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Hello all,

I'm about to change my plugs in my 2000 Insight. Many of you have given part numbers and letters for 4 spark plugs, A-D.

However, in all of the detailed photos, there are only 3 plugs. I know the car is a 3 cylinder. In fact, the dealer wanted to sell me 3 (three) plugs. What gives? Why are there 4 part numbers and 4 plugs, A-D? What am I missing? Please advise. I'm new to this.:confused:
 

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There are three.
The letters refer to how they are indexed. (Which way the tip is facing inside the cylinder when properly seated.) You have to check your particular letter marking on the head and purchase that plug.
HTH
 

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There are three.
The letters refer to how they are indexed. (Which way the tip is facing inside the cylinder when properly seated.) You have to check your particular letter marking on the head and purchase that plug.
HTH
Almost.

To clarify: There are four different spark plugs. You only need three of them. freezin4 is right: You have to check your particular letter markings on the head, and purchase the correct set of three plugs for your car.
 

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Be careful to perform the maintenance when the engine is cold, with these indexed plugs it is important to make sure you torque them down properly so the electrode is pointing in the right direction.

Apply a small amount of anti-seize compound to the plug threads, and screw
the plugs into the cylinder head, finger-tight. Torque them to 23 N.m (2.3
kgf.m, 17 lbf.ft).
 

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also dont over-tighten them. Sometimes even correct index letter plugs may not line up the way they are supposed to. I tried to make it go a little further to get it to line up, and I broke it inside the head, but i got lucky and was able to get the remaining threads of the plug out using an extractor.
 

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Indexing spark plugs

Instead of paying silly prices for "indexed" plugs, just
use indexing washers; $10 a set, and reusable...

Also, you can adjust angle w/the washers, instead
of over/under tightening to force line-up.

Auto stores should have in stock, or here's a link:

YourOilShop - Spark Plugs and Indexing Washers
The only sure way to make certain that the spark plug if facing in the ideal direction is to remove the head and directly observe the position. The next best way is to buy the correct "indexed" plug.

Due to the manufacturing process, the electrode/thread/seat relationships are pretty much random. Indexing is an inspection/classification process done after manufacturing.

The washers are okay if you have the head off and can trial and error your way to getting the correct washer/plug combination by direct observation.
 

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The only sure way to make certain that the spark plug if facing in the ideal direction is to remove the head and directly observe the position. The next best way is to buy the correct "indexed" plug.

Due to the manufacturing process, the electrode/thread/seat relationships are pretty much random. Indexing is an inspection/classification process done after manufacturing.

The washers are okay if you have the head off and can trial and error your way to getting the correct washer/plug combination by direct observation.
It's easy, done all the time; just mark the plug tips so you can see where
the electrode open side points, and direct it toward the intake side;
add/subtract washers as necessary. ...The pricey marked plugs from Honda
have to be lined up too, and often when tightened properly; they don't.
Drag racers have been indexing spark plugs for 40 years...
 

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You can also observe the direction of the letter on the tip of the plug before removing the old plug, when you pull it out, aim it in the same orentation and you will see how the old plugs were sitting in their seats.
 

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You can also observe the direction of the letter on the tip of the plug before removing the old plug, when you pull it out, aim it in the same orentation and you will see how the old plugs were sitting in their seats.
I have "A" plugs so I used the top of the letter as a pointer. Replaced one plug at a time (instead of taking all three out at once). Noticed the orientation of the A before removal then checked the A stamp on the replacement (was stamped in the same orientation) and when torqued, checked where the A pointer ended up...They pointed in the same direction as before (give or take a few degrees).

JoeCVT = Just your average CVT owner
 

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Since there are 4 different indeces, the thinking is that each one covers a range of about 90 degrees. So I would guess that being a couple of degrees off really wouldn't matter.

As to indexing washers, not sure how that changes the loction of the electrode tip in relation to stock. Washer(s) would raise the tip it up slightly, although I don't know if such a small change would have any real world effect on fuel efficiency.

Regards,
Jerry
 

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Since there are 4 different indeces, the thinking is that each one covers a range of about 90 degrees. So I would guess that being a couple of degrees off really wouldn't matter.

As to indexing washers, not sure how that changes the loction of the electrode tip in relation to stock. Washer(s) would raise the tip it up slightly, although I don't know if such a small change would have any real world effect on fuel efficiency.

Regards,
Jerry
Indexing washers come in a variety of thicknesses. By trial and error,
these washers are switched around till the side opposite the ground electrode
points in the direction of the intake valves.....They don't raise the plug
but a few thousands.... And, no, the exact degree is not important.

Indexing washers have been in use for many years. Not to worry...
But, consider this: the only way one can know if the plugs have
been indexed or not, is if they personally installed them,
or watched someone else do so. The difference is that subtle.....

That does not mean indexing is not valid; but that the difference
by any measure, is slight...so, reusable washers make more sense
than expensive "special" plugs.
 

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Indexing washers come in a variety of thicknesses. By trial and error,
these washers are switched around till the side opposite the ground electrode
points in the direction of the intake valves.....They don't raise the plug
but a few thousands.... And, no, the exact degree is not important.

Indexing washers have been in use for many years. Not to worry...
But, consider this: the only way one can know if the plugs have
been indexed or not, is if they personally installed them,
or watched someone else do so. The difference is that subtle.....

That does not mean indexing is not valid; but that the difference
by any measure, is slight...so, reusable washers make more sense
than expensive "special" plugs.

I think we pretty much agree. I never said indexing is not valid; to the contrary, that is what Honda requires in our application.

But since I am only changing plugs every 6 or 7 years, I find it easier to buy the indexed ($$) plug and consider I have it close to right (Honda went through the trouble of 4 different indexed plugs, so I would expect they would be roughly where Honda thought it best in the head to maximize the spark for fuel efficiency) without the trial and error of adjusting the index by using various washers.

Since there are only 4 choices, the index isn't ever going to be exact, but within a range of 90 degrees. That is a pretty big window. I can't imagine a few degrees is going to matter, unless the 4 indeces are supposed to be precise. I don't believe that to be the case, but I didn't engineer the motor, so I can't speak with any authority about that.

Regards,
Jerry
 

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I think we pretty much agree. I never said indexing is not valid; to the contrary, that is what Honda requires in our application.

But since I am only changing plugs every 6 or 7 years, I find it easier to buy the indexed ($$) plug and consider I have it close to right (Honda went through the trouble of 4 different indexed plugs, so I would expect they would be roughly where Honda thought it best in the head to maximize the spark for fuel efficiency) without the trial and error of adjusting the index by using various washers.

Since there are only 4 choices, the index isn't ever going to be exact, but within a range of 90 degrees. That is a pretty big window. I can't imagine a few degrees is going to matter, unless the 4 indeces are supposed to be precise. I don't believe that to be the case, but I didn't engineer the motor, so I can't speak with any authority about that.

Regards,
Jerry
Makes sense..: and since the ground electrode only occludes a few degrees
of the "firing range", exactness is not necessary. I like the washers because
they can be used on any vehicle, any 14mm plug, there's no need to locate special plugs,
and the Insight is not the only vehicle that can benefit from that subtle improvement...
Which is probably better than techniques such as improving pickup-truck mileage by leaving the tailgate down.
 
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