> "Run as lean as possible above 8K and it'll stay clean and last forever since at WOT you're only pulling 70% power or less. At the altitudes I fly (10.5 - 13.5) I'm pulling about 50% power and going 150 MPH. Down low just keep cylinder head and oil temps within limits. That's all there is to it. It's a great engine."
************ I wrote that presuming everyone knows I use a very coarsely-pitched prop (52x56 Sterba) compared to many KR flyers. WOT gives me 3100-3200 at altitude, about 2800+ static. The engine is right on the edge of fighting back with full throttle on takeoff. After I'm moving a bit the engine is very happy with full throttle. In fact, not having to fight back pressure from a throttle plate makes it very happy. With full throttle static it's right on the edge of complaining. With a flatter prop WOT would be giving me more RPM but that's what I'm wanting to get away from. For my prop diameter of 52 inches, tip speed faster than 3100 produces mach drag and also produces heat from increased friction within the engine. That heat is easily seen on the cylinder head temp gauge and oil temp gauge. The coarse prop takes big bites of air, especially the thinner air where I fly, each revolution making thrust which I would otherwise get by running it at a higher (inefficient) RPM. The coarse prop does not significantly affect my takeoff distance or climb rate. It increases the former by a little and reduces the latter by a little but the benefit rendered at altitude far outweighs these very minor penalties. Ken's design, it's 20' 8" wingspan combined with the narrowed fuselage or maybe it's the beautiful Diehl wingskins . . . for whatever reason this plane really likes to get off the ground and really dislikes coming back. It likes to get up high since with my cooling drag this plane could use some cleaning up, so going high minimizes the induced drag of that and a couple other little things. There's room for improvement but whatever the reason Ken's plane really gets off the ground easily and returns reluctantly. With a coarse prop, running at lower RPM's with WOT - extracting power through higher cylinder (manifold) pressures instead of through turning the engine faster, dramatically affects (lowers) cylinder head temperature and oil temperature. Below 8K I cannot run WOT without pulling more than 70% power with resultant high cylinder and oil temps. So when below 8K I use partial throttle and enough mixture to keep the heads within temp limits. The excess gas with a rich mixture is wasteful but necessary for cooling when using full power on takeoff and initial climb. If running at 70% power or less whatever our altitude might be, there's nothing we can do with the mixture that can hurt the engine. Unless we run it too rich - which does indeed hurt the engine in a variety of ways. John Deakin: http://www.avweb.com/news/pelican/182084-1.html Flying down low is not as efficient as flying up high, but sometimes the trip length doesn't warrant going high. Whether high or low, keep the VW cool and it'll keep us cool. Mike KSEE ____________________________________________________________ Want to place your ad here? Advertise on United Online http://thirdpartyoffers.juno.com/TGL3141/559c6cad1c9796cac73c4st03vuc
