Continental 65 HP or more, Ok on Model 4 ????

[rogerh12]

Howdy Gang;

Does anyone know of someone that has installed a Continental 65 HP on a KItfox-4-1200, or perhaps something bigger, like the C-85?

I think the 65 HP version would provide enough power for a 1050 Gross plane, but a 1200?? Would the engine just be too heavy for the noise, or to big to fit???

I think the A65 was much lighter than the C85 or 0-200, and they are fairly cheap, but I would want it with electric start, if it's possible to get one that way.

I am considering this, or the new 2300 cc VW conversion.

Let me know what you think !!!!

Roger

[jtpitkin06]

Roger,
We get this question every four weeks or so. “What do you think about using an XYZ engine in the Kitfox?”

First, you need to know the answer to, “What is your motivation for using an alternative engine?” The term “alternative” here applies to any engine not directly supported by the factory.

Most of the time, it is cost. Many times the builder already owns an alternative engine and thinks it might be a good match for the Kitfox airframe. Sometimes it may be someone on a budget who is trying to build a Kitfox cheaper than when using a Rotax.

Sometimes, the reason is brand loyalty. You may just prefer Continental or VW over Rotax. In that case there is no amount of logic that will sway you.

When installing alternative engines there is more than the cost of engine acquisition. There is the firewall forward issue.

Be aware, there is little factory support for most of the engines you mention. You will need to find a suitable cowling to modify as the length will not be the same to the spinner plate. You are on your own for the engine mount, the firewall, all of the firewall forward accessories, baffling, and fitting the cowling. If your starter bumps the fiberglass, don’t call the factory and ask how to solve the problem. It’s not part of a package they sell and you can’t expect them to do the work for you. You will need to fabricate an exhaust system, intake system, carb heat box, and more.

If you decide to use an alternative engine, you need to be quite focused on your choice and have solid reasons for not using the Rotax. If cost is the motivating factor and you don’t already own an engine, you may be surprised at the final expenses. You indicate you can get a used Continental for cheap. Be sure to include the cost of overhaul or compare your used engine to the price of a used Rotax, then plug in the above firewall forward expenses.

Are you considering this engine for a new airframe or swapping a Rotax two stroke out of an older airframe? The current Model IV is designed for 80 to 100 hp. It is a completely different fuselage from the early Kitfoxes that flew with lower hp motors. Read the Kitfox history to understand the evolution.
If you are considering this installation in a new Classic IV, you should look seriously at something with an appropriate power rating. The 65, 85, and 90 Continentals do not have the power to weight performance to warrant their installation and you seriously degrade the resale value of the aircraft.

Know the answer to, “What is your attraction to the Continental over the Rotax?”

Next, you bounce over to the VW campsite. What is your attraction to VW over the Rotax?

Yes, almost any engine in the 100 hp range will fit inside one of the larger smooth cowlings. Very few will fit inside the round cowling because of width at the front.

Are alternative engines too heavy on the nose? If you do some homework you will discover Kitfoxes flying with O-200s, Lyc O-235s, Subaru EA81s and others. A Rotax equipped Kitfox has the engine mounted pretty far forward. There is a lot of room for a shorter engine like the Continental to shift aft.

All the weight and balance information is freely available. If you know your engine weight and dimensions you can accurately predict the CG. If this is beyond your capability I would not recommend your pursuing the project.

All of the above is not just an opinion; it is actual experience. I am installing a Corvair engine in my Model 7SS. As one who has done this I can tell you it is not an easy task fitting a cowling and engine mount for an alternative engine. The windshield, glare shield and cowling all must join together and fit flush at the base of the windshield. The cowling front end spinner height and depth must match the engine. Any clearance issues are problems you must deal with alone. Your custom mount must hold the engine at the proper height, depth, angle, and not interfere with intakes or exhaust. Everything under the cowling is custom fitted.

This is not to say it can’t be done. It can be done and can be very rewarding at the same time. Engineering the components is part of the challenge. However, if you are even the least bit weak in being able to design components, systems and solve mechanical problems using aircraft quality standards and techniques, I recommend you stick with one of the supported engines.



