Flygas balance tube

[Madhatter]

FYI, I installed the Flygas balance tube on my SW however it does not work. It causes reduced power despite what the manufacturer advertises.  I believe the issue is due to the airbox system on the CT causing a pressure difference for the carburetors vent lines. The company requested that I re evaluate the balance tube orifices however I feel that the potential benefits do not outweigh my time to correct the problem. My understanding is that the Flygas balance tube works well on other 912 installations but it should be up to Flygas to re engineer their product for the CT.

[Runtoeat]

Curious about the Flygas design.  Do you have pictures of the Flygas balance tube before installation?  Pictures of your factory  balance tube while removed from the airbox too?

[Madhatter]

[Runtoeat]

It appears to me that the Flygas system does the same thing as the factory Rotax balance tube.  The Flygas appears to include unique intakes for engine.  Must be very expensive to buy.

[FlyingMonkey]

I guess I'm unclear on what problem this kit is meant to address.  Is it supposed to be a less restrictive intake system producing more power?

[Madhatter]

Go to the Flygas website.

[Jacques]

https://www.flygas.info/kit-intake-manifold/

 

"claimed" advantages

• Absence of vibration regardless of the difference in the opening of carburetor.
• Possibility of continuing to fly (at 50% of power) even in the case of breakage of a wire command of a carburetor.
• Better balancing equally used cylinders independently from each other.

[FlyingMonkey]

53 minutes ago, Madhatter said:

Go to the Flygas website.

I read the website description.  None of the claimed "issues" with the factory setup have been issues for me or my engine.

[Roger Lee]

1 hour ago, Jacques said:

https://www.flygas.info/kit-intake-manifold/

 

"claimed" advantages

• Absence of vibration regardless of the difference in the opening of carburetor.
• Possibility of continuing to fly (at 50% of power) even in the case of breakage of a wire command of a carburetor.
• Better balancing equally used cylinders independently from each other.

#1 can’t be true. Which makes #2 less accurate and #3 not an issue anyway.

[Madhatter]

I think this is one of the modifications that was poorly engineered and is being used as an excuse for being lazy on syncing the carbs.I forwarded my previousl post to Flygas but I doubt I will get a response. I view this as a hustle for $ from people not informed. My reason to try this was to give benefit to the possibility that there might be something I missed. There are a lot of people in the LSA business that promote this but think they are only seeing a placebo effect ( they want to see success so bad that they will believe it actually works).

[FlyingMonkey]

12 minutes ago, Madhatter said:

I think this is one of the modifications that was poorly engineered and is being used as an excuse for being lazy on syncing the carbs.I forwarded my previousl post to Flygas but I doubt I will get a response. I view this as a hustle for $ from people not informed. My reason to try this was to give benefit to the possibility that there might be something I missed. There are a lot of people in the LSA business that promote this but think they are only seeing a placebo effect ( they want to see success so bad that they will believe it actually works).

That's unfortunate.  There are certainly opportunities to improve aspects of the Rotax design and increase performance with better intakes, exhaust, cylinders, etc. 

[Madhatter]

Exhaust yes, stay tuned. 

[Tom Baker]

1 hour ago, Madhatter said:

Exhaust yes, stay tuned. 

Pun intended?

[Madhatter]

I thought about that but figured no one would notice.  That's 2 for 2 for you.

[Anticept]

The rotax balance tube is undersized, so a larger tube would help. Guys in my area have been putting on tubes that are much larger, and it DOES help. It's NOT a substitute though for garbage carb balance. The further the fuel has to travel, the more issues with mixture you will have because the fuel will naturally want to condense on the intake walls and run as a liquid. This is why direct injection is so insanely efficient, multiport injection is really good, and long intakes with carbs are really poor with fuel efficiency.

#1: It won't fix extremes. As said, it's not a substitute for garbage balancing.

#2: possible. At least the engine wont act like it's about to shake off the mounts. You'll have a full open carb and a partial open carb with a throttle break, and the full open will be supplying some of the other side of the engine where the partial open would normally be a restriction, so it would help balance it out. It's not going to be smooth though the further you pull back, that's still a long travel distance.

#3: Don't understand what this is, wording is weird.

[Madhatter]

There is more to this than just balance tube size. If there wasn't it would have worked for me, I was trying to duplicate what Flygas engineering claimed they had. It may work for some 912 intake designs but not for CT's. I have some equipment to measure some of the engine intake parameters but like I said before it's not worth the time for minimal benefits. Flygas even indicated possible hp increase but backed off on that when I questioned it. If this was so good I'm sure Rotax would have jumped on it.

I have done a lot of performance enhancing attempts on the CT, some were good but this was a total failure.

[Anticept]

There's a certain point where if it's too large, I could see the tube itself just acting like an accumulator, and interfering with carb action.

I will clarify though: that flygas tube is huge. The ones around here are bigger, but not THAT big...

[Europaflyer]

Just a brief comment on the Flygas balance tube, as I have flown with one on my Rotax 914 equipped Europa that has a constant speed prop for several years.

I have no doubt that it provides smoother idling but the engine seems to smoother overall as well. The intake valves on one side of a 900 series engine are both closed intermittently when the engine is running and the larger balance tube smooths the flow through the carbs as when the intake valves are closed, the flow is not interrupted as it continues to the opposite cylinder bank, which has open intake valves, via the large tube.

I noted, after installation, that the constant speed prop was momentarily overspeeding on takeoff at WOT, making me suspect the prop was running up against the coarse pitch stops as the engine output had increased at WOT.

The pitch stops were changed to allow a coarser pitch, and the problem disappeared.

One further note. I had a carb malfunction soon after takeoff one day, due to an issue with a recent carb overhaul. The larger balance tube permitted a low power return to the sirport and saved a potentially risky outlanding 

In light of this, I'd say it is a good idea. If you are having problems, my first thought would be an induction leak after installation that needs attention.