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  #1  
Old 12-14-2020, 03:13 PM
Lt Dan Lt Dan is offline
 
Join Date: Dec 2014
Location: Utah
Posts: 94
Default Experience w/Copper vs Iridium Plugs?

I've done a fair bit of searching and pouring through the forum looking for this data but does anyone have actual anecdotal evidence from running standard automotive plugs and then switching to iridium plugs?

I have an RV-8 with an IO-360-M1B running dual P-mags with automotive plugs. Time to change them out and I am considering switching to iridium based on listening to Mike Busch's very interesting webinar on Diagnosing Engine Roughness, of all things. Sounds like the science suggests that you should be able to smoothly run further lean of peak with them due to less cycle-to-cycle variation resulting from the more even early flame kernel nucleation you get with the spark from iridium plugs.

https://youtu.be/eATwKz5XCCE?t=1052
Highly recommend this webinar it if you haven't listened to it yet.

I know opinions on iridium plugs are quite mixed. Even with swapping them out every 100 hours, you could quickly recoup the additional costs if you are able to smoothly burn, say, a 0.5 gph less on the LOP side in cruise. Wondering if anyone has seen any such results in flight.
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  #2  
Old 12-14-2020, 03:37 PM
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Carl Froehlich Carl Froehlich is online now
 
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Location: Dogwood Airpark (VA42)
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Default

I’m of the camp that standard NGK BR8ES plugs is the best value. I have experience with an RV-14 running Iridium plugs and found no difference in performance. With dual pMags running BR8ES plugs I can go deep into LOP, to the point of engine cut out, with no roughness at all.

Note: Smooth LOP operation is also dependent on how well you balance your injector nozzles. On my IO-360-M1B I changed out two of them and enjoy a GAMI spread of 0.0 to 0.1 GPH. Replacement nozzles of various sizes are available from AirFlow Performance for ~$28 each - and Don will help you on what sizes to get.

And the BR8ES plugs are so cheap I just replace them every year or so instead of cleaning.

Carl

Last edited by Carl Froehlich : 12-14-2020 at 03:48 PM.
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  #3  
Old 12-14-2020, 03:43 PM
swjohnsey swjohnsey is offline
 
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Location: Kingsville, TX
Posts: 287
Default

What he said. Copper is more conductive than iridium. Car racers run copper plugs. Iridium plugs last longer but I run plugs for 100 hours then throw them away.
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  #4  
Old 12-14-2020, 04:03 PM
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rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 3,744
Default so cheap

Quote:
Originally Posted by Lt Dan View Post
I've done a fair bit of searching and pouring through the forum looking for this data but does anyone have actual anecdotal evidence from running standard automotive plugs and then switching to iridium plugs?

I have an RV-8 with an IO-360-M1B running dual P-mags with automotive plugs. Time to change them out and I am considering switching to iridium based on listening to Mike Busch's very interesting webinar on Diagnosing Engine Roughness, of all things. Sounds like the science suggests that you should be able to smoothly run further lean of peak with them due to less cycle-to-cycle variation resulting from the more even early flame kernel nucleation you get with the spark from iridium plugs.

https://youtu.be/eATwKz5XCCE?t=1052
Highly recommend this webinar it if you haven't listened to it yet.

I know opinions on iridium plugs are quite mixed. Even with swapping them out every 100 hours, you could quickly recoup the additional costs if you are able to smoothly burn, say, a 0.5 gph less on the LOP side in cruise. Wondering if anyone has seen any such results in flight.
They are really cheap - the one you want with the solid terminal is only $7.49 here:

https://www.ngk.com/ngk-6747-br8eix-...-ix-spark-plug

I've used both regular and iridium, but only have a few hours on my engine, and can't see much difference.
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  #5  
Old 12-15-2020, 08:41 PM
Lt Dan Lt Dan is offline
 
Join Date: Dec 2014
Location: Utah
Posts: 94
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I appreciate the good data!

Since the P Mag installation manual strongly recommends changing any automotive plug after 100 hours, I will go with the standard copper plugs this time. Maybe next swap I will try the iridium plugs and do a back to back comparison trying to gather my own data.

Good point about the GAMI spread. My assumption which I failed to mention was that it is low enough so as to be no factor. Mine is about 0.2-0.3. 0.0 is very impressive.
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  #6  
Old 12-16-2020, 09:40 AM
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Raymo Raymo is offline
 
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Location: Richmond Hill, GA (KLHW)
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I found no difference between the two. Bill R. recommended to use the standard BR8ES and replace every 100 hrs.
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RV-7A - Slider - N495KL - First flt 27 Jan 17
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