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Thread: Tach signal without stock igniter?

  1. #1
    Forum Member 1st year Apprentice
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    Default Tach signal without stock igniter?

    Hi!

    just wondering if anyone can shed some light on this issue.

    I have a 2jz with a haltech ps2000 running it. I have retained the factory ecu to control the a/c, speedo, central locking etc etc. A while ago i swapped to GM D585 ignition coils to combat breakdown i was getting.
    The coils are driven directly from the haltech, so i don't have the stock igniter anymore, and now with no IGF signal my tacho doesn't work.

    I know there are a few electronics savvy people on this forum, anyone know of a way around this?

    I have tried using the tach output of the haltech connected to the rpm input on the stock ecu with a few different settings but haven't had much luck.

  2. #2
    Forum Contributor 1st year Apprentice robk's Avatar
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    Default Re: Tach signal without stock igniter?

    This is a common problem when changing from a distributor to coil-on-plug with many different Toyotas. I had to solve it on my 3S-GTE SW20 MR2.

    When there is a wire from the igniter to the tachometer, the wire effectively connects to the ignition coil negative inside the igniter. This means that every time there's a spark, a voltage spike is generated on the wire to the tachometer.
    The tachometer then detects the gap between each voltage spike from the igniter to calculate the RPM.
    The problem is, a normal tachometer-style output from an aftermarket ECU will simply generate a square wave signal, but it may not exceed the voltage threshold expected from the voltage spikes in the standard setup with the igniter.

    The solution is:
    Use a relay coil (ignoring the switch contacts) to pull the tachometer output up to 12V. When the ECU pulses the tachometer output to ground it will activate the relay coil, and because it's a coil it will generate a voltage spike as required.

    Do a Google search and you will find slight variations of this concept mentioned on heaps of different forums :-)
    1990 SW20 MR2 with '5S-GTE'.
    418rwkw @ 32psi of boost on E85.
    289rwkw @ 20psi of boost on 98 RON.

  3. #3
    Forum Contributor 1st year Apprentice robk's Avatar
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    Default Re: Tach signal without stock igniter?

    This should point you in the right direction:
    https://www.google.com.au/search?q=t..._AUIBigB&dpr=1
    Last edited by robk; 18-08-2016 at 03:55 PM.
    1990 SW20 MR2 with '5S-GTE'.
    418rwkw @ 32psi of boost on E85.
    289rwkw @ 20psi of boost on 98 RON.

  4. #4
    Forum Member 1st year Apprentice
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    Default Re: Tach signal without stock igniter?

    hi mate, thanks for the info.

    Your google link lead me to this thread: http://www.toymods.org.au/forums/thr...-Tacho-Booster

    as i understand it, the stock ECU sends an IGT signal to the igniter triggering the coils to fire, and consequently sends an IGF signal back to the ECU (this is the rpm input for the ecu). It then sends this information along with other things which are monitored by the ecu (e.g speed, water temp, fuel level and any warning lights) to the dash cluster via the CAN bus system.

    If i were to try this tacho booster, basically i would be using the tach output of the haltech as the 'ign signal' and the 'to tach' output of the booster to the rpm in on the stock ecu?

    I seem to recall trying a 12v option of the haltech output, i could be imagining things. Will have to check if it's possible. If the Haltech did have a 12v option for the output, would it fair to say that this booster may not fix the issue?

  5. #5
    RZN169R+2JZGTEVVTI+R151 Domestic Engineer madmont's Avatar
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    Default Re: Tach signal without stock igniter?

    [QUOTE=Moose;1612306]as i understand it, the stock ECU sends an IGT signal to the igniter triggering the coils to fire, and consequently sends an IGF signal back to the ECU (this is the rpm input for the ecu). It then sends this information along with other things which are monitored by the ecu (e.g speed, water temp, fuel level and any warning lights) to the dash cluster via the CAN bus system.

    Are you sure the tacho signal is sent through the CAN bus. My ex JZS161 2JZGTE sends the tacho signal through a separate wire.
    Jealousy is a curse

  6. #6
    Forum Contributor 1st year Apprentice robk's Avatar
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    Default Re: Tach signal without stock igniter?

    ^I was going to ask the same thing.

    Sorry I totally missed where the CAN bus was mentioned in the OP.
    My suggestion only applies if your stock tacho was driven by a single wire from the igniter, rather than a CAN signal.
    1990 SW20 MR2 with '5S-GTE'.
    418rwkw @ 32psi of boost on E85.
    289rwkw @ 20psi of boost on 98 RON.

  7. #7
    Is a Chief Engine Builder wilbo666's Avatar
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    Default Re: Tach signal without stock igniter?

    I wouldn't use a tacho booster as going from your profile you have a JZS160...

    You should be able to connect the Haltec tacho output to Pin 2 of the 9 pin engine to body loom plug (plug part number 90980-11710) near the engine ECU.
    <wiki here>

    Does your Haltec output need a pull up resistor to allow it to work as a tacho output?


    Also JZS16x doesn't have CAN, it has "Toyota Multiplex". They are different things

    Note: I did update my wiki as I had the engine ECU TACH pin being an output... that doesn't make a whole lot of sense to me, but then again I can't find any reason for it to exist as an input either so I'm sure exactly sure of that pins operation...! Regardless I'm pretty sure the dash tacho signal comes from the Igniter, as the JZS160 / 2JZ-GE Engine ECU doesn't seem to have a TACH pin at a very quick look?

    Cheers
    Wilbo
    Wilbo's Wiki (Includes 2JZ-GTE Wiring, etc! )

    Wilbo's JZA80
    Wilbo's JZZ12

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    Default Re: Tach signal without stock igniter?

    thanks for the replies.

    wilbo, you are right, i'm not sure where i pulled CAN bus from.

    In any case it seems that i was thinking of it wrong. I found my wiring book, which basically shows what you guys had mentioned.




    I would say that EA3 is the plug you are referring to above wilbo as the schedule mentions it being in the engine ECU box.

    I also had a look to confirm, and there is no TACH pin on the ECU. The inputs schedule mentions that the ECU receives the RPM signal from the cam position sensor.

    I think i was connecting the TACH output from the Haltech to the IGF input on the ECU (thinking that the tacho received info via the multiplex system) in an attempt to get it working.

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