China and California
    #5 24000rpm, Feb 16, 2019
    ok, so i did an experiment today (fully aware the danger of it)

    My existing LH exhaust timing is 656 bits as shown on my leonardo.

    I open the end cap on the back of the engine. with 21mm wrench, with somebody holding the timing belt at the interior of the car, rotate the exhaust cam counterclockwise (if you face the direction the car would go forward) by 1 timing belt tooth. I got everything back and ran the car, the leonardo shows 678 and threw a code.

    so, there are 32 teeth on the timing gear. so each tooth = 360 degree/32 = 11.25 degrees.

    times 11.25 by 2 we have 22.5 degrees, which is roughly the same as 678-656 = 22.

    So the "bits" on the FSM indeed means "degrees"

    ha!
     
    MCASEY and flash32 like this.

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