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Indexing Spark Plugs, Anyone?

Discussion in 'Member Tips and Ideas' started by swatski, Mar 31, 2017.

  1. swatski

    swatski Jetboaters Fleet Admiral

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    I don't recall this ever being discussed here. Maybe for a good reason, lol. But, @Kevin Sargent recent posts in the old ribbon delete thread made me think about it...

    Would indexing spark plugs make a difference, especially in the 1.8l engines? What could the gains be?
    What's the approach? - mark the gap position and use (copper?) washers w/various thickness?
    Which way is the intake valve, anyway?

    [​IMG]

    Here is the general idea:
    [​IMG]
    The grounding strap of this plug (above) is shielding the electrode, and will result in a less effective burn.

    Below, the gap side of the plug is directed to the intake valve. This provides the desired fuel mixture combustion that yields a greater horsepower output.
    upload_2017-3-30_23-57-37.png


    --
     
    • Informative Informative x 1
  2. biglar155

    biglar155 Jetboaters Commander

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    Based on the condition of those heads, it clearly makes for a cleaner burn!! :D:D:D
     
    • Funny Funny x 1
  3. biglar155

    biglar155 Jetboaters Commander

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    Seriously though, I'm interested in hearing other's thoughts on this. Is there really any gain to be had here? Or is that more something you worry about once you've tweaked and tuned everything else and now you're just looking for the last 1%?
     
  4. swatski

    swatski Jetboaters Fleet Admiral

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    Yeah, right, lol.
    The 1.8l N/A engines could use some refinement, no doubt, and every little bit could help. To me, those just seem to run a bit rough albeit one gets used to it, I guess.
    I wouldn't think there is much room for improvement in the MR-1 HOs, or Rotax for that matter, which seem very refined.

    --
     
  5. FloJet

    FloJet Jet Boat Junkie

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    What's the model # for the spark plugs I need to replace my stock in 2016 AR240?
     
  6. seanmclean

    seanmclean Jet Boat Addict

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    NGK's thoughts on the topic:

     
    • Useful Useful x 1
  7. Jgorm

    Jgorm Jet Boat Addict

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    Indexing plugs is for dyno racing and big money racing only. Don't you need to file off the threads, test, repeat? Ideally this would be done with the heads off.
     
    • Agree Agree x 1
  8. F.M.

    F.M. Jet Boat Addict

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    My $.02

    I heard this discussed years ago while hanging out at the local drag strip and helping wrench on some motorcycles. Indexing doesn't really help unless you've spent big bucks on an ignition system. And even then, you would still need to dyno with the plug gaps facing different directions to determine which direction actually yields a quantifiable result.
     
    • Agree Agree x 2

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