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100hp Cylinders on a 912 UL

43 posts in this topic

Posted

This balance tube conversation is very interesting. I always have a out of balance situation somewhere in the mid rpm range and it’s next on my list of things to do. I am going to use 1/4 to 1/2 inch off of manifold then 1/2 inch Id pipe for crossover as I can do this quick...if it gets rid of mid range out of balance I won’t go any further. My cowl only will give me about 1/2 of clearance over the stock balance tube so it going to be a challenge to go 1”. I increased discharge hose size on my sprayer nurse tank from 2” to 2 1/2” without changing anything else and it was a day and night differance so hoping it works on the balance tube as well.

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Posted

I tried a 1” tube without changing the elbows inlet and outlet but could not tell any difference.  I removed it after a trial period.  Let us know how it goes for you. Even with my new EFI there was a substantial imbalance but at least with tuning the ability to balance the cylinders at cruise is nice.

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Posted

What EFI are you using? 

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Posted

SDS

 

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Posted

intake2.thumb.jpg.bb1f439a76be6634304dbbI planned to tap the manifold so i could adjust the direction of the fitting, but there was not much material left after machining the hole. I opted to weld and prey its where i need it. hope to try it out this weekend.

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Posted

How high is top of elbow compared to stock?

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Posted

I tried a 1” tube without changing the elbows inlet and outlet but could not tell any difference.  I removed it after a trial period.  Let us know how it goes for you. Even with my new EFI there was a substantial imbalance but at least with tuning the ability to balance the cylinders at cruise is nice.

It will not make any difference if you retain the small size elbows as they restrict the air from flowing 

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Posted

intake.thumb.jpg.5063fcaaaebc33ba1a49dcdintake3.thumb.jpg.f99ed8c0d7da01292d4bfe

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Posted

Crossover doesn't seem to make much of a difference. The Ballence Master helped more. I have a slipper clutch on the way. By no means do I feel like my engine runs ruff. I just think it could be as  smooth with the ULS cylinders as it was with the 80hp

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Posted (edited)

Crossover doesn't seem to make much of a difference. The Ballence Master helped more. I have a slipper clutch on the way. By no means do I feel like my engine runs ruff. I just think it could be as  smooth with the ULS cylinders as it was with the 80hp

What about your idle speed??? What about starting and shutting down the engine??

In the usual operation RPMs the crossover does not do much..  where it shines is smoother /much lower idle speed, softer starting and shut downs 

If your engine was running a bit rough before the crossover, it will run the same after the crossover mod...the rough running I found can come from 3 main sources and I found myself searching for 3 months...:

1. air intake rubbers leaking/cracked/porous

2.carb issues....took me two rebuilds to get it right (slider spring length difference/choke valve seal leak/float hight adj./float chamber overflow tube badly positionned in airflow etc..)

3. ignition issues: Pick ups not at the right distance to targets/coil malfunction/coil bad grounding wire connector corrosion/bad ignition wire or chafed wire/spark plug caps/ spark plug electrode gap/ignition module power supply wire intermittent

Edited by flywise

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Posted

Wow, it sounds like your Rotax has been nothing but problems. It stinks that you have had so much trouble with yours. Mine runs great, I'm just tinkering. Even if I didn't do one thing to it i would still be happy with the way it operates. BTW what year was your engine produced? Some of the early ones had ignition wiring issues. Did you complete the 5 year rubber replacement? Mine was over due and my carb sockets still looked new.

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Posted

Wow, it sounds like your Rotax has been nothing but problems. It stinks that you have had so much trouble with yours. Mine runs great, I'm just tinkering. Even if I didn't do one thing to it i would still be happy with the way it operates. BTW what year was your engine produced? Some of the early ones had ignition wiring issues. Did you complete the 5 year rubber replacement? Mine was over due and my carb sockets still looked new.

My engine is a 1994 model and I have done everything to it...Sb and SL. Now at last I am happy with the way it runs

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Posted

Well the slipper clutch install is going as expected, I need to order some different sizes of shims. Now i wait on CPS. Also doing a ratio swap. Hope this quiets the prop some.

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Posted

The slipper clutch is huge. 

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Posted

Slipper clutch is the best upgrade i have done! It really help with startup and shutdown operations. I can defiantly lower my idle stop screws now.

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Posted

Amazing isn't it? Changed everything with regard to start up and shut down.

I was dealing with 2 problems. The start up and shut down which the slipper clutch completely cured. Absolutely awesome.

I also had a midrange vibration. Like something just a bit out of balance. The prop is a Whirlwind very carefully adjusted for equal pitch. I had previously bought a balance master and installed it. I thought It helped some but not a lot. it seemed more to just change the character of the vibration. I was so unimpressed with the Balance master that when I installed the slipper clutch I did not reinstall the balance master. The vibration was still there. All this time every time I took off the prop for any reason it went back on exactly the same way and place it came off. For no good reason I am anal that way. Still frustrated with the vibration I decided to put the balance master back on the plane, except this time I moved the prop one set of bolt holes when I reinstalled the balance master. All of the vibration vanished completely! My engine is now perfectly smooth throughout the entire operating range. I've never known this kind of smooth before except with IVO ultralight props.

I remember when I flew behind the 582 with even gear reduction ratios I would mess with prop timing to affect vibration. I don't know what the ratio on my 912 is, but do not think it is even. Anyway, I need to remove the balance master again leaving the prop where it is to see if timing the prop made the difference or if it is the balance master (which did not work before) or some combination of the two. Right now I am enjoying flying the smoothest 912 I have ever felt so am not going to take the prop off again until there is a reason, and then I will try it without the balance master again to absolutely determine if prop timing affects vibration which I never thought it could. We'll see....

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Posted

I'm running a 2 blade tapered tip warpdrive. I have a 75" Whirlwind I will install after the landing gear upgrade. Can't wait to see if it's as smooth as everyone says it is. I got my WW used so I won't be bias cause it cost twice as much as my other prop.

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Posted

Not impressed with the WhirlWind. I see no improvement over the Warp Drive. 

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