Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 1 of 2 12 LastLast
Results 1 to 10 of 20

Thread: Zipper Big Bore

  1. #1
    Senior Member
    Join Date
    Nov 2017
    Location
    Bailey, CO
    Posts
    225

    Default Zipper Big Bore

    Which would be the better choice and why?

    Buy the 80hp 912 Rotax and have the 104 hp Zipper upgrade installed, or just buying the 100 hp Rotax in the first place. Do Zipper engines make TBO and beyond without excessive wear?

    In my experience, pushing a smaller power plant harder leads to a shorter life. I have also read on this forum that engine mods will void the warranty, so it seems like a better choice to go with an engine that produces the output you want rather than upgrading a smaller engine to the same power.

    Steve

  2. #2

    Join Date
    Sep 2015
    Location
    Crawford, CO
    Posts
    165

    Default Re: Zipper Big Bore

    I think you answered your own question. That is my way of thinking too.

  3. #3
    Senior Member
    Join Date
    Nov 2017
    Location
    Bailey, CO
    Posts
    225

    Default Re: Zipper Big Bore

    What seems logical isn't always correct due to missing facts. I just wanted to make sure I wasn't missing anything.

    So, next question: What does fuel injection offer over carburetor? It costs more. Carb ice ever an issue? Which is easier to maintain? Which is cheaper to maintain?

  4. #4
    Senior Member efwd's Avatar
    Join Date
    Jun 2015
    Location
    Yorba Linda, CA
    Posts
    2,817

    Default Re: Zipper Big Bore

    Can you even buy a car that has a carburetor these days? Just askin.

  5. #5
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Re: Zipper Big Bore

    IMO:

    1. I would go with the 100 hp ULS engine right away rather than mod a 80 hp engine if you are buying new. In my case it was far cheaper to mod my existing engine to get the performance I was looking for. If this engine quits, I'd upgrade to the ULS.

    2. I am not a fan of the complexity and cost of EFI. I understand the benefits and agree with them, but to me these benefits aren't worth said complexity and cost.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  6. #6
    Senior Member
    Join Date
    Nov 2017
    Location
    Bailey, CO
    Posts
    225

    Default Re: Zipper Big Bore

    That is my plan until someone shows me a better plan.

  7. #7
    Senior Member jiott's Avatar
    Join Date
    Jun 2010
    Location
    Portland, OR
    Posts
    2,960

    Default Re: Zipper Big Bore

    IMO, the EFI engine is the way to go these days. Yes its more complex and costly, but you get definitely better fuel economy, no carb ice concerns, and very simple maintenance. I run a 912uls and have never experienced carb ice issues here in NW Oregon, but in the back of my mind I still worry about it a little. The dual carb sync is the main issue with the ULS engines, however, I will say that once I got the sync nearly perfect it has stayed that way with no more adjustments for 300 hours. I do check every 100 hours just to be sure. Those with EFI engines also claim somewhat better power, as well as great fuel economy.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  8. #8
    Senior Member
    Join Date
    Nov 2017
    Location
    Bailey, CO
    Posts
    225

    Default Re: Zipper Big Bore

    Jim,

    I am just going by the numbers from the Kitfox web site. It looks like both engines are 100 hp. Are you saying that the injected engine holds power to a higher altitude than the carb engine?

    What is the fuel flow difference between the two models?

    I am looking for an economical way to go fly and extra power is nice for climb rate, but a few horsepower adds very little speed at cruise. Simple is cheaper, unless it requires an overhaul or parts more frequently. More parts and more complexity usually leads to more maintenance and expense.

    What is the routine maintenance for the EFI engine? Parts? If I can justify the cost, I might be persuaded to go that route.

    And again, I am just going off the KF web site. They don't give much info, so I may be totally off base.

    Steve

  9. #9
    Senior Member jiott's Avatar
    Join Date
    Jun 2010
    Location
    Portland, OR
    Posts
    2,960

    Default Re: Zipper Big Bore

    To see the difference in torque and hp curves go to the Rotax-Owner website and look at engine specifications for the 912uls and the 912is. You will see that the 912is Sport has a little higher and flatter torque curve at the high rpms (5000-5800 rpm), which gives a couple more hp thru this range. I doubt that it is very noticeable. The fuel economy is much more noticeable; I believe the Kitfox factory is saying about 10% improvement, but I am going on memory (not always the best) on this.

    As far as recommended maintenance, you can get all that in detail from the Rotax website, download the maintenance manuals for each engine for free. My own opinion, is the EFI engine is simpler to maintain. However if something does break, fuel injection systems, computers, pumps,etc. can be more costly than a simple carburetor.

    As far as longevity, the jury is still out on the EFI engine because it is so new. The classic ULS engine has been around a long time and its 2000 hour TBO is well proven.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  10. #10
    Senior Member jrevens's Avatar
    Join Date
    Aug 2009
    Location
    Arvada, CO
    Posts
    2,146

    Default Re: Zipper Big Bore

    Quote Originally Posted by Av8r3400 View Post
    IMO: ...


    2. I am not a fan of the complexity and cost of EFI. I understand the benefits and agree with them, but to me these benefits aren't worth said complexity and cost.
    I feel the same way. As has been pointed out before, the increased cost will most likely never be made up by the slightly better fuel economy, by the average owner, even after many years. There is also a weight penalty. Compared to many aircraft engines, the Rotax 912 ULS is already a much more "complicated" engine. The fuel injected engine takes this to a new level. I'm not saying they aren't good engines, but just that these are the thoughts that I have about them.

    Flyboy66 - the injected engine is not turbocharged and doesn't maintain it's rated horsepower at any appreciable higher altitude than the 912 ULS to my knowledge.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •