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  #21  
Old 07-06-2022, 11:08 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 3,740
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From the FT-60 (Red Cube) install manual:

Mechanical Interface:
If the aircraft has a fuel pump(s), the flow transducer MUST be installed downstream of the last fuel pump.
Installing the transducer upstream of the fuel pump(s) can cause vapor lock and jumpy/inaccurate readings.
The Red Cube FT-60 has 1/4" NPT ports. Apply thread sealant to fittings, assemble and torque fittings to
8-10 ft. Lbs., DO NOT EXCEED a torque of 12 ft. Lbs. The Red Cube FT-60 should NOT be installed with the wires pointing DOWN (the best situation is with wires pointing UP). Also, the fuel line on the outlet port should not drop down after exiting the transducer. Both of these configurations can trap bubbles in the transducer causing jumpy readings. The inlet port, outlet port and flow direction are marked on the top of the Red Cube FT-60.

Here is one way to meet the rules (and yes I know the steel fitting need to be aluminum):

Last edited by Carl Froehlich : 07-06-2022 at 11:17 AM.
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  #22  
Old 07-06-2022, 11:32 AM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 167
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Ahead of the firewall; best practice is to use steel fittings only. That should include the fittings on the ends of the hoses also.
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  #23  
Old 07-06-2022, 01:03 PM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
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What happens if you fly inverted? And the RV10 stock had the transducer in the tunnel. Kinda goes against the "guidelines"
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Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders
Ridgeland, SC
www.tsflightlines.com, www.asflightlines.com
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  #24  
Old 07-06-2022, 01:30 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
Posts: 3,740
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Quote:
Originally Posted by TS Flightlines View Post
What happens if you fly inverted? And the RV10 stock had the transducer in the tunnel. Kinda goes against the "guidelines"
Yep - when inverted I suspect having an error in fuel flow reading will be low on your priority list.

Yep - the RV-10 plans do put the transducer in the tunnel, and yep it gives erroneous reading when the boost pump is on, and yep that placement provides an unnecessary fuel pressure drop to the inlet of the mechanical fuel pump. All this is first hand knowledge.

Now look at the RV-14 FWF instructions that put the cube between the fuel pump and the Fuel Manager on the engine. Good placement except the instructions have you hard mount the cube to the engine in a high heat area (goes against the guidelines). Here too I have first hand knowledge of the fuel flow going to ~11GPH when above 7K, regardless of mixture setting. Moving the cube to a proper location solved the problem. Note - other RV-14 builders have not reported this problem but I have second hand information that the same issue presented itself on an RV-12.

We changed out the red cube, no joy. Engaging the appropriate vendors yielded no technical feedback. We can only postulate that the combination of vibration, heat, atmospheric pressure along with inlet and outlet hose lengths set up some kind of resonance that the little spinning wheel did not like.

We do know that meeting the guidelines eliminated the problem - so that is how I install the flow meter.

Carl
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  #25  
Old 07-06-2022, 02:51 PM
ian greenland ian greenland is offline
 
Join Date: Jul 2013
Location: goondiwindi qld australia
Posts: 8
Default Fuel Pressure

I too run a Wheldon pump from within the cab through the Facet pump to the gascolator I have no engine driven pump so there is no vacuum in the line in the engine bay. Has been very reliable and no problems, at take off pressure drops from 6 psi to 5psi which activates Low Pressure warning, you could change you Red line settings in the Efis but manufacturers warn that below 4 Psi these sensors become out of tolerance. I dont like turns bends and loops in a vacuum line with heat as long as you have booster pump on at take of and landing it is probably ok👍
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  #26  
Old 07-09-2022, 09:04 AM
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MacCool MacCool is online now
 
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Location: central Minnesota
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Quote:
Originally Posted by Carl Froehlich View Post
Mac,

I suggest you have some basic issues that need to be fixed before you go chasing possible fuel line heat causing your pressure drop.

Looking at the photo, I note that you have the fuel line going into the (new) red cube, then into your electric boost pump, then I assume to your mechanical fuel pump. I also note a bunch of 90 degree fittings.

I refer you to the EMS install instructions on placement of the red cube (as in between the engine driven fuel pump and the engine and not mounted on the engine) and fuel line considerations on the input and output of the cube.

Carl
Carl, I pulled the cowl a couple of days ago to review the fuel line routing. I found that you are correct...the fuel line goes firewall -> Red Cube -> boost pump -> engine-driven pump -> fuel servo -> engine. Fuel pressure readings come from a T-fitting off the engine-driven pump and routed to the fuel pressure sensor. This was apparently the routing chosen by the guy (Don Swords) who did the firewall-forward work for the original builder 11 years ago. Performance on fuel flow readings isn't affected. I'm not sure if this arrangement causes or contributes to the hot-engine fuel pressure issues I'm seeing (gauge fluctuation and mildly hard hot-weather starting), but I think I'm going to start with insulating the exposed fuel lines and figure out a way to insulate the Red Cube. I appreciate your input.
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IO-320D1A (factory new), C/S
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  #27  
Old 07-10-2022, 05:20 PM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 3,085
Default I have stayed--

away from this discussion, because of our transducer mounting kit. BUt in this case, I'll bring up something that may have been overlooked. I know I did, until last year. Vans engineering when designing the RV10 and the RV14, went against the 'recommendations' of EI on the location and plumbing of the FT60.
In the RV10, the outlet of the transducer isnt 2+ inches and the OE Rigid tube makes a 90* vertical bend. Against EI's recommendation.
The RV14 uses a AN823-6D 45* adapter on the inlet port, again going against the recommendations.

So here is a kit manufacturer that has several engineers that decided that placing the transducers in those locations was fine. And---I kinda think that for the most part, they work just fine. Yes, everynow and then you'll get an anomalous unit, but givent he number of these that are flying, I think the crazy reading numbers are relatively small. If they werent, I think Vans would have put out an SB on the subject.

YES---we went against the 'recommendations' too, bu mounting it at the flow divider. (Actually my reason was laziness.) In mounting in in a lower location like near the servo you have to have 2 hoses, 1 long to the flow divider and one short, from the servo. The short one is ALWAYS a PITA to get right---ask Dan Horton, and a few others. So gee, lets eliminate 1 hose, but you still have to connect to somehow to the system. In our case, YES the wires are NOT pointed up, but evereything seems to work just fine. What happens it you have them pointed UP and make a banked turn? UH---the wires are not up. Does the unit quit, or stop flow? Doesnt seem so. Even sustained inverted flight, it doesnt stop the flow.

So 'recommendations' are just that in my opinion for whatever thats worth. But, if you are going to deviate, then its kinda important to think out of the box and look at things from all angles, including inverted.

Flame war starts now---

Tom
__________________
Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders
Ridgeland, SC
www.tsflightlines.com, www.asflightlines.com
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