Iridium plugs

[Jabiru Phil]

Still a goer for mine,

 

Thanks

 

Phil

 

 

[Jaba-who]

I'm in need of education on this.

 

I have been using D9EA plugs since I got my engine new roughly 500 hours ago.

 

Not had any issues or problems with them. Cost about $4.00 each and I change them every 100 hours at a cost of about $48.

 

Best price I have seen for the iridium plugs is about double and a half the D9EAs. So I superficially they would need to be pretty spectacular to justify changing to them on cost grounds.

 

What is the benefit of them over D9EAs?

 

 

[jetjr]

Easier starting, better performance, more than double life, bigger spark

 

Also they are resistor type being quieter

 

I did near recently that they may not deliver to promise on some types of coils supplied by Jabiru.

 

Older "real" honda ?? Coils have more output and have no problems, some newer copies or below spec cant drive past resistor effectively

 

 

[Jaba-who]

Okay thanks. Useful informtion

 

But In my case essentially a costly useless exercise I think.

 

Never have problems starting it, get good power now. Don't care how long they'll last cos I'm gonna change them every 100 hourly regardless. Only plus might be if they are a bit quieter because I still have some noise issues on the radios. But it's now not too bad.

 

So on balance I suspect the D9EAs are right for me.

 

Thanks

 

 

[Russ]

I'm on for a spare set please ( 8 )

 

Russ

 

 

[jetjr]

Deal closed as of 3 weeks ago

 

 

[Russ]

Ok...

 

 

[facthunter]

One should really find out IF resistor plugs are a good idea. They definitely are not with magneto's as neither are carbon thread leads. These will cause magneto failure. Shielded leads and plugs are non resistor also. The points will wear less due to lower current. ( caused by the high resistance) The spark cannot be fatter with lower current. We shouldn't be guessing., about this stuff. Nev

 

 

[Russ]

Month back I mailed NGK asking for a suited iridium plug ,equivalent to our normal plugs , they came back saying there was only the one available, ie

 

These ones we are discussing here. I further asked if we had a heat range choice....answer was no.

 

For what it's worth, I've noticed no side effects in comms etc, all seems as norm.

 

 

[jetjr]

Its not a triaL, Many have been running them for a long time

 

I have heard of some having no benefit or rough running and removing them.

 

It now seems there are different coils out there, real full spec "Honda" ones and some lower spec Jabiru ones

 

Newer Jab ones are not as strong and have trouble with resistor plugs maybe

 

We are talking abou the jabiru system, not really sure how it compares to true magnetos. Jab dodnt have points?? Do you mean rotor and cap?

 

 

[Keenaviator]

I've been running the iridium plugs now for a few hours. When I installed them I gapped them to Jabiru's recommended setting .021". Now that summer is gone and Victoria is pretty cold I've been finding that it hasn't been starting as well as expected, needing choke longer etc. Also in cruise there has been a bit of barely perceptible hesitation.

 

Anyway, on the weekend I was talking with a knowledgeable mate from West Sale who said, "Did you re-gap the plugs?" And if so, "Don't. Just leave them as they are set by NGK." That's about 0.028".

 

This morning I re-gapped the iridiums to 0.028" and lo and behold, it started much more energetically with little need for choke. Also in cruise it has never been smoother nor more even.

 

So the moral of this story, leave the iridium plugs gap alone as they are set by NGK - they know what they're doing.

 

 

[Picker]

Old thread but curious to know where you are getting these NGK iridium DR9EIX plugs from in 2018. Best price I have found is around $13 each delivered from UK.

 

 

[scsirob]

In Europe €7.86 each: https://www.amazon.de/dp/B001OCZBWU/?smid=A25L8D6K1JOVXT&tag=idealode-mp-pk02-21&linkCode=asn&creative=6742&camp=1638&creativeASIN=B001OCZBWU&ascsubtag=Bm42aUdB4V56IZ-7VISzYg

 

Been flying my set for 8 years now, still doing great. Transplanted them from Jabiru to CAMit two years ago, still going strong.

 

Resistor hasn't bothered me with (cold) starts and lowers ignition noise.

 

 

[facthunter]

Why are you using resistor plugs in an aircraft? It DOES load up the rest of the ignition system, and the spark will try to go somewhere else.(leak) with bigger gaps as well. What the maker sets is not for an aeroplane application.. At altitude, the leaking is more likely also and for cold starts a big gap will require a faster cranking speed to get the sparks you need to fire it up. Nev

 

 

[Bruce Tuncks]

Keenaviator, I don't doubt your report but I am puzzled because my understanding is similar to Nev's.

 

Can you give us any more details or explanation?

 

 

[scsirob]

The series resistor is fairly small (~5kOhm), and does not affect the ignition system by much to initiate a spark. The resistance of the wire insulation is orders of magnitude larger than the series resistor. When the high-voltage energy travels through the ignition wire, it sees no resistance. Even when it gets to the resistor, it passes right through without energy loss, as no current flows just yet. The voltage potential builds up, trying to find a way to ground.

 

When the HV potential reaches the tip of the spark plug, the air gap between the tip and the ground pin breaks down and the spark starts. That's when current flows, and that's when there's an effect on energy. The spark will be slightly less energetic as less energy is available to 'feed' the spark and keep it going. But the effect is also that RF from the spark which tries to make it's way back to the ignition wire gets dampened by the series resistor. For RF, the ignition system has a low impedance so the impact of the series resistor is large.

