I was perusing Barnstormers and came across and ad for a Kitfox SupeSport experimental. The ad stained that it has a -200 and burns less gas than a Rotax 912S. The -200 runs off of 100LL only, right? I suppose the higher octane will give greater energy per volume the way diesel does over gas.

So in the same plane at 100 mph I can believe that the -200 will burn less per hour, but does that equate to a lower cost? Is the gph savings equal, better, or worse than the $pg savings of 91 octane mogas over 100LL?

I feel like the benefit of a folding wing plane is the ability to keep it at home in a garage (my potential future location is about $500 per month for a hangar with over a year waiting time). The ability to use mogas is a pretty convenient association with the take home plane as you can fill it up at the gas station on the way to go fly.

There are so many cool planes out there though!

Cooperd0g wrote:
The -200 runs off of 100LL only, right?

I think I just wet my pants laughing.... NAAHHHH there's never been any O-200's run on car gas !

Cooperd0g wrote:
does that equate to a lower cost?

The ability to use mogas is a pretty convenient association with the take home plane as you can fill it up at the gas station on the way to go fly.

IMHO the O-200 should in most cases be cheaper to own and operate than the Rotax, just on parts alone if nothing else. If you think O-200 parts are expensive, just talk to anyone who has ever bought Rotax parts!

This has been discussed several times, but the ethanol fuel problems lie mostly in the fuel system, not the engine. You can put the right kind of rubber O-rings and seals in the engine ("Viton" if I recall, but CHECK this with someone like Harry Fenton first before you risk your life on my offhanded opinion) and it will withstand ethanol. The old-school neoprene rubber fuel hoses, valve seals, tanks, etc. are the causes of more ethanol-related issues than the actual engine itself. Remember, all those thousands of ultralights and millions of cars run on gas with ethanol. It's not the big metal parts in the engine that a re the problem, it's little stuff like gaskets and O-rings.

This has been mentioned already, but you can remove the ethanol out of the car gas, and/or purchase off-road gas without ethanol. To take the ethanol out, you have to invest a little money in a couple of mixing/settling tanks and some sort of a pump, and invest a little extra time in your fueling procedure.

An 0-200 is never going to come close to the fuel burn of a 912S, and it may give you pause and reason to reconsider if the person selling the plane is telling you this. He is either mis-informed or a used car saleman on the side. Maybe he meant to say the 0-200 is heavier?? Less expensive parts for sure, but the 912S is, I'm sad to say, worth the outrageous sums they get for them. Parts cost arn't a big problem if you never need any but yeah when you do (I havn't, in 845 hours of totally trouble free flying with mine) it's going to take some of the money saved in the fuel costs. Planes the size of the Kitfox, Highlander and the S-7 take a pretty big hit from the extra weight of an 0-200. They have less range, less useful load etc. etc.

Higher octane does NOT equal more energy. Quite the opposite actually. Higher octane fuels burn slower and are harder to detonate which makes them useful in high compression engines (which the O-200 is not.) The O-200 was originally designed to run on 87 octane. I believe there is an STC for unleaded fuel. I don't know the specifics of it.

Now as to the economy of one engine to another, I haven't a clue, sorry.

Joshua

On a J3 cruising at 80-81 mph at 2350 rpm on car gas, my O-200 burns 4.3 gph and my buddy's burns 4.7 gph. I don't know what the 912 burns.

JimC wrote:On a J3 cruising at 80-81 mph at 2350 rpm on car gas, my O-200 burns 4.3 gph and my buddy's burns 4.7 gph. I don't know what the 912 burns.

At those speeds, which I spend a lot of time at, it's 3.2 gph in my S-7S. 65 or so 2 to 2.5 gph, 95 a bit over 4.

joshuajayg wrote:Higher octane does NOT equal more energy. Quite the opposite actually. Higher octane fuels burn slower and are harder to detonate which makes them useful in high compression engines (which the O-200 is not.) The O-200 was originally designed to run on 87 octane. I believe there is an STC for unleaded fuel. I don't know the specifics of it.

