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Thread: TPI SBC vss and adding an electrical speedo

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    Fuel Injected! EDZIP's Avatar
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    TPI SBC vss and adding an electrical speedo

    Have a street rod with speed density TPI/700R4 (SBC) setup via a 730 ecm and am considering installing an electrical speedometer requiring a vss signal also. Not sure how to run both the ecm and speedo via one vss. (DRAC? our just get a GPS unit)

    Thanks

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    Super Moderator dave w's Avatar
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    The 1227730 chip can be programmed to work with a 8000 pulses per mile (8K) VSS. Some Dakota Digital electrical speedometers use an 8K VSS. Two 8K outputs from one VSS should work. Digital Dakota offers a Universal Speedometer Signal Interface that will convert an 8K VSS to 4K for a stock programmed 1227730 chip: http://www.dakotadigital.com/index.c...rod/prd126.htm & http://www.dakotadigital.com/pdf/SGI-5e.pdf

    dave w

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    Fuel Injected! EDZIP's Avatar
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    Thanks Dave...FYI I really would like to use one of these Intellitronix speedos, American made, lifetime warranty:

    https://www.intellitronix.com/produc...edometer-3-3-8

    They don't discuss which VSS pulse they use and of course recommend buying their vss. Other manufacturers indicate that their electronic speedos will program with various pulse rates.

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    When reading the installation instructions for the speedometer, it notes a 8000 ppm vss signal.

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    Super Moderator dave w's Avatar
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    When the park switch input to the 1227730 is grounded, the 1227730 will not need a VSS input. I strongly recommend USING a VSS input to the 1227730. The engine will run without a VSS, when the computer "thinks" the vehicle is in park.

    dave w

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    Fuel Injected! EDZIP's Avatar
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    Thanks guys...the street rod currently has a 4000 pulse vss and the 700R4 (shifter) is wired for park and neutral to the ecm.

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    Fuel Injected! EDZIP's Avatar
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    Just rec'd an email from Intellitronix support, they said their speedos will work with any vss...just needs to be calibrated.

    Again...would there be any problem splitting the vss signal to both the ecm and speedo?

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    Super Moderator dave w's Avatar
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    Quote Originally Posted by EDZIP View Post
    Just rec'd an email from Intellitronix support, they said their speedos will work with any vss...just needs to be calibrated.

    Again...would there be any problem splitting the vss signal to both the ecm and speedo?
    VSS signals are usually AC sine wave signals. Splitting one VSS output into TWO separate signals will work. Usually two wires sets will be required, one set of two wires going to the computer, and one set of two wires going to the speedometer. Sometimes using two wire sets will cancel out the VSS signal, so no signal is going to either the computer or speedometer. If that happens, reverse the + / - on ONE set of the wire sets, keeping the VSS AC sine wave signal "In Phase".

    dave w

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    Fuel Injected! EDZIP's Avatar
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    Quote Originally Posted by dave w View Post
    VSS signals are usually AC sine wave signals. Splitting one VSS output into TWO separate signals will work. Usually two wires sets will be required, one set of two wires going to the computer, and one set of two wires going to the speedometer. Sometimes using two wire sets will cancel out the VSS signal, so no signal is going to either the computer or speedometer. If that happens, reverse the + / - on ONE set of the wire sets, keeping the VSS AC sine wave signal "In Phase".

    dave w
    Thank You...may be a few weeks before I get to this...but at least I have a direction now!

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