Kitfox Model II (950) Engine options

[estepec]

Hi , what are my 4 stroke options for a Kitfox II 950 gross weight? Currently with a KFM 112 and needs to be replaced. Thanks for your input.:)

[Mnflyer]

Check out the HKS its a great engine I have 490 hrs on mine in a Model III 1050.

[Geowitz]

I second the HKS 700E!

[Dravenelle]

hks is very good engine but just the part is
not easy to have ....japon is not rapidly

but with a good engine, you don't need a part

Dave

[SkyPirate]

Some have used the GEO conversions with a raven redrive

[SkyPirate]

Im waiting to see if someone is going to use the new ecoboost fiesta motor, 3cylinder 100 hp plus motor that will fit in a suitcase :)

[SkyPirate]

Ive only seen one, but it was a smaller harley motor mounted on the nose of a plane (ultra light)

[Geowitz]

Im waiting to see if someone is going to use the new ecoboost fiesta motor, 3cylinder 100 hp plus motor that will fit in a suitcase :)

:p Maybe we can get him to do all the research for us... But seriously, it depends on whether you want to spend a lot of time doing a retrofit or get back in the air quickly. The HKS has a lot more support than any of the other 4 stroke options except the 912 and will get you back in the air quicker. Engine mounts and cowling issues aren't as big a deal.

[SkyPirate]

Possibly George :) he wanted options, just throwing some out there, the bigger the " box" of options, the better chance one has to meet their needs, financially, time, ability, as for research boeing uses inline 4 cyl. auto 2 liter motors on one of their hydro planes, experimental yes :) and of course Boeing has allot more in their " experimental fund" then we do, it's no different then the geo conversion with exception to injection is more common now then when the geo's where first used

[SkyPirate]

There is another option i just remembered, Larry Smith uses an industrial motor with his own redrive and his own prop ( culver) on his " backyard flyer" i havent followed what he has done as for engine options on heavier then ultralight planes, but he can retro fit a redrive system on just about any option you choose

Larry Smith 'Valley Engineering" 1 (573) 364-3611

Or do a search for " backyard flyer"

[Geowitz]

Skypirate - Didn't mean to come off that you shouldn't suggest it. Was just mentioning the differences ;)

[SkyPirate]

No problem George :) i didnt take it wrong, just thinking of options :)

[estepec]

Thank you all for the responses. Currently have a KFM 112 and looking for a replacement. Seems my best choices are a HKS and a 912. I've seen the used market for both and the used prices are the same. If you had a choice between the two, both at the same price and to refit a model II, what would yours? Again, thank you for your responses.

[SkyPirate]

Being its a model 2 id go for the lightest option

[SkyPirate]

The kfm 112 produces 62 hp (46 kW) at 3400 rpm for three minutes for take-off, 60 hp (45 kW) at 3200 rpm for five minutes and 54 hp (40 kW) at 3090 rpm continuous,..it weighs 119 including the starter, alternator and carb,..
fuel burn 4.3 US gal/hr) at full power, 2.97 US gal/hr) at 70% power

912ul 134.2 lbs 79 hp burn rate in a model 2 is going higher then in a 4 because more drag on the 2 i'd guess 5 plus n hr
I don't know much about the hks as far as weight,..fuel burn..etc
Wikipedia says
700EInitial version, normally aspirated and producing 60 hp (45 kW) at 6200 rpm for three minutes for take-off and 56 hp (42 kW) at 5800 rpm continuously.[1] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-Cliche-1)[3] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-HKS700E-3)700TTurbocharged (http://en.wikipedia.org/wiki/Turbocharger) version with a 62.5 mm (2.5 in) stroke and a compression ratio of 8.8:1, that produces 80 hp (60 kW) at 5300 rpm for three minutes for take-off and 77 hp (57 kW) at 4900 rpm continuously. The engine's dry weight is 57.5 kg (127 lb) equipped with electrical system, electric starter, fuel injectors, gearbox, exhaust system and turbocharger. The initial time between overhauls is recommended as 500 hours, but this is expected to rise with operational experience.[4] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-HKS700TIntro-4)[5] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-HKS700TSpecs-5)
The reduction drive is a choice of two integral gearboxes: the A-type gearbox has a 2.58:1 ratio and can accommodate propellers of up to 4,000 kg/cm2 inertial load; the B-type gearbox has a 3.47:1 ratio and can accommodate propellers of up to 6,000 kg/cm2.[1] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-Cliche-1)[3] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-HKS700E-3)

The 700E burns 9 L (2.4 US gal) per hour in cruise flight at 4,750 rpm. The recommended time between overhauls (http://en.wikipedia.org/wiki/Time_between_overhaul) is 800 hours, although this is expected to be increased as experience is gained.[3] (http://en.wikipedia.org/wiki/HKS_700E#cite_note-HKS700E-3)
Producing 60 hp (45 kW) at 6,200 rpm for three minutes for take-off and 56 hp (42 kW) at 5,800 rpm continuously

Dry weight: (121 lb)

knowing this,,between the 912 and the hks,..the hks would be a better swap and have similar weight /fuel burn

Chase

[SkySteve]

I know nothing about all the technical stuff. I do know I have a model I, highly modified, with a 912A, 80hp. Wouldn't trade it for the world. Love it.

