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This message was automatically forwarded on behalf of Bill Bayne. Please address any responses to the mail list or directly to Bill at: [EMAIL PROTECTED] -----Original Message----- From: William R. Bayne [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 22, 2006 11:29 PM To: Ed Burkhead Subject: Re: [COUPERS-TECH] C-85 STC, Performance, Props rlytech Hi John H., The C-90 is a 90 hp engine rated at 95 hp for one minute (take-off). I believe the prop would have to be pretty close to a "climb" pitch for the engine to turn necessary rpm to develop 95 hp in a cruise-climb configuration. The charts, specs., etc. are all in the "A & C Series & 0-200 4 Cylinder Engines Continental Aircraft Engine Operator's Manual, Form X30012 (mine is dated 1980). The single prop curve plotted for each engine model is of little use in prop selection. The STC engine remains officially a C-85, but one from which a savvy owner can extract more than the average owner gets from a "real" C-90. On the other hand, if you choose to cruise at 75 hp rpm, you will probably get better fuel consumption than a C-75 because you have a more efficient engine. The chart for the C-75 and the C-85 are on the same page. The two engines are mechanically identical except for the recommended rpm limits, which Erco ignored. Spin up a C-75 to 2575 rpm (prop must be selected or tweaked to allow the engine to do this) and voila! 85 hp (with the 75 hp venturi and jet). In "hot rod" terms, stroking an engine and increasing the compression ratio are both serious modifications. As previously stated, the modified engine has an entirely different power curve reflecting increased efficiency (compression ratio) and displacement. The Ercoupe is a compromise easily tailored to one's flying. Live at high altitude or in a hot area? You may need a climb prop (and that means slower cruise for a given horsepower). Want to fly at 1400# gross weight? Be prepared to accept an approximate loss of 1000' in service ceiling for every fifty pounds over 1250 gross. Want to fly far and efficiently? Shut the windows, learn the art of proper leaning, know your upper winds, and choose efficient cruise speeds. Weigh 250+ pounds? You have a single-place airplane with generous luggage capability or you can take up a small child as passenger.. How many "fly this way" (knowledgeably)? That distinct minority that pursue the knowledge and experience necessary to become skillful. Most of us weekend "wood butchers" have a hammer around that cost under ten bucks. It serves our purpose and skill level until lost or broken. A skilled carpenter, on the other hand, will achieve better results with less effort using one of several recent designs of titanium hammers (with a variety of handle designs) that is perfectly matched in weight and shape to his/her physical attributes. It will cost $60-$100, last forever, and return added value to its owner far beyond any difference in initial cost. In the very same sense, those who view (or fly) the Ercoupe as a "one size fits all" plane settle for an "average" level of performance that is easily achieved. Those who want or expect more have to understand the possibilities before choosing from them to get that "extra edge". Regards, William R. Bayne <____|-(o)-|____> (Copyright 2004) -- On Feb 23, 2006, at 02:34, Anne and John wrote: > So in amongst this verbage another question comes to mind, is the C90 > a 90 hp or a 95 hp engine, and where do I go to get these > torque/horsepower charts to compare one against another. If the C90 > does infact produce 95 gross horses, all else being equal, then the > change would seem to be more economically inviting, however do either > of you, or anyone else that has manage to follow this thread this far, > have any idea of the cost of just regrinding the crank by 10 or 20 > thou, as opposed to buying crankshaft, rods and pistons. > > Another question is if it takes so much to get from 85hp to 90/95 hp, > how come it is so simple to go from 75 to 85 with just the minimal > change of venturi size. Do the charts tell a different story, and was > this just some advertising mumbo jumbo ??? > > I guess the bottom line is that most of us can handle the cruise > speed, but most want better climb, especially on those hot summer > days. > > Regards, > > John H. ============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm
