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Thread: Single 40mm Rotec TBI / 912uls zipper custom setup

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    Premium Member (Donated) GravityKnight's Avatar
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    Default Single 40mm Rotec TBI / 912uls zipper custom setup

    *I mentioned this latest project in another thread, but for information/reference purposes down the road I'll start a separate thread.

    Background
    Rotax's dual carb setup sucks pretty bad. In my opinion it's not for the reasons most people complain (carb sync, though that, along with double fuel lines, intake stuff etc. is a cluttered mess). It's because the crappy intake manifold design doesn't allow for equal fuel distribution across the throttle range (physical throttle range). The throttle plate in the carb deflects fuel in different places causing the front cylinders to run lean at WOT, and the rear cylinders to run lean at lower throttle settings (cruise).

    I have tried a lot of things to bring the EGT's back in closer. Some things helped, and I saw actual good results for power and efficiency. I won't get into all that here - as I never could get them close enough inline. My goal is to see EGT's at the very most 50 deg off, hopefully even closer than that?! 20-30 really should be doable. Maybe better with the superior atomization of the spray bar in the Rotec TBI, and of course a more equal intake manifold.

    Setup
    -1 40mm Rotec TBI (floatless, slide, spray bar carb) TBI-40-S
    -Custom 1 into 2 into 4 aluminum manifold placing the carb back slightly behind the engine (above and behind). The manifold will come up from the heads with 1.375" pipe (1.250 ID) about 5" tall so that the main larger pipes will clear the coolant tank. This of course is the major PITA part of the project. I can't tig aluminum very well, so bought the spool gun attachment for my 220v lincoln 180. I have used spool guns before and can do acceptable work. Nothing I'd enter into a beauty competition, but strong.

    *The Rotec has a built in regulator so no adjustments to the fuel system have to be made

    *It also has a feature to prevent fuel from leaking through the spray bar when the engine isn't running and flooding the intake or hydro locking the cylinders etc. if you forget (inevitable) to shut down the fuel system at some point.


    First step was to machine up the flanges to hook to the heads. I did those tonight. 5/16 6061 aluminum is what I used. I left the main holes that feed the heads a little small on purpose, I'll finish those by hand to make sure they line up with the heads nicely (no lip). The 1.375" alum tubes that feed it are a little larger ID than the factory manifolds on purpose. Since my tubes are longer, I didn't want to take a chance of choking off the engine at higher RPM. I will taper the .060 difference in the flange.





    Just been collecting parts other than this. Lots of different size and shape aluminum pipes, cones, couplers, clamps etc.


    I'll update this thread as progress is made, this project (hopefully upgrade!) will take a bit to complete, test, and hopefully put to work!
    S6S 116 w/VGs|MGL/FDS/AoA
    114hp zipper912|homebuilt headers/muffler/ram-air
    75"WW STOL|22x8.50mains/21x8.00nose/custom fork
    YouTube Channel

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    Premium Member (Donated) scsirob's Avatar
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    You are having waaaaay too much fun!

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    Premium Member (Donated) WWhunter's Avatar
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    Gravity, I need you for my neighbor!! I am looking forward to your progress and reports!

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    Basic Member Denali's Avatar
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    @ GravityKnight :

    Amazing work on that Rotax. I heard through the grapevine that you are Austrian and that you used to work for Rotax? True?



    I am sure many forum readers would be interested in seeing what your shop looks like re the tools, drill presses, lathes, 3D Printers, etc. that makes these amazing projects possible. I keep seeing small lathes for sale, and your posts here makes it oh so tempting to start buying a few things like a quality drill press and a small metal lathe.

    Love your images. Please keep posting re the progress on your Rotax.

    Vielen Dank Tshuss...

    Grizzly small metal lathe
    Last edited by Denali; 12-05-2017 at 02:28 PM.
    " It's Always Something" - Gilda Radner (1946-1989)

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    Premium Member (Donated) GravityKnight's Avatar
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    Quote Originally Posted by scsirob View Post
    You are having waaaaay too much fun!
    haha.... I dream up ideas that sound like fun in my head. Then I'm running that mill last night and it's 22 deg F in the shop and I'm telling myself I should not be allow to start anymore new projects for a long time!

    Quote Originally Posted by WWhunter View Post
    Gravity, I need you for my neighbor!! I am looking forward to your progress and reports!
    Thank you sir! Hopefully some good results, well.. result from this...


    Quote Originally Posted by Denali View Post
    @ GravityKnight :

    Amazing work on that Rotax. I heard through the grapevine that you are Austrian and that you used to work for Rotax? True?


    I am sure many forum readers would be interested in seeing what your shop looks like re the tools, drill presses, lathes, 3D Printers, etc. that makes these amazing projects possible. I keep seeing small lathes for sale, and your posts here makes it oh so tempting to start buying a few things like a quality drill press and a small metal lathe.

    Love your images. Please keep posting re the progress on your Rotax.

    Vielen Dank Tshuss...

    Grizzly small metal lathe
    Thanks Paul!

