Anybody ever tried indexing your spark plugs?

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LouDawg

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I've read about this in a couple of places and just wondered if anyone had ever tried it? It's basically where you mark, or index, the plug so that the electrode gap/spark are facing the intake valve so that there is theoretically no obstruction between the spark and air/fuel mixture. By marking the insulator and using a keying kit (i.e. crush washer for the plug), you can make sure the plug is turned the right way in hopes of improving performance or efficiency.

Anyone ever tried it?
 
tried it with minimal gains. ive heard of some racers filing the electrode down so it is very thin, but the plugs only last a short time.
 
Yes, I have done it on my Harley's. I think I bought the kit from Jeg's. Not worth the time IMHO. Getting the jetting and timing curve right is the big gainer. I doubt you could actually see a HP gain on a dyno because the gain would be so small.

When I did it, I pointed the open end of the electrode towards the intake valve. I would think that if you use multi-electrode spark plugs, you would achieve the same effect as indexing.
 
Used to do this on our racing snowmobiles. The bottom line was even on a dino the results were very minimal but we did it anyway for what little edge it gave us.
 
Yep, used to do that (not with a kit, but by select fitting plugs to get the gap where I wanted it), as well as filing the ground to half way across the centre electrode.

Never achieved much.

But working with turbines, I've realised that there are improvements that are real, but can't be measured, as the measuring tools are too coarse.

If it floats your boat, and doesn't cost you money (select fit), then play to your heart's content.
 
Indexing was done on blown dragsters running nitro. The plugs have to last 300-400 feet and indexing helped. You could see the results. After 400 feet you can turn off the ignition without slowing down.
 
Quote:

When I did it, I pointed the open end of the electrode towards the intake valve. I would think that if you use multi-electrode spark plugs, you would achieve the same effect as indexing.

Click to expand...

I tried it with no ill effects on my 85 SAAB 900 8V.

Myhtbuster say: It makes no sense when you think about it. By the time ignition is reached, the intake valve has long ago closed, and the piston has squished the mixture into a volume one tenth its original size. It doesn't matter which way the electrode points. (For racing purposes or extreme internal combustion chamber geometries I could imagine it useful.)

Also, can we put to rest the benefit of multi-electrode plugs, and write them off as a gimmick (or does the guvment have to get involved)? A spark on average jumps the closest gap (causing the surface to wear out). Sometimes the spark takes a slightly different path. So what? It's better to have a specific concentrated gap with long wearing electrodes. And I don't think there are many instances where the manufacturer wasn't the best judge of which plug to use.
 
You can tell the prevailing winds, by which side the ash builds up on the spark plug, but that's not necessarily which way they blow before ignition.
 
He must have been hypnotized by the dazzling sparks during the NGK demo. I thought BMW worked closely with Bosch. I'm sure there's an interesting story behind its choice.
 
There is no way to determine which it the best way to point the electrodes. Different engine conditions would likely require different positions.
A modern wider gap with high energy ignitions reduces the need for any indexing.
Racers often indexed spark plugs for piston clearance.
Multi tipped plugs only fire one at a time. Maybe the BMW gets longer predicted plug life by this left handed way. Is it then the best, or the longest service life?
Why would anyone shroud the intake/expulsion of gas and the flame front from this critical area?
 
Tosh,
the theory is that the side electrode "blinds" a pie shaped section of the combustion chamber, which requires the mixture to burn back into it. That tiny bit of gas stays around longer than the rest.

In theory, you don't want that "end gas" to be around the hot exhaust valve, as it can spontaneously ignite, creating knock.

So (in theory), you should arrange the gap (i.e. most open flame front) to point at the hottest spot (the exhaust valve), which should allow you to run the most compression and advance for a given fuel and fuel air ratio.

In a normal engine made to run with street fuels, and allow for 200,000 miles of octane creep, you'll never see the difference in practice, only theory.
 
Hoo, boy! "Can we put to rest the benefit of multi-electrode plugs...?"

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i believe this was an old timers trick for cylinder heads with poor combustion chamber shape. think 60's era american v8's and espically earlier flathead motors.

with a modern pentroof wedge shaped chamber, you get such a violent swirl and squish in the combustion chamber that indexing a plug has no value at all. the air and fuel as it gets compressed is basically thrown around the chamber pretty violently before the plug fires. it gets mixed through out the entire chamber pertty thuroughly and that includes around the sparkplug.

oems go to great lengths to maximise fuel economy and engine power. if there were any real benefit to indexing a plug in a modern engine you can bet that every OEM in the buisness would have a tsb out on how to index plugs for their engines. even if it was a tiny benefit, it would not make sence for them to leave free economy and power on the table when they struggle to meet CAFE requirements.
 
The Honda Insight (their first hybrid) has factory indexed plugs. Plugs have letter suffixes on the type number that are specific to each cylinder that will ensure indexing when plugs are correctly torqued.
 
ITSMR2U - Isn't that for a waste spark ignition, with electrodes only on half of some plugs, and both sides of the corresponding ones?
 
Mech tech2 - as seen in "Auto Inc." on line

As mentioned earlier, the Vetronix Mastertech with Honda aftermarket software will give you IMA codes and functions. The DLC is located right of the center console near the heater core. No cover; just look hard. Honda uses its lean air/fuel (LAF) sensor. It has been around a while and has five wires. Use NGK spark plugs only, ILZFR5A-11, iridium tipped. There are four standard plugs; check cylinder head for mark stamped onto head, either A-B-C-D, near spark plug hole. Make sure you install the proper plug per hole as the tip of the plug is indexed. Spark plugs have an A-B-C-D stamped on the top of each plug. Honda says “100K life” for plugs. We will see! Gap them at 0.40", but be careful because iridium is extremely soft.
 
A ILZFR5A-11 plug should come pregapped at 1.1mm / 0.043". Oddly, NGK would probably say not to regap it. http://www.sparkplugs.com/glossary.asp?kw=Should+I+gap+my+Iridium+Plugs?&manID=0&pt=

BMW's been using a multi-ground NGK plug since about '91. The earlier cars used NGK BKR6EK, it's copper w/ 2 ground electrodes. In '98 they started switching to the NGK BKR6EQUP, a platinium plug w/ 4 ground electrodes. Longer plug life seems to be the reasoning.

I think indexing plugs matters more on sohc or ohv valve designs where the spark kernal can be pointed away from both valves and the center of the chamber.
http://www.fordmuscle.com/archives/2000/07/indexplugs/

Multi-ground plugs from a rotary engine used to be the trick plug for hi-comp Datsun/Nissan engines. There's also rotary plugs that just use one round ground electrode.
http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1192340
 
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