[SkyPirate]

what are your specs Steve? fuel burn..cruise etc

[SkySteve]

Cruise at 100 mph burns 4.5 gph.
Cruise at 95 mph burns 4.2 gph.
Cruise at 90 mph burns 3.2 - 3.5 gph.
Cruise at 85 mph burns 2.8 - 3 gph.

Home airport is at 4,200 MSL. Most of my flying is between 5,500 - 8,500 MSL.

[SkyPirate]

impressive :) I figured the model 2 would burn more because of the underchambered wing..higher speeds higher drag,,unless you have different wings on then model 1 wings ..that's pretty good spec's :) thanks

[SkySteve]

Mine has model III wings.

[SkySteve]

Mine has model III undercambered wings.

[DesertFox4]

If I couldn't find a nice 912 , I'd go with the HKS on Geowitz's and Mnflyer's
positive experience.
I have flown Steve's model 1 with the 912 and found it an excellent performer with two good sized guys in the seat and a good load of fuel on board. Having 1,200 plus hours behind just my own 912, not counting all the others I've flown, I can highly recommend the 912 with the HKS as a very good option based on the above mentioned members experience. It's nice to have two good choices to replace your KFM. I think you'd be happy with either.

[SkyPirate]

as for airfoil the model 2 and 3 are the same right?
if my memory hasn't failed me,..the difference's ..model 3 had both wing tanks option where the model 2 had right wing and panel/dash tank,..or at least my 2 had right wing and panel/dash tank

[RobS]

If you haven't seen this yet, there is an HKS on Barnstormers.

HKS 700E, 1000 HOUR TBO • $6,000 • AVAILABLE FOR SALE • 102 HOUR TT, 3.0 GEAR BOX, TYPE II EXHAUST, HKS 700 E, COMPLETE, LOW RIDER ENGINE MOUNT AVAILABLE. • Contact Daniel Kessinger, Owner - located Munfordville, KY USA • Telephone: 270-473-0690 • Posted September 17, 2013

[Geowitz]

My opinion :)...

Brand new the HKS is about 5k cheaper, but it always seems, as you mentioned, that the used HKS's and 912's are around the same price. It seems the HKS holds a larger percentage of it's value and there aren't as many available as "used" on the market.

If you're looking to get back in the air quick and you find a nice 912 I would probably go for it as getting a mount and accessories for a model 2 are relatively easy, but if a used HKS pops up it should suit you fine as well. Just be sure to learn about the lineage of HKS's and the early serial numbers.

The Rotax will definitely give you better overall performance in climb and speed, but with a slight weight and fuel burn penalty. If your mission is to just tool around you can get great economy out of the HKS with certainly acceptable climb and cruise for a model 2. In my opinion it would more mirror the performance of the KFM, but slightly better because of the prop options the HKS allows with the gearbox.

I personally think either will be an improvement over the KFM.

The one below deserves serious consideration, but confirm the gearbox ratio and that it fits your mission and the serial number is later. Lots of info on the net about the gearbox choices and how it affects prop selection.

[Av8r3400]

912ul 134.2 lbs 79 hp burn rate in a model 2 is going higher then in a 4 because more drag on the 2 i'd guess 5 plus n hr


Actually the fuel burn would be exactly the same regardless of the aircraft. Per my engine: Cruise power (5000 rpm) is ~3.5 GPH and full power (5500) would be ~4.0 GPH.

Your speed at that power setting may vary quite a bit, but the fuel burn would be the same.

[SkyPirate]

cool on that Larry,..the 5 I'm buying ,..I was told 4.8 gal per hour at 110 cruise,..I hope your 4.0 gal per hr is closer to true :) less fuel burn is always better

[Dave F]

Thank you all for the responses. Currently have a KFM 112 and looking for a replacement. Seems my best choices are a HKS and a 912. I've seen the used market for both and the used prices are the same. If you had a choice between the two, both at the same price and to refit a model II, what would yours? Again, thank you for your responses.


If you can do 912 for same price as the HKS -- it is a hands down choice to go with 912.

reasons - more HP - more dealers/ support

Kitfox 2 is 950 lbs Gross weight.
Kitfox 2 should be around 450 to 500 lbs max empty with a 912 add another 60 lbs so up to 560 or so......... Still leaves you 390 load .

Performance would be awesome - likely about 1500 to 1800 fpm climb
cruise would be 95 to 110 -- VNE on KF 2 might be breached pretty easilly.

Good Luck

[LSS]

How about the 670 Rotax being put together by Rotax Rick ?:)

[Dave F]

I have not tried Rotax Rick but I have heard some positive and negative.

I think that I would like to try one of his engines.