whats the heaviest motor ever put on a Kitfox

[Captaindean]

I was watching a couple videos from Oshkosh this year about the different motor that were on display and came across the delta Hawk seems like a cool motor I am just in the beginning stages of research on a kitfox plane and if I am going to build one or not. I live in Hawaii and trying to get one shipped is going to be crazy expensive so I am trying to save $$$$where I can the deltahawk is really heavy though not sure it would make a good candidate or not since dry it weighs like 340lbs.
been looking at all the auto motors but cant wrap my head around them being a good long term solution with the High RPM they run. Might be wrong but a automobile engine usually run at 2000-2500 or lower when cruising but in cruise mode I am seeing them on youtube run in the high 4000's.

[Captaindean]

Guess i should have listened more carefully to the video they want $$$$$$$ for that motor i think ii could buy 2 kitfoxes for what they want for the motor

[KitfoxSS]

Car engines and Airplane engines have pistons and are internal combustion engines.
That's about where the similarity's end.

A car engine is designed to operate in the low rpm range coupled to a transmission with periodic high rpm pulls to make maximum power for brief moments of acceleration.
A car engine when cruising down the road is not making much more then 20 to 25hp at any given time just maintaining 65mph.

An aircraft on the other hand has to not only propel a plane forward with thrust, it must also do so with enough force to generate wind that allows for the creation of lift. Enough so to at least over come gravity's pull and over come the drag made from the plane going through the air. This requires more hp then merely rolling a car along a road where only wind drag is being dealt with on a car. As simple as I can put it anyways. Higher HP is needed at any given time thus the higher rpm being required. They are two different things requiring two different applications of engine use.

An airplane engine is designed to run at nearly maximum rpm all day long with out issue.
A car engine is not.

Now, yes, some people have used car engines on airplanes and had good results but car engines are typically heavier as you've seen. So why take the weight penalty for an engine that was not designed or intended for constant high rpm use as needed in an airplane?

It hard to beat a Rotax, 100hp at 140ish lbs dry weight.
You might want to look into the Yamaha RX1/Apex motor. 150hp at not much more then the rotax in weight. They are abundantly available in Yamaha Snow mobiles and it seems to be becoming a more frequent choice for engine in airplanes. And they can be picked up for far cheaper then a Rotax 912 will cost you new. Of course you'll have to fab and make parts to fit it so it will still cost you some. I know one guy on youtube is building a Kitfox with this engine, he's having to fabricate motor mounts as Kitfox Aircraft does not have a FWF package for this engine. But Just Aircraft has put them on a few of their planes and I believe their is a FWF package for their aircraft now. So maybe in time we might get one for the Kitfox. In a few years time I may consider going this route if I end up building a kitfox myself.

Best luck in your planning and search.

[PapuaPilot]

That is probably similar to a dressed out IO-240. Yours looks so much cooler though.

[efwd]

I'm not sure of the weight but John McBean told me that the heaviest engine they have installed on the Series 7 was the Rotec 7 cylinder radial. That was three or four years ago. Since then they have installed the 915 as well as another larger engine on the STI plane. I don't recall what engine it was. I was at the factory at the time that engine was in a crate. 180hp if Im not mistaken. A guy had his KFS7 at Oshkosh last week that had a 9 cylinder Rotec.

[Mesteve]

I chatted with the guys at Rotec (maker of the 7 and 9 cyl radials). They said the 9 cylinder engine basically made it a single seat airplane since with 2 real size humans, they only had capacity for about 45 minutes of fuel. That ended the conversation for me... Even the 7 cylinder weighs about 80 pounds more than the 912. As much as I love the look, pretty much squished that dream from a realistic use-case perspective.

[Slyfox]

I'm not sure of the weight but John McBean told me that the heaviest engine they have installed on the Series 7 was the Rotec 7 cylinder radial. That was three or four years ago. Since then they have installed the 915 as well as another larger engine on the STI plane. I don't recall what engine it was. I was at the factory at the time that engine was in a crate. 180hp if Im not mistaken. A guy had his KFS7 at Oshkosh last week that had a 9 cylinder Rotec.

absolutely my thought and there are people putting it in the 4. how do you spell heavy... HEAVY. so heavy you have to put the battery way in the back and I'm sure some more weight back there. yes they will fly, but how they handle next to my 4 is a serious question.

[jmodguy]

I'm not sure of the weight but John McBean told me that the heaviest engine they have installed on the Series 7 was the Rotec 7 cylinder radial. That was three or four years ago. Since then they have installed the 915 as well as another larger engine on the STI plane. I don't recall what engine it was. I was at the factory at the time that engine was in a crate. 180hp if Im not mistaken. A guy had his KFS7 at Oshkosh last week that had a 9 cylinder Rotec.

I believe you were thinking of the O-340... The videos of John flying it looked pretty good 👍🏻

[David47]

Just out of curiosity Bruce and Phil, what are the stick forces like on landing with a fwd cg i.e. are they heavy ?. And have you ever felt close to reaching the limit of elevator power when in that config ?.

[airlina]

David , It was very important to me to be able to trim out all forces on final when at my over the fence speed, so I put anything with weight aft (battery, elt, big fat boost pump etc.) While this tactic got me close to that goal, the trim assist kit put me over the hump and allows me to trim to hands free on final when fully configured at 55 mph. Actually still have a touch of up trim left when its all said and done. So to answer your questions , no heavy stick forces and no I do not run out of elevator , I have full authority for a full stall 3 point landing. Another thing that helped was installing a elevator gap seal, hard to describe , but it gave the elevator a touch more authority right at the end of the flare. With your engine package that is lighter than ours you should be fine . Bruce N199CL