Megasquirt on a K75

Discussion in 'Some Assembly Required' started by wmax351, Dec 5, 2011.

  1. wmax351

    wmax351 Been here awhile

    Joined:
    Mar 13, 2011
    Oddometer:
    743
    Location:
    Marin County and Berkeley, CA
    I needed something to fidget with. So I figured I'd do some mileage and emission improvement on my K75.

    I'm going to install a Megasquirt fuel injection system, which has several advantages over the stock system.

    - Closed loop control: Adapts to changing conditions, such as altitude, and wear in the engine. I am installing an O2 sensor for this.
    - Improved fuel economy, also through closed loop: I can keep the AFR close to ideal during high speed cruise conditions, rather than the default, rich setting on the stock jetronic computer.
    - Future option to add ignition control, including spark advance and knock sensing. Increasing spark advance on a k75 is dyno proven to add power, and this will allow me to widen the advance curve, leaving a (relatively) retarded spark for idle.
    - Fewer expensive sensors: I can eventually dump the flapper type MAF sensor, although I may keep it.
    - Will be a direct plug in system, when finished. I sourced a connector that plugs into the EFI harness, so I can swap back to the jetronic computer with ease. The only thing missing will be the Throttle position switch, updated to a throttle position sensor.

    More details will be posted on the Motobrick forum: http://www.motobrick.com/index.php?topic=936.0



    These are for offroad use only. :evil

    However, I think the spirit of the law is satisfied with this: when done, there will be greatly lower unburned HC emissions, and less fuel usage.
    #1
  2. wmax351

    wmax351 Been here awhile

    Joined:
    Mar 13, 2011
    Oddometer:
    743
    Location:
    Marin County and Berkeley, CA
    Been working out how to set up the Megasquirt ignition system, which would give me better control of the advance.

    I'm going to start with fuel only, then go from there.

    The Megasquirt system is not designed to work with the twin hall sensor, 2 window design on our bikes. I need to trick it into thinking it is something different, like 2 timing wheels.

    If I set up two logic gates, I can get 3 evenly spaced pulses per crank revolution, as well as 1 pulse per crank revolution to identify a cylinder.

    I can set up an AND gate for the 1 pulse, which will come from both of the Hall sensors, and an OR gate which will pulse 3x per revolution.

    Not to sure on the exact circuitry, but it seems pretty easy to implement. If anyone is familiar with circuit logic, it would be very helpful.
    #2
  3. Mr. Vintage

    Mr. Vintage Family Dude

    Joined:
    Jan 19, 2007
    Oddometer:
    867
    Location:
    The Palouse
    I'm of little or no use to you technically. But, I'm staying tuned - I'd like to do something similar with the open loop EFI on my Guzzi.
    #3
  4. wmax351

    wmax351 Been here awhile

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    http://www.youtube.com/watch?v=_izb1QAvd7I&feature=player_embedded

    http://www.youtube.com/watch?v=WEOktt40BBA&feature=player_embedded



    Seems like this guy (who made the turbo K75) made his own trigger wheel with optical sensors. Its a 15 tooth wheel, with a 1 tooth wheel underneath. the one tooth (deeper cut) wheel triggers both sensors, and the other windows only trigger one sensor. From that, megasquirt can interpret the two sensors, with the deep cut coinciding with a specific crank position, syncing the shallow cut sensor, which then counts the windows, in order to trigger the ignition.

    I could definitely do this: I have access to a CNC shop at Berkeley.

    I sent him a message, I will see if he sends me some more info on the project.
    #4
  5. wmax351

    wmax351 Been here awhile

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    Location:
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    A Guzzi should be quite easy to do.

    Fuel-Only can be done with a tap off of the coil-->It just needs an RPM signal

    Fuel and Spark is pretty easy on a 90* Vtwin. You use two pickups on a 1 tooth (missing or otherwise) wheel. You should be able to use the stock system.
    #5
  6. wmax351

    wmax351 Been here awhile

    Joined:
    Mar 13, 2011
    Oddometer:
    743
    Location:
    Marin County and Berkeley, CA
    Well, its running very well. Check out the motobrick forum for the writeups.
    #6