Surefly Fired Spark Plugs Darker?

[Ragsf15e]

So started my annual today.  So far engine and prop looking good according to my IA.  All I saw was the 1000s of access panel and belly screws as I pulled them.  How did that possibly take me 6 hours?

Anyway, my top plugs are in this picture before cleaning.  The dark tips are from the Surefly, cleaner looking white-ish ones from the mag.  Thoughts?

[chriscalandro]

Top VS bottom plugs?

Edited January 18, 2022 by chriscalandro

[Ragsf15e]

4 minutes ago, chriscalandro said:

Top VS bottom plugs?

Those 4 are all top.

[RLCarter]

Doesn’t one mag fire the top plugs on one side and the bottom plugs on the other side?

[chriscalandro]

1 hour ago, RLCarter said:

Doesn’t one mag fire the top plugs on one side and the bottom plugs on the other side?

No. 

[Ragsf15e]

6 hours ago, RLCarter said:

Doesn’t one mag fire the top plugs on one side and the bottom plugs on the other side?

Yes.

those 4 are all my top plugs, so 2 fired by the right mag and 2 by the Surefly.

[rbridges]

what does your IA think about it?  I'm curious, too.  

[Ragsf15e]

1 hour ago, rbridges said:

what does your IA think about it?  I'm curious, too.  

He just grunted, cleaned them, tested them and reinstalled the 3 that tested ok.  One of the SF plugs was only firing intermittently.  I can’t specifically blame the SF as those plugs are about 8 years and 800 hours old, so could have just worn out.

[A64Pilot]

8 hours ago, RLCarter said:

Doesn’t one mag fire the top plugs on one side and the bottom plugs on the other side?

That’s been my understand and one mag fires opposite current too, so you “rotate” plugs top to bottom to even the wear.

Of course I could be wrong.

[StevenL757]

46 minutes ago, Ragsf15e said:

He just grunted, cleaned them, tested them and reinstalled the 3 that tested ok.  One of the SF plugs was only firing intermittently.  I can’t specifically blame the SF as those plugs are about 8 years and 800 hours old, so could have just worn out.

When was your non-SF mag inspected/OH last?  Depending on how long the SF mag has been in there, I tend to agree with your IA that they should be cleaned appropriately, reinstalled and observe in about 25-50 hours (or appropriate interval).  If it recurs, I'd certainly want to know more about the situation, and if the SF mag is causing undue wear, I'd personally switch back to a conventional mag.  Just got back from TX last night, and based on a couple of other instances I've been privy to as of late, these new SF mags haven't outgrown their teething pains.

Edited January 18, 2022 by StevenL757
Additional context

[N201MKTurbo]

The color difference must be caused by something about the SureFly that changes the temperature of the plugs. I would have to assume that it has to do with the advance changing the flame front behavior. The temperature of the plugs determines how well they evaporate lead bromide. 

It is possible that that change just happens while at low power where the timing difference is greatest. If you did a high power runup and a quick shutdown, you may not see that difference.

[Ragsf15e]

I’ve also posted this question to SF so I’ll let you know what they say.  Both the mag (overhauled) and SF were installed 2 years ago and now both have about 160 hours.

[Ragsf15e]

56 minutes ago, StevenL757 said:

When was your non-SF mag inspected/OH last?  Depending on how long the SF mag has been in there, I tend to agree with your IA that they should be cleaned appropriately, reinstalled and observe in about 25-50 hours (or appropriate interval).  If it recurs, I'd certainly want to know more about the situation, and if the SF mag is causing undue wear, I'd personally switch back to a conventional mag.  Just got back from TX last night, and based on a couple of other instances I've been privy to as of late, these new SF mags haven't outgrown their teething pains.

Mine is on a 14v system so I didn’t have any issues with the power fluctuations that some 28v folks suffered.  It also does provide slightly better LOP ops if you fly high where the advance is greater.  I have pretty good data showing a couple knots faster LOP above about 8k.
I am concerned about what it does to the plugs though.

[PT20J]

No idea why the difference. Are the bottom SureFly plugs also darker?

The left mag fires the left top plugs (even cylinders) and the bottom right plugs (odd cylinders).

