BMW ignition booster - anyone knows where to get one? - Page 2

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    #11
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    Quote Originally Posted by TheEnd View Post
    They compensate for varying battery voltages, they can't detect bad coils, but it does mean the spark "requested" will always be constant if the battery is at 11.5v or full on 14v when running.
    It will also adjust for the engine RPM as there is only a certain amount of time to charge a coil before it is needed to be used again.

    With the table, it will figure out how long it has got and what power is available, and produce something of the same energy.

    Old distributor systems couldn't do any changes like that, and one coil would constantly have to be running to spark every cylinder.
    There would be longer leads for the spark to travel down, the coil would start getting pretty hot and it would have a pretty rough time, but BMWs have been using coil-on-plug for quite a while now, each cylinder has its very own coil, the lead is only about 2-3 inches between the bottom of the coil and the top of the plug so they are a very strong system.

    Where it can start to go wrong is when the coils start to get old and break up inside, and they can start short circuiting. A coil of 20 loops of wire might end up shorting between a couple and giving less of a spark.
    I always like reading your technical posts, very interesting!
     
     

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    #12
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    That's how the coil-on-plug set up works, and as with a lot of cars, the switch is the negative wire in the ECU.

    The interesting part you'll see is that the plugs aren't electrically connected to anything. The coil acts as a transformer, and when the ECU grounds the primary (top) coil, it'll become a little electro-magnet.

    When the power is switched off again, the magnetism collapses, and the magnetic flux shoots through the secondary coiland induces a much higher voltage, as in 20-40,000 volts.

    The problems you get are the individual coils (top and bottom, primary and secondary) breaking up so they act like less loops, or the real bad one, the secondary coil ends up short circuiting to the primary coil and sending 40k Volts into the ECU.


    Older single coil systems have one massive coil instead which has to fire for every cylinder-




    You can see all the loops of wire, and they are the ones that can start to short circuit when the coil breaks down.
     
     

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    #13
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    i remember doing that at college.
    nice to have a decent diagram to visualise it better (Y)
     
     

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