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The mkiv Supra Owners Club

Spark Plugs - how often to change??


Steve Cargill

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Originally posted by eyefi

5-6k miles ive read somewhere, cant remember where. like gaz says theyr cheap enough to do that.

 

Thats pretty much what I thought, every service and as they are about £10 a set why not :)

 

Andrew - the stock Toyota are 60K miles, but they are too hot, misfire prevented me going above 16PSI, making me think the FCD had a soft cut and was set too low :eek:

 

The HKS or Denso ones may be an option - there is the labour rate every service to add to the cost of the plugs.

 

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the iridium plugs r supposed to offer better performance, but that only lasts about 5-6k miles after that they perform just like normal. i think that the copper plugs r a better bet, u have a newer plug, they r cheap, its a 15 min easy job to change them (this also offers u the chance to read yr plugs often - a good habit once u start modifying), they r easy to get hold of and the performance benefit of iridium plugs is negligable (i think).

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i dont think they do a cool enough plug for 18psi (heat range 7).

 

ive never seen a platinum plug in a 7.

 

dont forget the quoted 60k miles for plat plugs is for standard engine in standard conditions, not for an extra 7psi boost, track days and drag runs.

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Originally posted by eyefi

the iridium plugs r supposed to offer better performance, but that only lasts about 5-6k miles after that they perform just like normal. i think that the copper plugs r a better bet, u have a newer plug, they r cheap, its a 15 min easy job to change them (this also offers u the chance to read yr plugs often - a good habit once u start modifying), they r easy to get hold of and the performance benefit of iridium plugs is negligable (i think).

 

Can i ask why you say the iridium plugs lose there perfomance after 5-6k miles.

Surely as long as you keep them gapped correctly they should be fine.

 

Regards

Andrew(dunk)Shaw

Black uk mkiv tt

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Originally posted by Andrew Dunk Shaw

 

Can i ask why you say the iridium plugs lose there perfomance after 5-6k miles.

Surely as long as you keep them gapped correctly they should be fine.

 

Regards

Andrew(dunk)Shaw

Black uk mkiv tt

 

Don't gap Iridium plugs, they come pre gapped if you do gap them the tips will either break or if you're really unlucky they will wait until they are in the engine until they do.

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Originally posted by eyefi

i dont think they do a cool enough plug for 18psi (heat range 7).

 

ive never seen a platinum plug in a 7.

 

Standard Integra Type R Platinums (NGK PFR7G-11) are 7s.

 

Currently looking to get 8s Porbably DENSO Iridium (24 on their range scale) or HKS (40 on theirs I think)

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andy, sorry i got my mile to km conversion wrong. the info i got in an email from denso, quote "...the optimum performance for power is 20,000km....", so thats about 12000 miles.

 

wilfman, thanks for the link. earlier this year the ngk book and website didnt list a plat plug of temp range 7. i stand corrected :)

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Originally posted by HardHead42

 

Don't gap Iridium plugs, they come pre gapped if you do gap them the tips will either break or if you're really unlucky they will wait until they are in the engine until they do.

 

Thanks for that info, they have only done about 7000 miles so i'll leave them alone, plus my cars not been modded much yet, its only got HKS S Drager second cat out induction kit and FMIC.

 

Regards

Andrew(dunk)Shaw

Black uk mkiv tt

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Originally posted by eyefi

andy, sorry i got my mile to km conversion wrong. the info i got in an email from denso, quote "...the optimum performance for power is 20,000km....", so thats about 12000 miles.

 

wilfman, thanks for the link. earlier this year the ngk book and website didnt list a plat plug of temp range 7. i stand corrected :)

 

No prob eyefi, i suppose the performance drops off as the iridium tip burns away and if you cant gap them as hardhead says then the gap gets bigger and the plug loses its performance.

Hmm not sure there worth buying now at approx £100 a set.

 

Regards

Andrew(dunk)Shaw

Black uk mkiv tt

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Guest Terry S

This depends on so much, but mainly what level of tune you are running. I would say do a simple oil/filter change every 3k & the plugs every other change.

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andy, i didnt mean the performance drops off to crap levels, its more a case of the performance benefit from iridium drops off to the point where they r really no better than copper after 12k miles. they will last alot longer than 12k tho.

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Platinum plugs are good for longevity but not for performance. I had a mysterious lumpy running problem when I swapped a new set of platinums in, then swapped out for Bosch copper ones and all is now well again. I know others have suffered the same problems...

 

IMHO iridiums are not worth the extra cash (900% extra!!!)

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Originally posted by Terry S

This depends on so much, but mainly what level of tune you are running. I would say do a simple oil/filter change every 3k & the plugs every other change.

 

Can't go wrong with that!

Mainly it depends on engine condition and level of tune, mod etc.

General plugs can last a very long time!

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  • 3 weeks later...

OK I have got my set of HKS "Super Fire Racing" sprak plugs from https://www.takakaira.com, They are made by Denso so no chance they won't work just because they are HKS :p . A set of 4 worked out to £55 (Plugs ¥7828 + shipping ¥2760), which was cheaper than I had been quoted in the UK for the Denso ones. You guys will obviously have to pay arounf 50% more for 6, although 6 may still fit in the lower shipping weight bracket if your lucky. Not fitted them yet though.

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Originally posted by Terry S

Rich, I run Denso's which are exactly the same as HKS ones, but 1/3rd less. If you get the PN then you can get Denso's over here OK.

 

How much are the Densos? I got quoted 15quid a plug by one company. IK24 (ISO standard fitment) I think are the ones I would have wanted (basically NGK 8 heat rating, HKS 40 heat rating)

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Guest Terry S

I paid 8.75 + Vat for IK22's. Matt U shouldn't need to regap them!! Still waiting for the cost of the stereo & install

;)

 

Rich, I think 8's are too cold for the Supra.

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Originally posted by Terry S

I paid 8.75 + Vat for IK22's.

Where from I could do with spending a little less next time.

 

Matt U shouldn't need to regap them!!

 

I have heard the weld on the side electrode gets very weak if you regap.

 

Rich, I think 8's are too cold for the Supra.

 

Yes they are for the Integra, standard they run NGK Platinium 7s, but Spoon Sport recommend 8s for ITRs on track (which they charge £20 a plug for, and they are Densos also).

 

I have looked at my HT wires and they look a bit worn and tatty, anyone seen those wires with the grounding straps, whats the benefit if any or are they just so they can charge x2 the price of normal wires.

 

Next I have to install the 440cc injectors, and sort out a center box for the exhaust (the Group N system is too loud and getting on my nerves a bit).

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