We all know that plugs have heat ranges, gaps, electrode sizes etc.

Now, all the Iridium plugs are advertised to have smaller/finer tips - Denso has 0.4mm, NGK has 0.6mm etc. We also know that the advantage of Iridium as a material, is that it has a higher melting point than platinium, by a couple of 100's degC.

What puzzles me, is - Is the Iridium plug's electrode tip operated at a higher temperature than a Platimium plug's tip? One would naturally think so, as its smaller (and is advertised as having a higher melting point).

On most cars that aren't close their det-limit, this may aid in producing a hotter, more "complete" combustion. But maybe in a turbocharged car tuned to the limit with platinium plugs, this extra temp could cause it to det.

Just wondering...
Thoughts?

 

RT ,

Sti sell Iridium plugs for the STI VII .... was also wondering .

Ray

 

Yes, I also noted that. The STI Iridium is made by NGK and has a 0.6mm electrode size.

???

 

You know what RT , I think its a worth while investment . I'm gonna try them and get back to you . Wonder why no-one ever communicates with STI , maybe language is a problem . See what I can find out through Subaru HQ not far from where I work . They look like motorbike racing plugs and I know what they did for me . I also fancy the white oil free air flat panel air filter mmmm . BTW what restrictor did you eventually end up with to cure your overboost ?

Ray

 

A friend tried iridium plugs in his Viper, just before Elvington, and noticed a marked reduction in performance. He couldnt figure out what was wrong on the day, but then remembered that it was the only thing he had changed. Replacing the plugs with the correct ones, restored the cars performance.
I have had similar experiences with other plugs, in various engines. Some engines may respond well to a plug change, others may not.
I dont know how many have tried S**tfire plugs, but the name says it all....Any people I know who tried them, were not long in removing them again

 

RT ,

I get 1.1 in first 1.15 in second , up to 1.25 in higher gears with standard restictor (.75) running on 102 racing fuel I've not experienced any pinging . This with Twindump exhaust and standard STI VI silencer on my STI VII ! I removed the straight through silencer when I saw 1.4 bar regularly between 3500 and about 4500rpm . The ECU definitely pulls this back too far then back to standard boost . Not a problem when revving higher though when standard boost applied . BTW the ECU eventually starts limiting this overboost and the car smooths out but it retains a modicum of extra boost that really helps accelerating . My car got .9 bar in standard form in first etc.

Ray

 

Thats the catch - 102RON racing fuel! Am sure it is magical when it comes to high boost pressure performance.

I'm just not so sure the car can run 1.2-1.3 odd bar on regular 98RON with tropical heat. Certainly not without pulling some timing.

Cheers.

 

The plugs fitted to the viper were the same heat range , ie they were the ones specified as a replacement with irdium tips.
I also read an article recently about bosch platinum plugs ( not sure if it was specifically to bosch only, but the article was by bosch )
It said that they recognized there was a problem in wasted spark systems, whereby the plugs would actually wear out quite quickly. This was due to the reversed polarity spark on the wasted spark cycle eroding the smaller platinum tip. On the normal full spark cycle, it is not a problem, as the plug was operating the way it was designed. It is also not a problem on normal, single spark/ dizzy/coil per plug systems
I would be sceptical about changing plugs from the experiences I have had. Manufacturers do a lot of development, and choose what plug they deeem best for the engine/ignition system on the car.
I dont have a problem going one heat range or so cooler with a plug of the same type, but trying different plugs completely can cause strange things to happen.

 

RT , Subaru South Africa have developed our PPP on the STI VII on 93 RON pump gas ..... I went for a drive in it and it was very strong and smooth . Your point about timing is taken however and I think thats where your theory of double boost maps come in . The interaction of timing versus boost is a very interesting one . I noticed how strong my WRX MY01 was in first gear and was surprised no end when I found out after fitting a boost gauge that it was NOT boost I was feeling . In fact the hotter the ambient the better it seemed to pull .
Steve , thankyou for that hard earned advice , always nice to profit by someone else's expense if you what I mean M8 .
RT , yes 102 does give a substancial benefit over 98 ROn on the road performance , but the car still goes through a bedding in phase when the overboost is first felt by the ECU . Damn it maybe no answers will come without the DELTA dash logging to actually see the effects . I'm gonna try get my brother to go in with me for a buy of that .

Ray

 

I have blown an IK22 on a std STI7 engine, WOT gears 3 and 4. Poof! It went.

Had to drive to my mechanic on 3 cyl. Good job it wasn't far.

 

Stevie,

"A friend tried iridium plugs in his Viper, just before Elvington, and noticed a marked reduction in performance. He couldnt figure out what was wrong on the day, but then remembered that it was the only thing he had changed. Replacing the plugs with the correct ones, restored the cars performance."

And it was still slow !!!!!!!

What with RT's, and another friends experiences with the Denso brand, I wouldn't put them anywhere near my car.

NGK PFR7B: Cheap (relative) reliable.

Mark.

 

If the Iridium plugs were operating too hot in the Viper and causing det, the ECU could've retarded the timing and hence compromised engine power.


I eventually settled for a 1.1mm restrictor, std exhaust, std engine. JDM MTY01 STI 7. It gives me (WOT) 0.9bar in 1st, 1bar in 2nd, 1.05bar in 3rd, and 1.1bar in 4th. Approximately.

I like to be a little conservative, but I guess whatever restrictor size we eventually end up with depends greatly on the individual owner's preference for the climate and driving conditions.

Cheers!

[Edited by RT - 8/10/2002 8:47:46 AM]

 

I had IK22 set on my MY98. They where died after cca. 30 000km after I have changed boost from 0,9 to 1,0 bar held with actuator rod. I`am very confused now. This spark is very good for drag starts but I can`t decide between IK22 (may by they where at end of his live after 30kkm) and IK24.
May be that Comparative Spark Plug Table from Denso is not 100% OK and IK22 is more NGK PFR6 and IK24 like NGK PFR7. I`am afraid only from cold starts.

http://www.denso.co.jp/PLUG/iridium-e/q16.html

[Edited by Erik - 8/12/2002 9:04:33 AM]