Zipper Big Bore

[Flyboy66]

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

[Clark in AZ]

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

[Flyboy66]

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?

[efwd]

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

[Av8r3400]

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.

[Flyboy66]

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

[jiott]

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.

[Flyboy66]

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

[jiott]

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.

[jrevens]

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.

[Esser]

To quote Scott Noble:

“'THIS IS HOW A ROTAX 912 ULS(Now Injected Sport) IS SUPPOSED TO OPERATE' My main goal for this installation was to get a smooth running engine. I couldn't be more happy with the results. This engine runs very smooth throuout the RPM range. With the ULS dual carbs I couldn't sync the carbs perfectly throughout the full RPM range. There was always a little rough spot around 2700 RPM and various other vibration issues. I can only imagine a smooth engine will help this engine last. An added benifit was a bit more HP and better fuel burn. At this point I'm think I gained about 4 mph in cruise and gains in fuel burn as well. I will update this post as I continue testing.”

For me and the Rotax 914 the EFI set up is lighter, smoother, less fuel burn or more power. In fact I no longer have to worry about my manifold pressure being higher than my boost pressure and if I wanted to I could run over boost and increase my power to 125hp with no other mods. No more cold start problems and no more hot start problems.

The US military in a nutshell used the same EFI boards I have for the predator drones.

Not for everyone I suppose.

[HighWing]

... 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 many reasons that one airplane might be more fuel efficient than another. Fuel efficiency goes beyond engine efficiency and aerodynamic cleanness. In the early 1980s. I started working at United Airlines on the ramp. Baggage, Mail and Galley changeout were what I did in the beginning. This changed to fueling, then as a SOR in the Control Center. I sat in front of a computer calculating loads on outbound flights. My ultimate responsibility was to create an accurate Manifest that was then ACARS transmitted to the pilot as he taxied for takeoff. This gave him the load and the location of that load so he (she) could make the final judgement as to where everything fit relative to maximum takeoff weight and CG location. It was while working here, I learned about the parameters that were developed during the Arab Fuel Embargo, ten years or so years earlier. Since any airplane is most aerodynamically efficient when the CG is near the aft CG, that was determined to be the ideal. Passengers were spread through the cabin to achieve that goal. Baggage, freight and mail were also loaded accordingly. This was to minimize fuel burn during the flight using the scarce fuel more efficiently.

Now to Kitfox. When I finished my first Model IV in 1998, I was disappointed that my empty CG was a bit aft. This was due to the 8 lbs. or so that I added to the empennage when adding full airfoil shapes to both vertical and horizontal tail surfaces and gap seals – plus the electric elevator trim. As a result, I was forced to placard the baggage sack at 20 lb. Max vs. the 40 lbs. standard. Then the Ah! Ha! moment. On our first, Flight of 6, trip to the Idaho back country we stopped in Winnemucca, Nevada for fuel. All were curious as to fuel use during the three hour flight from Rancho Murietta. Number one was a Rans S-6 that burned almost 14 gallons. The others – Model IVs - varied between 9 and 11 gallons. I burned 7.6 gallons which included my 30 minute flight from O61.

Now things are a bit different. A new Model IV, completed in 2016. Not wanting to have to limit luggage after doing even more to the empennage than the first time, I moved the engine forward using a home brew engine mount. I calculated 2.5 inches further forward which, in practice, proved to be too much. Now with a CG closer to the forward limit, I find that the airplane is much draggier than the first one. I don’t have fuel use data on this one, but the airspeeds are not impressive compared to the first one. From my experience we could install the most fuel efficient engine there is and still buy more fuel at that three hour fuel stop than the other guys flying with a regular old Rotax mounted in a lighter, better balanced more aerodynamic airplane.

[jrevens]

...

For me and the Rotax 914 the EFI set up is lighter, smoother, less fuel burn or more power. In fact I no longer have to worry about my manifold pressure being higher than my boost pressure and if I wanted to I could run over boost and increase my power to 125hp with no other mods. No more cold start problems and no more hot start problems...


