Originally Posted by AdamFrisch
The new Skycatcher has a carb and carb heat. Don't think there's a FI option. This is on an aircraft that hasn't even been released yet - the newest of the new!
Not any product that was made in 2011 and has a Cessna label on it is neccesarily good. Using the Continental O-200 instead of Lycoming IO-233 (which isn't yet certified) was one of the major mistakes in the design of Skycatcher. Using carbureted Lycontinental engines on new trainer in 21st century is just bad, you can't even lean them
properly. OK, they do 100°F ROP without any problems, but if you want to get near optimum BSFC, most of them needs full throttle (well actually it's usually better to close it just a bit to create some turbulent airflow, which distributes fuel more evenly between cylinders), but for using full throttle at normal cruise powers (75% or below), you would need to climb to 5-6 thousand feet. As IO540 states, the altitude compensating carbs or fuel pumps do simplify things, but you lack the control over what kind of mixture do you want to have - best power for fastest cruise, deep LOP for maximum endurance, ... And using FADEC and "new" technology, such as diesel engines, the old engines remain competitive when comparing SFC, if you understand aircraft piston engine management and know how to lean properly. Besides, it's very difficult to destroy low-powered engines with leaning, especially if they are running a fixed-pitch prop: unless you don't see a problem with CHTs over 420-430°F.
Originally Posted by IO540
Engine efficiency is strongly dependent on the compression ratio
Agreed, but even then it's dependant on how much load you put on the engine. Thielert's Centurion 2.0 has a compression ratio of 18:1, but provides very little advantage in SFC over C172's "default" engine O320-D2J, which has a compression ratio of 8.5:1. I think the only really notable differences between the engines are: ability to use Diesel/Jet A-1 and constant-speed propeller, which gives a few knots increase in cruise speed, but FADEC has a very strange way of setting propeller RPM dependant on the load. I think if you set load below 20%, the RPM starts increasing (contrary to normal CSP), which actually means blades' pitch is going to very very fine and can indeed be felt with the aircraft slowing down significantly. Well speaking of electronics, Centurion 2.0 (one of the rare certified FADEC aircraft piston engines) doesn't have really the brightest history with clutch issues (although that was more of a problem on 1.7), the FADEC sometimes can't really decide on the RPM, especially when using somewhat medium loads with medium speeds on a C172 (say 45% load at 75 knots) and then it ends up by changing pitch and your passengers wondering (as well as you) what is going on
Basically, as was written lots of times: if there were any magic formula for creating mass of energy from nothing, it's likely that it would have already been developed, at least in some sorts of experimental version