Why iridium plugs are so expensive

[PT20J]

I spoke with the Tempest rep at the NW Aviation Conference yesterday. There are only two sources for iridium: Russia and South Africa. The suppliers in South Africa know we cannot buy from Russia due to the sanctions, so they have raised prices accordingly. Automotive plugs are platinum, but that doesn't work with 100LL. He confirmed my experience that you can get all the operational benefits (EXCEPT reduced maintenance and longer life) from the BY extended electrode plugs (assuming they are approved for your engine -- they are for my IO-360). He said that the increased life just doesn't offset the increased purchase cost anymore.

[philiplane]

besides the increased life (which is 2000-3000 hours, versus 600-800 hours for massive electrode plugs), you get more power and better fuel economy with fine wire plugs. This is proven and documented by a RAM Aircraft study. Even at the higher prices, fine wire plugs pay back within 1500 hours on owner flown planes.

But in training environments, they pay back even faster, by virtually eliminating the downtime and cost of cleaning student-fouled massive spark plugs. I can attest to that, since I swapped over a local training fleet more than eight years ago. They used to lose several thousand dollars each year in canceled flights and spark plug cleaning. Since switching to Tempest fine wires, they have lost nothing.  

[MikeOH]

Interesting.  It looks like iridium has increased in price from $50 per gram pre-COVID to $200 per gram.  My question is how much iridium is actually in an aviation spark plug?

[Fritz1]

Love iridium plugs in Bravo engine, starts better, runs better, lower TIT, think they were $135 a piece, worth every penny

[Ragsf15e]

I like them too but glad I only need 8!  Some people have luck just running them on the bottom plugs or maybe id just run them on my SF, but it’s easier to keep them all the same.  And whats $1000 in spark plugs over 1000 hours in aviation terms? Not much.

[philiplane]

I have 24 of the Tempest fine wire plugs in my Aztec. Would not go back to massive plugs for any reason, even if they were free.

[A64Pilot]

It is thought that the source of all or almost all of the iridium came from the object that impacted 60 something million years ago that caused the mass extinction that wiped out the dinosaurs.

https://en.wikipedia.org/wiki/Iridium_anomaly

https://en.wikipedia.org/wiki/Iridium

Iridium spark plugs for automobiles aren’t uncommon, they cost on average less than $10 ea. Pretty sure all high performance GM come with them.

https://www.summitracing.com/parts/ado-41-162?seid=srese1&gclid=CjwKCAiAivGuBhBEEiwAWiFmYQCkbfpJGy4pB5Sk6lIrYpgIjpLsYHkvhEOm0W-eePs77dZd7nao1BoCRS0QAvD_BwE.

I’ve run fine wires on both of my previous aircraft, there was some slight improvement as in my 540 did seem to start a little easier and may have been able to run LOP a little smoother, but it wasn’t by much.

Knock on wood, but I’ve never fouled an aircraft plug, I’ve had my C-140 for 15 years or so and always have run massives, my Mooney has massives and I’m running a little experiment, I’ve never cleaned them. Used to be I always cleaned plugs at the 50 hour oil change. I’m seeing how long it will take to foul one on the Mooney

Whether or not you think they are worth the cost is I guess a function of how much money you have to spend. 

[GeeBee]

https://www.statista.com/statistics/1421822/iridium-mined-production-worldwide-by-country/#:~:text=Between 2018 to 2022%2C South,6.16 metric tons in 2022.

 

[PT20J]

There are four advantages to fine wire plugs:

1. They don't require frequent maintenance

2. They last a long time

3. They are easy to set larger gaps for SureFly

4. The exposed electrodes provide easier starting, better LOP operation and are less prone to oil fouling

The long life used to offset the higher cost, but not so much anymore. The operational advantages can be had with the BY extended electrode plugs. 

