Do these plugs really make a difference? If so then how? Are NGK Iridium IX good plugs? Is $38 a good price for four plugs? Thanks in advance for the advice and insight.

 

$38 for a set is great.

I am not certain about Iridium, but Platinum is better than Copper only where longevity is concerned. Copper plugs are better for performance, but they don't last as long as Platinum. Iridium may be better for performance than Platinum, but I would be surprised if they are better than Copper.

I am using Denso Iridiums (IK24) primarily because I wanted to go a step colder than the OEM plugs. I think the car runs fantastic with them.

 

Iridiums are probably good for a longer service life.

Will you see any appreciable performance gains? Unlikely.

I've read a few articles about "subjective" tests with different types of plugs, such as platinums, split-fires, and the like. On 1/4 mile runs, there were no true (or reproducible) differences.

Now I've heard about drag racers indexing their spark plugs. The theory is to align the gap in the "sweet spot" of the combustion chamber for maximum effectiveness. This is achieved by removing the cylinder head and installing the spark plugs, making a note and mark of where the gap is.

Does indexing make a difference? It depends upon the geometry and efficiency of the cylinder head. I'm pretty sure that Honda put a lot of research into the design of the motor. I don't think much would be gained from all that work on the S2000 since it's very well optimized from the factory.

 

Actually there is evidence to suggest differently in both cases..

The performance oriented Denso Iridium plugs that many of us have installed have a very thin center electrode and a sharply defined v-groove to promote a hot spark with minimal current. This design has a shorter service life (est. 30K miles) than either the iridium or platinum plugs with heavier components that are designed for regular passenger car use.

The iridium material is a better conductor than platinum so a given level of current can produce a hotter spark over a larger distance. A number of us have found an improvement in response (and subjectively a small improvement in high rpm smoothness and power) by setting the iridium plugs about the maximum recommended gap.

BTW, it has been reported that the S2000 head is threaded in such a way the plugs that are evenly torqued will be properly indexed.

 

Would that be the original 13ft/lb or the new 18ft/lb recommendation?

 

I'd like to see some results of experiments to back this up. Perhaps a rear wheel dyno?

 

I was at Honda school yesterday (Pilot and Hybrid Civic) and we were told that the new Civic Hybrid comes with Iridium plugs because they allow a spark using a lower voltage, giving a higher reserve voltage.

I don't think that the S has a plug indexed head. The Insight has 4 different types of spark plugs (A-D) and each plug hole is marked with a corresponding letter so the correct plug could be installed and end up properly indexed. If it were as simple as careful manufacturing, I'm sure Honda would not have gone to all this trouble for the Insight.

 

why go to all the bother to "index" the plug that way when you can just stick it in your plug socket, make a mark on the socket extension that corresponds to the armature side of the plug, and turn until you are in the spot you want it? i've always turned mine so that the "spark" faces the intake ports. i doubt it makes a difference, but

 

Now I thought that to properly index a plug *AND* get the proper torque setting, you absolutely need to use washer/shims.

 

half a turn MAX usually isn't going to make *that* much difference. never had a problem.

but yes, you're correct, if you wanted to make sure it was exactly at the proper torque, you would need to torque it, check the location of the armature, then remove it and place the proper thickness washer to acheive the correct torque value with the armature where you want it. huge PITA.