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Thread: R90/6 with dual plugs

  1. #16
    Day Dreaming ... happy wanderer's Avatar
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    When the ignition is too far advanced and spark happens before the piston is at TDC what is that called?
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  2. #17
    Registered User toooldtocare's Avatar
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    Preston, all four plugs would fire on a standard system where the coils are in series, so what you say is true on a system with the coils in series. But, with SOME Dyna III ignitions like my Motorsport has, and now my old R90S, there are two pick up's, one for each cylinder, thus one for each coil.

    So coils are not in series, each has its own trigger source. Thus, you time one cylinder, then the other, which makes it nearly impossible to get both to fire exactly at the same time all through the RPM range. Swapping plugs wires (one coil firing say top plug on left and top plug on right, other coil firing both bottoms) probably would not do much since the top and bottom plugs would not fire at the same time in the real world. Which ever fired first would start the ignition and it may be over before the second one fired.

    The idea of dual plugs is to get the flame to combust faster, which it would if it starts ignition from both sides and travels to the middle, it has 1/2 the distance to travel than with a single plug. This is why you also retard a dual plug bike since it takes less time for the gas to burn.

    The benefits of dual plugging, and even electronic ignition are up for debate, I think they improved the starting of my bikes and made it ping less once the timing was set right. But, it was only measured by my seat-in-pants measurement.

    Wayne

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    Registered User DonTom's Avatar
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    Quote Originally Posted by toooldtocare View Post
    Preston, all four plugs would fire on a standard system where the coils are in series, so what you say is true on a system with the coils in series. But, with SOME Dyna III ignitions like my Motorsport has, and now my old R90S, there are two pick up's, one for each cylinder, thus one for each coil.
    Yes, there are two configurations. One gets rid of the waste spark, the other does not. My two six volt Dyna coils are in series, so I do have a waste spark. But that has the advantage that I could easily put the points back in, but then I should have a thingie in there to deal with the higher primary coil current of the dyna coils. But this becomes irreverent, because I carry a spare Dyna ignition anyway. I like to carry a lot of spare junk in case of trouble.

    What I would like to know is if there is any real advantage to getting rid of a waste spark. I kinda doubt it. I would think the only difference would be a little less ignition current wasted, which I doubt has any advantage at all.

    -Don- SSF CA
    Original owner of:
    1971 BMW R75/5, 1984 Yamaha Venture
    2002 Suzuki DR200SE, 2013 Triumph Trophy SE

  4. #19
    Administrator 20774's Avatar
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    The Dyna III system doesn't eliminate the wasted spark ignition...that I know of. All the Dyna III is allow for indepedent timing of when each cylinder will fire during engine rotation.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
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    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Registered User DonTom's Avatar
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    Quote Originally Posted by 20774 View Post
    The Dyna III system doesn't eliminate the wasted spark ignition...that I know of. All the Dyna III is allow for indepedent timing of when each cylinder will fire during engine rotation.
    There is one, or at least there used to be. It used 12 volt ignition coils and the whole idea of it was to get rid of the wasted spark. I had the Dyna ignition already with stock coils, so unless I wanted to change out the entire Dyna ignition, it wasn't an option for me to go with the Dyna ignition system that got rid of the wasted spark when I decided to have my heads dual plugged.

    It was made by Dyna, but perhaps it wasn't called Dyna III. Perhaps Dyna IV? CRS.

    -Don- SSF, CA
    Original owner of:
    1971 BMW R75/5, 1984 Yamaha Venture
    2002 Suzuki DR200SE, 2013 Triumph Trophy SE

  6. #21
    Registered User toooldtocare's Avatar
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    Quote Originally Posted by 20774 View Post
    All the Dyna III is allow for indepedent timing of when each cylinder will fire during engine rotation.
    Did not know that all could time each cylinder, thanks. On my soon to be new 77 R100S I will be making the decision to add a Dyna III or leave the points in. Right now I am thinking of just running points if the bike runs ok.

