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  1. #1
    Member Woznaldo's Avatar
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    Megasquirt users, how are you driving your OE Tacho

    As per the title I'm trying to work out how the MS users in the club are driving their tachos.

    I'm running MS1 extra on a V2.2 board with EDIS4 ignition. I've got a post in the MS1 Extra support forums but as it depends on what tacho your are running, I thought the answer may be a little closer to home.

  2. #2
    Non-member SCHWARTZ's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Isn't there a driver you can buy for fourpots? Looks like 2 wires into 1 with a resistor in the middle or something. Then you can cut the blue (i think) wire off the back of the clocks like what you do with the b18ft loom.

  3. #3
    Member Woznaldo's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Yes there is but I'd like to drive it off the EDIS module if I can. I've got a reply from the MSExtra forum and been advised to try Pin 2 (EDIS) first and see what happens.

    It all depends on what the OE tacho requires to drive it (voltage of the pulses).

  4. #4
    Non-member SCHWARTZ's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    It will be good to see what you find out as I will be going megasquirt soon but will be using standard coil and tdc sensor etc...

  5. #5
    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    2x diodes into 1, i'll get the info, i think i have some diodes spare, i had to do this on the KA when i put a zetec in so that the rev counter didn't read 'half'

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    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho


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    Re: Megasquirt users, how are you driving your OE Tacho

    I tried driving a GTT tacho with EDIS4 once before, it didn't work so I had to connect it to the ECU instead.

  8. #8
    Non-member SCHWARTZ's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Yeah that's the kinda thing I'm on about mark.

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    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by SCHWARTZ View Post
    Yeah that's the kinda thing I'm on about mark.
    if u need any diodes lemme know i have squillions, i ended up buying about 20 in the end to make one as it was cheaper to buy bulk than just 2

  10. #10
    Non-member SCHWARTZ's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Cheers fella il bear that in mind

  11. #11
    Member Woznaldo's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Mark, I did read this for other cars on the MSExtra forum so sounds like it might be the way to go, especially if Scoff was having dramas too!

  12. #12
    Member Woznaldo's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by Scoff View Post
    I tried driving a GTT tacho with EDIS4 once before, it didn't work so I had to connect it to the ECU instead.
    Did you try Pin 2? Just try to rule it out before I start.

  13. #13
    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by Woznaldo View Post
    Mark, I did read this for other cars on the MSExtra forum so sounds like it might be the way to go, especially if Scoff was having dramas too!
    i wired it off the plug to the coil, the 2 outer pins just chipped into the wiring and ran to tacho

  14. #14
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by markey b View Post
    i wired it off the plug to the coil, the 2 outer pins just chipped into the wiring and ran to tacho
    On the ford coil you mean ? You will have had to couple to those via resistors, is that what you did ? Not just connect them together obviously

  15. #15
    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by Scoff View Post
    On the ford coil you mean ? You will have had to couple to those via resistors, is that what you did ? Not just connect them together obviously
    yea ford coil, via two diodes so you get a 4cyl pulse without backfeeding the coil. i think megasquirt actually do a loom for it but its 20p in diodes to make your own

  16. #16
    Non-member SCHWARTZ's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Triggerwheels do one 2 wires into 1 with diodes in middle about 9odd quid.

  17. #17
    Non-member markey b's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Quote Originally Posted by SCHWARTZ View Post
    Triggerwheels do one 2 wires into 1 with diodes in middle about 9odd quid.
    thats the kiddy! 20p to make though

  18. #18
    Member Woznaldo's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    I've just made one up after buying a pack of 50 diodes for about 4 quid. Yet to be tested but at least I'll have 48 spares.

  19. #19
    Member Woznaldo's Avatar
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    Re: Megasquirt users, how are you driving your OE Tacho

    Ok, I've finally got around to trying the diode setup off the coil pack to drive the tacho and it's working! I also tried pin 2 and 11 (this is all using an EDIS4 setup) but, no luck.

    I went with 2 x 1N4004 diodes and a 15-18v Zener diode and I've got a nice clean signal and the tacho is stable.

    It took a while to actually get this far due to spark issues and an idle problem:

    https://www.rtoc.org/boards/showthread.php?t=31041
    Last edited by Woznaldo; 03-01-2013 at 05:17. Reason: correct zener voltage rating

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