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How to trigger an EFI computer

Discussion in 'General Electronics Discussion' started by GeoffM, Jun 10, 2013.

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  1. GeoffM


    Jun 10, 2013
    Hi guys,

    First post on here so I hope im in the right place.

    I am fuel injecting an outboard motor project and need help switching the EMM

    I need a voltage trigger between 4 and 12 volts for the EMM

    My outboard has a sensor coil that puts out 0.5volts to a powerpack. The powerpack then puts out 200volts to the ignition coils .

    Would it be better to use the 0.5 volts or 200 volts to trigger the EMM.

    I was think of making a circuit board that gets switched by either one of the voltages and uses that to switch a 12volt supply to switch the EMM.

    It will need to be able to switch up to 11000 times per minute..

    Any help or guidance is greatly appreciated . I am an outboard technician so my electronics experience is limited.
  2. duke37


    Jan 9, 2011
    What is an EMM and what is an EFI computer?

    I would tend to keep away from the ignition coils since there could be large voltage spikes which would be difficult to handle.
  3. GeoffM


    Jun 10, 2013
    An EMM is the engine management module ( computer)

    EFI is electronic fuel injection. They are both the same thing.

    The computer I am using is off a mercury outboard which uses the ignition to switch it. The problem is mercury system sensor coil outs out 4volts + and my outboard puts out 0.5volts.
  4. mrmodify


    Feb 13, 2010
    EFI = Electronic Fuel Injection.

    I am assuming that this is a 2 stroke outboard.

    I am not sure what you will need but i am just about positive that you will not be able to use the power pack trigger coils. The power packs fire the spark plugs 3 - 30 degrees before top dead center depending on RPM's. The fuel injection timeing, depending on type of fuel injection, needs to be before the ignition is triggered.

    Unless it is a direct port injection system but I still think fuel will have to be injected some point before the coils fire.

    Someone please correct me if I am wrong.
  5. GeoffM


    Jun 10, 2013
    Thanks for your reply. Just for everyone to know, this system is off an outboard motor that works absolutely fine and is a Mercury factory race engine system.

    I am putting it on a johnson outboard. The reason it wont trigger is because the voltage on the johnson is too low.

    The ignition will trigger another cylinder to inject the fuel on the intake stroke (yes its a two stroke).

    So all I need is a way to use my ignition to trigger the computer to fire.

    If it can't work, I will install 3 sensor coils and fit a magnet to the flywheel to drive them. That is a last resort as it will take some fabricating to make brackets to hold the sensors.
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