Fuel Flow Cube

[NWade]

Notwithstanding our modest fuel flow needs and a lot of folks indicating success with red cubes.

The Gold Cube is indicated for Gravity Carbureted and Injected Engines

The Red Cube for engines supported by a fuel pump.

As they are both the same price at Aircraft Spruce at this time - Go with the Gold! :-)

Graeme - In the past, Sonex builders found that the Red cube tended to work better than the gold, even though the gold is what is indicated as the “proper” one (for carb’ed gravity-fed engines).

It seems backwards, but there was a consensus around this as of a few years ago.

My red cube has worked fine with my AeroVee Turbo & Aeroinjector over the last 4 years of limited ground-running (dear god my build has taken forever to finish); hopefully I’ll be able to use it in the air very soon!

—Noel

[mike.smith]

I recently replaced my Gold Cube with a Red Cube. Not really any better readings using the published K-factor. So I've been dialing back the K-factor incrementally and measuring the results. Another couple of tweaks and it should be reading close to actual before/after fuel measurements. So if you're having trouble, try modifying the K-factor setting.

[GraemeSmith]

Graeme - In the past, Sonex builders found that the Red cube tended to work better than the gold, even though the gold is what is indicated as the “proper” one (for carb’ed gravity-fed engines).

It seems backwards, but there was a consensus around this as of a few years ago.

My red cube has worked fine with my AeroVee Turbo & Aeroinjector over the last 4 years of limited ground-running (dear god my build has taken forever to finish); hopefully I’ll be able to use it in the air very soon!

—Noel

I could believe that. Perhaps there was a problem with the Gold cube?

It has recently been redesigned. Spruce are selling the new version. The tech notes on the Spruce site tell you the difference and how to tell them apart.

[Thermalflyer]

I have the gold on a OneX. The RDAC- XF does noy have a FF signal input. I have the red on the 5 volt and the white on the FF1, Ground is at the engine block. I do not get any reading on the MGL Light.
Since there is no signal port I am not able to install the resistor to comply with the setup shown on the MGL install sheet. Any help?

[XenosN42]

I have the gold on a OneX. The RDAC- XF does not have a FF signal input. I have the red on the 5 volt and the white on the FF1, Ground is at the engine block. I do not get any reading on the MGL Light.
Since there is no signal port I am not able to install the resistor to comply with the setup shown on the MGL install sheet. Any help?

The FF1 connector on the RDAC-XF is the fuel flow signal input. You've already connected the white wire from the gold cube to FF1. Just add the resistor as shown in the install sheet and you'll be good to go.