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Off topic gm wasted spark ignition coils

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  • #16
    Ok Doozer, why don’t you just come out & say what you’re thinking ;-) I thought this was a friendly forum & I’m just providing some observations from 50 + years of active mechanical experience & not standing on a soapbox. I don’t think anyone deserves the comments you made. Perhaps you should reread what you’ve said and reevaluate your own mental & esteem issues.

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    • #17
      Originally posted by Richard P Wilson View Post
      Sorry to be stupid, but what is the purpose of these twin spark plug systems? What do they do that is better than a coil/ single spark plug system, especially when many of you have said that spark plug life in a twin system is about half of what it would be for a single plug system?
      Less complexity and lower unit costs are the driving factors.
      Home, down in the valley behind the Red Angus
      Bad Decisions Make Good Stories​

      Location: British Columbia

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      • #18
        Thanks to higher voltage ignitions, (less current eroding the electrodes) and unleaded fuel, plugs last a long time. I worked on wifey's 2014 Altima yesterday, trans fluid and filters, coolant change, air and cabin filter (an absolute contortionists nightmare) and wait for it,,, spark plugs.
        At 101,000 miles they looked new and with a little anti seize they went back in. I'll probably lose the set of new ones I have before they are needed.

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        • #19
          Sorry. I just see a lot of non believers here when facts are presented. Not aimed at you. I apologize if you have taken it as such. I do indeed have some mental issues. I have to ask for forgiveness from time to time.

          -D
          Last edited by Doozer; 07-23-2021, 02:50 PM.
          DZER

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          • #20
            Originally posted by old mart View Post
            It was common on smaller Japanese twin motorcycle engines with 360 degree cranks. One double ended coil and only one set of ignition points. In theory the polarity difference was supposed to give uneven plug wear, but it wasn't noticable in the real world.
            This is quite true, and many older twins used that system. Two which I have direct experience of is, Harley-Davidson, and Wisconsin engines. In both cases ignition is by magneto, with no distributor on the older models. It was much simpler, more reliable, and less expensive to engineer it that way.
            25 miles north of Buffalo NY, USA

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            • #21
              Originally posted by old mart View Post
              It was common on smaller Japanese twin motorcycle engines with 360 degree cranks. One double ended coil and only one set of ignition points. In theory the polarity difference was supposed to give uneven plug wear, but it wasn't noticable in the real world.
              on wifeys sh..citroen the plug wear was really uneven. Two cylinders that wore the center electrode and another two that wore the side electrode.
              Location: Helsinki, Finland, Europe

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              • #22
                Originally posted by I make chips View Post
                Thanks to higher voltage ignitions, (less current eroding the electrodes) and unleaded fuel, plugs last a long time.
                Not to forget accurate fuel/air mixture control. Catalysator needs close to stoichiometric air/fuel ratio and that is easy to ignite compared to really rich or lean mixture.

                Location: Helsinki, Finland, Europe

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                • #23
                  Originally posted by Willy View Post

                  Less complexity and lower unit costs are the driving factors.
                  Are you saying that a 2 plug system is less complex than a 1 plug system? A long time since I worked on a spark ignition engine, but single plug systems seemed pretty simple to me.
                  'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                  • #24
                    Originally posted by Richard P Wilson View Post

                    Are you saying that a 2 plug system is less complex than a 1 plug system? A long time since I worked on a spark ignition engine, but single plug systems seemed pretty simple to me.
                    These are not twin spark engines. Waste spark are used in some 2, 4, 6 or 8 cyliders with 1, 2, 3 or 4 coils and no distributors. Each coil serves a pair of cylinders
                    Helder Ferreira
                    Setubal, Portugal

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                    • #25
                      Originally posted by Richard P Wilson View Post

                      Are you saying that a 2 plug system is less complex than a 1 plug system? A long time since I worked on a spark ignition engine, but single plug systems seemed pretty simple to me.
                      One plug for two cylinders?
                      There are no stupid questions. But there are lots of stupid answers. This is the internet.

