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My experience with the 114hp zipper big bore setup on the 912uls


GravityKnight

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As requested.... different airplane, but same engine so those of you considering going ELSA might be interested in this...

 

When I bought my RANS it had a 100hp 912uls. Performance was really good considering I live at 6650ft elevation (plane weighed 693 empty then)... but my home strip is 1600ft of dirt and I wanted to be able to fly out of here at gross on a hot day and not be dodging the power lines (at one end, two story house at the other). I also wanted to do some other modifications that would add a few pounds etc.

 

I called and worked with Jay http://zipperbigbore.com/ to get my kit on the way. He was a pleasure to work with, and we still keep in contact. There are several options of kits, and my RANS builder friend who knows Hal and the history on the setup gave me a little back info which was all positive towards the 1484cc versions. The really big bore 1622cc version requires case machining and I was told there had been some issues with that version they were still possibly working out.

 

Anywawy, the kit came quickly and I got to work. It's a pretty easy/straight forward install. Took a day to do, not being in a rush. They give instructions and info on break in etc. All pretty straight forward. The kit knocks like 4 lbs off you engine. The CNC cylinders have better cooling they say, but I have no data to argue that either way.

 

I knew there was a pretty good increase in power right off because I had to add a couple degrees to my prop (68" 3 blade taper tip warp drive at the time) to get the RPM back in a similar area. Take off roll was shortened quite a bit, and climb went up 300 ft a min easy, maybe more.

 

I already had already installed a wideband o2 gauge in the plane, and a hacman leaner and 1 egt. Since then I have installed some MGL avionics instruments, 4 egts, CHT, some other stuff etc.

 

I also added a Rotax airbox and did some custom intake stuff. I've actually had several different intake setups, but that's not really related. Anyway.. when I started modifying the exhaust is when things got interesting. But that is also not really related to the zipper kit.

 

Anyway, I felt I wasnt taking full advantage of the zipper with the small-ish prop, so I bought a 72" KOOL Scimitar 3 blade prob. They are light for their size, have leading edge protection and are fairly affordable.

 

But to do that, I had to put larger tires on...which I wanted to do anyway, as I enjoy the off airport stuff. So I had to modify the nose fork to get a 16.5"x6-6 tire there, and I have 21x8-6s on the mains now. This gave enough clearance for the longer prop. The prop gave another 150 fpm in climb. I have it pitched real fine for take off and climb now. The plane at around 1025lbs take off weight will get airborne in about 200ft or less at 6650ft field elevation by grabbing a handful of flaps and yarding it off the ground at 40mph. I have seen as good as 1200ft / min climb at a very steep angle (60mph) at that same weight between 7500-8500ft altitude. I can't imagine what a monster it would be at sea level.

 

Probably the most amazing and somewhat unexpected change has been economy. The slightly higher compression is probably mostly responsible for this. But even dragging this big tires through the air on a plane that is nowhere near as clean as the CT's I see ~3.75gph at 110+mph indicated cruise. And this is at 5500ish rpm. I have slightly larger main jets in my carbs right now, as somewhat of a precaution because even though the carbs adjust somewhat for altitude, I'm not taking my chances until I can visit low altitude and see for myself. 

 

Anyway, it starts good, runs smooth, gets good economy, makes good power, is lighter, and really I don't have anything negative to say about the setup. It costs some bucks, but I don't know how you get could get more performance for less!

 

I'll update this if I think of anything I left out!

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To touch a little more on the HACman leaner. It's a simple system that uses manifold vacuum to pull a vacuum on the carb bowls. Easy to install, fairly simple to operate with one minor 'kinda have to get used to' characteristic. It is far more potent at low throttle settings (due to there being much more manifold vacuum when the throttle is closed). Where this can get you a little is if you have it cranked up pretty good to lean at full throttle or higher cruise, and then pull the throttle back, it will go very lean. Only takes a couple times before you stop doing that. But the unit does the job.... but it only leans, unlike the mixture control on a cont/lycoming. This works fine as the bing runs richer the higher you fly - regardless of it's altitude compensating functions, it still gets richer as you climb. I'm sure if you fly at 4000ft the difference it will give you isn't enough to warrant having one.... but up higher it's pretty handy to have! I really think having a wideband o2 gauge makes it that much better.. you can see air fuel ratios in real time, and it makes adjustments quick and easy and precise.

