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An alternative Mini ECU for Imp Mod Injection

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  • An alternative Mini ECU for Imp Mod Injection

    A very nice project introduced by Alex Davidson on doing fuel injection controller on the cheap.

    As I had planned to use Megasquirt but have to live within the constraints of that system this alternative might go down well, plus code is available and the programming enviroment is easy enough to develop in.

    Still same issue on coil packs as i mentioned above, plus the Webcon body is very expensive so one for another day, but if I can collect the bits and get the ignition side driven first off a standard modded 25D with no rotor etc, will be a start

    To be continued. Just started the thread as unlike FB I know where i can find this and update as needed. FB sucks for this stuff !

    Alex is currently building one so I would invite him for a few comments as he goes, may be some time before i get back to it though as you could easy spend weeks experimenting on this.

    - John
    / John

    If it can be fixed with a hammer, I am your man

  • #2
    And another one for the scratchpad, cheers Alex
    / John

    If it can be fixed with a hammer, I am your man


    • #3
      Good idea having a spot for this. I'll keep tinkering away with my speeduino build. Because I want to keep it under $100 for a complete build (I am a full blooded Davidson after all...) I am taking my time to seek out parts cheaply. I need to find the best place to get the parts off the BOM from. Maybe order 5 of everything because I'm sure I'll be building more in the future and most of these ECUS seem to use similar bits.

      I am hoping that Speeduino will release a board in the future that can run 6 injector drivers so I can build one to suit a sports car build I want to do involving a Mazda V6 (and another project idea I want to play with...)

      I am not at all an expert at this stuff btw. Just dabbling. But I can say its extremely addictive- the immense satisfaction of starting a car up and tuning it with a ECU that I put together from lots of tiny little bits. Very fun! Also building these is a great thing for winter nights by the fire



      • #4

        I am kind of just getting together in my head now what is actually needed such as accuracy of the timing and so on.

        The Megaquirt and Emerald and sothe systems tend to use a 120 tooth trigger wheel at about 150mm diameter, in fact Robin Human used to make a end crank pulley with integrated trigger wheel.

        This effectively gets rid of the distributor completely and you can add 1, two or 3 hall sensors on, unfortunately its an exposed area really, a good stone getting kicked up in wrong place and you are screwed. OK on rally track but bugger all use 30 miles form home in the dark

        So I am kind of firing down my random thoughts and ideas to be collated later, sometimes a good brain storming session over a few weeks can give tinking angles

        Ignition triggers need to come from dizzy which means simpler maths as its one full 360 for one cyle, the crank however is 2 cycles TDC/TDC

        code wise, especially on the Arduino platform with the maths library in place is a piece of wizz, normally maths takes process cycles and can only be done sequentially which means the time the processor works out an average or offset value the moment has passed, with the maths lib its send to lib, get result back even with floating point.

        i think it will be fun, with the maths set for 120 3 deg steps, the system would adapt to any engine really the A10 / A12 datsun engine would be a breeze.


        Pat Alex has the same A12 engine in his imp as I did in the 120Y, the A10 is same 998 engine you had in the 100A that ran great even on 3 cylinders and the carb off an A10 (nikki) is what we have on Boris (930)

        Will take a bit of time Alex, few non-sensical sorting out of ideas but that the fun

        BTW the site suport tagging same as FB does, so if you want to pull any user to the thread just do @ then first letter or two of username and a drop down list should appear, they will see the tag notfification on the top bar when next they log in, same for the like button

        / John

        If it can be fixed with a hammer, I am your man


        • #5
          On my Vauxhall Viva with the Mazda V6 I ran batch injection- mainly due to that fact that the ms2 ecu I built would only run full sequential on more than 4 cylinders if I added a daughter board. So all I needed was one VR sensor which i used in the stock position. I made a 36-1 trigger wheel by hand with a hacksaw and file. Printed the tooth pattern on paper, made a stencil, traced the pattern onto a steel disc I whipped up in a lathe. Tigged the wheel onto the back of my pulley. You dont even need to get it perfect- the teeth or the placement in degrees. In tunerstudio, as used by speeduino or megasquirt one can 'adjust' the position of the missing tooth in a drop down window. Soooo easy

          But next time I want to run full sequential. Power is easy with injection. It is with carbs too. But making an engine run super smooth at idle, just off idle and in all other daily driving conditions is the tricky bit which is also more fun trying to attain. I had it pretty good but batch injection just cant match sequential. Also extra mpgs can be had with finer control. Especially on a 6.

          My ignition was wasted spark with an old mitsi coil. I mounted my ignitors (bip373) outside the ms case onto an alloy heatsink for two reasons. They run fairly hot so why not move that heat away from everything else. It allowed me to run much fatter cables too and from the board and to the coil rather then silly little things through a terrible plug (the lovely DB 37 that ms use) The V6 was so smooth and quiet when cruising that we could actually hear the clicks from the transistors switching (the magic they do inside)

          On the Imp, whether its the Datsun I inject, or later on a bmw, or possibly a different engine, I'll be going for full sequential. I presume that the Bimmer K engine doesnt have a cam angle sensor if from what I have learned they just run batch injection? Its certainly not that hard to add one in somewhere though if you can do a little bit of fab work within the cam cover etc. Or on an Imp engine the dizzy shaft could be used.

          I'd not bother trying to run ignition through a dizzy when full dizzyless ignition is so easy. Makes for a better spark, cleaner engine bay. Coil packs mount nicely away under the rear parcel shelf eh

          Here's some pics of my first foray into diy engine electronic management lifted from my Viva thread over on Its just so much fun!

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          • #6
            Alex, I seen the pictures on the wiring at the other place,some serious fine work, makes some of my cabinet work look positively untidy !

            Over here you should see what gets picked out the back of an imp after a good run around in the wet not really wet friendly however the original later engine from rootes did come with electronic ignition.

            I borrowed this cut away engine from Clark for a show a few years back, hall in the dizzy and locator for another on the pulley. I have no idea what was ever fitted but a simple CDi would be all that is needed

            Might try and see what would have bene used.

            That work bench is too idy BTW you can just about find me in the mess when i get started !

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            / John

            If it can be fixed with a hammer, I am your man