912 IS retrofit in Kitfox?

[SWeidemann]

I am wondering if an engine change in my Kitfox 5 Vixen (currently with a 912 ULS) to the new fuel injected 912 IS could be easily accomplished? I know the fuel injected version costs more however it is less maintenance and uses less fuel.

Info and/or opinions?

Skot

[Danzer1]

I'll take a WAG at this (and that's all it is).

Assuming you do all the work and sell the ULS.

New 912is all in, including exhaust, rad, alt, etc. a hair over $28,000 new.

Misc. changes: plumbing, electical, panel (ems support), etc. $1,000 (?).

Sell ULS in good shape, complete, reasonable hours and log, maybe $12,000 (?)

Net plus $17,000

Rebuild carbs (yourself) every year for 10 years $300 x 10 = $3000

New net plus $14,000

Assume all other maintenance is the same.

Assume fuel savings of 1.0 gph (?) at $5.00 a gallon (?)

$14,000/5 = 2,800 hours of flying/10 years or 280 hrs a year to break even over a 10 year span.

Other factors would be:

Increase in value of 912is equipped aircraft over uls - I can't guess at that.

Fuzzy feeling of fuel injected vs carbureted.

I'd do it for the fuzzy factor, if new from scratch, but a swap wouldn't make economical sense to me.

[SWeidemann]

To clarify a bit, I am hoping I could retain my current engine mount, oil cooler, coolant cooler, oil tank, and exhaust system. IF I could keep these items (I already have) and bolt on the engine and make mods to accomodate the unit inside the cowl lines, it would make more sense than completely starting all over FWF.

Skot

[Danzer1]

I kinda figured that, but my thought is then you would get less for the uls, being incomplete. So relatively I don't think your net numbers would change much. Savings on the front end would cost you at least as much on the back end sale of the uls.

[HighWing]

Mostly opinion and sorry, not direct to the stated question.


Rebuild carbs (yourself) every year for 10 years $300 x 10 = $3000



First, My experience is with the 912 UL, but I rebuilt my carburetor once in a nine year span averaging 100 hours per year. I should mention that the rebuild was not without issues as the new float needles would spill gas all over the place on return to idle on landing as they refused to perform their proper function. The solution was to go back to the original needles These performed flawlessly for the entire nine years. I saw no wear whatsoever on the rubber tips, no corrosion on the body. Question, is an annual carb rebuild recommended?

I was originally interested in the IS and asked my most trusted "expert" friend about it and his response was, "Why". I couldn't come up with a good answer, at least for me. Personal choices are seldom bad choices but in many instances one option can't be proven over an other.

The main reason for me was that most of my flying was more on the satisfying an addiction sort of thing. Often I just had to go up and get it out of my system before I could concentrate on real life. Pegged airspeeds was not the norm. Then there is our real purpose for the whole airplane thing. I recall when we were on the last leg of returning from Airventure several years ago. Our flight of six Kitfoxes and one Rans were down on the deck making steep banks as we flew over the meandering Humboldt River down stream from Rye Patch Dam. Monitoring the Air to Air we heard a flight of RVs overhead. All they talked about was manifold pressure, airspeed and where are the rest of you guys. It took us twice as long to get home, but I still wonder which of the flights had the most fun.

[Totophe]

If anyone could be interested, there is a french adaptation kit for injection on the 912 and 912S that cost about 3500$ which I heard works quite well an is easy to mount. The guy is a racing car preparator. (tuner). His name is Dieu (God), I'm not shure he speaks english but you can see it there: http://www.ladaero.fr

[Kurt.A]

I agree that changing out the entire eng would not be cost effective.
The fuel injection would be nice to have for:
1) The added reliability of eng operation.
2) Better fuel economy.
3) Increased power.
4) Better cold start up
A retrofit kit for $3500.00 is definitely a good deal in my opinion but I would definitely research the kit thoroughly prior to purchase.

[Totophe]

And lower idle for shorter landings

[Esser]

I bought an SDS fuel injection kit for my 914. It is also for the 912. Sweet setup. I'll be installing it on the engine in the next month before I hang it. I'll keep everyone updated.

[Icefox]

I agree that changing out the entire eng would not be cost effective.
The fuel injection would be nice to have for:
1) The added reliability of eng operation.
2) Better fuel economy.
3) Increased power.
4) Better cold start up
A retrofit kit for $3500.00 is definitely a good deal in my opinion but I would definitely research the kit thoroughly prior to purchase.

Have anybody tried it in minus Celsius temp for cold start. Is necessary to heat the engine much before cold start or will it start without heating before start? I would like to know it if I have to take with me propane heater for winter flying.:confused:

[jrevens]

Regarding a kit to add fuel injection to to a 912/914 -
1. How much weight does it add, if any?
2. Are there potential HOT start issues?
3. What does it cost? (I agree that the $3500 figure is very reasonable)

I know that the 912is seems to be considerably "busier" in the engine compartment, as well as heavier all up. I'm not sure you're going to see any increased power. Better fuel economy, yes, but I'd like to see legitimate testing results of any power claims.

[Esser]

Our setup weighs much less than the carbs but we are putting a second alternator on so I think we are going to be about 4 lbs heavier in the end. I can confirm this later when we actually move everything around.

Hot starts can be an issue depending on how you route your injector lines. Basically if you go straight to your injector as a dead end then you will probably have issues. The way we are doing it is one fuel line "Loop" per side of the engine with short 3/4" tees off of that loop to the injector if that makes sense.

You are able to buy complete kits for under $4000 so I think it is a good way to go.

http://www.sdsefi.com/rotax3.htm

[Esser]

This is what I mean by a loop.

http://www.sdsefi.com/eg33side.jpg

I think this setup below would give you hot start issues as you have to clear the vapour all the way down.

http://www.sdsefi.com/edge119.jpg

[Kurt.A]

Icefox,
I have done several automotive conversions and all have turned out to be far superior in cold start up as compared to the carbureted original. I have yet to do a conversion on a Rotax to see if the results are similar but will be doing mine in the near future. I have no reason to doubt that the Rotax would cold start and idle like your modern day family vehicle when set up properly.

[Kurt.A]

Regarding a kit to add fuel injection to to a 912/914 -
1. How much weight does it add, if any?
2. Are there potential HOT start issues?
3. What does it cost? (I agree that the $3500 figure is very reasonable)

I know that the 912is seems to be considerably "busier" in the engine compartment, as well as heavier all up. I'm not sure you're going to see any increased power. Better fuel economy, yes, but I'd like to see legitimate testing results of any power claims.

John,
Hot start issues if any would relate to plumbing issues as stated in Essers reply. Also I would add that Intake Air Temp sensor location is critical to hot start issues as well as state of tune in the ECU. I am sure that some weight will be added but the differences will depend on the installation configuration. A well thought out system would be minimal difference. With regards to power production, there is a magazine out called "Eng Masters". They have proven several times that a fuel injected system will produce more power on the same carbureted eng every time. The same accuracy of the fuel curve that provides the better fuel economy is also responsible for the better power curve. It really depends on how far off the fuel curve that the current carb set up is. What I have seen for test results on automotive engs is with both systems tuned ideally there will be a 2-5 hp increase with EFI. These increases are usually seen in areas of the power curve that the carb is transitioning from one circuit to another.