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The mkiv Supra Owners Club

Changed the plugs yesterday.. look at the old ones! (pics)


Jim_1979
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I'd have thought you'd need to look more closely at the gap and contacts on the plugs to decide if they are knackered or not - the black around the thread surely has no impact on the way they work?!? - they are like that because they are used - just like any other engine component that you remove from the engine.

 

Well - just my opinion anyway.

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They look ok in the pic and as said a much more expensive plug than the ones going back in.

Why change your plugs every oil change? do you only change the oil every 30 - 60 k miles?

Only wasting your money that could be better spent on beer :D

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At high BPU levels (1.25 bar) I found iridiums only last about 8k miles. The copper ones about 5k. The copper are far cheaper in the long run and I've never heard of people having problems using them on a *correctly* working BPU or single.

 

Iridiums should not be gapped, coppers need to be gapped dependant on the grade and maximum boost level run.

 

I did 36k miles at BPU (and driven hard too) so have plenty of real world experience of these.

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The advantage, as I see it, with coppers is you are forced into looking at your plugs more frequently. With Iridums there is the temptation to ignore the plugs for tens of thousands of miles. In my new engine, I shall only run copper plugs.

 

Your plugs are probably never getting very hot if you have only covered 500 miles in eight to 12 weeks.

Edited by Terminator (see edit history)
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If it were my car I'd put the old ones back, I'd much rather have a slightly elderly iridium tip than a new copper one.

 

You always say that Chris, but have never explained it adequately for us mortals (at least to my knowledge). No offence intended at all Chris and I'm sure your shoulders are large enough :D

 

What I don't see is why the iridiums are recommended when such a huge number of us run the coppers with no issues what so ever, be it stock, BPU or single.

Edited by Homer
updated to elaborate (see edit history)
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I am not being specific about brands and their foibles, just stating that the much wider heat range and fine precious metal tips of platinum and other precious metal plugs resist fouling FAR better than the relatively narrow heat range of copper tipped plugs. So when you foul up your el cheapo copper tipped plugs with some "safe mapping" to get you running, or to drive to the dyno (or worse still, whilst you "just run it on low boost whilst deciding who can map it") they will stay fouled. They will give weird on boost misfires et cetera. Those with platinum tipped plugs will still maybe see some fouling, but the nature of these beasts means the fine electrode burns off carbon and other deposits far far far better than copper and the plugs self clean to a large extent.

 

A precious tipped plug will withstand running outside the higher end of its heat range without the tip failing far more reliably than a copper electrode, too, so you have some safety margin in there, which can be a Godsend, but obviously a far from ideal way to abuse a plug.

 

Since the introduction of precious metal tipped plugs the need to warm up race engines on "warm" plugs and quickly change to "cold" plugs is all but redundant as the precious metal tips will burn off the contaminants that build on cold starts themselves.

 

I have had umpteen experiences of turbo engines exhibiting weird, random or even supposedly impossible to cure misfires directly attributable to copper plugs being subject to less than optimum combustion conditions at some time in their lives, and never recovering. It's VERY rare for this to happen to the more expensive and much wider range precious metal tipped plugs.

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I'd have thought you'd need to look more closely at the gap and contacts on the plugs to decide if they are knackered or not - the black around the thread surely has no impact on the way they work?!? - they are like that because they are used - just like any other engine component that you remove from the engine.

 

Well - just my opinion anyway.

 

I didn't know when they were last changed so I thought it should be done. Also it was to possibly cure a high boost hesitation issue.

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