EGT Fluctuation

Kupde · #1 02-22-2021, 05:52 PM

Just changed out the fuel restrictions on cyl#3 and #4 on my RV-10 from an 0.028 to a 0.027. Test flight shows a very brief EGT drop(3 to 5 seconds) while going through the leaning operation on cylinder #3 only. Cylinder #3 drops about 200 degrees below the others(1200F vs 1400F) for the 3 to 5 seconds and then recovers with no further fluctuations. This repeats anytime going back through a leaning operation at different altitudes and engine settings. Never seen this before- anyone have any thoughts?

Kevin
RV-10

Bill Boyd · #2 02-22-2021, 06:25 PM

Very interested in the replies you get on this. I'll be balancing my injectors soon as I progress through phase 1.

My EGT on one cyl scrolled quickly downward and back up again shortly before the Dynon-supplied probe in question went T.U. for good, and had to be replaced at about 5 hours TT.

Lt Dan · #3 02-22-2021, 11:11 PM

What did the CHT do?

Raymo · #4 02-23-2021, 06:34 AM

Sounds like #3 is running too lean. Can you upload the data to Savvy and share a link?

bjdecker · #5 02-23-2021, 08:16 AM

Quote:

Originally Posted by Kupde

Just changed out the fuel restrictions on cyl#3 and #4 on my RV-10 from an 0.028 to a 0.027. Test flight shows a very brief EGT drop(3 to 5 seconds) while going through the leaning operation on cylinder #3 only. Cylinder #3 drops about 200 degrees below the others(1200F vs 1400F) for the 3 to 5 seconds and then recovers with no further fluctuations. This repeats anytime going back through a leaning operation at different altitudes and engine settings. Never seen this before- anyone have any thoughts?

Kevin
RV-10

I would be very suspicious of that EGT probe/wiring. I had a similar pre-failure signature on one of my ALCOR EGT probes very early on (~50 hours).

Swap the probe, see if the signature follows the probe -- if so, replace the probe.

Usually, issues with fuel injectors resolve themselves VERY quickly -- like a stumble that the EIS doesn't even see, or they don't resolve at all -- total blockage.

lr172 · #6 02-23-2021, 08:37 AM

Quote:

Originally Posted by bjdecker

I would be very suspicious of that EGT probe/wiring. I had a similar pre-failure signature on one of my ALCOR EGT probes very early on (~50 hours).

Swap the probe, see if the signature follows the probe -- if so, replace the probe.

Usually, issues with fuel injectors resolve themselves VERY quickly -- like a stumble that the EIS doesn't even see, or they don't resolve at all -- total blockage.

+1

Sounds more like an indication problem than a fuel delivery problem. Pretty hard to have a fuel issue that can cause an EGT to drop then regain 200* in 3 seconds.

Larry

Kupde · #7 02-23-2021, 08:37 AM

https://apps.savvyaviation.com/fligh...3-b3c28bb00ca0

Not sure if you can get to the data with the link above? Also, no change in CHT and I'll do as suggested with the EGT probe.

Thanks

Kevin
RV-10

Raymo · #8 02-23-2021, 09:04 AM

Quote:

Originally Posted by Kupde

https://apps.savvyaviation.com/fligh...3-b3c28bb00ca0

Not sure if you can get to the data with the link above? Also, no change in CHT and I'll do as suggested with the EGT probe.

Thanks

Kevin
RV-10

Thanks for the link. Definitely a probe connection issue, as mentioned above. GAMI spread is pretty good with #2 trending leaner.

Time: 00:14:28-00:14:54
EGT2 peaked at 12.2
EGT3 peaked at 12
EGT1 peaked at 11.8
EGT4 peaked at 11.8
EGT5 peaked at 11.8
EGT6 peaked at 11.8
GAMI spread is 0.4

bjdecker · #9 02-23-2021, 09:56 AM

You can definitely see something going on there --

EGT on #3 drops out frequently, 9:08, 16:20, 19:29, and so on, regardless of fuel flow settings.

bjdecker · #10 02-23-2021, 03:51 PM

Keep an eye on the #2 CHT.

Note 11:41 to 14:32 and 21:08 to 26:41 -- #2 CHT is NOT following the normal distribution or rate of change.

This tells me the #2 Cylinder is burning too hot / too fast as the fuel flow increases (richer:faster, leaner:slower), change to a smaller orifice (e.g. .027" from .028") and see if that curve flattens out.