Copper spark plugs... erm.

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Copper spark plugs... erm.

Post by New Duke »

A friend has had their RX8 serviced by a mechanic who has fitted NGK copper spark plugs (the ones in the yellow box).

It's going to have a new Exedy clutch (I'm told) fitted, be MOT'd, then driven back to my friend's house.

My understanding though was that we need to stick to the Iridium plugs... cos hot spark and stuff.

Will they be OK driving their car for a while until the weather improves and I can change their plugs to Iridium ones? Or should I stage an intervention? Or does it not really matter?
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Re: Copper spark plugs... erm.

Post by 13Black »

Any idea what the part numbers were? As long as they're not BUR9EQ RX-7 plugs!

The box might not be exactly what's inside, a set of 4 plugs will often come in a 4x trailing or a 4x leading box, but of course they have a pair of each.

Also the proper laser iridium plugs have a copper construction also - its fantastic at conducting both heat and electricity, exactly what you want with a spark plug.
It's only the centre/ground electrodes that are iridium/platinum.
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Re: Copper spark plugs... erm.

Post by New Duke »

Thanks Nick. I don't know what the part numbers are sadly, though I did ask for them. All I know from photos is that the plugs were individually packed in the yellow NGK packaging, and I couldn't see the top of each box where the part number would be stamped.

Very relieved I had a certain specialist fit my plugs 8)

If they are indeed copper plugs, it's not a big deal then?
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Re: Copper spark plugs... erm.

Post by 13Black »

I think the vast majority of plugs will have copper in them, so it's not a detail I think that should be focused on.
It's the iridium centre electrode.

Get the chap to pop the HT leads off of the spark plugs and look for the part number on the ceramic. It's probably the only way to know for sure now.

Unless they're fakes in fake yellow boxes with the correct part number fraudulently painted on them.
I've seen it before.
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Re: Copper spark plugs... erm.

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Re: Copper spark plugs... erm.

Post by PeteH »

I'd say swap em!

I don't think NGK make non-iridium plugs that are suitable for a rotary(?)

Firstly, the key thing about rotary plugs is that they sit inside a hole, rather than being exposed to the mixture. To work they need very flat and very thin electrode. Because it's so small it needs to be iridium so that it isn't eroded away in two seconds. So "copper" plugs will fail very quickly.

Secondly, the other key thing about rotary plugs is that they have to be a very specific length. They need to get as close as possible to the rotor, without hitting it. The wrong length will either not work well, or smash the rotor.

Finally (the science bit). Did you know that the precious metal bit is just a tiny patch on the end of the electrodes? They don't make the whole conductor from it because that would cost many pounds. So if you are thinking of making a wedding ring from your plugs..... forget it. You'll need about a thousand plugs. :(

Ps. I know you can get "racing" plugs that look conventional, but I think these were really designed for the RX-7. I've never tried them in an RX-8. I wonder if anyone else has.
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Re: Copper spark plugs... erm.

Post by New Duke »

Thanks guys. Yeah I think that either they're completely the wrong plugs. Or they're the right plugs, just individually packaged into different boxes than NGK supplied them in for whatever reason... ease of transit/storage/fakes/just to stress me out. Who knows.

Guess I'll have to take them out and have a look.
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Re: Copper spark plugs... erm.

Post by RenesisRaceBuggy »

I'd be very wary, I don't think they do any described as copper plugs, and the RX-8 plugs are a very specific shape, the wrong plugs can kill the engine.
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Re: Copper spark plugs... erm.

Post by warpc0il »

I had a guy arrive at our place a few years ago with his 8 running rough and making chuffing noises, which I *thought* was probably an exhaust leak.

He'd just bought the car and the previous owner had admitted that there "had been a few problems..." including a faulty 02 sensor in the manifold. This being back around 2010, this was the first O2 sensor fault I'd heard of, but hey, things can died.

Sure enough the O2 sensor had been replaced, with some nasty generic thing attached by scotchlocks, but it wasn't leaking.

The "leak" turned out to be the front rotor trailing plug was loose, which I very nearly just tightened, until something suggested that I take it out to check. It was a Champion N9Y, and so was the rear trailing :shock:

The electrodes had been crushed down onto the end of the plugs, so there was no spark gap and the coil outputs were just shorted.

The leading plugs were both correct but clearly hadn't been changed for the 40-something thousand miles on the clock.

I gave him a set of my old plugs, as he barely had enough money for the fuel home, and the transformation was instantaneous. Engine ran sweet and quiet.

He was appropriately grateful, until I pointed-out the miss-matched ditchfinder tyres, the inner front brake pads being down to the metal, a too-small battery with no retaining clamp, the soaking wet boot carpet and his only key being the grey "courtesy" key.

He didn't join the OC and I never heard from him again.

Nine years on and there's got to be a lot of cars in circulation in as bad a state, or worse...
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Re: Copper spark plugs... erm.

Post by 13Black »

Just a note about the spark plugs and fakes.

A load of people were recommending cheap plugs from Greece, I've told of this before, but piccies.
Ordered a set for poops and giggles, this is the junk they sent.
Probably even in the correct boxes, maybe fake boxes, I can't remember.

So just looking at the part number isn't really good enough, I'd say remove them and check, might as well.

