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Most HP on a Kitfox?

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darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat Apr 07, 2007 9:39 pm Post subject: Most HP on a Kitfox?

I am curious as to what is the most HP (horsepower) that has been put on a Kitfox.  I think the most I have seen is the 125 from the IO240.  It is possible that some guys have done some work to their engines to get more than this but I am not aware of it.  So another question:



What is the maximum hp that the kitfox is rated for?  And, is the issue total hp from the engine or the weight of the engines that produce these larger hp outputs?  



I am asking because I am trying to determine what engine to use and I think I have narrowed it down to either a 914 turbo or the Ram Engines 140 hp EA81.  I am leaning toward the EA81 simply because of price and I do like the extra hp that it puts out.  However, Ram also offers this exact engine but with a low boost supercharger that kicks in around 4000 rpm and produces up to 200 hp at WOT (6200 rpm).  That redline is a bit high for my blood but 170 hp at 5500 rpm would be awesome!  What is the groups thoughts on this...can the Kitfox (this is a Series 7 by the way) handle this kind of power?  I am not worried about the weight as it is less than the IO240.



I am an engineer so I have contemplated using the static thrust produced by the engine and calcing the stresses in the frame members but thought it would be nice to see if anything like this has been done before.  After all, I have seen an IO540 (260 hp) in a Super Cub before...  



All thoughts and comments are very appreciated.

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smokey_bear_40220(at)yaho
Guest

Posted: Sat Apr 07, 2007 10:32 pm Post subject: Most HP on a Kitfox?

Hi Darin,



Some of the Ea-81 guys have had engines up to 160 HP

that I have heard of.  Mine is rated as 143 hp.  So it

has been done to 160 anyway.



 	  Quote: 	
		  From my testing, I find the prop gyro forces are

something to consdier too.  If you have a lot of
	


power, you need a prop that will handle it.  Prop

weight and gyro forces should be watched.  Could be

bigger stressers than engine weight alone.



I say this because I have some cowl scratches from my

spinner cause by my spin testing.  My CAP 140 prop

weighs 125 lbs.  My engine mounts are fairly soft

though....



If you can get the HP and stay under the IO-240 weight

with a light enough prop, it would seem a good package

to me.



What thrust in pounds are you expecting to see from

your desired engine?



Kurt S.  S-5 w/NSI 140 turbo



--- darinh <gerns25(at)netscape.net> wrote:



 	  Quote: 	
		   I am curious as to what is the most HP (horsepower)

 has been put on a Kitfox.  I think the most I have

 seen is the 125 from the IO240.  It is possible that

 some guys have done some work to their engines to

 get more than this but...so another question:

 

 what is the maximum hp that the kitfox is rated for?


	




 

8:00? 8:25? 8:40? Find a flick in no time 

with the Yahoo! Search movie showtime shortcut.

http://tools.search.yahoo.com/shortcuts/#news

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Brett Walmsley

Joined: 10 Jan 2006
Posts: 47
Location: Savannah, GA

Posted: Sun Apr 08, 2007 3:48 am Post subject: Re: Most HP on a Kitfox?

I don't want to make anyone mad here, but lots of extra horsepower is not always your best friend. It seems that certain airframes and gross weights have a HP number that will be in harmony. I think the kitfox family was designed around the 80 to 100 HP engine range. Remember extra horsepower means increased stress on the airframe.....and the pilot. Increased HP requires increased skill. Again, not trying to stir up a hornet nest, but flying these airplanes is supposed to be fun and relaxing.

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_________________
Brett
Model IV 1200/912UL

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sun Apr 08, 2007 10:00 am Post subject: Re: Most HP on a Kitfox?

Kurt,



I haven't looked into the thrust seriously yet so I don't know the answer to that.  I am not too worried about the 140 hp engine as I know guys have flown this on the Kitfox without problems...the 200 hp is a bit different but as I said, I would limit the rpm to something lower than the 6200 redline, say 5500 which should produce something around 170 hp.



Brett, 



I agree, horsepower is not everything but when you fly from high airstrips with high density altitues, sometimes it can be everything.  I also agree that these are supposed to be fun airplanes to fly...well, fun is in the eye of the pilot and I think the power in the backcountry of Idaho would be fun.  That said, I need to do a bit more thinking and research to determine the exact engine for my 7 but I know the 912S is not the one...I want better performance than this engine will give.  The 914 would be great but the nearly $27k price tag isn't so great.



Thanks for the comments,



Darin

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smokey_bear_40220(at)yaho
Guest

Posted: Sun Apr 08, 2007 1:04 pm Post subject: Most HP on a Kitfox?

Darin,



This was my thinking way back when I got my engine. 

It may be "only" 140 hp, but it stays there up to

12-14,000 feet, due to the turbo, before starting to

die off.  Makes it something like a normally asperated

180 HP engine at altitude.



I would agree that you should get what you can in HP

for the weight, keeping the weight down, then use only

what is needed for -this- takeoff.  Remember that if

you go heavy, you may end up dragging around some lead

that does nothing for you except keep it balanced.



The RAM system is worth looking at IMHO.



Kurt S.  S-5/NSI turbo



--- darinh <gerns25(at)netscape.net> wrote:



 	  Quote: 	
		   Kurt,

 

 I haven't looked into the thrust seriously yet so I

 don't know the answer to that.  I am not too worried

 about the 140 hp engine as I know guys have flown

 this on the Kitfox without problems...the 200 hp is

 a bit different but as I said, I would limit the rpm

 to something lower than the 6200 redline, say 5500

 which should produce something around 170 hp.


	




 

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n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Mon Apr 09, 2007 7:25 am Post subject: Re: Most HP on a Kitfox?

I think the Kitfox wing doesn't like to fly heavy, so regardless of the

power you put in it performance is gonna suck once it gets heavy. That

wing starts making a lot of drag when the loading on it gets high, and

then you'd need orders of magnitude more power to overcome the 

drag. So You might get 20 more hp in it, but if you get closer to Max GW 

in doing so you probably sacrificed all the power to drag. So a 20-30

hp gain, carrying an extra 100 lb.s might actually cost you performance.



Based on flying mine, that's my unprofessional conclusion. 



Jeff Hays

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