Indexing Spark Plugs, Anyone?

[swatski]

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?

Here is the general idea:

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.



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[biglar155]

Based on the condition of those heads, it clearly makes for a cleaner burn!!

 

[biglar155]

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%?

 

[swatski]

Based on the condition of those heads, it clearly makes for a cleaner burn!!

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.

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[FloJet]

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

 

[Bluewater272]

NGK's thoughts on the topic:

However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.

In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500 hp engine, you'd be lucky to get 5 hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.

 

[Jgorm]

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.

 

[F.M.]

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.