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PH-SCP

Well Known Member
Hi Guys,

Today I flew my RV-9 at 5500 ft/2370 rpm/fp prop/mixture ROP, with the following CHT and EGT temperatures, engine is a O-320-D2J;

5csd.jpg


There is a 24F difference between CHT1 and CHT4 and a 77F difference between EGT1 and EGT2. All in all not a very steady and well balanced situation.

My first question is whether or not this is bad for the engine and if so, what is the best approach to cure the difference ?

What are you guys seeing in CHT/EGT temps and the difference between them ?

Cheers !
 
Although you didn't say, I assume your question is posed because you have relatively few hours on the engine. If that is not the case, then I have to assume these temps are a change from what you've seen in the past.
Assuming the "few hours" scenario...
CHTs: It is not at all unusual to see significant temp differences between front and back cylinders. Given #4 location as the most aft cylinder, it's often the hottest. Until I installed a small airflow deflector in front of #1, I had a 35F difference between #1 and #4. Today, #2 runs the coolest and #4 the hottest. I have fab'd, but not yet installed, a small air deflector to go in front of #2 to push more air back to #4.
EGTs: Your max difference is not a cause for concern in my world. My EGTs are always closer when I run LOP, and they're closer today after 90 hrs than they were in the first 30 hrs.

Note that I have a Sam James cowl; that most likely results in somewhat different cooling air flow characteristics.
 
normal

very normal indications for a carb Lycoming. with those numbers you should expect a long & happy life. While one can always make improvements i.e. smaller spread in numbers, you will receive minimal benefit. It would be challenging to see a practical difference in engine wear and life over the life of the engine between your engine and a hypothetical engine with no spread... you only get so much. Operationally I prefer that your highest EGT be around 100 degrees below peak EGT so you may need to lean some, but that depends on were the probe is vs. the exhaust port. Good luck Russ
 
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