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Bob, et. al.,
No need to be "sorry"... you're not disagreeing with me, as I am simply relying on the published materials/manuals from American Aviation, Inc., who manufactured and flight tested the intercoolers that came with the airplane.
Insofar as the AA charts are concerned, my limited three years of experience with this equipment in a variety of flight regimes indicates that the fuel flows, fuel burns and airspeeds associated with the published parameters is right on target.
Bob, I'm not sure how you obtain "peak hp = peak egt = best efficiency = A Constant". While it is true that peak EGT will get you best efficiiency, i.e., best fuel economy, if "peak hp = peak EGT", how do you explain the Cessna POH wherein it states that, "...beste economy mixture settings (peak EGT) results in approximately 8% greater range than shown in this handbook accompanied by approximately 4 knots decrease in airspeed?" It seems to me that if you were obtaining peak hp, you would also be obtaining max airspeed, no?
Well, perhaps all of these technical gymnastics have moved us far afield of the end result, which is why some of us have the interccolers to begin with, and that is, to provide cooler and denser air from the compressor section of the turbo before it enters the induction system and throttle servo which equals better efficiency of the engine. That would also appear to be the reason for limiting the takeoff to 35.3" MAP at sea-level ISA, as the cooler, more densely packed air molecules would tend to create an overboost situation if you run the engines at 37" like a stock airplane... but I'm not in a position to argue that technical point, as AA has the STC and their FAA authorized placard says to limit the takeoff power to 35.3" MAP. I'm sure that American Aviation, Inc. had to provide certified flight test results to the FAA in order to obtain the STC... they wouldn't arbitrarily limit the takeoff MAP without substantive reasoning.
BTW, with respect to Mike's comments about burning cylinders on a regular basis, I wonder what operating parameters caused this? Our AA intercoolers were installed in 1978, a year after our airplane was manufactured, and reviewing the logs I don't find any evidence of a cylinder burnout in the 25-year logbook history.
SkyKing
SkyKing
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