[StevenL757]

34 minutes ago, Ragsf15e said:

Mine is on a 14v system so I didn’t have any issues with the power fluctuations that some 28v folks suffered.  It also does provide slightly better LOP ops if you fly high where the advance is greater.  I have pretty good data showing a couple knots faster LOP above about 8k.
I am concerned about what it does to the plugs though.

Understood.  I think the question you need to answer is whether those ~2 knots are worth blowing through nearly $275 of iridium plugs prematurely.  I might be overstating my case, but do agree with you in that you shouldn't just accept the present situation without more due diligence and investigation.

[Yetti]

29 minutes ago, StevenL757 said:

Understood.  I think the question you need to answer is whether those ~2 knots are worth blowing through nearly $275 of iridium plugs prematurely.  I might be overstating my case, but do agree with you in that you shouldn't just accept the present situation without more due diligence and investigation.

Or the question could be would you keep the 2 knots by switching back to massive and save money on plugs.

[Ragsf15e]

4 hours ago, PT20J said:

No idea why the difference. Are the bottom SureFly plugs also darker?

The left mag fires the left top plugs (even cylinders) and the bottom right plugs (odd cylinders).

The bottom plugs were similar but much closer in color so tough to say for sure.  The SF folks answered right away but didn’t have anything to add: “I don’t know why that would happen?”

[Ragsf15e]

3 hours ago, Yetti said:

Or the question could be would you keep the 2 knots by switching back to massive and save money on plugs.

Possibly.  Also right now try buying a Tempest fine wire UREM 38S.  I ordered a couple in November from Chief.  Nobody has them even now.  Maybe in a couple weeks I keep hearing…

[LANCECASPER]

49 minutes ago, Ragsf15e said:

Possibly.  Also right now try buying a Tempest fine wire UREM 38S.  I ordered a couple in November from Chief.  Nobody has them even now.  Maybe in a couple weeks I keep hearing…

When I was trying to buy Tempest fine wires in late November/early December I ran into the same problem. Aviation Parts Inc had them in stock and I got them in three days. It looks like they have yours

https://www.aviationpartsinc.com/product/tempest-iridium-fine-wire-spark-plug-urem38s/

[PT20J]

1 hour ago, Ragsf15e said:

The bottom plugs were similar but much closer in color so tough to say for sure.  The SF folks answered right away but didn’t have anything to add: “I don’t know why that would happen?”

It might just be "one of those things". I could speculate that there would be differences in operating temperatures when operating at manifold pressures where the SF is fully advanced because one plug would fire 13 deg earlier than the other (assuming you have 25 deg BTDC timing on the other mag; 18 deg earlier if the other mag is set at 20). Normally the spark plugs run hotter than anything other than the exhaust valve because they have small parts, relatively long cooling paths and the fire starts there so they are exposed to high temperatures for the longest period. Normally, the two plugs fire at the same time and the flame fronts progress until they meet. But with one plug advanced, the SF plug gets a head start and is exposed to combustion temperatures longer so it might run hotter. I'm not sure why that would make it darker.

Skip

[Ragsf15e]

1 hour ago, LANCECASPER said:

When I was trying to buy Tempest fine wires in late November/early December I ran into the same problem. Aviation Parts Inc had them in stock and I got them in three days. It looks like they have yours

https://www.aviationpartsinc.com/product/tempest-iridium-fine-wire-spark-plug-urem38s/

Thanks. I just ordered them!

[Yetti]

I am going to ponder that firing them at a different timing setting is putting them in the cold or rich firing place.   a hotter plug would be interesting to run.

[Ragsf15e]

34 minutes ago, Yetti said:

I am going to ponder that firing them at a different timing setting is putting them in the cold or rich firing place.   a hotter plug would be interesting to run.

Jeez it sure does look like that doesn’t it.

[A64Pilot]

Don’t run a hotter plug, a hot plug can cause detonation. a cold plug will foul but cause no damage, so if anything err towards cold.

 

[N201MKTurbo]

9 minutes ago, A64Pilot said:

Don’t run a hotter plug, a hot plug can cause detonation. a cold plug will foul but cause no damage, so if anything err towards cold.

 

I hate to be a nit picker (well, maybe) but a hot plug causes pre-ignition not detonation. Pre-ignition may cause detonation.