The Zipper kit was mentioned; I am curious, does anyone know what the compression ratio becomes with the Zipper kit on a 912ul and on a 912uls? The Zipper kit increases the bore but not the stroke, right?
The Zipper kit was mentioned; I am curious, does anyone know what the compression ratio becomes with the Zipper kit on a 912ul and on a 912uls? The Zipper kit increases the bore but not the stroke, right?
Jim Ott
Portland, OR
Kitfox SS7 flying
Rotax 912ULS
The Zipper (1484cc) replaces the Pistons and cylinders, increasing the bore only. The bottom end of the engine is not touched.
There are high (11:1) compression and low (9.7:1) compression kits available. The low compression kit allows the continued use of 87 octane fuel to make about 105 hp, where the high compression requires 92 octane, and a hd starter and slipper clutch in the gearbox are recommended, which will produce about 115 hp.
There is also a 1622cc kit which requires some machine work and change of the cam to achieve 125 hp.
Thanks for the input on going to the higher hp engine on the Model 4.
I guess if it is that obvious it would probably be even more so on my Kitfox since I'm dragging around an additional 200 lbs of floats, not to mention all the additional drag. I'm honestly surprised it is so significant as my plane even on floats is like a ro ketship compared to most other float planes.
Larry, did you install your Zipper kit by yourself? Did you do the 105 or the 115? I really like my 912ul, so I've been hesitant to install a big bore kit in it. But you got me thinking...
87 vs 92 oct fuel shouldn't be a big deal as generally I always buy premium fuel anyhow, as non ethanol 87 octane isn't easy to find.
(I moved these posts out of the other discussion so we don't hijack any further)
My engine is the low compression 105 hp version. I didn't want to upgrade the starter and add the slipper clutch.
Yes, I did the Zipper upgrade myself. Pretty easy, actually. Here's a couple photos.
Here is the engine stripped of the OEM parts.
BB1.jpg
New Pistons and Cylinders.
BB2.jpg
Fully assembled long block.
BB3.jpg
I talked to a friend today, by coincidence. He has the low compression Zipper kit. I watched as Hal installed it last year and asked him today how he liked it. Big smile. Great! I was mostly interested in issues. None.
Larry,
First, thanks for moving this off the other thread I was hijacking. All of us here are lucky to have such great moderators!
And 2nd, thanks for the great info. I think I'm gonna do the same thing to mine since everyone is having such good luck with theirs. And my pushrod tubes are leaking a bit anyhow, so I will be able to kill 2 birds with 1 stone.
I can hardly wait now until next year at the fall seaplane fly in where the only planes that can beat me off the water are two Rans S-7's with 100 hp 912's. If I gain 24 hp (or even better 34 hp ) I will literally "Blow them away", as I'm almost able to beat them now. That will be priceless...
I will probably do what you did and simplify things by just going 105 hp on my 912ul on my Kitfox. And if I'm as impressed as you are with that Zipper kit mod, later I'll bump my Highlander to the 115 hp as that already has the slipper clutch and HD starter. And honestly, when it's on amphibs it is nearly 100 lbs heavier than my Kitfox (bigger, heavier floats, and my Highlander airframe is 45 lbs heavier), so it could use some extra power.
It truly is amazing how well these 912's work on our planes, and all you can do with them, all while burning very little car gas. I just love these planes...
Last edited by av8rps; 06-17-2016 at 04:31 PM.
I'm also looking at the 105 hp version for my 912UL...80HP. One thing that I have to consider is I have the ultra light IVO IFA prop which has a 100HP limit. With the zipper kit being 105HP, a new medium prop would be recommended. I talked to IVO and they agreed that the heavier prop would be best. Sooooo, while the zipper kit would be great on my Speedster, I'm going to stick with what I have......which is really all I need....
Just a thought..
Russ
Russ
Model IV Speedster
912UL IVO IFA
RV6A
Needle, Ball and Airspeed
Maybe a little GPS
Good point regarding the prop,so far the only point against the zipper!
Would 5 hp over the prop limet be a deal breaker?
IVO seems to think so. But I think it's just lawyer talk.
Russ
Model IV Speedster
912UL IVO IFA
RV6A
Needle, Ball and Airspeed
Maybe a little GPS