[mfshook62]

Proper Leaning without an EGT Gage

We have a carbureted RV-9a, O235, with CHT gage, and no EGT gage. After we installed 2 P-mags, we found that we could lean to about 300 rpm from peak rpm without much engine stumbling. The engine just slows down. So when we are cruising we lean by reducing about 100 rpm from peak rpm. CHT temps are about 375 deg during cruise. Some people say EGTs of 50 deg lean of peak is optimum, so without an EGT gage, how should we lean? Can I use rpm drop as a method to lean? Is 100 rpm lean of peak rpm an acceptable value? When you lean using an EGT, what is the typical rpm drop at cruise?

 

[JonJay]

Do it the old fashioned way....

Lean until roughness, enrichen 1/4 turn. I have done this on my injected 360 and then used my fancy Engine Monitor to check the results. Amazingly, the good old fashioned method puts me at my max for LOP operations almost perfectly.
I dont think CHT's are a good sole indicator as other variables can influence them.
I would suspect your RPM drop would be variable at differing altitudes?

Not sure who said 50 LOP is optimum. I know many who run much leaner...
I think it is a choice you can make Power over Efficiency.

 

[turbo]

the main thing is to keep your cht below 380 F.

heat is a killer to your cylinders. thats it. fly more.