                      Location: SF Bay Area

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                      • #26
                        Just to add some details "for completeness".

                        There are spark plugs that have an internal "gap" in the center conductor. The added resistance is to increase the voltage at the plug gap .
                        And on that topic. All plugs fire at the very LOWEST VOLTAGE that it takes to jump the gap. High voltage ignitions are cute though.

                        And a third detail. Spark has an easier time jumping from a Hot surface to a cold one i.e. sparks at a lower voltage.
                        Or is that the other way around?....;-)

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                        • #27
                          Originally posted by MattiJ View Post

                          on wifeys sh..citroen the plug wear was really uneven. Two cylinders that wore the center electrode and another two that wore the side electrode.
                          This phenomena is due to the difference in polarity between the pair of plugs firing off of that coil.
                          This from NGK:

                          Wasted Spark Ignition Systems

                          Wasted spark ignition systems are a type of DIS, which uses one coil for every two cylinders. The coil provides the spark for one of the paired cylinders on the compression stroke and to the other on the exhaust stroke. Because the coil fires the spark plug on the exhaust stroke as well, it is appropriately named 'wasted spark ignition'. In effect, the spark plugs fire simultaneously and twice as often.

                          One of the two paired spark plugs is always negative polarity while the other spark plug is always positive polarity. Negative polarity means the spark plug's center electrode is negatively charged and its ground electrode is positively charged. Positive polarity is the opposite. Each time the plug fires, a rapid exchange of the protons and electrons occurs, called ionization.

                          The negatively charged electrons will be attracted to whichever side of the spark plug that is positively charged. The positively charged protons have much more mass than electrons, and thus cause more wear on the electrode they collide with. Hence, one plug will exhibit more wear on its ground electrode, while the other plug will experience more wear on its center electrode. If a spark plug with a precious metal on only the center electrode were to be used with this type of ignition system, there would be uneven wear on half the plugs. Although single precious metal or standard nickel plugs will still allow the engine to run, plug life will be greatly reduced.

                          Therefore, if a vehicle was originally equipped with dual precious metal spark plugs, replacement with a single precious metal or standard nickel plug may reduce plug life and engine performance.
                          Home, down in the valley behind the Red Angus
                          Bad Decisions Make Good Stories​

                          Location: British Columbia

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                          • #28
                            Originally posted by nickel-city-fab View Post

                            This is quite true, and many older twins used that system. Two which I have direct experience of is, Harley-Davidson, and Wisconsin engines. In both cases ignition is by magneto, with no distributor on the older models. It was much simpler, more reliable, and less expensive to engineer it that way.
                            Harley V-Twins up until the early 1960s used the "wasted spark" system, for points and battery ignition as well. And they don't have a distributor, just a thing that looks like one, with the points in it, but no plug wire connections.

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                            • #29
                              Originally posted by andywander View Post

                              Harley V-Twins up until the early 1960s used the "wasted spark" system, for points and battery ignition as well. And they don't have a distributor, just a thing that looks like one, with the points in it, but no plug wire connections.
                              Yep, those are the ones I'm remembering. Most anything I deal with had a Faibanks-Morse magneto. My Wisconsin engine has a Wico magneto. You can tell I have a love affair with flat-head engines... they are getting hard to find tho.
                              25 miles north of Buffalo NY, USA

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                              • #30
                                Here is something to ponder. I have a.. 2 cylinder vertical 4 cycle Polaris 700. It has a separate coil for each cylinder. Both coils fire EVERY REVOLTION. Once on the compression stroke and once on the exhaust stroke. I THINK the reason ? is that the spark is timed off of the crank shaft ,rather than the camshaft. OH YEA one more thing. Dont ever buy a polaris . It is my opinion they are a horrible company.All of the information on their fuel injected machines ,is on encrypted dealer only software called digital wrench. Only a dealer can buy it.RUN AWAY FROM POLARIS. Edwin Dirnbeck

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