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The mkiv Supra Owners Club

FAQ: Spark plugs


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What to use when MAPPING?

A. Use only copper plugs when mapping. Iridium plugs should be saved for an engine that is already mapped and tested on coppers. This is because the mapping process is fraught with danger and that danger is det. Detonation will ruin a copper plug, but the engine will be kept safe. An iridium plug is much more immune to det and other parts of the engine can suffer long before the plugs do. Stay safe and use copper plugs when mapping!

 

Cont.

 

-Alex

 

 

Would it then just make sense to use copper all the time and change frequently?

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  • 3 months later...

Great info. that I don't want to detract from in any way (just come here from another thread) so I hope my input isn't confusing. I can't see the following mentioned anywhere before in this thread.

 

I believe for a August 1997 onwards TT (I guess this means VVTi), the OEM spark plug has changed slightly:

 

  • NGK BKR6EKPB-11
  • DENSO PK20TR11

 

The new plug is a 'multi-ground' (not multi-spark) design and seems very expensive (see NGK website for more details).

 

Interestingly, the Iridium equivalent plug hasn't changed which leads me to think that the original style OEM plug would still work quite happily. I wonder why they decided to go for a different design for OEM - somehow related to VVTi engine changes?

Edited by spartan
Bit clearer maybe (see edit history)
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Multi ground = multi spark, the spark jumps from the central electrode to the ground electrode(s).

 

http://www.sparkplugs.com/services/image.asp?path=http://www.sparkplugs.com/productImages/1/NGK4302-2.jpg&width=130&height=200

 

Doubt it really makes any difference (or we'd all be fitting Bosch Super-4's!) and in a modified application I'd say they're more dangerous given there's more ground electrode to break off. Iridiums would be of a multi ground electrode design if there was a benefit to be had IMO.

 

The original style OEM plug will still fit given they're all the same fitment for the head design, so everything in this guide still holds true.

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Found this extra info. on multi-ground spark plugs:

 

This is an attempt by manufacturers to increase the service life of the spark plug. The ground electrodes can wear down rapidly in some engines. Tiny particles of metal are removed from the ground electrode each time the plug fires hence they gradually wear away. There is a misconception that a multi ground plug will produce mutiple sparks - this is not true, only the nearest electrode to the centre (i.e. currenty the longest) will spark, as that becomes worn, another electrode will become the longest and replace it as the sparking electrode.

 

So not really multi-spark (no simultaneous spark). There is also some debate as to whether the extra metal within the combustion chamber helps channel heat away/retains it, thus preventing/causing det. etc. :blink:

 

Maybe the Toyota service interval was extended for VVTi engined cars, hence the requirement for a plug that lasted even longer?

 

Anyway, "as you were" is the message to take forward (I'll get me coat).

Edited by spartan
Grammar (see edit history)
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I wasn't but I think you've just hit upon the reason for the change - as wasted spark ignition was introduced with the VVTi engine - each plug is igniting twice as often as before (eroding quicker) hence the need for a plug which will last longer! Does that make sense? Does it mean that owners of VVTi engined cars who aren't using this new style of plug should potentially be changing them more often? I guess not if you're already using Iridium ...

Edited by spartan
Iridium (see edit history)
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No idea why you'd wanna fit platinums over iridium though, given the iridiums have the longer rated service life + other benefits.

 

Mr Toyota you mean? Perhaps the Iridium plugs weren't available back in 1997. If they were, it does seem a bit strange as the cost of the multi-ground platinum (now) exceeds the iridium equivalent plug.

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  • 3 months later...
  • 1 month later...
After reading this to get an idea of what plugs I should use, is there a recommended torque setting to install the sparkplugs to? I always like to make sure things are torqued up correctly (I'm probably a bit too anal about this sort of thing hehe).

 

I would be interested in this too, but as there is no mention on this thread I dont think there would be...? could be wrong..!

 

I got a bit confused with this VVTI multi spark plug, do I need different ones for my BPU '400bhp' VVTI it runs mainly on 1 bar but once in a blue moon i like it to bump it up to 1.2bar...?

 

Should I go for either,

 

NGK - BKR7E (6097) - gap 0.7mm

 

NGK Iridium - BKR7EIX - leave gap alone

 

Thanks in advance...:D

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