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Gravity Knight, you might consider getting your turbo here.

And maybe fuel injection, too.

 
How does 160hp sound?
 

https://www.facebook.com/edgeperformance.no/

 

Enjoy!

 

By the way, at 3.75gph and 5500, it seems like there's some extra performance in there that you're not making the best of, especially considering all that extra displacement.

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Hey Todd...

 

If you run the HacMac set to full rich (essentially "off"), does the carb work just like the standard setup?  That's what I've heard.  For people that live at lower elevations but makes high altitude trips a few times a year, it seems like you could leave the thing at full rich for normal flying and have it fly like stock, but then use it to lean out when flying to to higher elevations or making long cross countries cruising at 9500ft.

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Sounds like you need a turbo more than anything :P

Thought about it. My past deals mostly with turbocharging and fuel injection. A little voice inside my head told me to keep it simple, and light lol

 

Gravity Knight, you might consider getting your turbo here.

And maybe fuel injection, too.

 
How does 160hp sound?
 

https://www.facebook.com/edgeperformance.no/

 

Enjoy!

 

By the way, at 3.75gph and 5500, it seems like there's some extra performance in there that you're not making the best of, especially considering all that extra displacement.

160hp just sounds plane fun. There was a video released the other day of a Just StuperSTOLwith a 180hp Titan engine. Now the engine is so heavy, they had to extend the plane almost 2 ft to balance it out, but this thing takes off in 15ft with it's slats and climbs literally straight up.

https://www.youtube.com/watch?v=iOcrNdxOtvU

 

I'm sure I'm giving up some economy with my fine pitched prop, but I'm not willing to give up take off and climb performance. I do more landing in someones field if they will give me permission than I do cross country.

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IrishAl, on 24 Feb 2016 - 03:41 AM, said:snapback.png

I also note that you didn't upgrade your starter motor - are you getting on okay with the standard item?

Mine has the newer, HD starter already. So far so good. 

 

 

MrMorden, on 24 Feb 2016 - 06:22 AM, said:snapback.png

Hey Todd...

 

If you run the HacMac set to full rich (essentially "off"), does the carb work just like the standard setup?  That's what I've heard.  For people that live at lower elevations but makes high altitude trips a few times a year, it seems like you could leave the thing at full rich for normal flying and have it fly like stock, but then use it to lean out when flying to to higher elevations or making long cross countries cruising at 9500ft.

 

Andy, that is exactly right. You only have to use it, when you want to.

 

 

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MrMorden, on 24 Feb 2016 - 06:40 AM, said:snapback.png

Also, what fuel is required for your Zipper kit?

 

I was told 91. Which makes sense you wouldn't want to go any lower of course. I know a guy with the 105hp 9.7:1 version with over 500 hrs on his (started as an 80hp 912), and he runs regular! If I was literally at sea level, I would hope I could get 93 for the extra insurance. But supposedly 91 will do. Of course combustion chamber design, camshaft overlap, timing, fueling all play into how much compression you can get away with.... apparently, it will work on this setup but I have never been anywhere lower than about 5300ft since I did the zipper.

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Here is a video of the zipper in action from a little while back. Take off rolls measured about 220ft. Making some big changes to my exhaust right now to see if I can bring EGTs more in line (rans exhaust system uses smaller pipe that rotax uses, and has very unequal length headers), and maybe squeak out some more power.

 

https://www.youtube.com/watch?v=mSe75BSvHyM

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I have to vacuum it out now and then... I actually fly shoes off lol, so the cargo area behind the seats actually needs cleaned more often because my shoes ride in there.

 

I know that sounds weird, but it makes me shorter! I drive with shoes off, hell I drag raced my cars with stiff clutches and such with no shoes. The rudder pedals in the plane are wide, fairly smooth, and are easy to move with the noes wheel disconnect.. so it doesn't hurt the feet w/o shoes.

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  • 1 year later...

Hello,

I’m building a Zenith 701 and plan to use the Rotax 912.  I’m considering finding an 80 hp engine and adding the low compression zipper mod as I will be operating off of a 1,000 ft grass strip with trees at each end (my back yard), field elevation of 1,000 with DAs typically reaching 3,000 in the summer.  The zipper kit seems like the answer.  Only thing giving me pause is the overall reliability impact to the engine of installing the big bore kit.  Wondered if there were any updates to this thread regarding how the Rotax holds up after several hundred hours of big bore operation.

thanks

Jim

 

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  • 4 years later...

