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Thread: Any auto electrician wiz kids out there?

  1. #1
    Guest dan_evans's Avatar
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    Any auto electrician wiz kids out there?

    So... to get my Tachometer to work in the E30 with the SR20 you have to make a small circuit board that boosts the 5V Nissan signal to 12V for the BMW tacho....

    I have made the board following what this guy did... and using a multimeter It has boosted it from the Nissan ECU wire to 12v..... but, I still have no revs..

    Can someone confirm what colour wire it should be out of the 76pin plug (4-3-3-3) as I have used the blue/black line as shown here....

    If it is the correct wire then any other suggestions as to how I can get the E30 tacho working?....

    Got mapping next Thursday so ideally want this working first




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    Guest norfy's Avatar
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    to confirm, you have the correct wire for the tacho from the nissan side.

    is it a straightcam sr20? just thinking the earlier s13 engines/tacho sr/ca use a negative pulse tacho signal (negative-off), whereas the later sr20 as fitted to s14/a use and alternating pulse (negative-5v). We usually have issues getting the tacho to work when fitting a later sr20 into a s13. In this case you need to fit a 33k pull up resistor to the blue/black wire on the ecu connector.

    im thinking, if youve got an earlier straight cam and the bmw tacho needs a negative-12v pulse then youll need to fit a pull up resistor to get that. You could quite easily fit that to your pcb.

    just a thought, and its something to check

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    Guest dan_evans's Avatar
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    Quote Originally Posted by norfy View Post
    to confirm, you have the correct wire for the tacho from the nissan side.

    is it a straightcam sr20? just thinking the earlier s13 engines/tacho sr/ca use a negative pulse tacho signal (negative-off), whereas the later sr20 as fitted to s14/a use and alternating pulse (negative-5v). We usually have issues getting the tacho to work when fitting a later sr20 into a s13. In this case you need to fit a 33k pull up resistor to the blue/black wire on the ecu connector.

    im thinking, if youve got an earlier straight cam and the bmw tacho needs a negative-12v pulse then youll need to fit a pull up resistor to get that. You could quite easily fit that to your pcb.

    just a thought, and its something to check

    Mines a S14 blacktop (vvt)

    I was reading something online that when a conversion is done for the S13 to SR20DET you need to use a wire from the CAS for the tachometer to work.

    Might just check the board iv made to make sure the resistors haven't burnt out.


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    Guest speedingmofa's Avatar
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    I can't remember it exactly as it was a yr ago, but i believe this is the scheme I used for wiring in my apexi RSM which also requires the tach signal. I also have a zenki, so 4-3-3-3. Judging by the pictures, you seem to have the correct wire

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    Hi,

    i've tried it myself (no internet wisdom). using 7.5Kohm resistor pullup to switched 12V makes the signal a clean 0to12v square pulse. I got it on scope view but not on this computer.

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    Guest dan_evans's Avatar
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    Quote Originally Posted by KennyJ View Post
    Hi,

    i've tried it myself (no internet wisdom). using 7.5Kohm resistor pullup to switched 12V makes the signal a clean 0to12v square pulse. I got it on scope view but not on this computer.

    Tried a couple different things today but still no joy, getting frustrated now


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    I had a similar problem when doing a conversion on S14 uk spec Sr20det vvt. I used a different wire off the ecu loom. Il check it for you and post it . But top of my head it was the red and yellow wire. But il have to confirm

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    Guest dan_evans's Avatar
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    Quote Originally Posted by s12_drift View Post
    I had a similar problem when doing a conversion on S14 uk spec Sr20det vvt. I used a different wire off the ecu loom. Il check it for you and post it . But top of my head it was the red and yellow wire. But il have to confirm
    Great stuff if you can mate appreciate it!


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