I've not tried the latest iridium plugs, but the small diameter center electrode is very similar to the platinum design. I had trouble with platinum plugs in my GN and so did every other person I talked to that had any kind of upgrades and knew what pinging was. The heat range may be the same as a normal plug in a normal engine, but they sure don't work the same when under boost. The engine had terrible detonation. I would save my money and just replace the plugs more often. I am quite sure you would have trouble with them and a turbo under boost.

Your cooling system will work much better with a good overflow tank. Getting all the air out of the system really helps. Not only with cooling but limits the corrosion as well. I prefer the radiator cap that has a spring in the check valve, it may or may not be the "correct" stock cap for these years.

After buying the NGK ZFR6F-11's today, I stopped off and talked to the folks at a local speed shop, and they said the knew lots of turbo guys using 7's 8's and 9's as far as heat range goes. They liked the NGK's very much, and use them . They recommended colder then 6's for my application. So the 6's will go in, and I will likely play with this awhile before swapping in a set of colder plugs still.
Sam

_________________

I'm not quite so sure as you are, having owned and driven several turbo cars myself. Now, if people were buying Bosch platinum plugs, I can definitely believe there were all kinds of problems, but I never saw any such problems with NGK platinum or iridium plugs.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan, that could be a big part of the problem. it actually was Bosch plugs. After thinking about it, I remember running some of the NGK platinum plugs in one of my two strokes that was on the ragged edge. It had no problems and the plugs let it idle a bit better and have better off idle response. They cost so much more I could pretty much get the same results with normal plugs by changing them every 12 hours or so. They were cheaper by the box.

If you have a mild or stock type of turbo setup they are probably ok. I am used to one that is being pushed to the limit for whatever fuel is being used. They pretty much need the coldest plug you can get by with for normal driving, and it could stand to be a bit colder for strip use. I think the newer plugs are really aimed at the 100,000 mile tuneup interval that new cars have. I don't see them lasting so long in a older, non efi engine anyway. If they work , great. I just think that with the thrashing plugs get in a street turbo that is turned up, it is easier to put in new plugs more often.

The 12 hours for the two stroke was correct. You don't even want to know how many hours a crank lasted.

I installed the new colder NGK ZFR6F-11 tonight, and started it up. It absolutely does not idle as nicely as it did with the extended tip ZFR5N's. I really liked those plugs. I hope this colder plug performs better regarding the preignition. I got the engine running cooler now, so I will see how she goes. I really wish someone made an extended tip plug in colder heat ranges. As always, I am thankful for the advice, and shared wisdom here.
Sam

_________________