vems trigger problems on aan

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  • diesel des
    replied
    No Its not bad at all Marc, but is a harder push than the Spec pressure plate i had befour. Maybe thats why it slipped though...

    So back to the vems. Here are some pictures of the pin i made and a stock aan flywheel.

    I basicly made a piece of steel with a hole in it that was a press fit over the stock 7a pin. I ground down the steel untill the hole was almost broken through at the outside so the steel wouldnt get too close to the sensor.

    There is a nice big "pin" now for the sensor to see. Motronic is still happy but not vems.
    Attached Files

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  • a4kquattro
    replied
    Originally posted by diesel des
    Ok do I take the belt cover off the cam sensor and crank pin should be both lined up in there sensor at the same time.
    right, just peel back the cover a bit so you can see the cam shutter wheel and watch for when its lined up with the hall sensor. then pull the little reference sender block on the tranny that has the two VR sensors in it, and verify that the reference pin is near the center of the sender hole in the tranny.

    On the cam hall inverter, you can tell if you've got one via your primary trigger settings (if you've got the right config anyway!). If your "First Trigger Tooth" is 8, you DO NOT have a cam hall inverter. If its set to 0, you DO have a cam hall inverter.


    Thanks for the help marc. Ps your south bend clutch is now installed and has great bite. It is a bit harder on the leg though. I will just have to man up a bit lol.
    I'm 5'5 130lbs dripping wet and it doesn't seem bad to me. MAN UP!

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  • diesel des
    replied
    Ok do I take the belt cover off the cam sensor and crank pin should be both lined up in there sensor at the same time.

    Thanks for the help marc. Ps your south bend clutch is now installed and has great bite. It is a bit harder on the leg though. I will just have to man up a bit lol.

    Leave a comment:


  • a4kquattro
    replied
    Originally posted by diesel des
    Right I welded a piece of steel on the flywheel. It's about 12 mm tall and wide so covers about 2 or 3 crank teeth like the one in the pictures. And my problem is worse! The trigger error happens just about 1500rpm now. I swaped the red and purple wires again at the sensor to I think stock setup. Red in middle. This helps but still not perfect.

    Now I'm lost people .help. I will try and get a config file posted tomorrow night. Cheers des
    no idea where you bought your ecu (not from me) but:

    1) check your trigger input configuration (ask your dealer). specifically the pullup resistor size.

    2) does your ecu have a cam hall inverter installed? It should.

    3) verify that when the hall sensor window is centered over the hall sensor that the reference pin on the flywheel is also centered on the VR sensor. If its offset by too much it might be going out-of-window when the engine starts up from cam belt flex. The stock ecu can deal with the reference pin going out of window by a little bit, the vems cannot because of the way the noise filtering works.

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  • diesel des
    replied
    Right I welded a piece of steel on the flywheel. It's about 12 mm tall and wide so covers about 2 or 3 crank teeth like the one in the pictures. And my problem is worse! The trigger error happens just about 1500rpm now. I swaped the red and purple wires again at the sensor to I think stock setup. Red in middle. This helps but still not perfect.

    Now I'm lost people .help. I will try and get a config file posted tomorrow night. Cheers des

    Leave a comment:


  • diesel des
    replied
    Going to pull starter and look at this tonight. Should the new piece of steel have its mid point where the center of the hole is now. Or should the edge of the new piece line up where the pin was. Eg does the ecu trigger on the edge or center point.

    And mild steel rods ok.

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  • a4kquattro
    replied
    yep, drilling a hole and fitting a larger pin works too. Just be sure that the pin is ferrous (magnetic) and in the same location as stock (which puts the pin in the middle of the VR sensor when the cam hall shutter wheel or the distributor hall sensor in the case of a 3b setup is in the middle of its window).

    If you compare the size of the pin on a 7a or 3b flywheel to the pin on an AAN you'll see the size difference.

    I use hardened steel dowels from mcmaster-carr (industrial supply house here in the USA) when I run into this problem on customer cars.

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  • A80Avant
    replied
    the pin is magnetic, apparently due to noise vems cannot pick it up correctly sometimes. I believe if you take it out and put a bigger one in it should work as well. I dont have any info on that though. We just went for a secure solution to make it work and welded some iron next to it to make it visible to the sensor

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  • QuattroFever
    replied
    what is the problem exactly is the pin too thin or the wrong shape or not magnetic? I have a 7a alu flywheel expected to run on vems and havent had the pleasure of turning the key yet. Can you just tap a hole in the flywheel same place and srew bigger steel rod in?
    its relevant but sorry for hijack.

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  • diesel des
    replied
    Ok. Did you weld this yourself? What sort of rods should I use. Dissimilar or normal mild steel. Cheers

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  • A80Avant
    replied
    i suspect it should run ok,but i havent tried it. My motronic has way different eproms in and i dont dare plug it in again.

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  • diesel des
    replied
    Thanks for the picture! that helps a lot. does the car still run on motronic if needed with this mod. cheers des.

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  • A80Avant
    replied
    that is what i was told as well. I dont get any problems with vibration or anything else etc.

    The pin itself may not be more than 1 gram if you weigh it. Ok on 7000rpm spining even that 1gram is much heavier i suppose. Ideally it should be taken off, weld and rebalanced to zero. But as i say, mine was done as is and the amount of welding material is so little that it doesnt seem to affect the balancing. I have been speaking to a lot of respectable mechanics and shops around the UK as well regarding balancing and personally im getting the idea that it is being overrated when it comes to street cars or minor changes. Not everyone is building a race car.

    On top of that, as mentioned above, solution 1(sensor moving) did not have any effect on vems reading the damn pin any better. So we had to go with solution 2.

    Use material that is strongly magnetic and test it with the sensor before hand. Make sure it sticks to it, Or use a magnet for that matter.

    Marc was telling me that there are variants of 7A flywheels and not all will cause this problem, hence why some have a problem and others dont.

    managed to find a couple of photos from the garage days.

    here is the pin and shows how small it is:



    here is the weld ( picture was taken while still in the process. it needed refinement anyway)

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  • Jamo
    replied
    Originally posted by diesel des
    Ok will do tommorow when I'm on my computer. I haven't actually looked at the config file is it just a text file. Jamo I really don't feel like swapping the flywheel 2 days after doing the clutch. I don't want to ever see the dam flywheel again LOL.
    Config is just a text, you could just post screenshots of the ignition settings

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  • Jamo
    replied
    Originally posted by diesel des
    A few grams won't make a difference on this. It's not a full race engine. The sensor already seemed less than 1mm away so I think welding is my best option. Would like a picture though. Cheers des.
    Agree welding a pin isn't going to affect the balance of a street car

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