Indian Motorcycle Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter #1
Does someone here know if the Spark Plug Indexing Washers really help combustion?

Can you foresee any down sides of Spark Plug Indexing Washers for regular street (not a track) riding?

585902


It is time for me to change air filter, and a chance to change the spark plugs at the same time. I meant to use NGK Iridiums, and I found that some recommend Spark Plug Indexing Washers, claiming some gain in HP.

Manufacturers claim that Spark Plug Indexing Washers provides for better combustion by correct positioning of the spark plug mouth facing the intake, as depicted here:
585901


If anyone has used those washers, what is correct Indexing Washer Size for the Scout 60 (.030 / .040 / .050 or .060 Inch; Available in 12 and 14 mm ID)?
 

·
Registered
Joined
·
332 Posts
Indexing washers have to be selected fot your plug and location as neither plugs nor heads have timed threads,all starting in the exact same place.With a modern hi turbulence combustion chamber you would probably need a lab spec dyno to see any increase.
 

·
Registered
Joined
·
235 Posts
I would also note that the anodized coating on those aluminum washers are not conductive.

Tim
 

·
Silver member
Joined
·
4,812 Posts
My standard disclaimer....I'm no wrench LOL. But I do not believe indexing the plugs on a street bike will net much if any discernable gain in HP or performance. But then, ya don't know unless ya try it (y)
 

·
Silver member
Joined
·
5,264 Posts
even if you wanted to index the spark plugs, do you know what the optimum position is without taking the heads off?

that illustration talks about a two stroke btw...
 

·
Registered
Joined
·
21 Posts
Discussion Starter #6
I still don’t get it fully how those Index Washer work.

I imagined that Index Washers are meant to provide some space/low friction turning for (easy) alignment of the spark plug once it is fully bolted down the head thread, in order to resolve the issue of non-timed thread/plugs. Like, one should mark the ceramic insulator w magic marker to ensure the proper orientation of the plug, when used with the Index Washer.
(??)
 

·
Bronze member
Joined
·
2,635 Posts
Indexing plugs isn't some kind of snakeoil - it is a very old, fully vetted, guaranteed enhancement.

Problem here ( and all V-Twins) , are numerous tho..

1. When indexed "correctly", a cylinder WILL produce a small performance gain. The problem is to figure out exactly what "correctly" is for a given combustion chamber .. While there are known general guidelines for the basic combustion chamber design variations, even these guidelines can disagree..

NOTE: Nothing about the indexing position is intuitive. Knee-jerk thinking - such as arbitrarily deciding to point the plug gap at an intake valve - is simply rolling dice and likely a total waste of time and effort. Performance loss is even possible if the "stock" position was better !

2. The gains are cumulative based on the number of cylinders. With only two, the small cumulative performance increase would only make sense for those wanting every last horsepower they can find and would require dyno testing to verify results.

NOW, having pointed out the caveats.. Here is a closeup of our chamber(s) for anyone to deduce their own idea of a "best" gap direction..


585943


P.S. There's no need to spout junk about swirl and tumble. Many won't understand such subjects and those of us that do know that we have no knowledge of whether one, or the other, both, or neither, are designed into the 111. A few of us may be able to "connect the dots" (nuances of, and the effects, of the stock ignition programming, etc) to deduce that perhaps no "special" airflow techniques are being used..
mmmm, MM.. The possum potluck stew smells glorious.. You Cro-Mags don't know what ur missin..
 

·
Bronze member
Joined
·
5,078 Posts
That combustion chamber pic is for a traditional 2 stroke, where the plug is generally center of the motor. In practice, that even flow of the arrows is not guaranteed as slight differences in porting stir it up. Back in the days when 2 stroke was king on dirt bikes I used to build up performance motors. Fuel delivery was more important than combustion chamber flow and grinding out transfer ports gave results that showed at the finish line.

Four stroke manufacturers have been experimenting with plug tip design for ages, it seems to be a constant battle to be the next big thing.

From traditional single tip plugs they went to two tips, then three, then four, and even six. Multi-tip plugs means it makes no difference what direction the tips face.

585960



And this one goes in a different direction again.
585961


There are also copper core, platinum tip, iridium tip, ruthenium something or other.

