My car is an 01 with just under 14,000 miles. The last 1,000 have been with a Comptech aftercooled SC, installed by Comptech.

Yesterday I swapped my OEM plugs for Denso IK24s (gapped to .035 per other members' recommendations - thanks!).

Below are pics of my old plugs as well as my A/F on Comptech's dyno before and after the SC.

So, thoughts? Too lean... too hot? Of course, I can't tell how much of the deposits are from the last 1,000 miles and the same goes for the scorching. What to do next?

 

Your AFR getting into the 14's around 4400rpm should concern you. Have you had a chance to get AFR plots after the plug swap?

The white on the electrode indicates it is a tad lean. Not to be worried as this is normal from my experience with OEM plugs as the are probably too hot to start with. Could be residue from before too. The scorching is normal (brown residue on the white part). You might want to post close ups of all 4 electrodes as this is where you probably want to get input from others. ['Too lean' and 'too hot' are the same thing]

Hopefully XViper will give you his opinion....

Check the new plugs after a few hundred miles. Get your AFR checked and add fuel so you don't have a lean spot.

 

Thanks!

The electrodes on all 4 plugs have the same whitish (rather than brownish) residue as the close-up I posted. The camera did a pretty good job of getting the color right.

As I just installed the plugs, I haven't been to dyno it again. However, would plugs affect the A/F anyway?

I was planning to check the torque on them in after the next tank of gas, so I can pull them and see what they look like.

 

The plugs don't affect the A/F, but they indicate the after-effects of the A/F. I think they are showing a healthy "Lean Cuisine" tune, but remember that this is an overall result, not an RPM-specific result. You could be dangerously lean over a 1 1K RPM range and put a hole in a piston or fry a valve.

A bit of experience from the SVT Cobra scene - the OE A/F looked "pig-rich" to a lot of members, and the aftermarket tuners kept leaning out the mixtures, even with cars with undersized pulleys. There seemed to be a bragging rights HP war going on - well, 5K down the road, and there have been a lot of reports of grenaded pistons. They leaned a bit too hard - remember that the pig rich settings may have lost some ponies, but helped cool the innards, and with a SC'd engine, those innards can get awfully hot.

The only prudent approach is to get a series of dyno runs from an experienced and reliable tuner, and then notch down the settings a few points below "tuner says it's safe". Also remember that octane demands go up over time, so safe today could be risky tomorrow. Intake fuel cleanliness is efven more critical in a blown car than th stocker - a momentary loean condition from intake valve deposits could be catastrophic.

I am not trying to rain on anyone's parade, but the Ol' Pressor wants to see smiley posts, not "I torched my engine and am out $8K" posts. Those SVT engines are quite expensive as are the S2000's.

Hope this is useful to you.

 

So RR,
Changing the gapping and switching to colder plugs won't effect the AFR at all?

 

Yes, those plugs do show a slight generalized lean condition, which is backed up by your A/F chart. The lean condition at the beginning of the rpm band is not a real concern. That little spike at around 4400 might be broader than desireable. The rest of the upper rpm band doesn't appear to be too threatening.

 

Thanks for all the replies. The next question is, what hardware do I need to own before a tuner can adjust the A/F in that spike ~4000?

 

Well that depends. You could use the Greddy emanage which has it's own set of limitations or opt for the AEM EMS (more costly and there are also a few points against it). It really depends on where you will be going in the future with further modifications. If you are not planning on exceeding the 6psi boost level then it may not be worth going for the EMS (I would personally disagree). Whatever you go with, make sure you go to a trusted tuner.

Since you are in CA, make a trip to see Ultimate Lurker in SoCal.

 

I don't think you can say that the heat range of the plug won't effect AFRs. It is true that they don't effect AFRs directly, but if the ECU detects any knock due to the hot plugs, it will richen the mixture (and retard timing). I wouldn't be surprised if going to the IK24s may cause your AFRs to lean out a bit more, since the ECU will not detect as much knock, and will be slightly more aggresive with fuel and timing. That said, I think you should get that biatch tuned for safer AFRs then switch to IK24s.

I have no FI experience, but those plugs look just like my OEM plugs did when it was stock.