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Pulse rate of the VSS on an NP241C ???

Discussion in 'The Garage' started by 74kay5, Nov 27, 2004.

  1. 74kay5

    74kay5 1/2 ton status

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    I need to know the specifications of an NP241C for my new engine computer, anyone know where to get this info or does anyone know pulse rates off hand? Kinda technical I know, but any help would be greatly apriciated. Thanks
     
  2. jac6695

    jac6695 1/2 ton status

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    40 pulse per revolution. Look here for a lot of good info. What engine/computer are you going to?
    JTR (the site the link is from) sells inline VSS for many applications.
     
  3. 74kay5

    74kay5 1/2 ton status

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    [ QUOTE ]
    40 pulse per revolution. Look here for a lot of good info. What engine/computer are you going to?
    JTR (the site the link is from) sells inline VSS for many applications.

    [/ QUOTE ]

    That info says that "The two-pulse (2000 pulses per mile) square wave (D.C. current or direct current) used on all TBI engines through 1992, all computer-controlled-carbureted engines, and on 1985–1989 TPI engines."

    Wouldn't a 1990 K5 that the T-case is from be a 1990 TBI, which is 2000 pulses per mile as a signal instead of a 40 pulse per revolution singal?
    I'm going with a 6.0 vortec with a programmed PCM. I need to tell the programmer what kind of VSS signal to use from the T-case.
     
  4. jac6695

    jac6695 1/2 ton status

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    I get really confused by that information also. I have a VSS and 40 tooth reluctor ring from a 241 on my 205. I have a LT1 out of a 94 Caprice and it works well together. I used JTR's inline 4 pulse VSS(#5 on page 5), and my PCM wouldn't see it correctly (my scanner would read approximately 1/10 actual speed). Also, I just noticed this:

    [ QUOTE ]
    There are 4 types of VSS signals required by the ECM:
    1. The two-pulse (2000 pulses per mile) square wave (D.C current or direct current) used on all TBI
    engines thru 1992, all computer-controlled-carbureted engines, and on 1985-1989 TPI engines.
    2. A four-pulse (4000 pulses per mile) sine-wave (A.C. current or alternating current) signal is
    required by the 1990-1993 TPI, 1992-1993 LT1 engines, and 1990-1993 Camaro 3.1/3.4 V6
    engines.
    3. A 40 pulse per driveshaft revolution speed sensor used on 1993 and newer trucks with automatic
    transmission, 1994 and newer rear drive cars with the automatic transmission

    [/ QUOTE ]

    Notice the part of the quote in bold. That is information that the ECM requires, not VSS output. In 94, GM switched from an ECM to a PCM, which eliminated the need for DRAC's and VSS Buffer's. For example, my 94 LT1 PCM can be programmed for any tire and gear combo, and has an output to an electric speedometer. I am sure that the 6.0 PCM you are using is the same.

    Are you even using an electronic transmission? If not, and if you do not need emmision controls, your programmer should be able to eliminate the need for the VSS completely.

    I hope all of this makes sense to you and helps. Keep me updated. I like to learn as much as I can about this stuff. /forums/images/graemlins/thumb.gif

    Edit: After I went to bed (and thought even more about this crap /forums/images/graemlins/1zhelp.gif), I realized that I hadn't clarified something. The 40 tooth reluctor from the 89-91 241 creates the 40 pulse signal. On the TBI trucks until 92 or so, the DRAC converted the 40 pulse signal to what JTR states the the ECM requires- in this case a 2 pulse, square wave signal. So, depending on what the truck the 6.0 has, you could use the DRAC or Buffer you have, or wire straight from the VSS on the 241 to the PCM (which is what I did, but I don't have a speedometer yet and I am not sure if the PCM signal will operate an electric speedo from a 89-93 S10).
     
  5. 74kay5

    74kay5 1/2 ton status

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    I am also using a 241C and I will be using a 700R4 for my transmission. I'm also running non-emmissions. The idea is to keep the fuel injection system as simple as possible. I know people who run the 4L60E with swaps and have problems with their PCM. The programmer is going to tune out the transmission functions by changing the PCM to manual transmission functions.
     

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