John Pitkin
Greenville, Texas

[rogerh12]

John;



I guess the VW is now an offically supported engine, at least on the Kitfox model 3 & 4. I say this as Great Plains VW has a firewall forward kit for the kitfox, which includes Engine, Engine mount, Intake, Exhaust and aftermaket cowling (made by a guy in WI), all predesigned to work together. There are also several flying examples I have seen on the internet anyway.

I have used the VW in a few planes before, and am familar with it's strenths and weaknesses, and issues in installation and cooling. It's probably the way I am going right now with my model 4, however, I guess I am really asking more about A65 or C-85 installs, and how well that worked out.

Thanks again

Roger

[rogerh12]

Avid Flyer;

I am not knocking the 582 as an option for people, I had one on my kitfox model 2 and yes, it had good power, light weight and I really didn't have to do anything two it, mechanically. It was also the heaviest engine the airframe could take, and still have a decent payload. Having said that, I have other two stroke engines on motorcycles, boats and others things and have learned some things about two strokes.

1) They fowl the plugs and can be very had to start.
2) They typically have only one or two cylinders, and if one goes out, you’re not going anywhere (or worse)
3) They drink fuel like mad.
4) They need Oil and Gas, and without oil in the fuel (such as when my oil injector pump failed on my Yamaha RD 350 at 60mph) the engine will suddenly seize.
5) Water cooled two strokes can seize if cooled too quickly (that’s how I acquired my kitfox, the owner had a hard landing after he shock cooled the engine in a power off decent, it seized on him.)
6) They rev high and wear out fast, loose compression or shell out the roller bearings and maybe send the rod through the case
7) The sound funny, make lots of smoke, get oil on everything and smell bad (and are just messy)
8) Are expensive to fix (compared to a auto 4-stroke)
9 ) Require special mail order parts (can’t just go to NAPA).
10) And Finally, they quit running too easy (I.E. part of the tuned exhaust falls off and the engine dies).

Though any one of these reasons is not enough to make me go 4-stroke, combined into a group of 10, and installed in an airplane I will be flying, they are enough to make me go 4-stroke. I understand 4-strokes are not an option for ultra light aircraft, but the kitfox-4-1200 has the capacity for something heavier, with better fuel economy, lower cost, over all reliability and perhaps more power.

Of course, all comments are welcome.

Roger

[HighWing]

All good comments. I especially liked John's thorough review. One thing possibly was not mentioned - performance. I doubt there is an optional engined IV out there that will even be close to one with a 100 hp ULS or even the 80 hp 912 UL. John has gone through the engineering and his advice is definitely worth a listen. The factory supported a Subaru conversions when I was first building. I considered it - this was back in 1995 or so. There is a long histrory in auto conversions in the Kitfox and a few are still flying with their original builders. I am in the relatively final stages of a IV project and it will have a "previously owned" 912 UL - 80 hp. It was a 150 hour engine in a pusher style home built that fell out of the ceiling - literally - in a shared hangar. Being high mounted there was no prop strike. No S for me as I can't justify the cost. The old money thing. And the S model is not entirely without issues. My guess is that I will have right at $12 or $13,000 in front of the firewall. And based on almost a thousand hours in a previously owned 912 powered IV, I expect it to perform quite well.

As an aside, I put in a year and a half helping a friend who was building a Lancair IV. When he had it signed off, the inspector was a close to retirement FAA guy that had spent a career in Alaska as an accident investigator. His favorite subject was the otherwise survivable crashes that turned into fatalities due to the missiles (baggage) stowed in back. The most striking - no pun intended was the fishing pole that impaled a passenger in an otherwise survivable crash. How does this relate to the current discussion? It was common practice in the old days to put a heavy battery in the tail secured with adel clamps to bring the alternative guys into W/B compliance. Be careful

Lowell

[rogerh12]

Lowell;

I myself am not a fan at all of batteries in the tail cone. I think they should, if at all possible, simply go on the firewall. After you add up all the additional weight for extra length cables, thicker cables and a larger capacity battery required to install a battery in the tail cone, you lose most if not all advantages of having the batteries back there.