Josh,

I’m not sure if this is part of Scott Nobles’ quote or not, since there are no quotation marks, but I hope all of this is true for you when you finally get yours running. I’m surprised that it would be lighter than a stock 914. The 912is is a heavier installation than a 912uls, but that may be like comparing apples to oranges. I think I’d personally be a little leary of running over boost, also. I hope it proves to be a very reliable engine for Scott, and you too! Fuel injection is great, but the options right now are just a little out of my comfort zone. Guess I’m not much of a true experimenter, but I admire the efforts of you “trail breakers”!

[Guy Buchanan]

Well I read a post last week that said an iS Kitfox travelling across country averaged 125mph at 3.2gph. Now my 100uls IV only can manage 5.6 gph at 120mph so I'd say the injected engine is worth about $12/hour in 100LL. So the re-pay might be worth it over a engine's lifetime. ($12/hr is $24k over 2000 hours.)

[AirFox]

Hay John, the Edge Performance EFI installed on the 912ULS is lighter than the Rotax 912IS. On the 912IS the Auxillary control box, Fuel pumps etc add to the weight. If I remember correctly the 912IS is aproximately 20 lb heavier than the ULS. When I weighed my EFI prior to installation it was about 2 lb lighter than the stuff I removed. I removed the carbs, fuel pump and all the tubing.

As far as performance I am very happy. Almost 10 more HP way better fuel burn and runs very smooth. I have almost 100 hours on the EFI now and I am very happy with it.

My fuel burn in the past 100 hours averages 3.4 gph. Doug also installed the EFI on his engine at the same time. Doug(Floog on Teamkitfox) just did a trip across the Cascades at 50% power and got 2.6gph at over 100mph. My 10.8 hour trip to the High Sierra Fly in I got 3.4gph flying at 60%HP averaging 108mph. The Rotax engine has been very reliable and I expect with the smooth running EFI installation I'll get even more reliability. My fuel burn range prior to EFI on the Rotax 912ULS was between 4.12 and 5.4. Compare that range to 3.04 and 3.9 with EFI installed.

The return on my EFI investment will be covered within the TBO just in fuel cost. I paid about $5500 for the EFI kit. Go to BadAssPowersports for the N American rep if your interested. Jason is a good guy to work with on the install.

Your going to be very happy with your engine Josh. Good luck getting it flying.

Scott

[Esser]

My earlier post was supposed to say I don’t have to worry about my manifold pressure being higher than my fuel pressure like s traditional 914 set up.

Im not going to have this make extra power but it is an option for people looking for that.

I honestly think that the success of these after market systems were so good it caused Rotax to come out with the 912iS and 915. A warranty would be nice though! :o

[av8rps]

Going by memory here, but I think the same people (Hacmann?) that made kits to convert rotax 582 carbs to include a mixture adjustment, do the same for the 912 bing carbs. Obviously the fuel injection units are running much leaner, more efficient fuel settings compared to how most of us have our carbs set up. So with a little effort and cost I'm sure we could get our carbureted 912's to run close to the same efficiency.

Just my two cents...

[Av8r3400]

HACman for Bing 64. (https://www.greenskyadventures.com/bing/4strokePG2.htm)

[av8rps]

Thanks Larry. I just read that link and thought I would forward the one for the 4 stroke details for those that want to read more

http://www.greenskyadventures.com/bing/HACman_4stroke.htm

For only $198 it's kind of a no brainer.

Is anyone here on the forum using the Hacman mixture control option on their 912?

[Floog]

Before I converted my 912 to EFI, I ran the HACMAN for a couple of years. One of the best investments I made. (At that time, it was around $150.) I saved so much on fuel, I was able to afford EFI. Well almost :) I used it from the moment I took off but especially above 6,000ft. Eliminated fouled plugs caused by overly rich mixtures, too.