670 & 277 Engine
Is this what you have? Which Model A, B, C? The last model made the 180 C model has a MTOW of 512 lbs = 232.2393 kg / 10 kg = 23.22393 kw needed = 31.1438 hp needed. It was 262 lbs with a Single Carb 503, and carried 7 Gallons, so it didn't make Part 103 with a 503. A purpose built 277UL, 377UL, 447UL or Kawasaki 340, 440, would have been better Engine Choices.
Rotax puts out a Fuel Consumption Graph in there different Manuals. As I showed you at 6000rpm where it actually made Max 25.4hp@6000rpm on the Dyno. It works out to (0.134) for gph for the 277. Each Plane & Pilot Weighs are different and has different Drag.
277UL using Rotax graph. All GPH Approximate's off Graph. Each Engine will be a little different.
6500rpm = 4.1 gph 20.5hp -2.8hp
6250rpm = ?.? gph 23.3hp -2.1hp
6000rpm = 3.4 gph 25.4hp <--- At 6000rpm is where it made Max 25.4hp. 3.4 / 25.4 = (0.134).
5500rpm = 2.7 gph 23.2hp x 0.134 = 3.1088
5000rpm = 2.0 gph 17.9hp x 0.134 = 2.3986 (2.4) gph
4500rpm = 1.4 gph 12.3hp x 0.134 = 1.6482 (1.6) gph
4000rpm = 1.0 gph 10.1hp x 0.134 = 1.3534 (1.4) gph.
The Lazair Ultralight flew on 11 hp very Marginally. Was soon upgraded to 18.8hp, and people still wanted more hp. If you run the Lazair Numbers MTOW: 450 lbs = 204.1166 kg / 10 kg = 20.41166 kw needed = 27.37249 (27 hp) needed! The Solo 210 15hp each was the ideal setup. Today a pair of these Honda/Clone GX200's 4 Strokes Singles built for 15hp@5000rpm each is the ideal setup.
Stock Rotax 277UL Dyno Numbers with Rotax Exhaust. You will notice it was Avg +2.8hp per each +250rpm. It starts losing Power after 5500rpm. It's probably Rotax's Muffler is too Restrictive. More Prop rpm means more Thrust made. If your 277 Engine kept making +2.8hp per each +250rpm like it should at 6500rpm it would be making around 34hp!
So learn what you can do to make your Engine more efficient. Example: A 377UL is 35hp@6500rpm. The 377F/380F in a Sled is 36hp@7000rpm. A Stock 380HO is 48hp@7000rpm. A stock 380HO with an aftermarket Tuned Pipe Dynoed 57.26hp@7000rpm. It made 52-53hp@6500rpm. A 377F/380F/380HO is 368.4cc/7cc = 52.6hp@6500rpm!
Magasquirt EFI Open Source, you can build your own ECU.
Cylinder & Case Porting alone can Gain you 10-15% more Power. This guy is Good and also does the Engine Coatings.
Using Rotax Spec's and if Ported:
277 26hp +10% = 28.6 hp
377 35hp +10% = 38.5 hp
447 40hp +10% = 44.0 hp
503 50hp +10% = 55.0 hp
582 65hp +10% = 71.5 hp
The #1 Single in the World today is the Simonini Victor 1 Super, 400cc, 54hp@6500rpm using 9.5cr, 34mm Carb, with a Tuned Pipe. 70 lbs Complete. Same Engine just different Bore & Stroke, 362cc = 44hp, 382cc = 48hp. The 400cc/7cc = 57.1hp - 2hp = 55.1hp for the 9.5cr vs 11.5cr is about as Perfect as you can get.