 

At altitude, thinner air will have an effect when your ignition wire insulation is in poor shape and a path through the insulation and thin air breaks down before the path through the spark plug does. This may happen sooner with a resistor spark plug, as the energy that is supposed to feed the initial spark at the plug now has to overcome the extra resistance and finds an easier path. When your ignition wire is in good condition, this is not going to happen.

 

As for gapping the plugs, leave them as delivered. The spec from Jabiru is for regular plugs which have a much larger tip surface. The Iridium plug tips are much thinner, concentrating the HV energy onto a smaller surface. That makes it easier to bridge the gap at factory setting.

 

 

[facthunter]

You should not be using any other than copper wire leads either. They may be shielded for radio suppression but not a high resistance carbon thread. It will destroy a magneto. Where do you get that information.? The worst thing you can do to a high voltage system is open circuit it.. A shorted out circuit does no harm at all. If you recommend things relating to an aeroplane, you have an obligation to not publish anything that may be dangerous. Nev

 

 

[scsirob]

The worst thing you can do to a high voltage system is open circuit it.. A shorted out circuit does no harm at all.

Agree. The energy has to go somewhere. Without a spark plug to dissipate the energy, it will find some other path. That may well be inside the magneto, causing irreversible damage to internal insulation.

 

If you recommend things relating to an aeroplane, you have an obligation to not publish anything that may be dangerous. Nev

Can't see that I made any recommendations, other than not to fiddle with the Iridium spark plug gaps.

 

 

[Keenaviator]

Thanks for your detailed explanation scsirob. All I can report is faultless operation for well over 100 hours.

 

 

[Old Koreelah]

Now I'm confused. There was a long discussion about Iridium plugs a couple of years ago.

 

Someone was ordering them, so I got a set for my J2.2. Quite happy with them, starting in winter is okey.

 

(My LiFePO4 initially cranks over the engine painfully slowly, as if the battery is flat, but it speeds up until the cold start circuit kicks in.)

 

 

[facthunter]

Why would the setting for a motor vehicle primarily done for environmental reasons be OK for the aeroplane situation.? Completely different circumstances.. The plug manufacturer certainly doesn't suggest the plug type or the original gap is optimal for the aero motor.l Nev

 

 

[scsirob]

NGK does not recommend using their product on aircraft engines at all. I can't find a link right now but recall seeing something along the lines of "Not for aircraft use" on the box that the NGK spark plugs ship in. The gap spec for the D9EA comes from Jabiru, we must take their word for it that that's a good starting point in their engines.

 

As for gapping in common terms, NGK FAQ ( FAQ : NGK Spark Plugs Australia | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils ) says the following:

 

"What is the maximum I can open or close the gap?

 

For nickel spark plugs the maximum is 0.1mm. We do not recommend adjusting the spark plug gap any further than this as the centre and ground electrodes won’t line up properly, hindering spark plug performance.

 

For precious metal spark plugs, NGK Spark Plugs (Australia) do not recommend adjusting the gaps as the fine centre electrode is not designed to withstand mechanical force and can easily be damaged."

 

 

[jetboy]

I have been on R plugs in my 2200 for 12 yrs - ever since replacing the original resistor carbon leads with the inductor type.

 

This was done to reduce the radio interference that Jabs are so well known for.

 

Extensive testing with lab equipment showed no change to the loading or stress on the coil packs or any other part of the system. The coils are for Honda lawnmower engines and have a resistor plug or resistor integrated cap depending on market. I never clean the plugs, just replace at 200 hrs. They are gapped to the Jab setting as these are standard plugs. This would more than make up for the perceived effect of the resistor. In reality the resistor doesnt lower any voltage to the electrode because there is no current flowing at the time - see scsirob post

 

If I were to fit Iridium, I would leave the gap at the wider setting its because the spark threshold voltage is lower to break across a pointy end.

 

Next plug change I might get Iridium, but the cost benefit is not great if I'm getting 200hrs on regular plugs

 

 

[facthunter]

I agree you can't change the gap satisfactorily on an iridium plug. I question using it at all. It's expensive and the problem with most aero plugs is not point wear or the extra efficiency of the point shape but contamination of the insulator by additives from the oil and fuel and dust. The insulator runs at red heat to self clean (carbon etc) but other chemicals infuse into the electrode. Lead and fuel and oil additives which contain the metals Zinc and phosphorus. which are all conductors.

 

Cleaning plugs is a thing of the past as the time costs more than a new (ordinary) plug. and it's not that effective.. It destroys the smooth surface of the insulator. I would rather see the cheaper plug used and changed more often in an aircraft.. More expensive is not always better in this instance. The iridium plugs do a good job used where they are intended to be used. They were designed for maintenance reduction and firing lean mixtures more reliably at light loads and when idling in traffic.. Some engines have very inaccessible plugs that require other parts to be removed to access.

 

Carbon leads are the most failure prone part of a modern ignition system. I wouldn't even consider using them in an aircraft to make the radio work better. Your engines reliability is a much higher priority. A resistor MUST lower the AMPS. and it does affect the spark. It may jump the gap but it's much less intense. The plug points last longer because the spark energy is less. That's one of the claimed advantages... "R" plugs and silicon leads are NOT recommended for any conventional magneto. as it will fail usually by current tracking internally inside the coil and the low tension points visibly show more arcing.. Silicon lead failure also contributes to coil pack failure, as it's an open circuit in the HT part which no type of ignition system tolerates . Nev

 

 

[jetboy]

Pity NGK dont make their shielded plugs BS-6E and BPS-6E in 12mm. Aircraft shielded leads are constructed with a helical wound wire core which is good RF supression without the carbon which hasnt been used in cars for 30 years and Jabirus for the last 10 or so....