Spark plug indexing, is it worth while

[timberwolf]

Has anyone bothered indexing chainsaw sparkplugs, so that the plug is in the proper orientation in the combustion chamber?

I know that this is done for some high preformance applications, but was not sure if it was a worth while exercise for a chainsaw.

I just can't stop trying to make a good thing better.

Timberwolf

 

[bwalker]

I think most tuners would agree iindexing is of little use in two stroke. When I fooled around with it a bit while dyoning my sled engine I noticed no gains or losses for that matter. I tried to index it towards the exhaust, the back of the cylinder and at the transfer ports. Try it out and report back what you find. Depending on what way the transfers are pointed I would index it with the gap faceing the rear of the cylinder.

 

[rupedoggy]

Thank you for a subject that I think is what this forum should be about. I get so tired of "what chainsaw should I buy", "what mix ratio is best" and who's ass can hang out for all to see. PEOPLE, if you are going to respond to a thread please keep to the subject or start your own thread! BTW I don't care if you use your scrench to tighten your gas cap or your nuts!
Now that I have that off my chest I want to say I have tried indexing my plugs. I can not discern any difference. I don't think it would be measurable except with sensitive equipment. The proper heat range is something that does make a measurable difference. If the wrong plug is used it will breakdown or miss and sometimes it is hard to know the cause. Mike

 

[timberwolf]

Yes well put about topic, it is nice to knock about about technical ideas.

I think I will experiment a bit with this as it is easy to do, I didn't think it was goint to be a big preformance gain, but I wondered if it might help some with heat issues.

Are there options to improve preformance with plug ratings? or is the spec plug usualy the best?


Timberwolf

 

[HUSKYMAN]

I know guys who swear this helps in 600 hp dragsters and guys who say it doesnt, so I am sure the benefit would be nil in a chainsaw motor. Ken Dunn must have done a few tests at least with different plugs, I wonder if he has anything to add?

 

[Dennis]

From the people I have talked to regarding "indexing", there is little to no benefit in these smaller 2 stroke engines...I personally have never tried it, but if Rupe has, and checked for gains...I would stand behind that all the way.

As far as the other type threads go.."what chainsaw....what mix...etc..." We are always going to have these type threads come up, as we are always gaining new members. We as a group, need to remind ourselves that these people feel they are asking honest questions, and are just looking for some answers...we can suggest they use the Search function, or answer the questions as we feel... Possibly what we need is a technical side to the chinsaw forum, as it is growing rapidly.

 

[HUSKYMAN]

A "hotsaw only" forum would be a good idea. I think this particular one should remain exactly as it is. There are too many new people in here to turn it into a tech only and high performance forum

 

[tundraotto]

Plug indexing is not worth the effort in an engine that develops under several hundred HP. On a 500HP drag car indexing will at best lead to 5HP gain (1%). Is this worth it on an 372xp for example at 5.4hp (factory figure) to get 5.454HP - I dont think you will notice a difference, even on Dougs' video replay.

 

[bwalker]

A four stoke head witha intake valve aimed directly at the plug is a bit of a different animal than a two cycle head. Since the intake cycle is complete bfore the piston even comes close to the plug I believe its useless. The mixture simply is not flowing in any one direction once the transfers close. I could be completeloy full of **** on this, but its just a thought.

 

[tundraotto]

intake air is still coming from the same direction in relation to the plug and the plug is at a different angle.

 

[Fish]

response

My response is so good, I had to start a new thread, to handle
all the traffic!

 

[bwalker]

intake air is still coming from the same direction in relation to the plug and the plug is at a different angle.

Intuitivly what you say sounds right Otto, but unsteady gas flow never behaves like we think. I can see where there would be some directional charge motion in a 4 stroke but with a 2 stroke I cant. It seems to me that four transfers dumping into the same cyclinder causes a more or less chaotic flow event that changes with rpm. Add to that fact that the squish band is pushing the fresh swirling charge to the center of the chamber anyhow and it becomes pretty apparent indexing is of little use. From a combustion chamber standpoint the two stroke head is also way more efficant in that it does not have a bunch of hot valves to mess with charge motion. That fact alone may be why two stroke do not respond to indexing.

 

[tundraotto]

you maybe right ben, but we can both agree that indexing doesnt work well enough/not at all in saws to practice it.