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Thread: How To: Set CO Dwell

  1. #11
    Senior Member Domi's Avatar
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    Quote Originally Posted by dmcnc View Post
    This PDF is one of the better how-to's I've come across for setting CO
    Attachment 57912
    Thank you for sharing this PDF

  2. #12
    Administrator Ron's Avatar
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    Quote Originally Posted by dmcnc View Post
    This PDF is one of the better how-to's I've come across for setting CO
    Attachment 57912
    It's very well done but some of the settings and procedures are different for a D...

  3. #13
    Administrator Ron's Avatar
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    CO °Dwell, %Duty Cycle, 4/6/8/x Cylinder

    The manual says to "switch dwell operation for 6 Cylinder engine....dwell operation for duty cycle is 50%" +/- 3.0%"
    (WSM D:04:01, CO EMISSION ADJUSTMENT, 2, 11) [Open Loop]

    The Specification section says "Normal Operation (Sensor connected and CO properly adjusted) 35-45° (reading pulsates)" (WSM D:04:01, A) [Closed Loop]
    Here, they give Dwell values with the meter switched to 4 Cylinder (w/o mentioning it, anywhere)!
    AND people have been using these checking values as a setting value by averaging 35-45 = 40° and selecting 4 Cyl on the meter instead (or 20° on 8 Cyl). This is supposed to be for checking the closed loop operation, not setting CO while in closed loop! [Note IF the system is OK, it would not matter.]
    Open Loop Checking Values:
    O2 Sensor Connected
    Duty Cycle of 44.444% OR Dwell of 40°, switch in 4 Cyl mode = (26.666° in 6 Cyl mode, 20° in 8 Cyl); Pulsing.

    The section continues with "Oxygen sensor disconnected - 40-50° (steady reading)" (WSM D:04:01, B)
    This is correct, if your meter is switched to 4 Cyl instead. [Closed Loop!]
    This is the same as the CO EMISSION ADJUSTMENT section (above).
    Closed Loop Setting Values:
    O2 Sensor Disconnected
    Duty Cycle of 50% OR Dwell of 45°, switch in 4 Cyl mode = (20° in 8 Cyl mode, 22.5° in 6 Cyl mode); Pulsing.

    We have: the manual using a 6 Cyl setting and then 4 Cyl later (w/o mentioning it anywhere), setting the CO in closed loop and checking in open loop (that's backwards), and meters that don't have 4 Cyl so it is converted to 8 Cyl. Made for a lot of confusion and questions for years...

    Why they don't use 6 Cyl all the time is a mystery to me.

    All checking values can be found below:

    SETTING CO Using Dwell-Duty Cycle.jpg

    P.S. Thanks to Dave (Bitsyncmaster) for bumping heads with me!

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