I have a few questions, but first here are the facts of my situation.

I have a 385whp/339wtq (MD) Evo 9 tuned on 91oct on 1 step colder Denso IKH24 gapped at 0.024. I track 6-8 times a year as well as daily drive my car. I will later be tuned on E85 for the 2012 season and will probably make around 430whp/390wtq. I have been reading this thread for spark plug information, but they don't take road racing/tracking into consideration. https://www.evolutionm.net/forums/ev...ead-plugs.html

The reason I am now thinking about running something different is because after 2-3 track days, I get some misfiring/ignition break up/stuttering under wot around 5-6k rpms while on track in the first session. Or if i WOT on an onramp or what have you after 5-10min of starting the vehicle. So is it just that my plugs are getting "worn out" from tracking? I now have to replace them every 4 track days or every 8k miles. I feel that it is a little bit excessive.

Here are the plugs im considering. Correct me if im wrong with the model #s for 1 step colder spark plugs.
$44/set - Denso IKH24 - http://sparkplugs.com/more_info.asp?AAIA=&pid=17357
$140/set - Denso IKH01-24 - http://sparkplugs.com/more_info.asp?AAIA=&pid=19714
$48/set - NGK ILFR7H - http://sparkplugs.com/more_info.asp?AAIA=&pid=20451
$166/set - NGK R7437-8 - http://sparkplugs.com/more_info.asp?AAIA=&pid=17377

As you can see the 2nd and 4th options are VERY expensive if they still required to be changed every 8-10k miles. 1st and 3rd options are more affordable, however I don't know for certain if these are the best solution for road racing/tracking. I don't think the 3rd plug is right...can't seem to find an 1 step colder NGK plug that is not $41 a pop.

Please answer all 10 questions if possible and not pick and chose or else I would have to re-ask other members those questions mixed in with their new answers and might be confusing to filter through. Please indicate #s when addressing the questions.

1) If you roadrace/track frequently, what brand and model plugs are you running?
2) How long do they last in terms of mileage and trackdays?
3) Does the gap widen over time (mileage) does racing increase gap faster?
4) Should I be gapping the plugs to 0.022?
5) What is the difference between the 0.022 and 0.024 gap in terms of low rpms and high rpms?
6) Would I have to retune for this new gap?
7) Would my AFR become leaner or richer if i gap them to 0.022?
8. Would I lose or gain power with 0.022 gap?
9) Is there any benefit to running the "Iridium RACING PLUGS" vs normal Iridium plugs? What exactly are we getting for the extra $30 per plug? Longer lasting, more durable, what?
10) Does running E85 influence what gap and heat range I need to run?

What is your advice for my situation? Should I just keep it simple and stick with the Denso spark plugs and just deal with paying $40 every 8k miles / 4 track days. Or is there a better solution?

Okay that should pretty much cover it. Sorry for the long winded post. Thanks guys for your time reading and answering my questions.

 

Damn, that's a lot of questions. First off; I'm not answering all 10!

I've changed my plugs 1 time EVER. We put in NGK 7's I think (1 step colder). AMS does all my tuning, and I haven't touched them, changed them, regapped them or anything in years. Figure 50-60 track days and 15,000 miles. That's with 93 and 100oct tunes.

Shouldn't your tuner be answering all of this? I think you're either overthinking it...

 

My car is only a track car, about 380whp on 93. It's an 8, not a 9.
1) NGKBR8 (coppers, 8 range on the temp). Something like a dollar a piece.
2) I've never had them fail but I replace once a year... I mean... $4. Come on.
3) Yes and no. Gap can change in either direction but it won't by much. I regap maybe twice a year. Racing does everything faster. Anything that wears or changes happens faster while racing. More heat/vibration/rotation = more expansion/loosening/wear. Period.
4) That's a crazy gap IMO, but I've never run iridiums. On the coppers I run .025 just fine all the way up to 8200RPM. (I'm not recommending you take your motor there)
5) The tighter the gap the less complete the burn will be. You want it as wide as you can without misfire.
6) No
7) If anything - Richer
8) Neither. That's not what gap does. Gap provides contact area for your flammable substance to ignite upon. If you tighten the gap up so much that your burn is very inefficient then you will decrease power. Again - you want it as wide as the car will stand.
9) I can't see spending that much on plugs at all. lol I might spend $40 on plugs throughout the whole car's life!
10) No and yes. You don't have to change for E85, but you can take advantage of it's anti-knock properties (high octane rating) and increase heat range (hotter) to get better spark for the same gap.

FYI - keep it to 5 questions next time... that sucked.

 

Thanks for your responses. Nate, wow can't believe you were on same plugs for 50+ track days. Thats amazing. Didn't know that was possible lol.

Anybody else have input that have dealt with IX plugs. Yeah, those were alot of questions, but im glad you answered them. Thanks for taking the time in going through them.

 

If your misfiring after a couple track days, you need your car retuned. That doesn't sound like a normal problem related to spark plug wear.

 

AMS Tuned... That's all I know. I don't touch the engine.

 

As far as I know, if you have an Evo 9, stock plugs is the way to go. I've never seen a car running Densos that actually run well, even at idle. They are horrible plugs for these cars, even my local shop advises customers not to buy them. I also dont' know of any cars that run a colder spark using the NGKS other than very high horsepowerdrag cars. All of my friends with make 500 or below in their Evo 9s run the stock plugs.

 

^ I have 380WHP and I am still running stock plugs. I lap the snot out of it without issue. An EVO is not a DSM.

 

Im still on stock spark plugs and have never had a problem and im at just over 50K miles so far.

 

The stock plugs are better then most people think.

 

i got my evo 9 at the beginning of the year and it had Denso in it. the engine was breaking up at 22 psi of boost. i replaced the denso with stock plugs in and the car ran perfect ever since. i've put about 10k miles and about 25 track days on the car and no issues with the plugs. i'll replace them with stock plug at the beginning of next season

 

That's interesting to hear about the Densos. I've been using them since I bought my car and haven't really had any issues. I really want to switch over to stock heat range NGKs and see what the difference is (I'm on 1 step colder Densos now), but I literally just bought a new set of Densos yesterday...

Correction: Once I started running e85 and boosting ~29psi, I did notice some breakup, but it went away when i regapped my plugs. I do have to check and regap them every few months, but I thought that was normal... I guess not.

 

Was that directed at me? I don't think I suggested anything different?

 

42k ish and still have oem plugs

 

I've been running the denso's as well similar to the OP. On 91oct the plugs will last forever, but once I switch over to E85 they need to be changed every 8-10k miles and 4-5 track events. Maybe i'll go back to the stock spark plugs and see how they fair. Even then i'll probably change them at 20k tops if they do last