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EGT spike on throttle reduction

kaa

Well Known Member
Hi all,

I know what you're thinking - induction leak. This was the consensus in my previous thread about high CHTs (which I think I can get under control). The problem is that I cannot find any induction leaks. I replaced the carb (carefully checked all gaskets and mating surfaces along the way), installed the no leak kit from SDS. Then I tried pressurizing the intake manifold using a shop vac, and using a compression tester. Then my mechanic tried the compression tester method, then we tried spraying starter fluid around the engine - no leaks materialized.

At this point I don't know how to explain the data. Any ideas? I attached a picture of the test. The full flight is here: https://apps.savvyaviation.com/flights/4380720/d283a861-135f-4135-8e5a-9e8033dcbeec. It includes a lean test (the gami spread comes out to 0.5, which I think is ok for a carb) and an in-flight mag check (uneventful).
 

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At this point I don't know how to explain the data. Any ideas?

I see #1 EGT rising at full throttle, not with throttle reduction.
 

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I would start by cleaning the restrictor in the #1 injector. Also try leaning 2-4 to at least 1350 and see if #1 goes to a lower EGT and CHT.

Larry
 
I see #1 EGT rising at full throttle, not with throttle reduction.
I guess #1 is more complicated than just a spike. I highlighted areas that I'm confused about. At least #2 definitely increases there?

I would start by cleaning the restrictor in the #1 injector.
I have a carb unfortunately.

Also try leaning 2-4 to at least 1350 and see if #1 goes to a lower EGT and CHT.
They all increase together, I did a lean test later in that flight.
 

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I

They all increase together, I did a lean test later in that flight.

while at 24" of MAP, lean until 2,3,4 are at least 1300 and report results. Your graph shows all leaning at low MAP and they appear to move in a well organized fashion.

Larry
 
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