Ultralight's/Airplanes are used at a more continious rpms, usually 75% of Max Power for hours. Sleds Speed up, slow down, stop, speed up, slow down stop, etc. If ran up to 7000rpms, it probably would make 60hp, so going from 34mm to 30mm cost 10hp on the same engine. Later 550F's only come with 30mm Carbs, and are rated 58hp at 6800rpms. The Carb Size used does play into the HP made. The Carb Calc says the 293cc run at 7800rpms needs a 40cfm Carb.
Like the 293cc Skidoo Twin run at 7800rpms, the Peak Flow Calc says Peak Intake Flow Rate is, 73 cfm. That's Why, I'm asking, is there a way to figure their CFM Rating? The Higher Rpm's you Turn them the more Air they need. We have Rotax UL engines with mainly, 34mm, or 36mm, and then we have there Snowmobile counter parts with any thing from mainly 30mm, 34mm, 36mm, 38mm, 40mm, 44mm. In these Rotax UL/Snowmobile 2 stroke Carbs we don't. I understand the CFM Basic's for Auto Carbs, we have them CFM Numbers to work with. Like a 293cc Twin run to 7800rpms requires a 40cfm Rating.
How do you figure these 2 Stroke Carb CFM Rating? They are just listed as 30mm, 32mm, 34mm, etc? I started this thread on Home Built Airplanes, and haven't gotten a good answer yet.