Hi to anyone who has information about the Zipper Big Bore Kit for the 912S Rotax engine.  I am interested in increasing the HP of my 912S but when I tap on the Zipper website a message pops up saying "There has been a critical error on this website".  I am wondering if this means Zipper no longer sell/support this Kit for the Rotax 912S ??.  Can anyone shed any light on this please ?.  Thanks in advance. Regards, Allen B.

 

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On 2/24/2016 at 1:31 PM, GravityKnight said:

As requested.... different airplane, but same engine so those of you considering going ELSA might be interested in this...

 

When I bought my RANS it had a 100hp 912uls. Performance was really good considering I live at 6650ft elevation (plane weighed 693 empty then)... but my home strip is 1600ft of dirt and I wanted to be able to fly out of here at gross on a hot day and not be dodging the power lines (at one end, two story house at the other). I also wanted to do some other modifications that would add a few pounds etc.

 

I called and worked with Jay http://zipperbigbore.com/ to get my kit on the way. He was a pleasure to work with, and we still keep in contact. There are several options of kits, and my RANS builder friend who knows Hal and the history on the setup gave me a little back info which was all positive towards the 1484cc versions. The really big bore 1622cc version requires case machining and I was told there had been some issues with that version they were still possibly working out.

 

Anywawy, the kit came quickly and I got to work. It's a pretty easy/straight forward install. Took a day to do, not being in a rush. They give instructions and info on break in etc. All pretty straight forward. The kit knocks like 4 lbs off you engine. The CNC cylinders have better cooling they say, but I have no data to argue that either way.

 

I knew there was a pretty good increase in power right off because I had to add a couple degrees to my prop (68" 3 blade taper tip warp drive at the time) to get the RPM back in a similar area. Take off roll was shortened quite a bit, and climb went up 300 ft a min easy, maybe more.

 

I already had already installed a wideband o2 gauge in the plane, and a hacman leaner and 1 egt. Since then I have installed some MGL avionics instruments, 4 egts, CHT, some other stuff etc.

 

I also added a Rotax airbox and did some custom intake stuff. I've actually had several different intake setups, but that's not really related. Anyway.. when I started modifying the exhaust is when things got interesting. But that is also not really related to the zipper kit.

 

Anyway, I felt I wasnt taking full advantage of the zipper with the small-ish prop, so I bought a 72" KOOL Scimitar 3 blade prob. They are light for their size, have leading edge protection and are fairly affordable.

 

But to do that, I had to put larger tires on...which I wanted to do anyway, as I enjoy the off airport stuff. So I had to modify the nose fork to get a 16.5"x6-6 tire there, and I have 21x8-6s on the mains now. This gave enough clearance for the longer prop. The prop gave another 150 fpm in climb. I have it pitched real fine for take off and climb now. The plane at around 1025lbs take off weight will get airborne in about 200ft or less at 6650ft field elevation by grabbing a handful of flaps and yarding it off the ground at 40mph. I have seen as good as 1200ft / min climb at a very steep angle (60mph) at that same weight between 7500-8500ft altitude. I can't imagine what a monster it would be at sea level.

 

Probably the most amazing and somewhat unexpected change has been economy. The slightly higher compression is probably mostly responsible for this. But even dragging this big tires through the air on a plane that is nowhere near as clean as the CT's I see ~3.75gph at 110+mph indicated cruise. And this is at 5500ish rpm. I have slightly larger main jets in my carbs right now, as somewhat of a precaution because even though the carbs adjust somewhat for altitude, I'm not taking my chances until I can visit low altitude and see for myself. 

 

Anyway, it starts good, runs smooth, gets good economy, makes good power, is lighter, and really I don't have anything negative to say about the setup. It costs some bucks, but I don't know how you get could get more performance for less!

 

I'll update this if I think of anything I left out!

Good morning sir.  I have been trying to contact Zipper re them supplying a Rotax big bore kit but their website for the Rotax option isn't working.  Are you able to confirm if they are still supplying the Rotax parts please.  Their website only mentions motor bikes.  Thanks you, Allen

Screen Shot 2022-10-07 at 3.10.23 pm.png

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  • 4 weeks later...

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