VairHeads, We recently had a discussion on running lean of peak EGTs on CorvAircraft, and the conversation went from "don't you dare do it", to "I do it all the time" (that was me).
Today I was flying back from Jack Cooper's place and almost fell asleep an hour into the flight. I figured some testing would wake me up a little, so I decided to do some fuel consumption vs throttle settings throughout the flying range, and then after I was awake and bumbling along at 8500' at a lean of peak mixture of 137 mph true airspeed (I was a little low on fuel and stretching it) and getting 42 mpg at 3.3 gph, and wondered what would happen if I were running at peak EGTs instead. So I richened it up to max rpm without changing throttle setting and got 124 mph TAS and the fuel consumption climbed to 4.1 gph. So I gained 5 mph at the price of .8 gph. That means my 42 mpg dropped to 35 mpg with only a 5 mph penalty. That's about all that dropped...the average of the six EGTs climbed 59 degrees F (so I was operating a 59 degrees LOP), and the CHT's went up 26F. The difference in fuel savings may seem small, but it allowed me to get home with 2.3 gallons still in the tank, avoiding a fuel stop from 8500'. That's a half an hour (more than makes up for the 5 mph) and a lot of fuel burned in climbing back to 8500', wear and tear on the engine climbing out at full throttle, and I landed still burning my $2.10/gallon 93 octane fuel from the Raceway station down the road. If anybody wants to dissect the EIS flight data spreadsheet, snag http://home.hiwaay.net/~langford/performance/425_04TN.xls and enjoy. By the way, on the way up I was doing 3030 rpm (my favorite is 3050) and getting 155 mph true airspeed and burning 3.9 gph, which translates to 40 mpg, which ain't bad for 155 mph! At one point I'd slowed down waiting for Joe, and was doing 143 mph TAS and getting 51 mpg... Mark Langford N56ML "at" hiwaay.net website at http://www.N56ML.com --------------------------------------------------------