    Wayne

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    I don't mind being corrected in the least. All I know about this is when standard ignition was used and too much throttle was cranked/loaded into the engine before the engine was up on its rpm, it would rattle. With four plugs no rattle. On my bike left coil fires bottom plugs right top plugs, wires are the same length. Figgered it couldn't hurt and it seemed to make sense. No rattle good, rattle?, bad. Don't know if air pressure/density effects the ignition/intensity of spark. Good topic for a cold winter's day. should have added, standard points, '74 R90S, 9.5 pistons, 336 cam.
    Last edited by 8ninety8; 01-14-2013 at 02:54 AM.

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    Quote Originally Posted by Happy Wanderer View Post
    When the ignition is too far advanced and spark happens before the piston is at TDC, what is that called?
    If you have single plugs, spark before TDC would be called normal operation as it takes a finite length of time for the flame front to start propagating. Hence to get the full benefit of the fuel charge ignition comes before TDC. With double-plugging the flame front starts in two places and to avoid having the combustion chamber pressure trying to push the piston down against the engine rotation, the spark is retarded, most commonly to TDC.

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    Quote Originally Posted by 8ninety8 View Post
    All I know about this is when standard ignition was used and too much throttle was cranked/loaded into the engine before the engine was up on its rpm, it would rattle. With four plugs no rattle. On my bike left coil fires bottom plugs right top plugs, wires are the same length. Figgered it couldn't hurt and it seemed to make sense. No rattle good, rattle?, bad. Don't know if air pressure/density effects the ignition/intensity of spark. Good topic for a cold winter's day. should have added, standard points, '74 R90S, 9.5 pistons, 336 cam.
    Double-plugging reduces the octane requirement of the engine. The engine was "rattling" due to an octane deficiency. Double-plugging reduced the octane level required and the rattling stopped.

  10. #25
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by krpreston View Post
    If you have single plugs, spark before TDC would be called normal operation as it takes a finite length of time for the flame front to start propagating. Hence to get the full benefit of the fuel charge ignition comes before TDC. With double-plugging the flame front starts in two places and to avoid having the combustion chamber pressure trying to push the piston down against the engine rotation, the spark is retarded, most commonly to TDC.
    I realize spark is normally advanced slightly in normal operation. But I said too far advanced. When I have accidentally timed my motor too far advanced the engine makes a distinct sound that I thought was called pinging. It's the sound of your pistons being destroyed by pre-ignition. Or at least I thought that is what it was.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  11. #26
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    Quote Originally Posted by Happy Wanderer View Post
    I realize spark is normally advanced slightly in normal operation. But I said too far advanced. When I have accidentally timed my motor too far advanced the engine makes a distinct sound that I thought was called pinging. It's the sound of your pistons being destroyed by pre-ignition. Or at least I thought that is what it was.
    Happy Wanderer
    Timing set too far advanced does lead to pinging, knock, detonation, or whatever you want to call it; but the correct term is detonation and it is destructive. Timing advanced too far means that pressure and temperature will be rising quickly as the piston is not yet moving down increasing the volume of the cylinder. High temperature and pressure will cause pockets of fuel charge to spontaneously explode producing detonation.
    My problem understanding what you have been driving at is your incorrect use of the term "pre-ignition." Pre-ignition is initiation of the combustion process before the spark occurs, caused by a hot spot in the combustion chamber.

  12. #27
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by krpreston View Post
    Happy Wanderer
    Timing set too far advanced does lead to pinging, knock, detonation, or whatever you want to call it; but the correct term is detonation and it is destructive. Timing advanced too far means that pressure and temperature will be rising quickly as the piston is not yet moving down increasing the volume of the cylinder. High temperature and pressure will cause pockets of fuel charge to spontaneously explode producing detonation.
    My problem understanding what you have been driving at is your incorrect use of the term "pre-ignition." Pre-ignition is initiation of the combustion process before the spark occurs, caused by a hot spot in the combustion chamber.
    Ahhhhh OK. Now I get it. My bad on pre-ignition. Thanks for explaining this. And yes, it is definitely bad all around. Bad noise. Bad thing to do to the motor. And really really bad for the pistons.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  13. #28
    Registered User DonTom's Avatar
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    Quote Originally Posted by krpreston View Post
    The four plugs in a double-plugged engine all fire at the same time because the ignition system has two dual-output coils that are connected in series.
    True, but every 180 degrees, all four sparks can be at a different time than all four previous sparks, because of the extra pick up. Points only open once every 360, but there are two pick up coils (at least in my Dyna III in my 71 R75/5).
    Quote Originally Posted by krpreston View Post
    The plugs are not in series.
    Yes they are, on each side. Each so-called Dyna ignition coil is a true transformer with a complete primary and secondary winding.