Now as to the economy of one engine to another, I haven't a clue, sorry.

Joshua

What he said. The energy density isn't greater, it burns more slowly and evenly. Less chance of detonation. The rotax is more fuel efficient. Whether the savings in fuel makes up for the additional expense of parts and cost of engine, I don't know.

courierguy wrote:

JimC wrote:On a J3 cruising at 80-81 mph at 2350 rpm on car gas, my O-200 burns 4.3 gph and my buddy's burns 4.7 gph. I don't know what the 912 burns.

At those speeds, which I spend a lot of time at, it's 3.2 gph in my S-7S. 65 or so 2 to 2.5 gph, 95 a bit over 4.

My numbers are almost identical with my S-6ES.

courierguy wrote: An 0-200 is never going to come close to the fuel burn of a 912S, and it may give you pause and reason to reconsider if the person selling the plane is telling you this. He is either mis-informed or a used car saleman on the side......

I agree that at equal speeds the O-200 is probably never gonna get down to the fuel burn of a 912-- but are you gonna reject this airplane just cuz the seller engaged in a little bit of salesmanship?
The Kitfox people told me years ago that an O-200 powered KF isn't gonna be able to meet the LSA weight limit, but otherwise there's no reason not to run one as long as the CG & useful load work out. Years ago KF built a model 7 "Outback" with an O-200 & about a 1500# gross weight, and it looked & sounded like a pretty awesome little airplane. The newer "Super Sport" looks pretty similar to that model 7-- I'd love to have one on t/w gear with an O-200 or maybe a stroked C85. I'm sure the Rotax is a fine engine, but I'm pretty old school & (no offense) just prefer a "real airplane engine".
The O-200 in my old C150 ran great on pre-ethanol 87 octane regular-grade car gas with it's 7:1 compression ratio. Up to 8.5:1 should work fine with 92 octane premium. IMHO distilling out the ethanol in E10 is not practical on a large scale, but at least around here (pacific NW) there are still a few sources of E-zero mogas & in fact it seems to be on a comeback (hopefully).

My hamster told me that a 9.5:1 O-200 will run fine with no detonation on 92 octane mogas with alcohol as long as the fuel lines are suitable for alcohol.

My 912UL (80 hp) will burn 3.3 gph at 5500 rpm which is about 105-110 mph in my Kitfox IV.

On a J3 cruising at 80-81 mph at 2350 rpm on car gas, my O-200 burns 4.3 gph and my buddy's burns 4.7 gph. I don't know what the 912 burns.

The J-3 was built to fly. Not fly fast-not fly far. It is aerodynamically a catastrophe, but it generates a lot of grins per gallon.

Other newer slicker planes do to, of course.
lc

I used to do off-field search and rescue flying in my J3. Never found anything better for the purpose.

I run my 912S at 5000 RPM, which in my 701 gives me about 80MPH cruise. I have the prop set at 11degrees, so it's pitched to favor takeoff and climb. At that power setting I consistently burn 3.5GPH of unleaded premium.

My hamster told me that a 9.5:1 O-200 will run fine with no detonation on 92 octane mogas with alcohol as long as the fuel lines are suitable for alcohol.

Pretty smart hampster.
BTW, was in Denver at the Peterbilt place for a few hours mid day Friday. Sure glad I don't live there and have to breath that brown air. Was thinking, thank goodness for ethanol or might be much closer to Bejing air quality.

Correct me if I'm wrong but all this talk of props and fuel burn doesn't mean much without referring to the altitude....yesterday flying to Afton for breakfast, I was at 5100 rpm on the little Rotax, with an indicated airspeed right at 90, at 9500'+, real cold also, like in the 20's!

I vaguely remember the last time I got to play at sea level, 8 years ago I think, it is astounding the difference it makes (duhhhh) but being able to generate high indicated speeds, relatively, with little throttle, is pretty easy in that thick goopy air, my earlier reference to my fuel burn/speed was for 8,000' or so.