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Thread: Another Megasquirt conversion: VIN00910

  1. #21
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    Quote Originally Posted by FABombjoy View Post
    Gutted distributor and riveted / jbwelded (hell yeah jbweld) a single tooth on to the original pole piece.

    Attachment 63685

    The single tooth metal was an old pinball machine bracket. I tried to use as many old pinball machine parts as possible during my conversion LOL

    More pics
    It may work with one pulse on the distributor so you get a reference of which stroke your on for #1 cylinder but it's going to take some fancy software to keep track of when all cylinders need to fire. Your crank sensor needs a lot of teeth to know RPM quickly and when to fire the other cylinders.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #22
    '82 T3 FABombjoy's Avatar
    Join Date:  May 2011

    Location:  Lansing, MI

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    My VIN:    10270

    That's exactly how it works when in conjunction with a crank wheel. The cam signal is only polled once to obtain full RPM sync.

    If you tried to run fuel only on this setup it would be pretty sloppy. Ignition control would probably be very entertaining from a distance.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

  3. #23
    Senior Member ramblinmike's Avatar
    Join Date:  May 2011

    Location:  Alton, IL

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    My VIN:    00910

    Quote Originally Posted by FABombjoy View Post
    Gutted distributor and riveted / jbwelded (hell yeah jbweld) a single tooth on to the original pole piece.

    Attachment 63685

    The single tooth metal was an old pinball machine bracket. I tried to use as many old pinball machine parts as possible during my conversion LOL

    More pics
    Thanks for the pics. I've read about the "half-moon" shape used on the cam sensors and see you've used the same. What is the advantage of the half-moon shape rather than a single tooth passing? That's actually one of the things I'm confused about. Should the arm be in a half-moon or just a single 'tooth'?

    I've seen cam synchronizers on some vehicles use the half moon:
    images.jpeg

    ...and some that use a single 'tooth':
    IMG_0430.JPG


    The way you attached it under the original 'trigger' pins is similar to what I was seeing in my head, but I was going in the direction of using the plate at the bottom where the weights attach.

    Thanks!

    Mike
    Yeah, it's dirty. I drive it.

  4. #24
    '82 T3 FABombjoy's Avatar
    Join Date:  May 2011

    Location:  Lansing, MI

    Posts:    1,148

    My VIN:    10270

    I'm sure there are a lot of ways to go about this, I just picked one that made sense at the time.

    I still have the advance mechanism intact. In a crank+cam signal setup you don't have to clobber the mechanical advance.

    Because the advance weights are still there, if the tooth is mounted to the shaft, it's expected position relative to the crank wheel might change.

    Normally the tooth is only read at startup and it probably would always appear in a fixed position. But if you ever have a crank sync error, depending on your RPM a small tooth might miss the sampling window. It was easier to make a half-moon shape and set Megasquirt to look for cam tooth right in the middle of the range.

    Probably in an OEM computer situation, a full predictable half-moon would net you a faster full sync?
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

  5. #25
    Senior Member ramblinmike's Avatar
    Join Date:  May 2011

    Location:  Alton, IL

    Posts:    302

    My VIN:    00910

    Quote Originally Posted by FABombjoy View Post
    I'm sure there are a lot of ways to go about this, I just picked one that made sense at the time.

    I still have the advance mechanism intact. In a crank+cam signal setup you don't have to clobber the mechanical advance.

    Because the advance weights are still there, if the tooth is mounted to the shaft, it's expected position relative to the crank wheel might change.

    Normally the tooth is only read at startup and it probably would always appear in a fixed position. But if you ever have a crank sync error, depending on your RPM a small tooth might miss the sampling window. It was easier to make a half-moon shape and set Megasquirt to look for cam tooth right in the middle of the range.

    Probably in an OEM computer situation, a full predictable half-moon would net you a faster full sync?
    I think I'm going I'm going to remove the advance mechanism and trim the shaft to let me make some kind of cap to fit over the distributor housing. The way you described it makes sense. I'm going to build it with the half-moon and see how that goes.

    The quarantine is double-edged sword. I'm getting tons of time to do some pretty major stuff around the house but I'm not able to go out to get stuff for the car.

    I appreciate the help!

    Mike
    Yeah, it's dirty. I drive it.

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