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Hot idle roughness solved!

Zuldarin

Well Known Member
I have just turned a little over 47 hours of flight time with my RV-9A and I have learned in explicit detail what "experimental" means. I have had a few issues that I am working through (some of which I have posted about before) but one issue now seems to be solved thanks to Tom at TSFlightlines. When hot my engine would pop and sputter at idle due to fuel flashing in the supply lines. I had originally mounted my flow transducer (red cube) low on the firewall. Tom suggested I try a new configuration he was working on where the flow transducer gets relocated to the inlet of the flow divider. He sent me the parts I needed and after doing some hot taxiing on Saturday I am calling this issue solved!

Not only does this new configuration protect the flow transducer from exhaust heat but it allowed me to remove the red-cube-to-mechanical-fuel pump hose. One less hose means less air flow obstruction at the cooling air exit! I think that is a win win situation!

Here is a picture of the new configuration.

Thanks TOM!

2015-04-04%2B18.39.46.jpg
 
Support

Darin,
This might of solved your vapor in the fuel problem but I don't see any support for the red cube. With out support you will break one of the fittings over time! You could either support the red cube with some sort of bracket or move it behind the firewall! It would be great if some else could chime in on this as well in the name of safety!
 
Cube

I fully agree with the previous post, that looks like more mass than I would want hanging off the flow divider due to vibration concerns. When I installed these on Mooneys the fuel supply line came in thru the rear baffle and the cube sat on a steel bracket that mounted to 2 case half bolts. First one still going strong 15 years later. Will do something similar on my 9.


Don B A&P, IA

RV 9 rebuild in progress.
 
When I was initially thinking about this, I envisioned a bracket to mount where the lower bolt is on the flow divider bracket. Darin will probably test that part as he moves forward.
Plug goes out to Team AeroDynamix, that tested this location in various configurations last air show season.
Tom
 
Concur some sort of support bracket needed. It is a critical item IMO as well in that, should it break there is 100% chance of fire. A bracket from the divider mount bolt to the red cube is probably the solution. If there is any appreciable movement between the red cube and the divider you run the risk of breakage at weakest point. That would be the fitting, IMO.

I'd fix it before I flew behind it if it were me.
 
Also, I believe the red cube instructions specify that the cube mounting be oriented such that the wires exit vertically upward so that any bubbles in the fuel can flow through the cube and not be trapped within the fuel cube.
 
Compilation of the post from the manufacturer's employee on this board.....

As far as I know Dynon distributes both the FloScan 201B as well as EI's FT-60.

The FloScan unit is much more sensitive to the angles/fittings entering and exiting the unit. EI's unit does not care. You can run 90 degree fittings in and out of ours without problems.

JPI does not sell EI's FT-60:cool:

Maybe you can get Dynon to trade you for a FT-60?

Good luck!

Matt


You do NOT want to rigid mount the transducer to the motor (any part) using just a fitting. It is a huge safety issue. The fitting could theoretically fatigue and break. You absolutely need to have flexible line on both sides of the Floscan 201B or the EI FT-60 (that Dynon now utilizes).

After manufacturing/supporting flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after both fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more. Frankly we don't care if the thing flows straight up, or if you put 90-degree fittings in and out (FT-60 only) of the transducer. Just don't mount it upside down or flowing sharply downhill.



Hope this helps,

Matt Sharp
Hello All!

Your friendly neighborhood EI Tech support rep here!

There are really two issues in regards to EI’s specifications on flow transducer placement.

1. Accuracy of the output of the flow transducer.
2. Safety.

Issue one is pretty basic. After manufacturing flow instruments for a good number of years we have seen that flow transducers accuracy is typically better when mounted after the mechanical fuel pumps. They simply seem to prefer to have fuel pushed through them, not pulled through. The truth of it though is that many installation drawings still read as though we were still using the older Floscan 201 and 231 transducers. I have seen installs that mount the transducer between the pumps with claimed success. The Floscan units were much more sensitive in regards to mounting location, angles of fittings in and out, and attitude. Our new design will tolerate a lot more.

The other more serious issue is in regards to safety. We want to make absolutely sure that the fittings on the transducers never are subjected to conflicting vibration planes. The engine will flex in the motor mounts creating conflicting vibration planes between the engine and the airframe. This is why the “flexible line in” and “flexible line out” is called out so often. This is also why we don’t want the transducer rigid mounted, via a fitting, to a carburetor or fuel pump. A contradicting vibration plane will focus the energy directly to the fitting. It is our sincere concern that with the two conflicting vibration planes here could cause the fitting to fatigue and crack. This would be bad…and we have seen it happen….

On the bright side, we don’t care if the thing flows straight up, or if you put 90-degree fittings in and out of the transducer. Just don’t mount it upside down, flowing sharply downhill, or before the pumps. :eek:

Please let me know if you have any questions or if we may be of any assistance.

Matt Sharp
 
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I talked to the EI engineers a few weeks ago. FT-60 is to be mounted wires UP.
 
I don't want to throw a dog in this fight but the position of the wire (the cube) is the least of what's wrong. There is a good chance the vibration will break that connection and a fire will quickly follow. Less important: You are not supposed to use 90 deg fittings on either end - the cube should not get as hot as it's going to on this - the cube is designed to spin the turbine at the angle recommended (wire up).
 
I appreciate the constructive criticism and suggestions. I will fabricate some sort of support bracket for the cube before I fly it again.

I think Brantel's reply with manufacturer comments helps clear up any issues with cube orientation (except flow down), 90 degree fittings or wire orientation (except upside down).
 
I'm going to try to explain the reasoning, and testing behind Darin's install.
The object of this was to find a good universal location for the cube that would work for most all 4 cylinder Lycomings. Having built alot of hoses over the years, the hardest is the VERY short lengths some of you had in your transducer locations. Some as short as 2.625 inches flare to flare. In some of those locations, a difference of .125 to .250 inches means it wouldnt fit. Some of you know what I'm talking about.
So---with the help of Team AeroDynamix, last year a couple of the guys, mainly Kahuna, and Speedy (Danny Kight) tested 2 different locations, very near the flow divider. Kahuna, with his IO540 had his mounted horizontally, wire up. Speedy, mounted his vertical, wire facing aft. Both had hoses connect to the spider. Both members flew this way all year, and reported no disruption of flow, no reading errors, no issues whatsoever. (The old Flo Scan had to be mounted with the wires up, but I didnt find anything that said the FT60 had to be mounted horizontally, wire up. If so---I stand corrected-).

My attempt to simplify the plumbing and make this package as universal as possible led me to this configuration. There never is a one way fits all installation. So---this was an attempt to make life easier, and less expensive for customers.

Tom
 
I think Brantel's reply with manufacturer comments helps clear up any issues with cube orientation (except flow down), 90 degree fittings or wire orientation (except upside down).

You mean the part that says..

Originally Posted by Mathew Sharp
You do NOT want to rigid mount the transducer to the motor (any part) using just a fitting. It is a huge safety issue. The fitting could theoretically fatigue and break. You absolutely need to have flexible line on both sides of the Floscan 201B or the EI FT-60 (that Dynon now utilizes).
 
You mean the part that says..

touche' Ok the last thing I want is a fire. I will talk to Tom and see if we can come up with a less rigid mount.

Thanks all for the comments.

Darin
 
Randy--Darin is going to work on a bracket.
According to instructions---look under mechanical interface if you dont have the PDF version--states that the transducer should NOT be mounted with the wires DOWN, and the BEST situation is with the wires UP. The BEST situation is with the wires up, means (to me anyway) that this is recommended, but possibly optional. Team AeroDynamix flight tested this configuration last year for me.
The old Flo Scans were very specific on mountings, fittings, how much straight lengths in and out, etc. We've found the the FT60 doesnt really care----the flow readings are very consistant, as long as the wires are NOT pointed DOWN.

Tom
 
Tom & Darin.. Like I said, I don't have a dog in this fight but the evidence is obvious. You don't put a part with a max temp of 257F in a 400F+ environment. You don't hard mount the cube to the divider. Other then the bubbles there's a reason Red Cube whats the red cube mounted wires up, it's the way the turbine rides on the jewels. This is not all theoretical, these are solutions from past history. Inaccurate readings and early turbine failure is not that big of a deal, Fire is. Again, I wish everyone good luck.
 
Agreed---We all have dogs in this fight. Darin and I are working on a couple of options.
Ever see a transducer between the pump and the servo very near the aft side of the sumps? Gets pretty hot there to I suppose--enough to darken stainless braid teflon that was routed ON the exhaust WITH firesleeve.
Thats the good thing about this forum--if something DOES slip through, someone catches it.
Tom
 
This is how the cube is installed in my RV-8. It is below the cylinders with the wire on the side. So far it has worked well, flow indication after some calibration is quite accurate. The fuel lines and the cube are wrapped in a heat shield material.
Tom made the fuel lines and was patient enough to do the top line three times to get the length correct.

It is an alternative method to having it without flex tubing on the top. The bottom 90? fitting is steel.

317cbk0.jpg
 
Very nicely done David. What type of heat shield did you use? I have used a large diameter section of fire sleeve in the past and used safety wire or band clamps to close ends followed by silicone to seal things up.
 
Aircraft spruce has a stretchy fire sleeve that works perfectly. its is black and about 20 bucks.
 
I can get some large diameter AS1072 firesleeve.

David's install wasnt exactly typical! 1/8-3/16 of an inch DOES make a difference. Part of the reason for trying to come up with a better solution.
Tom
 
I was very concerned about the 90? steel fitting being so close to #1 exhaust pipe. Fuel pressure in this line is low, like 3-5 psi which would make it very susceptible to vaporization. The fix was a Van's heat shield and wrapping the fuel line and cube with surplus fire sleeve.

I like the Vans heat shields, must have 6 pr 8 of them installed protecting throttle/mixture cables and fuel lines.

v4q637.jpg
 
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