Thanks Walt, this is very interesting. Do we know if this depends on MP? Is the curve the same no matter the power setting? Just curious if the stresses are ok at high altitude/low MP/low power settings.I run at 2400 typically, if I need a lower RPM for rain penetration I go down to 2000 rpm <22".
The below is from WW but pretty typical recommendations.
2000 or 2100rpm is lugging a 4 cyl engine at full throttle/highMP IMO.
Recommended Continuous Operating Ranges
Whirl Wind follows historical industry standards and recommends that continuous operation between 2,050 - 2,300 RPM and 2,600 - 2,700 RPM be avoided when used on Lycoming and similar four cylinder aircraft engines. (Take off and climb out is not considered continuous operation.)
The full article from WW:
https://www.whirlwindaviation.com/faq.asp
Thanks Walt, this is very interesting. Do we know if this depends on MP? Is the curve the same no matter the power setting? Just curious if the stresses are ok at high altitude/low MP/low power settings.
Strangely, I find 2250-2350 RPM to be a very "smooth" setting for high altitude, full throttle, low MP cruising. Dropping below 2250 felt a bit too much like I'm lugging the engine, even at altitude.
I might need to see about checking my prop balance at 1950-2000 RPM, or just get used to the additional noise at 2450-2500.