    Hey that's a good idea! I'll get some pictures of the shop. In the hanger I have mostly the basics for tools, with a few extras (welder, grinders, just one small vice etc.) Big projects have to be brought home. Thankfully, I'm only 3 or so miles from the airport. I would drag more equipment over there, but we are building a hanger at home and eventually will move everything closer.

    My garage at home has a little bit more to offer... drill press, car lift, bench grinder etc. Nothing too crazy, usually reserved for working on cars of course. The real magic happens at my Dad's shop. My folks live 1/2 mile away, in fact my home runway (1600ft usable) is in between my house and theirs. I have pretty free reign to use my Dad's shop as long as I'm not in his way, and clean up afterwards. Most of my work there happens in the evenings and weekends. He is pretty good about me going wild in there and has been patient over the years. He taught me to weld when I was 6 or 7? And so on... I think he rather have me around making a mess, than not around at all you know. I can run a mill and lathe etc. well enough to make the parts and mods I've done to the plane, and a lot of car stuff in years prior to this... but I am no where near the machinist he is. Most of the things I build don't require the absolute precision of the things I've seen him do. But now and then I make something pretty precise that even works when done!

    He is old school, we have a surface grinder that was built in the 20's I believe it was? All mechanical, noisy clanking back and forth.. I grew up in the shop and still love to hear it clacking around. I used to come up with reasons I needed to flatten something just to run that thing. His largest lathe is like 18ft long, has a chuck on it probably about 2.5ft tall. It's a monster. I'll get some pictures of these cool old tools. He is a genius in his field and I was lucky to be born into a family where I was brought up to believe everything should be done yourself - and we had most of the tools to do just that.
    S6S 116 w/VGs|MGL/FDS/AoA
    114hp zipper912|homebuilt headers/muffler/ram-air
    75"WW STOL|22x8.50mains/21x8.00nose/custom fork
    YouTube Channel

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    Quote Originally Posted by GravityKnight View Post
    Thanks Paul!

    Hey that's a good idea! I'll get some pictures of the shop. In the hanger I have mostly the basics for tools, with a few extras (welder, grinders, just one small vice etc.) Big projects have to be brought home. Thankfully, I'm only 3 or so miles from the airport. I would drag more equipment over there, but we are building a hanger at home and eventually will move everything closer.

    My garage at home has a little bit more to offer... drill press, car lift, bench grinder etc. Nothing too crazy, usually reserved for working on cars of course. The real magic happens at my Dad's shop. My folks live 1/2 mile away, in fact my home runway (1600ft usable) is in between my house and theirs. I have pretty free reign to use my Dad's shop as long as I'm not in his way, and clean up afterwards. Most of my work there happens in the evenings and weekends. He is pretty good about me going wild in there and has been patient over the years. He taught me to weld when I was 6 or 7? And so on... I think he rather have me around making a mess, than not around at all you know. I can run a mill and lathe etc. well enough to make the parts and mods I've done to the plane, and a lot of car stuff in years prior to this... but I am no where near the machinist he is. Most of the things I build don't require the absolute precision of the things I've seen him do. But now and then I make something pretty precise that even works when done!

    He is old school, we have a surface grinder that was built in the 20's I believe it was? All mechanical, noisy clanking back and forth.. I grew up in the shop and still love to hear it clacking around. I used to come up with reasons I needed to flatten something just to run that thing. His largest lathe is like 18ft long, has a chuck on it probably about 2.5ft tall. It's a monster. I'll get some pictures of these cool old tools. He is a genius in his field and I was lucky to be born into a family where I was brought up to believe everything should be done yourself - and we had most of the tools to do just that.
    I grew up about the same and my dad still uses a bunch of old tools like a huge cast iron lumber mill table saw that the whole table tilts instead of the blade. However he's about a 6 hour drive away and still locks the shop up so I don't take his tools. Hahaha

    Maybe we need a new Thread just for shop tool pics

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    This is gona be a insteresting thread to follow!
    Is the standard 912 fuelpump good enough for the TBI?

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    Premium Member (Donated) GravityKnight's Avatar
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    Quote Originally Posted by Mitchell View Post
    I grew up about the same and my dad still uses a bunch of old tools like a huge cast iron lumber mill table saw that the whole table tilts instead of the blade. However he's about a 6 hour drive away and still locks the shop up so I don't take his tools. Hahaha

    Maybe we need a new Thread just for shop tool pics
    haha


    Is the standard 912 fuelpump good enough for the TBI?
    The injector requires anywhere from .5 to 12psi into the regulator. The pressure is regulated down to a real low pressure at the spray bar. The system relies on air running by the bar to pull vacuum on the backside (engine side) that is flat with the holes drilled in it, to draw fuel out. They work on gravity feed, so the rotax pump will work out good, and I'm leaving the electric pumps in the plane. Helps to fight vapor lock in the lines.
    S6S 116 w/VGs|MGL/FDS/AoA
    114hp zipper912|homebuilt headers/muffler/ram-air
    75"WW STOL|22x8.50mains/21x8.00nose/custom fork
    YouTube Channel

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