Flying 8 knots faster

Dear Dane,

You asked me for some information on your excellent exhaust system. After having run them for 150 hours I am raving about them more than ever. The engine is putting out distinctly more horsepower and running much cooler. For the same power setting on my IO-550 engine installed on a Cessna 185 on Aerocet 3400 Amphibious floats I am flying 8 knots faster and more than 25 degrees cooler CHT, than with the stock exhaust system. Equally as remarkable is how much cooler the engine runs. My normal flying in Alaska on a standard day would be full throttle, RPM set at 2550, the mixture set to 50 lean of peak, and the cowl flaps wide open to keep CHT under control. With the new exhaust system installed I now run at 25.5” of manifold pressure, 2500 RPM, mixture still 50 lean of peak, and the cowl flaps are now ¾ closed. This results in more than a gallon/hour of fuel savings while traveling faster than before. There were no other changes to airplane that would account for this startling increase in a very high drag float plane. Amazing results from improving the flow of engine exhaust. Your web site is 100% accurate on the explanation of this phenomenon. Thank you for making this dramatic improvement in my float plane. There are now lakes I can go in and out of with ease that I would have considered too dangerous in the past. I’m a believer!

Thanks again,
John Eckert