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  #1  
Old 02-08-2021, 05:49 PM
Drippy Drippy is offline
 
Join Date: Nov 2015
Location: Vermont
Posts: 141
Default EGTs 1&2 dropping

I was wondering if any of you Engine guys can help me understand the data I am getting on my IO540.

It is winter in VT and my #1 and 2 cylinders have been running cold - during higher MAP-RPM no issue but while I reduce the throttle to idle for landing the front two cylinders cool much quicker then the other four - so i decided to install the baffles pieces that go directly in front of these cylinders - but that I don't use in the warmer months.

Today was my first flight with the baffles installed OAT ~15F while the CHTs were more stable - the EGTs for these two cylinders dropped more quickly when I pulled it back to ide - 1&2 were about 200F below the other four.

Fight of concer
https://photos.google.com/share/AF1Q...x2Y0RpSkVCOHVn

This didin't occur to the same degree on the previous flight without the dams installed. Also you can see from the data that there doesn't seem to be any lag with the EGT during start up.

Prebaffles
https://photos.google.com/share/AF1Q...x2Y0RpSkVCOHVn

Thanks
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  #2  
Old 02-08-2021, 06:16 PM
karrelsj karrelsj is offline
 
Join Date: Jun 2016
Location: Vienna
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Would you mind overlaying MAP onto that EGT graph and zooming into the window that spans just past the event? What does it look like at 15" or 12", or did you pull from cruise to idle? Also, where is your mixture at in all of this? Do you see the same effect if you pull the mixture back at cruise to clean off your plugs and then pull power back to idle?
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Last edited by karrelsj : 02-09-2021 at 06:15 AM.
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  #3  
Old 02-08-2021, 07:28 PM
lr172 lr172 is offline
 
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Mags or EI?

If 1 & 2 are only going lean during idle or very low RPM, as shown in graphic, intake leaks are a good place to start looking for trouble. Hard to see, as rpm and map aren’t shown on graph.

Larry
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Last edited by lr172 : 02-08-2021 at 07:32 PM.
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  #4  
Old 02-09-2021, 06:24 AM
karrelsj karrelsj is offline
 
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Location: Vienna
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By the way. The reason I was going with plugs was because of the differential at :10 vs 1:10. The intake leak is also an interesting point though. i.e. is there something that heated up and expanded between :10 and 1:10 that is leaking more now. That said, not enough context to provide real value in response.
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  #5  
Old 02-09-2021, 08:03 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by karrelsj View Post
By the way. The reason I was going with plugs was because of the differential at :10 vs 1:10. The intake leak is also an interesting point though. i.e. is there something that heated up and expanded between :10 and 1:10 that is leaking more now. That said, not enough context to provide real value in response.
The engine was cold before :10. Even so, 1&2 still show somewhat lower than the others in this time frame as the engine was coming up to temp. Plugs typically either fire or don't and problems with them won't show this type of highly coordinated variability.
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  #6  
Old 02-09-2021, 08:04 AM
Drippy Drippy is offline
 
Join Date: Nov 2015
Location: Vermont
Posts: 141
Default ETG chart with MAP overlaid

Thank you for the inputs guys.

The intake leak seems to make sense and will check everything is tight - I did replace the gaskets last year as part of my annual.

It seems strange that this condition common for both 1&2 and seems to have been impacted/exaggerated by me blocking the airflow to the front two cylinders. - it is hard to see but the RED EGT#1 is hidden below the YELLOW EGT#2 in this graph. For example at time 1:00 EGTs are 1:764, 2:771, 3:950, 4:939, 5:1008, 6:942 - 1&2 are a 200F below everything else. the same temp differential seems to exist at each power reduction downward spike. Of note the CHTs for those cylinders remained the highest of the six during those spikes.

Below is the overlay with the MAP.

https://photos.google.com/photo/AF1Q...MNfRTibdGlC7nu

To explain a few of the spikes I will give you the thumb nail debrief.

I leaned at time 12 minutes or so. Did a stall at time 26 minute - to check the impact of my new dams on CHT temp - then flew an RNAV from 6K descending to 330ft beginning at time 57 or so - mixture goes to full rich at time ~ 1hr as part of the landing check. Then it was a couple of T&G in the Charlie, then back to my own little airport for the break and a few landings. I leaned during the RTB at time ~1:10 then go full rich at ~1:24 or so as part of the landing checklist - I then lean at ~1:37 for taxi.

I am not stressing this but am curious.
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Last edited by Drippy : 02-09-2021 at 08:10 AM.
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  #7  
Old 02-09-2021, 08:10 AM
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Raymo Raymo is offline
 
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Share the link to the flights and you'll get much better feedback. I agree with @lr172 to look / test for an induction leak but cleaning the injectors on those two would also be in order. If neither of those pans out, you should perform the flight test profile and share the link to that flight.
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