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Indexing Plugs -- Good Results

joefnh

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Indexing Plugs -- Good Results -- MPG gains

This past weekend I was going to try out some racing plugs from Autolite (model AR93) I have been trying a few different plug types out recently and this time around decided to try indexing the plugs as Al described in a previous thread.

I was able to find the indexing washers at a local speed shop for ~ $14.00 but could not find the nifty tool to help with positioning. I think that I came up with a fairly inexpensive yet effective replacement.

I first tried these plugs out without indexing them, then after about 30 minutes of testing I allowed the engine to cool down so I could try to index the plugs towards the center of the cylinder.

The 2 things that I noted with indexing the plugs was both a smoother idle and acceleration

The following is the method that I used:

First I gapped all the plugs to .065", inspected the plugs and prepared my 3/8" extension with a tightly applied tie wrap to be used as a marker as to where the electrode face of the spark plug is. See the 1st & 2nd pictures

Next I decided to try the new plugs without indexing them this was done to basically establish the performance of the new plugs un-indexed.

Aligning the tie wrap to match up with the electrode 'face' I installed all six plugs and noted that all but cylinder 3 had the electrode face in the worst possible position facing away from both valves.
I was surprised to see the repeatability of the position across all 6 cylinders and plugs when installed... Unfortunately in the wrong position. See the 3rd picture

After a 30 minute test run and cool down period, I reinstalled the plugs using the prescribed washer to bring the the electrode face centered between the intake and exhaust valves. As stated above good results were noted See the 4th picture

Overall this process only takes about 30 minutes longer than a straight plug change. I am currently monitoring MPG for any gains, but even if no gains are realized this was worth it to improve just the idle.
 

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35Remmy

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Joe, thanks a lot for the write-up and pics...EXCELLENT!!! I really like your idea with the tie..I'm DEFINITELY going to do this.
 








joefnh

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Update... I just finished my first tank of gas using the indexed spark plugs, the results are:


Before Indexing (Ford factory plugs Part # AGSF22FM) 476 miles used 20.15 gallons = 23.62 MPG

After Indexing (Autolite AR93) 427 miles used 17.34 gallons = 24.63 MPG


MPG gain using new plugs with indexing 1.01 MPG

Note: This is a 4.0L 4x4

Overall better than I expected, but I did use new plugs at the same time as introducing the indexing. The plugs that were in there before indexing were the Ford factory plugs with ~ 18K on them.

Overall the idle quality has improved as well. For the $15.00 in washers and a half hour extra time , this was well worth the investment

--Joe
 




Joe Dirt

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Wow- that's a marked improvement! Well done! :thumbsup:
 








MadExplorer93

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LMAO ok guys 1.01 MPG = what .. one more mile on gas tank.... ok just drive slower next time... lol

I was hoping to see a 10 mile gain.
 








abomb4601

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LMAO ok guys 1.01 MPG = what .. one more mile on gas tank.... ok just drive slower next time... lol

I was hoping to see a 10 mile gain.

no that would be almost 20 more miles on a tank of gas... thats roughly a savings of $3 per tank. sounds worth it to me

^dang al beat me to it^
 




MadExplorer93

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Sorry, your math is out to lunch.

1 MPG net = 21 more miles per tamk, not 1 more.

Oh yes my brain was on slow mo today ... lol

Thanks for putting me back in the fast lane. :thumbsup:

Wow 20 miles more, now thats good, 20 min more = more time to get to the next McDonalds on my North American Trip, hamburgers here i come. :p:
 




Hitchhikingmike

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great write up! I shall try this on my '02 SOHC very soon.
 




RickOTR

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Joe, what brand spark plug wires and coil are you using? .065" seems to be alot for a stock set-up. I am using a a Screamin demon coil and wires and have the plugs set at .065". I think indexing the plugs was one the top five best things I have done to my Explorer.
 




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