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I replaced my plus today with Autolite XP5325. I indexed them, not with copper washers (an indexing kit), but by selecting them from a group of 6 plugs purchased at Rock Auto for about $8. each including taxes and shipping. Thanks to Jim Isbell for the idea. So far they are not worse, possibly better, but it’s hard to tell with my irregular routes and this cold weather.

Here is how I indexed them. I assumed that the open gap should be aimed at the centre of the combustion chamber. I marked that opening with a Sharpie pen on the top of the plug and wound them in finger tight. I estimated that torqing them to 23nm would be half a turn. I moved around the 6 plugs until I had the best result and torqued those three down. Voila!

Jim Isbell thought that with the worst scenario of two tolerances, standard Honda plugs could be out by as much as 180 degrees. If I could make a correction here, Jim, I think they could be out by 180-45=135 degrees because Honda would have put the centre in the middle of the 90 degree “piece of pie”. That said, two of my original plugs were about 120 degrees off. Now, with my own indexing, all are within 30 degrees of correct which I believe is straight forward (or 12 o’clock).

But I think that getting as close as possible to 12 o’clock isn’t that important. What is important (for lean burn), is NOT BEING NEAR 6 O’CLOCK. Six o’clock makes for a “flame front shadow” behind the negative post. If I am correct then a plug 135 degrees to either side of 12 o’clock makes little difference as the flame front is unimpeded towards the main volume of gas.

Rick Hall
Caledon Ontario
2000 and 2005 Insights
 

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red1dr asked:

>It would be interesting to know where the plug gaps are aimed as the car is >supplied from the factory, and also how much variation in aim there is in the >factory-installed plugs. Has anybody done this? It would mean simply marking >the factory-installed plugs with a Magic Marker BEFORE removing them and >then checking where the marks are in relation to the gaps.

There might be a way to estimate Honda’s ideal aim during replacement. We could do this empirically by logging results of a number of members who are changing to stock, indexed NGKs. If people were to mark them before installing them, then install them and guess the position by looking at the plug and reporting. We could then plot the results.

To standardize we would need everyone to use anti-seize lube on the threads, the correct torque and state your index: A B C or D. I suggest that vertical (towards the front) be called 12 o’clock.

If Honda’s tolerances are as much as 90+45 degrees giving a 270 degree arc that is considered “in spec”, I suggest we would get a bell curve through that range with the apex at the Honda ideal. But if that broad arc truly is Honda’s spec, I doubt fine tuning will help much.

Sounds like a lot of work but if it could be done we might want to call it “cloud reverse engineering”.


Rick Hall
Caledon Ontario
2000 and 2005 Insights
 

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OK. That’s great Blue-Civic-Hybrid. Before you remove the plugs you will have to mark the tops by putting a marker down the hole. You won’t be able to see but your mark might have some kind of inkblot orientation that you can draw on paper. You'll need a flashlight.

When installing the new NGKs you should mark the 12 o’clock edge, that is, make it the same as the gap.

Remember: use anti-seize lube on the threads, the correct torque and state your index: A B C or D. Lets make vertical (towards the front) be 12 o’clock.

That should give us 6 readings and a good start!

By the way, what is that expression to be someone’s “Huckleberry”. As in Tom Sawyer’s Huckleberry Finn?

Rick Hall
Caledon Ontario
2000 and 2005 Insights
 

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Yes, the Autolites worked out perfectly. My best run was 87 USmpg (2.7 l/100km). No issues at all. I tried to install a set for another Insight and I ran into indexing problems. Like most Insights, this one was a "B" orientation and only one of the six plugs I had was acceptable. So I have quite a handful of plugs that might work for another orientation. (I think "C" mostly).
 

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I used the Autolites once. It was quite a few years ago but I think I bought six or eight of them. They worked fine. I suggest you buy them from two or more sources so you have plugs from different manufacturing runs. I think you would have a better chance of having different thread orientations that way. It's just a suggestion though. I don't know how they do the production run.

I don't think you have to be all that accurate with the orientation. My guess is that you can have maybe 270 degrees where they be good and will ignite well; If they are at the bad 90 degrees the negative post will make a flame shadow.
 
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