WHY DO HORIZONTALLY OPPOSED SIX-CYLINDER ENGINES RUN ROUGH ON THE LEAN SIDE OF PEAK?
The short answer begins with this thought: Some of our engines, a very few of them, don t run rough on the lean side of peak EGT. Read the following excerpt from a Lycoming engine manual for one of their 540-cubic-inch, flat, opposed piston engines: “Lean the mixture until EGT peaks and continue to lean until the EGT drops 25 to 50 degrees on the gauge. Flying on the lean side is permissible if extended range and cooler engines are desired. Operation at peak EGT is only recommended for mixture control adjustments or when induction icing occurs. The Amount of temperature drop can be determined by resultant fuel consumption and engine smoothness. “When operating on the lean side of the power curve, the pilot may observe that airspeed and power are less. If you desire to regain lost airspeed and continue to fly on the lean side of the curve, two steps are important. If sufficient throttle is available at the lower altitudes; first add two inches of manifold pressure to the standard cruise
