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  #1  
Old 02-17-2020, 03:30 PM
douglassmt douglassmt is offline
 
Join Date: Nov 2008
Location: Missoula, MT
Posts: 707
Default Why we have engine monitors

I haven't posted in a while but thought this might be of interest. I fly an RV-10 Aerosport Power IO-540 with a slick mag and a Lightspeed Plasma III ignition. Everything has worked flawlessly for 1300 hours until a recent flight. I didn't notice the behavior when it first started but on a subsequent flight I was descending into my airport, lean of peak but still plenty of throttle, 8500', when the Advanced Flight Systems EFIS gave me a visual and audible alert that the #6 EGT (blue line on the plot) was higher than the others. I downloaded the data and saw this:



It clearly shows the #6 EGT (blue) departing from the others. The only reason I noticed the slight departure was that it finally got into the range I had set for a yellow alert - at about the 25 minute mark on the above plot. On reviewing the data, the departure only occurred when I was lean and at high power settings, over 20". I then looked at previous flights and found this from a few days earlier.



You can clearly see the #6 EGT departure in cruise (LOP and WOT), as well as a corresponding drop in CHT. However, the EGT#6 didn't depart a lot (80-90 deg F) and never reached the temp (I think 1440) I had set for a visual and audible alert. I decided to do some diagnostic stuff, including several GAMI mixture sweeps and an inflight LOP mag check. Here is that flight:



All the mixture sweeps were normal, my GAMI spread is excellent at 0.1-0.2 gph, but when I did the inflight LOP mag check at 13,500' the #6 EGT dropped out immediately and the engine ran very rough. You can see this where the blue EGT trace spikes downward at about 56 and 59 minutes. The #6 EGT and CHT are also behaving differently than the others throughout much of the flight.

I returned to base and checked the #6 plug (fine-wire Tempest). It looked fine. The spark plug leads all looked fine. The plugs resistances measured normal. I replaced the fine-wire plug in #6 with a used massive-electrode plug I had, just in case, and flew again. The LOP mag check at 9500' again showed the #6 EGT dropping off, but much more slowly than it had at 13,500'. I Repeated it at 6500' and everything ran fine.

The mag was due for a 500-hour, actually overdue, so I pulled it and found this:




There was clear corrosion on the spring in the magneto cap for the #6 lead, and corrosion in the socket on the mag.

Takeaways from this are:
1. Without an engine monitor it would have taken MUCH longer to even notice this problem, much less to diagnose which cylinder was causing it.
2. The Lightspeed ignition covers a multitude of sins in the magneto, which is a good thing...unless I need the magneto. Also, the magneto is not contributing nothing, as some people think.
3. The engine monitor, and paying attention to it, allowed me to quickly isolate the problem to a specific cylinder and plug, then find the problem.
4. The absolute value of EGT means very little, so I've considered removing the EGT alerts that I have set in my Advanced EFIS. However, they are useful for just this reason, to get an audible and visual alert when "one of these is not like the other."
5. The engine appeared to be running fine, smooth, but this was a problem that would not get any better, and might have caused some damage had I not caught it when I did. The corrosion in the lead socket was weakening the spark energy for that cylinder to the point that, under the conditions when the most spark energy was required, it didn't get enough to light the fire. Most importantly, if the Lightspeed had quit working and I needed the magneto it would have been unpleasant.
6. I should be in the habit of downloading engine data every oil change or so, even if everything appears normal, to look for things like this.
7. I should also do high altitude, WOT, LOP mag checks on a more regular basis.

Hope this is of some use to somebody.
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RV-10 N242BD

Last edited by douglassmt : 02-21-2020 at 01:38 PM.
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  #2  
Old 02-17-2020, 04:01 PM
TShort TShort is offline
 
Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
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Default

I found the discussion interesting and would love to see the images ... but they just show up as grayed out "negative" symbols for me.

Clicking "view in new tab" doesn't work either.
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KUMP - Indianapolis, IN / KAEJ - Buena Vista, CO
RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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  #3  
Old 02-17-2020, 04:02 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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They don't show for me, either.

Dave
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  #4  
Old 02-17-2020, 04:05 PM
douglassmt douglassmt is offline
 
Join Date: Nov 2008
Location: Missoula, MT
Posts: 707
Default Try again

Try it again. I originally used my old Photobucket account but they somehow blocked the link. I moved them to Google Photos and now they show up on my screen.
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RV-10 N242BD
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  #5  
Old 02-17-2020, 04:25 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,574
Default

No pix show for me either...
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 437.8 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #6  
Old 02-17-2020, 04:29 PM
douglassmt douglassmt is offline
 
Join Date: Nov 2008
Location: Missoula, MT
Posts: 707
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Well shoot. They work fine on my screen but not on my ipad. Stand by, I'll try to figure it out.

[ed. You need to set them to 'share'. v/r,dr]
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RV-10 N242BD

Last edited by DeltaRomeo : 02-17-2020 at 04:36 PM.
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  #7  
Old 02-17-2020, 04:38 PM
douglassmt douglassmt is offline
 
Join Date: Nov 2008
Location: Missoula, MT
Posts: 707
Default

I switched to Flickr but now the images are too small to see very much. Standby unless someone knows how I can fix it.
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RV-10 N242BD
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  #8  
Old 02-17-2020, 05:03 PM
TShort TShort is offline
 
Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 976
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Quote:
Originally Posted by jrtens View Post
I think one has to use the chrome browser to see the google photos.

Another option is to use postimages.org.
Nope ... I use chrome and no pics.

I know how to post my own, but don't know how to fix the different ways they don't work on the site...
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Thomas Short
KUMP - Indianapolis, IN / KAEJ - Buena Vista, CO
RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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  #9  
Old 02-17-2020, 05:04 PM
douglassmt douglassmt is offline
 
Join Date: Nov 2008
Location: Missoula, MT
Posts: 707
Default

I think it works now. Sorry for the clumsiness.
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  #10  
Old 02-17-2020, 05:09 PM
moosepileit moosepileit is offline
 
Join Date: Dec 2010
Location: Floyds Knobs, IN
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Default

Works, android 9 chrome, great post!
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