[0TreeLemur]

1 hour ago, PT20J said:

better LOP operation

Last night I flew round trip from Tuscaloosa to Huntsville.  Wicked SW winds.  Flew there in 35 minutes (91 nm), at 5500 ft LOP in my J with fine-wire plugs burning 8.5 gph at 143 ktas and ~190 knot gs (WOT, MP 23.3 in. Hg, 2400).  I knew coming back would be painful, so I flew back ROP just to fully fight the headwind, and burn some of that expensive avgas that Signature made me buy to waive the $30 "service fee" for gracing their establishment.   At 4,500 90F ROP this resulted in ff=10.5 gph and 155 ktas with 115 gs (24 in. Hg, 2400). 

I rarely fly ROP, because my inner CB likes saving 2 gph at the cost of only 12 ktas.  Most of my flight hours are long x/c flights.  But I believe that those fine wire plugs easily pay for themselves the way I fly.  Up high, around 10k, I cruise at 7.5 gph and about 140 ktas.

[PT20J]

I get just as good LOP operation with BY plugs at a fraction of the cost of fine wires. Maybe it penciled out with to put in fine wires when they were cheap enough that the added life offset the higher cost over massives, but even Tempest isn't claiming that anymore (of course this is Mooneyspace, so I'm sure someone will be along shortly saying they have 10,000 hours on their fine wires and still going strong )

I think those that purchased fine wire plugs when the cost was more reasonable made a good decision. But, now, I think the cost/benefit tips to BY plugs. It's not the magic of iridium -- it's the extended electrode that provides the operational benefits: It puts the spark deeper into the combustion chamber for easier starting and better LOP operation and it runs the tip hotter to reduce fouling.

[0TreeLemur]

3 hours ago, PT20J said:

I get just as good LOP operation with BY plugs at a fraction of the cost of fine wires.

Sorry Skip, I have never heard of BY plugs.  What are they?   It seems like your missing the "OB"? 

-Fred

[Andy95W]

22 minutes ago, 0TreeLemur said:

Sorry Skip, I have never heard of BY plugs.  What are they?   It seems like your missing the "OB"? 

-Fred

https://www.aircraftspruce.com/catalog/eppages/temptestplugs8.php
 

[EricJ]

They don't seem to be available for 3/4-20 harnesses for some reason.

[A64Pilot]

Neighbor is building two RV-14’s with IO-390’s. Attached photo is the way they came from Lycoming.

It’s an automobile plug and an adapter, of course we can’t because we aren’t Experimental, but if Lycoming ships them this way it obviously works.

What does a new Certified Lycoming ship with? If fine wires made better power then surely they would come with them? I have no idea what they come with, Factory new engines are way out of my price bracket.

So far as LOP  my engine with massives will smoothly run so LOP that it won’t make enough power to maintain level flight. But then it’s a blueprinted engine too, but I can’t imagine what fine wires could do to improve on that. My last two airplanes had fine wires, I like them as I believe if properly cleaned they will likely last the life of the engine, but everything has a value attached to them and I think they are just simply priced beyond their value now.

 

[PT20J]

Lycoming currently ships certified engines with Champion massive spark plugs and AvStar fuel injection.

[haymak3r]

I saw some fine wire's the other day at my mechanic's shop. How in the world do those little tiny ground straps not burn away over time lol.

[FlyboyKC]

Question?

Can you mix and match Fine and Massive?

Fine on the bottom and Massive on the top?

Just curious if there would be any advantages.

Thanks

 

[Ragsf15e]

27 minutes ago, FlyboyKC said:

Question?

Can you mix and match Fine and Massive?

Fine on the bottom and Massive on the top?

Just curious if there would be any advantages.

Thanks

 

Yep, you can do exactly that and some people do.

[Shadrach]

There is a reason why Lycomings ship with massive plugs. Quite frankly, they are perfectly suited to the task at hand in most cases. They also offer good cost to performance value.