    The two 6 volt windings are in series, of course. I think we all understand that much. That means all four plugs MUST fire at the exact same time, on each fire, just as you say. But every other time can be a lot different timing for the group of four compared to the previous group of four, because of the different pickup coil used each 180 degrees of the cam.

    But for the HV secondary of the transformer (stick on either side of the engine, left or right only, for my below explanation, assuming one Dyna coil is for the left and the other is for the right side):

    The HV (transformer output) path is from the secondary coil output to the top spark plug wire, through the spark gap then to ground (the head) and then the bottom plug ground then back through the plug gap of the bottom spark plug wire back to the other secondary wire of the same coil (transformer).

    Don't let the fact that it uses the head (ground) for a piece of wire be confusing. It's being used as no more than a wire.

    If you ground out either the bottom or the top plug with a dead short, the opposite plug will get the FULL voltage from the ignition coil (transformer).

    Same for opposite side of bike, of course. But you can take both plugs out and run a wire between the threads of the plugs and both will fire normally. NO GROUND IS NEEDED!!! It's a complete circuit without anything in the secondary circuit grounded. Again, it only uses the head for a piece of wire, not for a ground. A true transformer does NOT need a ground in the same ways as an auto-transformer (the stock coils).

    The stock BMW coils (auto-transformers) need a ground to complete the circuit back to the ignition coil. A Dyna Coil (true transformer, not an auto-transformer) needs no ground at all, so it conveniently uses the head itself as a wire to complete the circuit to the opposite plug for that same side of the engine.

    -Don- SF, CA
    Original owner of:
    1971 BMW R75/5, 1984 Yamaha Venture
    2002 Suzuki DR200SE, 2013 Triumph Trophy SE

  14. #29
    Registered User toooldtocare's Avatar
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    A picture is worth a thousand words

    This may help. It is out of the instruction manual of my Dyna III ignition. It shows a sensor plate with two pickups. Two coils, each one with dual outputs for the plugs. A jumper between the coils for the common connection, and two trigger wires, one for each coil. I assume that since each coil has a trigger wire, and there are two pickup sensors, than the two coils are not in series. Of course, the internal windings of each coil is in series and the two plugs that each coil fires would be in series, but not the coils themselves. I have been wrong in the past, but if my memory serves me right, I never could get the plugs to fire at the same time when I swapped one plug wire left to right, and right to left, which would also suggest that they are not in series.
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    Last edited by toooldtocare; 01-15-2013 at 04:00 PM.

  15. #30
    Registered User DonTom's Avatar
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    Quote Originally Posted by toooldtocare View Post
    This may help. It is out of the instruction manual of my Dyna III ignition. It shows a sensor plate with two pickups. Two coils, each one with dual outputs for the plugs. A jumper between the coils for the common connection, and two trigger wires, one for each coil. I assume that since each coil has a trigger wire, and there are two pickup sensors, than the two coils are not in series. Of course, the internal windings of each coil is in series and the two plugs that each coil fires would be in series, but not the coils themselves. I have been wrong in the past, but if my memory serves me right, I never could get the plugs to fire at the same time when I swapped one plug wire left to right, and right to left, which would also suggest that they are not in series.
    Hard to tell by what that shows, but it looks like you might have the type that gets rid of the waste spark.

    Mine does NOT get rid of the waste spark and doesn't have the wire that goes to the crossover wire to the ignition module.

    -Don- SSF, CA
    Original owner of:
    1971 BMW R75/5, 1984 Yamaha Venture
    2002 Suzuki DR200SE, 2013 Triumph Trophy SE

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