Temporarily Undersquare?

You are the closest to actually answering my question. Majority of my time is in turbines (mil pilot), so the little blue knob is not something I really grew up with and I want to make sure I understand it in-depth.

I'm tracking with what you said -- if we're running at a lower RPM and high MP, valves are open longer and let more air into the cylinder. If we assume mixture stays the same, then the air/fuel ratio inside the cylinder is changing. More air per unit fuel. Or, said another way, less fuel per unit air. So a lean condition at a low RPM. Why is this bad? Is it too lean? Does it cause the engine to run too hot?

I just played around with this in flight sim (P3D), it seems low MP / high RPM = low EGT and high MP / low RPM = high EGT. So is that the proper conclusion? We'd be running too lean and too hot if we pull the prop back first? Appreciate your help...turbines are so much simpler, haha.

/r/flying Thread Parent