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  #1  
Old 02-19-2021, 09:24 AM
Jvon811's Avatar
Jvon811 Jvon811 is offline
 
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Location: KFNT Central Michigan
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Default Ruthenium HX Spark plugs and LOP? Question for the Spark Experts.

I run dual P-Mag's on my O-320. Using the recommended NGK BR8EIX Iridium Spark Plugs. No fuss, no muss, works good, last long time. I throw them out and buy 4 new bottom plugs every oil change, makes me feel good...

Anyways, I do like LOP ops when cruising on a long XC. Just under 200 hours on my airplane last year cruising around of trouble free enjoyment using LOP. I would regularly see 60-90* LOP across all 4 cylinders on the GRT EIS before one of them would get upset if I tried to go leaner.

My question is: Does anyone have experience with NGK's Ruthenium plugs? I'm just a pilot, not an engineer but they advertise them as "High Ignitability" plugs which I'm wondering if it could help with low AFMs.

I don't have any trouble starting with P-Mags, but maybe these could someone help with cold starts? Hot Starts?

I got suckered in by the advertising department and their "Flame Kernel Growth Test" pictures on the website.

https://ngksparkplugs.com/en/product...um-spark-plugs

Also, in my use of the BR8EIX Iridium plugs, I have noticed that LOP ops get harder to achieve as the plugs get some hours on them. Dirty, maybe... I lean as much as possible on the ground and do what I can to prevent them from loading up. Not convinced that their spark efficiency doesn't change due to electrode erosion after 25 hours or so or what... They're definitely not as pretty when they come out as they were when they went in, and I can't go as far LOP after 25 hours as when they were new, that's all I know.

But the webpage also mentions "better durability at higher temperatures" which has an included picture that got my attention. Maybe these plug's electrodes would hold up better at LOP ops? I understand my CHT's and EGT's go down LOP (hence lower combustion chamber temps), but are Lycoming combustion chambers "higher temperature" engines? Compared to what? Is our LOP temps still "higher temperature" compared to the car engines these plugs are probably designed for?
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RV-4 N249P
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  #2  
Old 02-19-2021, 10:14 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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I too run LOP 90% of the time on dual pMags, but I run the standard BR8ES plugs (good service over ~20 years).

I note that your run way more LOP than I do. After taking a lot of cross country data I find going past say 20 degrees LOP speed drops off faster than fuel flow declines (as a percentage). Assuming this is a new issue with the arrival of cold weather, I suggest your very low LOP operating point may be a factor in what you are experiencing.

If you are running with very cold CHTs, I suggest you try running just LOP and take some data. My thought is just a little LOP means that you are into the excess air range (instead of excess fuel) so the desired CHT reduction is in play, you are getting the most out of the fuel you are using, but perhaps keeping CHTs from going too cold.

Side note - on the last two cold weather cross country trips (12Kí) my CHTs were well below the 350 target to minimize valve sticking issues. I ran the engine right at peak to get CHTs into the 350-360 range. The difference:
- 20-30 degrees LOP, fuel flow 7.7gph, TAS 174 kts.
- Peak, fuel flow 8.7 gph, TAS 183 kts
So a ~7% reduction in miles per gallon, but I got to justify the higher fuel burn (and going faster) as ďtaking care of my engineĒ.

Carl
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  #3  
Old 02-19-2021, 10:24 AM
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Raymo Raymo is offline
 
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I'm with Bill Rippucci on spark plugs. Just use the BR8ES and replace them every 100 hours/annual. You'll find that reinstalling a plug in the adapter (if you have adapters) is very difficult after cleaning.
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  #4  
Old 02-19-2021, 11:07 AM
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Jvon811 Jvon811 is offline
 
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I don't have any issues running LOP or reinstalling the plugs. 500+ hours and 10 sets of plugs used and tossed (because they're cheap). When I say "problems going lean of peak" after 25 hours, I just mean that I can only get to about 30-40* LOP before it gets rough versus 60-90*. My thought is the plug has changed. Either it's just dirty or the electrode has changed. That's the only variable.

My question is specifically wondering if any spark guys or engineers in that field have experience with these NGK Ruthenium plugs can tell me the difference between them and Iridium with reguards to spark characteristics and what that may translate to with LOP operations.
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RV-4 N249P
O-320, Dual P-Mags, Warnke Prop, Short legs, Manual Flaps, GRT Sport EX

Last edited by Jvon811 : 02-19-2021 at 11:13 AM.
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  #5  
Old 02-19-2021, 12:47 PM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Jvon811 View Post
I don't have any issues running LOP or reinstalling the plugs. 500+ hours and 10 sets of plugs used and tossed (because they're cheap). When I say "problems going lean of peak" after 25 hours, I just mean that I can only get to about 30-40* LOP before it gets rough versus 60-90*. My thought is the plug has changed. Either it's just dirty or the electrode has changed. That's the only variable.