And out off all these choices, what do most car and bike makers use? Traditional plugs that have stood the test of time, unless they use long life iridium because changing them means too much time pulling the motor apart (like my Toyota 86 where they have to lift the motor to change plugs).

The OP asked if there was a downside to using idexing washers for street. The answer is no. But nor is there an easy advantage to be had, and even if you did the work of finding optimum orientation, you would not feel anything different in performance.
 

·
Bronze member
Joined
·
2,635 Posts
Ahh, hey @Buck Turgidson, nice studio shots.. Soooow, got anything interesting you can share ?
 

·
Registered
Joined
·
480 Posts
We always indexed when I used to race go karts, but we had old standard style plugs with the wide ground and single cylinder engines with 1 intake and 1 exhaust valve. It was easy to do and every little bit helps. On a street engine with multi valves and modern plug designs not sure you would see or feel any benefit.
 

·
Bronze member
Joined
·
2,635 Posts
Unbelievably, no one has asked what I'd do*...

How bout aiming the gap just to the left or right of that "button shaped protrusion or depression" that's between the valves, just below the plug..

I'd tell myself that (that) item is a "turbulence inducer" , creates a tiny swirl around it, and if I can ignite the swirl first, I can make big powah ! Being in the northern hemisphere, where toilets flush clockwise, I'd aim it to the left.

Completely convinced of my reasoning, my first ride is guaranteed to outperform all that came before - and as expected, it does - once again, I validate myself ....



* Sorry, I watch doc's on Quantum Physics, Newtonian Physics, Astronomy, etc, to remind myself that I am not the center of the universe - while this is proven, there's always a tiny doubt..

Don't yall's toilets flush clockwise ?
 
  • Like
Reactions: Dr.Shifty

·
Registered
Joined
·
21 Posts
Discussion Starter #16
Hey Indianster,

I've been to one world fair, a picnic, and a rodeo, and that's the weirdest thing I ever read on spark plugs. You comment here like a combustion prophet, or at least like Chinese Mandarin philosopher. It is obvious that your Kung-Fu is better than mine, so please use simple wording, like use them index washers, or don’t use them washers, if you want me to understand your advice. (And admit that I posted better pics, found on some used parts website, I forgot where.) ;)

Many thanks to all who put efforts, experience and time to comment here.

Best regards.
 

·
Bronze member
Joined
·
2,635 Posts
"Chinese Mandarin Philosopher" ?
Nope, don't see it..


Ok.. Maybe the "Mandarin" part, if you're talking species..



I advise anyone to use the washers if they are "into" indexing plugs - as you can't do it any other way (unless you create the washers yourself).
 

·
Bronze member
Joined
·
1,434 Posts
Unbelievably, no one has asked what I'd do*...

How bout aiming the gap just to the left or right of that "button shaped protrusion or depression" that's between the valves, just below the plug..

I'd tell myself that (that) item is a "turbulence inducer" , creates a tiny swirl around it, and if I can ignite the swirl first, I can make big powah ! Being in the northern hemisphere, where toilets flush clockwise, I'd aim it to the left.

Completely convinced of my reasoning, my first ride is guaranteed to outperform all that came before - and as expected, it does - once again, I validate myself ....



* Sorry, I watch doc's on Quantum Physics, Newtonian Physics, Astronomy, etc, to remind myself that I am not the center of the universe - while this is proven, there's always a tiny doubt..

Don't yall's toilets flush clockwise ?
Your right, no one asked.
 

·
Bronze member
Joined
·
1,609 Posts
In this pic the ground electrode should be straight up n down with the gap at the bottom. Since the plug sits offset in the chamber the open end of the gap should face towards the far side as the base of the ground electrode does impede flame travel away from the plug. Facing the open towards the squish area is also a good thing. The ground electrode as I have suggested also has the least negative affect on intake and exhaust flow, especially at low lift. NEVER use indexing washers IN ADDITION to the regular sealing washer as this "pulls the plug" out of the chamber, increasing chamber volume thus lowerin compression and reducing power. I experimented with using VERY thin copper washers in place of the standard crush washer on 4 valve engines (not for indexing purposes) and saw a bit more H.P. on my dyno, and as much as 1 more at the higher RPM. It is common in the SuperSport classes to eliminate the crush washer altogether!
 
  • Like
Reactions: Indianster
1 - 19 of 19 Posts
Top