The International Cessna^® 170 Association

The instructor that taught me to fly my 170B told me not to run the engine at low rpm (like below 2300) because it could detune the engine. Having crop dusted much of his life, flown just about everything, heard most stories, and proven himself right on a lot of things that seemed strange to me, I have a lot of respect for what he says. But that just seems odd, especially since the manual lists stats for rpms down to 2100 for fuel burn and range etc. I like flying slow and saving gas, but not if its going to hurt the engine. Is it true that flying at 2100 rpm can detune the engine? (all else being equal)

Detune? What does that mean?

What your instructor was teaching you is that these engines are designed and can be run all day long at high power settings. Lots of people think that babying an engine by running it at lower power settings will "save" it. This is not the case. Carbon and lead deposits build and are not illuminated as well at lower RPM. You may see a higher rate of fouled plugs. But if leaned properly at lower RPM this really shouldn't be a problem.

Would I spend all my time flying slow at low power settings, 1900-2000 rpm, no. Do I run my engine "hard" at higher power settings, 2500-2600, with out a doubt. Will I run my engine at any RPM I need for the time required to enjoy the type of flight I choose at a given time, without hesitation.

The engine manufacture I work for uses "detune" for the the crankshafts that have the counterweights...which can be done if not run correctly, but unless you have a balanced crankshaft, I do not believe you can "detune" anything in that engine.

v/r,
Jud

Bruce Fenstermacher wrote: Carbon and lead deposits build and are not illuminated as well at lower RPM. You may see a higher rate of fouled plugs. But if leaned properly at lower RPM this really shouldn't be a problem.

Bruce I didn't know my Carbon and lead were illuminated at any power setting .

How much "De" can you get from an engine that only produces 145HP. It is always de-tuned, even at full throttle! Sometimes I miss my F-15, of course, we complained about those engines being detuned as well. What only 40,000 lbs of thrust today? That's Bull!

Jughead