Still chasing high #2 CHT in cruise

[TigerMooney]

I made a previous post on this prior to signing up for savvy analysis, adjusting baffling, changing all 8 spark plugs and cleaning my injectors. 

I’m still seeing my #2 CHT shoot up close to 400 (and 35 degrees hotter than #4) when I run 20-25 LOP (before I intervene). My gami spread and ignition stress tests are all very acceptable, according to savvy.

I’m putting my plane into annual this week and am out if ideas, but would like to equip my IA with as much info as possible. Aside from this one issue, I’m very pleased with the engine. It’s just over 500 hours from an overhaul by zypher, does not consume much oil (1 qt every 12-15 hours), and the engine compartment stays very dry. 

Should I have the cylinders and/or valves borescoped? I’m truly at a loss…

The pictures are below from when I’m at 7k wide open throttle and as lean as I can get it before the engine runs too rough. If I were at a normal cruise setting, #2 would almost certainly settle above 400. And I’m pretty sure thats not acceptable for long term operations. 

Edited August 22, 2023 by TigerMooney

[anthonydesmet]

You mentioned your GAMI spread….are you running with GAMI nozzles?  Where are your cowl flaps?  RPM at WOT?  Is it still 34+ hotter at ROP?

aways borescope at annual. I usually borescope at every other oil change.

[PT20J]

Have you tried swapping the CHT probes between cylinders 2 and 4 to rule out instrumentation?

My CHT used to show a similar result for #2 after installing the factory rebuilt engine with new CHT probes. When I replaced the EDM 700 with a G3X/EIS using the same probes and wiring, CHT #2 fell in line with the others. 

Personally, when the engine is running well, but some gauge shows a problem, I have learned from experience to suspect the gauge.

[INA201]

I agree with PT20J. Start with the simple stuff like probes and baffling around the engine. The EGTs seem to indicate similar combustion and fuel flow as the other cylinders. What did savvy say?? Good luck to you. We have all been in similar situations. 

[philiplane]

post a photo of the #2 cylinder looking in from at the inlet area. And one from the top down.

[Shadrach]

Are you using the #2 cylinder as a reference when you lean? Something is very odd. If I leaned to just smooth of rough, I’m pretty sure all of my CHTs would be south of 300.