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The mkiv Supra Owners Club

Spark Plugs - BPU


Gerry

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Yep... I've done a search and got loads of good information.

On my last BPU Supe I fitted iridium as recommended, but recently I was talking to a much respected member on here, somebody that used to do lots of work on supes and has a very good reputation, and he advised against.

 

From what I remember of the conversation (I was in his frozen garage for half a day and my brain was numb) he said that if there was a problem with the engine and standard plugs were used it would destroy the plugs before big damage was done and stop more serious damage happening.

 

If Iridium plugs were used these could merrily carry on working even though the engine was slowly destroying itself.

 

If it han't been said by this gent I would have ignored it, but I just wondered if anybody else had the same view.

 

Sorry if the details are scant, I blame it on 1) brain freeze and 2) my vast age :)

 

G :)

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The theory is that iridium plugs (Denso in particular) are very prone to damage by small amounts of detonation, mostly due to the ceramic insulator breaking up, so its advised that if you want to use iridium, then get all mapping done on copper plugs (tougher) before fitting iridiums, personally i just stick to NGK copper and replace them more regularly;)

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There's two schools of thought on this one:

 

1. Detonation can cause destruction of iridium plugs which go on to cause more engine damage therefore use copper.

2. Enough detonation to knacker the plug will cause engine damage anyway, so you should avoid det in any case.

 

There's lots of hearsay but I've not seen very much (ok any) evidence to support either conclusion. If your engine is mapped correctly and you don't run stupid boost you shouldn't encounter det and it shouldn't matter anyway.

 

If you don't work on your car yourself then you're probably not going to want to get your plugs changed every few thousand miles. You'd be better off with iridiums than not changing your copper ones. If you change them yourself then it's not so much of an issue.

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As the only thing I know about "mapping" is the AA one I carry with me in case I get lost, I don't intend to go more than 1.2 BAR (occassionally) to keep things sensible.

 

I think your last paragraph makes lots of sense Simon.

 

I forgot that the guy who recommended copper can probably change a set whilst he has his morning coffee, but for me it would be a weekends work with lots of cursing and finishing up in a foul mood (with a broke car) !

 

Cheers

G

 

Are you down for the Ace cafe at the end of the month ?

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