My question is specifically wondering if any spark guys or engineers in that field have experience with these NGK Ruthenium plugs can tell me the difference between them and Iridium with reguards to spark characteristics and what that may translate to with LOP operations.
Considering this new information I do not understand why you think this is a spark issue.

Carl
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  #6  
Old 02-20-2021, 09:38 AM
lr172 lr172 is offline
 
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iridium plugs should last 1000's of hours. I have standard copper/nickel plugs and go hundreds of hours with similar performance. I highly doubt that a plug with 50 hours is impacting your ability to effectively light a 30* LOP mixture.

with that said, It is possible that the iridium plugs do not do well with lead deposits. Remember, these were designed for the auto world and were put into use LONG after leaded gasolline had been banned. Their primary benefit is long life, not better sparking, so see no upside to installing them if you plan to only use them for 100 hours. Personally I would stick with std plugs.

Larry
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Last edited by lr172 : 02-20-2021 at 09:42 AM.
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  #7  
Old 02-20-2021, 10:18 AM
Ralph Inkster Ralph Inkster is offline
 
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I too am a believer in just running standard (3 buck) plugs. Don't see any advantage in changing them every 50 or 100 hours, or running more expensive or exotic plugs in our low revving engines. I let the plug electrode & engine smoothness tell me when it needs changing.
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  #8  
Old 02-20-2021, 10:39 AM
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Jvon811 Jvon811 is offline
 
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Quote:
Originally Posted by lr172 View Post
I highly doubt that a plug with 50 hours is impacting your ability to effectively light a 30* LOP mixture. with that said, It is possible that the iridium plugs do not do well with lead deposits
Right, thatís my point. I can do 30* but not the usual 60-90* I can get with new/clean plugs. Im also a Mike Busch subscriber of LOP Ops and I donít really hang out in the 30* LOP area too much.

Iím not necessarily looking for everyoneís plug advice, I know what I like and what works just fine. And Iím not saying they wear out, Iím not saying they run bad, at all. But I CAN tell a difference between fresh clean plugs and 25-50 hour plugs when going real deep LOP. I could clean them (maybe even media blast them as long as theyíre cleaned really well) or just buy a ~$20 set of new plugs for the bottoms and be on my way...

My question is simply if anyone knows anything about these Ruthenium plugs. Whatís makes the special. Could it help keep LOP ops running cleaner longer? Iím talking like 98th percentile stuff, thatís all...
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  #9  
Old 02-20-2021, 10:43 AM
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Jvon811 Jvon811 is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
I do not understand why you think this is a spark issue.
Well, tips erode, get dirty, foul up, things change... when you’re on slim margins like 90* LOP, I assume a slight change in plug effectiveness or efficiency might result in the differences I can feel and see. But I don’t know for sure, I’m not an ignition expert or engineer. I just know what I’ve learned from several thousand hours behind piston engines and working on them. Also, I’ve got a FP wood prop. In a -4, the engine tells you a lot and you can feel many things through your feet before it shows up on the engine monitor.
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Last edited by Jvon811 : 02-20-2021 at 10:46 AM.
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  #10  
Old 02-20-2021, 12:07 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Jvon811 View Post
But I CAN tell a difference between fresh clean plugs and 25-50 hour plugs when going real deep LOP. I could clean them (maybe even media blast them as long as they’re cleaned really well) or just buy a ~$20 set of new plugs for the bottoms and be on my way...
Ok. We'll take your word for it. So, on a simpler level, why are you using a plug that degrades in 25 hours. I and many others get hundreds of hours on a std plug. You are now looking at even more exotic plugs. Learn the lesson and move to std plugs where your brothers are having good success; I can easily get 100 LOP. You are running a plug designed exclusively for unleaded fuel instead of a plug designed specifically for leaded fuel. Why are you surprised with your findings.

Also, regardless of what professor Busch says, I do most of my cruise at 30* LOP. Engine hasn't grenaded yet. I would take my advice from the boys in Ada (i.e. Gami) over Mike, who has done NO formal testing with a dyno and cyl pressure measurement devices.
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Last edited by lr172 : 02-20-2021 at 12:17 PM.
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