These fake Leading plugs have a cold blue-ish cheap (probably zinc) plating on them. The trailings are probably legit as they have more of a champagne-gold plating to them.

Sealing washer is loose on the cheapy Leadings.

Electrodes aren't anywhere near right, but they tried I guess.

IMG_20171101_162419.jpg

IMG_20171101_164553.jpg



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Re: Copper spark plugs... erm.

Post by warpc0il »

I'm thinking we should have a "fake plugs" thread along the same lines as viewtopic.php?f=58&t=51334
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Re: Copper spark plugs... erm.

Post by casey »

Good idea Dave :thumleft:
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Re: Copper spark plugs... erm.

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Re: Copper spark plugs... erm.

Post by CheekyWankel »

Thank you Haydn for creating this.

And thank you all for your input, I have messaged my mechanic hopefully he'll get back to me soon about what plug's he used. I've waited so long to have my car back, I don't want anything else happening to it.

If they are copper then I will get proper ones ASAP. Need to take it to a rotary specialist from now on I think :P
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Re: Copper spark plugs... erm.

Post by Essex2Visuvesi »

CheekyWankel wrote:
Wed Jan 30, 2019 6:18 pm
Need to take it to a rotary specialist from now on I think :P
Or learn to do it yourself :)
You have some very knowledgable members in and around Colchester.... Zippyonline, Ian Mothersole & Casey to name a few
I'll leave myself and Adam off the list as we're not to be trusted with power tools :shock:
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Re: Copper spark plugs... erm.

Post by Dr. FrankenRex »

Not being daft, but I'm 99% certain that NGK make both 'normal' spark plugs and iridium spark plugs for the RX8...

I've got a set in the barn, I'll go dig 'em out in a bit.
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Re: Copper spark plugs... erm.

Post by New Duke »

Thanks Dan. That would beg the question. If 'normal' plugs are fine, why on earth are we fitting expensive iridium plugs? My understanding was that the engine needs a specific amount of spark to ignite the air/fuel mix, as defined by Mazda. Surely more spark would be a waste, less spark just wouldn't work (and leads to the threads we see on failed ignition). I don't geddit. Unless it's always the case that more spark is always better, provided you're not blowing a hole in the housing. But then using 'normal' plugs would be consciously wasting fuel without a lean map and... and.... and.... it hurts my brain.


On another note, I think I unintentionally led us down the rabbit hole of wondering about fake plugs too. My question was really that: 'on the assumption that individually yellow boxed, genuine NGK spark plugs that fit correctly into the RX8's spark plug thread on the engine have been fitted... is that OK assuming no other variables exist?'
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Re: Copper spark plugs... erm.

Post by 13Black »

I'm not aware of non-iridium plugs being available from NGK for our cars. They have a rather good parts finder section on their website.


Think of it less in terms of more spark with iridium, there should be some tiny fringe benefits in terms of performance.
Longevity seems to be their best selling point though - something daft like 100,000 miles. Maybe in a modern piston car, however from what I've pulled out of 8, I wouldn't go anywhere near that. They still get caked in deposits.
Would this be worse with standard plugs? I'm sure it would be.


Bare in mind that FD RX-7s you can get either standard or *platinum plugs, a lot of folk going with the standard options.
I wouldn't be surprised if our iridium plugs were spec'd for slightly better emissions (every little helps) and that there'd be little drawback to normal plugs for most folk, if changed regularly.


*edit: platinum, not iridium :D
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Re: Copper spark plugs... erm.

Post by Dr. FrankenRex »

It may be that they're iridium in a normal box. Not been out to the barn as yet so will have a gander later.

They were passed on to me from a previous owner of a car I picked up, so potentially the wrong ones :)
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Re: Copper spark plugs... erm.

Post by SprintRX8 »

Straight off the NGK web site.
Only list these
Plug number RE8C-L Stock number 5745
Plug number RE9B-T. Stock number 2809

Sure I’ve seen a Essex Rotary video saying don’t bother with iridium plugs.
(Could off been iridium race plugs?)
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Re: Copper spark plugs... erm.

Post by 13Black »

The hotter RE7C-L are also okay and what most seem to be these days.


Yes it was Denso's plugs to avoid, not ALL iridium.
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Re: Copper spark plugs... erm.

Post by AndyBrad »

I think it would be interesting to get a standard plug and replace at 10k as its bound to be a lot cheaper.

Im sure ive read about hotter plugs fr short journeys. Is this right?
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Re: Copper spark plugs... erm.

Post by New Duke »

AndyBrad wrote:
Thu Jan 31, 2019 1:39 pm
Im sure ive read about hotter plugs fr short journeys. Is this right?
Chances are any new plugs you get now will be the hotter plugs. Jp4mance put the hotter plug as standard in their RX8 listing. They seem to have become the new standard.

But yeah they were originally suggested for cars that did mainly short journeys, but were suitable for all RX8s.
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Re: Copper spark plugs... erm.

Post by Phil H »

I fitted ones that came in Yellow NGK and they appear to be iridium ones, so think you should be ok.

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Re: Copper spark plugs... erm.

Post by New Duke »

Really interesting, thanks for that Phil. Perhaps just variations in packaging then for whatever reason.