Denso: IT16, IT20, IT22

I just pulled my Denso IT22 plugs and replaced them. They were 2 heat ranges colder which should make the IT16 stock and the IT20 1 range colder. All of mine were dry carbon fouled after one season of racing and would hardly run. None of these plugs have the extra extension that the stock plug has and are a tad short. I replaced them with NGK TR6IX iridiums that are 1 range colder and cross over the IT20. The TR6IX doesn't have the extra extension either but is noticably longer than the Denso plus is half the price. The Denso's are expensive. The NGK TR55-1IX is a direct replacement which Denso doesn't have.
 
If they are carbon fouled then you have tuning issues I think. Hopefully you get them sorted out this year.

I do know that the cold heat range plugs do not like to be allowed to idle much. My IT-24's fouled on me but a little "magic" got them going again.

Typically after just one year the plugs should still look almost like new. If you change plugs that often I'd just run copper plugs. That's what I've been doing with my car, especially when you have tuning issues. Nothing worse than fouling expensive plugs. When I have the car dialed in I will put the Denso's back in.
 
Well actually what happened on mine is that I noticed a slight coolant loss back in Sept and a slight degrade in performance. When we pulled the heads and lower intake off you could see where the lower intake water ports leaked into cyls 1 & 4. I replaced the O2 sensors, broke one open and found the sensor element heavily coated with white. My A/F gauge had started indicating extremely lean just before the teardown. I suspect the EEC saw a lean condition from the bad O2 sensors and tried to compensate by going over rich.
 
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