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ELECTRONICS INTERNATIONAL FUEL FLOW TRANSDUCER FT60 Red Cube - right? That's what everyone says. It's what Dynon and Garmin recommended on recent quotes to me.

But if you read the spec on Aircraft Spruce and especially at EI's web site - they specifically state that the red cube is "For use in Aircraft with engine-driven fuel pumps & Horsepower up to 350 HP"

For a gravity fed engine you need to go up to the FT90 Gold Cube. "For use in Aircraft with gravity-fed fuel systems or Horsepower between 350 to 500 HP"

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Is this why some folks think they are having trouble with vapor locking in the fuel cubes? The red cube is actually not supposed to be used in a gravity situation?

Just throwing it out there for discussion.

Yeah, I read the same thing. I did call Dynon and they said I could use the Red Cube with the Aerovee or Jabiru gravity feed systems. I ran the Red Cube in my Waiex 3300 gravity, RV-8 IO-360 Elec pump, and my current Waiex Aerovee Turbo gravity. The sensor is directly forward of the fuel petcock at the tank bottom and they were all accurate.

The red Cube is $100 less expensive than the Red Cube, so I saved the money and went Red.

I asked Kerry about this because I think the gold cube is actually called out in the B-model plans, even though the red cube seems to be more appropriate for the fuel flow of our engines. He said that gravity feed is the reason they recommend the gold cube. Not really sure why!!

It’s the pressure drop.

Red cube .6 psi drop at 30gph
Gold cube .05 psi drop at 20gph

With our little bit of gravity pressure, 1/2 psi drop is significant. It may work ok in some cases, but it’s still a lot.

GordonTurner wrote:It’s the pressure drop.

Red cube .6 psi drop at 30gph
Gold cube .05 psi drop at 20gph

With our little bit of gravity pressure, 1/2 psi drop is significant. It may work ok in some cases, but it’s still a lot.

But, as you know, Gordon, on Sonex products we're not running 30 gph. At 10 gph the red cube pressure drop is only 0.06 psi. Fuel flow testing confirms that the red cube works for many of us and because of a significantly lower price than the gold cube, it's been the chosen way to go.

Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,.Jabiru 3300 #261

Thanks Art

The only info I saw didn’t include the really useful data points. .06 at 10 gallons sounds fine, $100 bucks in my pocket sounds fine (that won’t last long...).

Gordon

We have the Red Cube and it works perfect. Exact readings which corresponds to fuel usage from tank. We have the straight fuel line according the Jeff Shultz design. http://www.sonex604.com/misc/Sonex_1374_Fuel_Sys_Mar_2018.pdf

Red cube has worked fine for me.

I have had the Gold Cube (as recommended by the manufacturer) since I built the aircraft and it has not worked worth a darn. It's been pretty much useless, and I have a VERY simple fuel system with the device located per the manufacturer's recommendations. I bought a Red Cube this year and plan to install it during my condition inspection this summer. I'm curious to see if it works any better.

mike.smith wrote:I have had the Gold Cube (as recommended by the manufacturer) since I built the aircraft and it has not worked worth a darn. It's been pretty much useless, and I have a VERY simple fuel system with the device located per the manufacturer's recommendations. I bought a Red Cube this year and plan to install it during my condition inspection this summer. I'm curious to see if it works any better.

Hi Mike,

I'm curious. What are the exact problems you are encountering?
What type of EFIS is the Gold Cube connected to?