I think a better idea, and the one I have gone with, is to install a small battery on the firewall, with short cables. This creates a simple and light weight install, that can still efficiently deliver the Amps to the Starter on cold days. Doing this way, I am probably looking at half the installed weight as compared to a remotely installed battery. Then, I take the weight I saved, and place it as far aft in the tail as possible, to be used a counter weight to the engine. Handling the battery this way should give me the same installed weight as doing it by placing the battery in the tail cone. But the really beauty of doing it this way is that I can easily add just the right amount of counter weight to shift the CG back into spec, and not an ounce more (I have a plate welded just forward of the tail spring mounting bolts, I install lead “rounds” on it to act as counter weights).

CG way out of spec? Fine, just add more counter weights, a simple and quick fix. Yes, the plane might weight a few more pounds more when I am done, but then again, probably only a few. For me, that ease of control over the CG is worth a couple extra pounds, and the peace of mind knowing I can fix a noise heavy engine install in a matter of minutes, if needed . This is of course a lot different than trying to fix a recently completed kitfox with a CG problem by trying to move the battery all around the fuse, just to find out it’s still not enough.

Would you agree?

Roger

[Av8r3400]

I've been watching this thread to see where it goes. Just a couple of thoughts:

Hand-Propping: I have a good friend with a Champ. C-85 with no electrics. It props nicely and works fine in that plane. Keep in mind, that plane was designed for the (220# +) weight of the Continental.

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. VWs work in a Thatcher or Sonex, but I have never heard of anyone even remotely satisfied with one in a Avid or Kitfox. Not to mention their actual reliability record is at best, spotty.

Continental (C-65 through O-200) in a model IV: IMO generally a bad idea. This motor even without electrics is too heavy. This airframe was designed around the 582 Rotax (~90#). The 912 is a good substitute (~140#). Anything more is too heavy, period. A friend of mine had a Subaru in his IV and once all the ballast that was needed was added to the tail, he had a poorly performing single seat airplane. His install was at about 230 pounds.

Finding a used, reasonably priced 912 is not impossible. Another friend of mine just bought one (80 hp 912UL, 120 hours TT) for $6500.


Innovation is a good thing. But in this case, IMO, you will be very disappointed in what would otherwise be a great little plane.

[DBVZ]

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. .

More discussion on this point, please. Someone with a VW powered Kitfox or Avid want to rebutt? I saw one with a 76HP Great Planes, that reported climb rate of 1000 (solo) and high cruise of 115MPH (just about 100kts) TAS at 4500 - 5500. Is that not "acceptable" performance for a Kitfox IV?

[HighWing]

I bought my first Kitfox Model IV kit in 1993. I have no personal experience with VWs in IVs, but have been involved with foruns such as this one since 1994. (Early forums were email lists where we recieved every post and most of us read every one - 582, Subaru, Rotax, VW, Model I,II,III,IV,V 6,7, and learned a lot, even about stuff we were not particularty interested in.) Kitfox has been around a long time as have VW conversions. If it was a mix made in heaven, I doubt you would have to ask for a rebuttal, as the forums would be full of talk and Model IVs would be full of VWs as an option to the much more pricey Rotax. Av8r3400 is spot on in his comments from a historical perspective. The issue with the Model IV vs. the Sonex has to be with weight and prop length limits if direct drive and the round cowl blanking most of the prop, where the Sonex has a smooth cowl and lets the wind fly. This phonemenon is an issue also with certain prop designs - Powerfin on the Model IV.

I know there are guys that believe that they will be able to manage the issues, but, I am unaware that anyone has. You can be sure that if the combination works and works well, there would be tons of the good news on the internet. I must say here, though, that if there is someone out there who has a VW powered IV and it is a screamer, Don't keep it a secret. Let us all know and we skeptics will stand corrected.

Lowell

[rogerh12]

Mr. Bill;

Thanks for posting the pics of the Continental. I see there is some real space between the firewall and the back of the engine, so I guess the engine weight was not really and issue CG wise, otherwise the engine would be mounted closer to the firewall if it was too heavy.

However, I am not too clear on the engine modification. Are you saying this A-65 now has the displacement and power of the larger A-85? It is still a hand prop'ed engine, correct?