HKS engine conversion

[WurlyBird]

Hey all, I am a new member to Team Kitfox and I look forward to getting to now you all. In the mean time I am insisting that we get a few up to date posts on this thread. I will be searching around in a bit to see what more info there is but I am amazed this thread died off. I am in the process of converting to an HKS as well, 2 years into the process. I started it after my last deployment and my two sons, ages 2 and 5, prevented me from having much time in the garage before I came over seas again. I am going to hit the project hard when I get home but I want to know how others worked a few problems as well

My conversion will be a bit unique. I got my FWF from Jerry at Green Sky Adventure but I couldn't stand the look of the high thrust line in the bump cowl. Since I was not a huge fan of the bump cowl I used this as an excuse to buy a cowl for an Avid Mk IV, so now I am actually raising the engine up an additional 2". This is also requiring a new firewall be made, a new windshield, and a new instrument panel. If I could do it again having read these posts I may have attempted to follow your leads. This is a LOT of work I am having to do. But I think it will look and perform awesome and I am anxious to see if the higher thrust line takes out some of my forward stick in cruise. I look forward to hearing from some of you on this.

So how did the final conversion look? Any more pictures? If you were back at the beginning what would you have done differently?

James

[rawheels]

Hey James,

Still working on my conversion. I have the fiberglass "bump" work yet to complete, and then I'll be able to start working on any bugs that pop-up. I was out at the airport this morning, and took this photo. Although, I was trying to get water out of the workshop from a recent monsoon, so I didn't have much time to work on the plane.

[WurlyBird]

Thanks for the update Rawheels. I really like the way that looks in the round cowl. Did you turn the PSRU downward to do that? (I think you mentioned that in a previous post but my internet is to slow right now to go back and check) I am going to post a couple pictures of how mine was coming before I left, can't wait to get back to finish it. I currently have the engine up an additional two inches to accommodate the cowl but I think I have figured out how to make the cowl accommodate the engine and I will experiment with that when I get home. Either way I will get a little extra prop clearance which I will like. I will also end up with much more of a view over the nose if I can adjust the cowl, awesome. You can see that the amount of room inside the cowl is quite spacious but you can also see that the cowl does not quite fit and I had to cut up the old cowl to make it extend back to the doors, which also made working out the mounting details really simple. I still have to extend the top cowl a bit to fill in back to the door. I will have to touch base with you when I get home so we can trade ideas. Take it easy.

[napierm]

My kitfox project is on a little hiatus because I picked up a Zenith 601HDS last fall and need to get it into good shape before I commit aviation in it again out of my short strip. The rotax 912 is an older one but is low time and in perfect condition. The airframe is also very well made. They both are in good condition but were flown and not upgraded from day one. I bought it to fly but now that I have it I have to fix a few things.

This is a picture with the new prop, spinner, alternator, and exhaust system. By all accounts, this prop is supposed to be the best in terms of climb/cruise performance compromise; way better than the GSC that was on it. That's from testing on the RV-12, 601HDS, and at least one ultralight dealer on the Rotax owners group forums. Fitting a cold air box and anything else that will make this ground hugger come off of the strip quicker. I've got 2400 feet to work with and on guy flies and Aztec twin out of here but I want all the margin I can get. It does fly very nice in the air - sort of a slow/cheap RV.

Oh yeah, the HKS? Yes, I have it mounted finally on the painted motor mount. Had to cut and weld on the Lost Hills motor mount to get the engine to fit. Sandblasting the crappy old paint off it to prep for repaint was a pain. Doing the same on the 601HDS mount now. The aluminum intakes fit well. I need to either buy the HKS type 6 exhaust or I think there is some extra HP available if an exhaust is fabricated. Will try to take a couple of pictures today.

[rawheels]

I'm finally taxiing my HKS-Kitfox project, and am having troubles with the CHT over temping on the HKS when I have the cowl installed. It seems to be OK when I'm moving, but it will redline if I'm stopped and run it up for a short while. And once the temps get high, they won't come back down at idle.

Some baffling may help, but I've yet to find any photos of a HKS in the cowl that has any baffles attached. So, I'm looking at the air exit for now. I've read quite a few times online about a 3:1 ratio to the cowling inlet as being a good exit size, but with a large 13" round cowl opening on the front, there is no way I'd get there without removing the whole bottom cowl. Anyone else with an air-cooled engine want to tell me how large their cowl exit is?

Another thought is that the airfoil portion of the prop blade appears to start at the edge of the cowl opening, so maybe there is no airflow happening at all in the cowl when stopped. I'd like to try out a venturii lip on the bottom edge of the cowl in hopes that it would create some suction from the prop blast going across it, but I haven't been able to find any info online on how to design one. I looked at two aircraft on the field (Stinson Voyager and Piper Pacer) both of which have an exit opening lip. They both appear to be 45 deg to the cowling surface (nearly pointing straight down when the aircraft are on the ground). The Stinson's is about 1.25" tall and the Pacer is almost 2". Anyone else played around with cowl exit lips?

[Esser]

Rawhells,

Go buy a book called speed with economy by Kent Paser. He has a cool chapter on cooling efficiently. It's more for drag reduction but the principals are the same. You can buy it online in an ebook format for a few bucks.

[Mnflyer]

Hi rawheels, what prop are you using? If you go to my album you can see a couple of pic of the opening I did on the cowl, you will definitely need a venturi lip (at least I did) the exact angle is that important mine is approx 1.25" if you would like I can measure the opening and the size of the lip, I also fabricated a couple of very simple baffles that improved cooling tremulously (can also be seen in my album) Another thing you need good air flow thur the oil cooler as you know the HKS has oil cooling for the cylinder heads if the oil cooler isn't getting good air flow from the prop the CHT's will be up.

[DLinn]

Surveyor

Might you be willing to share the mounting plate drawings?
I am look at converting my kitfox 3 from 582 to a HKS 700e.

Thank you for your time

Dana

[Dravenelle]

rawheels

i have exactly the same spec.

my plane is a kitfox 2 and empty weight is
595 lbs with my hks 700e and powerfine 2 blades prop

i have 6000 on the ground and at 55 mhp i have 650fpm
and cruise speed at 5400rpm is 65 mhp

what the empty weight on your plane?

Dave

[DLinn]

Dave

My Kitfox 3 weighs #525