I have happily watched the fine wire debate from the cheap seats and listened to the sermons of the devout. My takeaway after more than a decade is if they solve a problem for you, that’s great. If you don’t have a problem running massives, you’re not going to see much return. There are a lot of claims being thrown around about fine wire plugs. Let me make a few about plain old massive plugs. Excluding Champion’s past QC issues, I have routinely seen the following while exclusively operating massive with Bendix S series mags:

• 1000hrs (or more) of service with replacement based on time and electrode appearance not any significant degradation in performance that can be seen on an engine monitor or on start up.
• Excellent ignition performance across the mixture spectrum. Can easily run leaner than I would ever want/need to at any altitude.  Engine is smooth to >100LOP at high power settings.
• Easy and consistent starting hot or cold.
• Excellent lead scavenging. Plug cleaning and inspection at annual is a simple event with very little lead accumulation.

I am sure that fine wires are great in certain applications, but they answer a question that my four cylinder, injected Lycoming has yet to ask.

[EricJ]

1 hour ago, FlyboyKC said:

Question?

Can you mix and match Fine and Massive?

Fine on the bottom and Massive on the top?

Just curious if there would be any advantages.

Thanks

 

Lead fouling usually happens on the bottom plugs.   If you're having lead fouling problems, then putting fine wires in the bottom is often a successful strategy to mitigating the issue if nothing else works.   I wound up doing that and it cured the problem.    I would also agree that if you not having issues with the massives then there's no reason to change.

[N201MKTurbo]

A spark plug ignites the fuel charge. It either ignites it or it doesn’t. There is no difference in the fire after it is ignited. Anybody that thinks fine wires make more power is delusional and is subconsciously justifying the money they spent on the plugs.

The only thing I will accept is “fine wires misfire less than massive plugs” maybe they do, maybe they don’t. 
 

Back in the old days, fine wires were made with two platinum ground electrodes and a platinum center electrode. They changed to iridium because it is cheaper, not because it is better. The current plugs are iridium plated electrodes. When you erode through the plating, the base metal (nickel) erodes rather rapidly. 
 

I personally run SH260s. They are 3 electrode massive plugs. They haven’t been made since 1977. My ninja eBay skills have got me enough to last to the end. I think they work better than fine wires. And they are approved for the engine.

[John Mininger]

On 2/27/2024 at 5:06 PM, PT20J said:

There are four advantages to fine wire plugs:

1. They don't require frequent maintenance

2. They last a long time

3. They are easy to set larger gaps for SureFly

4. The exposed electrodes provide easier starting, better LOP operation and are less prone to oil fouling

The long life used to offset the higher cost, but not so much anymore. The operational advantages can be had with the BY extended electrode plugs. 

I'm just curious Skip. Just hypothetically, what do you think the optimum gap would be for UREM37BY plugs running on SureFly?

Again, just hypothetically of course. Say, you were running an IO-360-A3B6 in an RV-7 with a SureFly ignition system.

John

[MB65E]

35 minutes ago, John Mininger said:

I'm just curious Skip. Just hypothetically, what do you think the optimum gap would be for UREM37BY plugs running on SureFly?

Again, just hypothetically of course. Say, you were running an IO-360-A3B6 in an RV-7 with a SureFly ignition system.

John

The surefly manual states the required gap. It’s much larger than a normal mag. I personally love the BY plugs. .040 if I recall. Many techs might miss this during inspection or service. I did until I read it. 
-Matt

[John Mininger]

23 hours ago, MB65E said:

The surefly manual states the required gap. It’s much larger than a normal mag. I personally love the BY plugs. .040 if I recall. Many techs might miss this during inspection or service. I did until I read it. 
-Matt

Interesting. The last time that I asked this question to the SureFly guys at Sun N Fun or Oshkosh they said that even though the SIM could handle a wider gap, the plugs should still only be gapped to the mag spec. But when I looked at the current SureFly installation manual, it says up to .035. 

Third page:

f0684a_5c901873262249e59c4cb300f0fc8bbb.pdf (surefly.net)

My Slicks only have about 350 hours on them. I was going to wait until they hit around 500 to change over to SureFly. So I haven't really been following the latest SureFly news.

Has recommending a .022 to .035 sparkplug gap been a fairly new change?

Thanks

John