[N941WR]

I’m throwing this out there to see if others have experienced similar issues.

As the manufacture of the EICommander I answer a lot of questions (both on and off line) regarding issues with P-mags.

A month before my Condition Inspection was due my EICommander started giving me some odd readings regarding the health of my ignition. However, the P-mags were timed correctly, they were advancing in unison, they were both running the same configuration, the CHT’s & EGT’s were “normal”, and the engine just felt fine.

After going through every test, connection, and whatnot, I decided to change out the NGK BR8ES spark plugs with a new set. What the heck, I typically change them at every Condition Inspection, so doing it a month early was no big deal. Besides, they had about 105 hours on them. (I know, it was a slow year for me.)

The new plugs were gapped for .032 and installed. The old plugs were checked and the gaps were right at .032 and they looked fine. I could find no issues of any kind.

After changing them out, the EICommander reported all was fine.

Brad at Emag Ignitions, told me “There is some anecdotal evidence” that the plugs go bad at around 100 hours.

In discussing this with my partner in the EICommander, who flies a rotary powered RV-6A, I was sent this little gem:

Bill, having read about the ignition problem you refer to, I may have something to contribute.

As you know, I and most of the folks who fly rotary engine powered aircraft use regular automobile spark plugs. Most folks fly using auto fuel, but I and a few others fly almost entirely using 100LL av gas. What I and others have discovered is that after approx 100 hrs (it varies) on Av gas, the engine develops what we call "SAG" (Sparkplug Attention Getter).

The engine will take on a different note, rpm will drop and (in the early stages) after a couple of minutes things return to normal. The interval and duration of the SAG continues to increase - this can be quite disconcerting and lead folks off on wild goose chases trying to fix fuel and other problems.

We had one technical analysis which included cutting open the offending plugs - it appears that after 100-120 hrs running on Av gas the lead in the fuel gets deposited on the ceramic cone, also it appears that the continuous (hour after hour) of high engine rpm stress internal bonding of the auto spark plug components and leads to deteriorating spark performance. The only cure that we have found thus far is to replace the auto plugs.

So any time a new rotary flyer reports those types of symptoms, we tell them to change their sparkplugs.

Now without use of 100LL, those folks using auto gas generally get a several hundred hours or more - this SAG pertains to use of auto plugs with 100lL

FWIW

Ed

This is just food for thought. At less than $20 for a set of eight plugs, I now replace them all at 100 hours. Because of the cost involved, I don’t even bother with platinum plugs.

 

[miyu1975]

Thanks Bill. Just so happens mine are right at 100 hrs and my cowl is off for painting...guess I will go ahead a put new plugs in too.

 

[Toobuilder]

Bill,

Do you check resistance of your new plugs before install, and did you check the "old" plugs? I've found all the new ones to be right around 4,500 ohms.

Longest I went was about 120 hours, but they were performing well- I simply replaced them because... Well they're cheap!

 

[N941WR]

Good call Michael.

I just checked four of the eight plugs I removed and three of the four were between 4,200 and 4,3000 with one up at 4,500 ohms.

 

[MS19087]

BR8ES vs BR8EIX

Hi Bill - You may or may not have an opinion here . . . I'm running dual P-mags and am preparing for my condition inspection - just at 120 hrs on the top plugs - half that on the bottom since I added second P-Mag later. I currently am using the BR8EIX (expensive!) plugs. Any reason not to go with the cheaper BR8ES plugs?

Thanks!

 

[Toobuilder]

Mark, I know you asked Bill, but let my throw my opinion out there.

The primary benefit to the exotic plugs is consistent performance with low maintenance over a long life. New car drivers would never stand for a plug change at every "tuneup" like back in the 60's. these plugs are used to make cars "maintenance free"...

That said, I'd keep them in there as long as they are performing. Do a visual inspection and ohm check every year, and call it good. JMHO.

 

[dealfair]

Good info

Thanks mucho Bill. I'm a little over 100 hrs & burning 100LL. Have the plugs & cowl is off. Going to do the swap, very timely. Yes, at the lower expense and given the time, seems wise to go with the lesser plug.
Really appreciate the post!!

Cheers,

 

[dealfair]

Mark, I know you asked Bill, but let my throw my opinion out there.

The primary benefit to the exotic plugs is consistent performance with low maintenance over a long life. New car drivers would never stand for a plug change at every "tuneup" like back in the 60's. these plugs are used to make cars "maintenance free"...

That said, I'd keep them in there as long as they are performing. Do a visual inspection and ohm check every year, and call it good. JMHO.

Darn Mike, was typing my post then read this. Yeah, why not test & check?? Will do.

Thanks,

 

[rocketbob]

If 100LL were so detrimental to a spark plug's life then most massive electrode plugs would not last long. And this is not the case since I've seen them last over 1000 hours many airplanes including mine.

I think the BR8x plugs are too hot for a Lycoming.

On EI I run BR9ES plugs which I rarely replaced on condition inspections because I could see no visible wear. I easily got 4-500 hours on them and just replaced them even though they didn't need to be replaced

 

[MarkW]

Since I am not flying yet I sure can't argue with R Bob but I sure would be using the old color/condition method to find the correct plug.
I also can't imagine having to replace a properly choosen plug every 100 hours with or without lead.
NGK has an excellent website for that.
http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml

 

[DanH]

If 100LL were so detrimental to a spark plug's life then most massive electrode plugs would not last long.

Consider the difference in breakdown voltage due to gap....

We didn't start getting long plug life in cars until after we got rid of the lead.

 

[N941WR]

Hi Bill - You may or may not have an opinion here . . . I'm running dual P-mags and am preparing for my condition inspection - just at 120 hrs on the top plugs - half that on the bottom since I added second P-Mag later. I currently am using the BR8EIX (expensive!) plugs. Any reason not to go with the cheaper BR8ES plugs?

Thanks!

Mark,

Stay with the plugs you have until you feel it is time to change them.

I always have run the BR8ES's since my first flight in 2007 with the idea that I would just swap them out every Condition Inspection.

The only way I knew something was up this past year is because the EICommander told me something was going on.

I never felt anything odd, my CHT?s, EGT?s, etc. were all in line. In fact, if it wasn?t for the EIC, I would have kept the plugs until my condition inspection, which was due a month later.

As for keeping your current plugs because they were ?expensive?, that may be false savings.

 

[ColoRv]

Mark,

Stay with the plugs you have until you feel it is time to change them.

I always have run the BR8ES's since my first flight in 2007 with the idea that I would just swap them out every Condition Inspection.

The only way I knew something was up this past year is because the EICommander told me something was going on.

I never felt anything odd, my CHT?s, EGT?s, etc. were all in line. In fact, if it wasn?t for the EIC, I would have kept the plugs until my condition inspection, which was due a month later.

As for keeping your current plugs because they were ?expensive?, that may be false savings.

What was your EI Commander telling you?

 

[N941WR]

What was your EI Commander telling you?

The Timing Divergence Alarm (TDA) was off the chart and the coil pack data was out of the green, similar to the screen mockup displayed above.

The normal TDA value is 2.0 degrees and is determined based on comparing when the #1 plugs fire. The plug data is based on the dwell time it takes for the coil packs to recharge between each discharge. This is impacted by the condition of your plugs, plug wires, etc.

If the timing of the two ignitions were really out by that amount, my CHT’s would have gone off the chart and if the coil data was that far out the engine would have been misfiring but neither of these things happened.

As I said, once I replaced the plugs you could see the numbers come back into line. (We use some very unique “averaging” routines for these values and I could watch the numbers work their way down in the first few minutes of operation with the new plugs installed.)