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MKIV 912 Swap

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Posted (edited)

Well I guess it's time to let the cat out of the bag. I'm going to cross over to the 912 Darkside with my latest MKIV project. Now that the engine is home in the hangar I'm a little more excited about the project. I still have not decided when I'm going to fully commit to this project considering it's just about ready for the FAA inspection with a 582. I'll be picking some of your guys brains who have already done this along the way. I feel like I'm starting all over again with the Avid learning curve. My main concern is the radiator/oil cooler/cowl mods piece of it. The top pic is a nice example of the cowl mod required. I am also on the hunt for an oil tank set up. I have mostly everything else. I will update this thread from time to time. Not much progress until after the first of the year when I return from my Uncle Sam mandated Sandbox tour.

 

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Edited by C5Engineer
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Posted

I saw that engine in one of your other pictures Joey, I'm sure you will like it once all is said and done.  I do have a MK IV cowl with that added opening for air to a radiator, I'm going to use it on the Kitfox 4 I'm rebuilding.  (Don't like looking over the high round Kitfox cowl)  I'm  planning to just go with the regular Kitfox style under belly radiator though.  It seems to work good on the Kitfoxes with the 912, and I have one besides.  The cowl will need some work to fit on the Kitfox as you can see in the picture.  JImChuk

Kitfox 4 with MK IV cowl 003 (Large).jpg

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Posted (edited)

Joeys first photo is a friend of mine's Mk4.  He has discovered (on our trip to Idaho) that the cheek openings are too big and the prevent enough air from flowing through the chin radiator scoop.  

He's reworking them smaller this winter and adding an oil cooler on a Kitfox mount just under the spinner with a scoop of its own that can be covered for cold ops. 

Edited by Av8r3400

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Posted

Joey you don't need to do anything to the cowl except cut a hole in it for the radiator air flow. Everything else remains the same. If you want it to look fancy I have that fiberglass piece that Avid sold to make the hole look better. it's yours for paying shipping. 

Glad you are getting excited! Having flown both the 582 and 912 versions of these planes, I believe you will never look back once that 912 is installed and running. I sure like mine.

The only down side I can see so far is that my engine is the 100 HP version and I like to fly slower than the engine wants to push the plane. The plane flies sweetest at around 80-85 MPH in the low-mid 4000's. I've been told over and over that for these engines to last the longest you want to run them above the peak torque RPM which is close to 5000, and they are happiest running 5400. That will take the plane easily over 100 MPH, but to me the plane itself feels happiest quietest and smoothest around 85. In many ways I think the 80 HP version is probably better suited to the plane, but I imagine I am in the minority here because takeoff performance would not be as good and that is what everyone wants (and I am no exception), but it seriously does feel like 80 HP would be the better engine for just flying around once the plane is in the air.

Can't wait for you to start!

Chris

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Posted

Re: the comment about the cheek holes being too big. This is definitely a problem with this conversion. My two other friends here in the tri-Cities who have 912 conversions in their MKiV's have glassed the holes over and ended up with 2 inch openings on each side! That lowers the pressure in the cowl enough to pull enough air through the radiators and they NEVER overheat. I think it looks terrible with the cheek holes glassed over, so I am going to experiment with baffles, deflectors, screens, I don't know what to keep the open cheek look but still decrease the airflow into the cheeks.

I have already seen the problem start to emerge with my Fat Avid when the temps were over 80 a few weeks ago. Fortunately its cold out now and temps are just fine, but come early summer I will have to resolve this issue too.

Chris

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Posted

Paul has ran his plane (80 hp, no oil cooler and Ivo IFA) in our area (northern Wisconsin) for 10 years and only discovered the cooling issue while we were out in Idaho with the 100 degree heat and high altitude. 

His planned mods will help for our next trip out there and make things even better here. 

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Posted

This is an interesting set up that doesn’t take away from the look of the large openings. 

 

http://avidflyer.wikia.com/wiki/912_Cooling

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Posted

What radiator is being used on the Avid with the radiator inside the cowl?  (First picture)  JImChuk

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Posted

Jim it is the standard radiator for the 912 from Rotax.  If I didn't have the mounts I would just go with the KF style, Meryl Williams sells one at a fair price and easy to mount. 

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Posted

I run a belly radiator on my B model. I often wonder if it adds additional drag or not. 

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Posted

Are you retiring 279AF and making this your primary airplane? Are you planning on a gear swap as well? Im just being nosey. Good luck with the 912 I think you will like it way better.

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Posted

I'll have to downsize the fleet eventually but no immediate plans to do so right now. Not sure I could ever part ways with 279. Not worth it to sell for what I've got into it financially and emotionally. Going to stick with he custom wide gear and 21s that are on the MK4. 

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Posted

Joey thanks for the link to that guys cooling solution! Something like that is exactly what I want to do!

Call me and we can talk about getting you that fiberglass inlet if you want it.

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