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Installing red cube on carburated engine

raisbeck

Member
I've been following the various red cube threads for a couple weeks, but can't decide how/where to install my fuel flow sensor on a RV8 with a Lyclone engine.

Basically, it seems that these sensors are very susceptible to heat and vibration. In fact Vic Syracuse, in his most recent EAA webinar called out a couple of installations that had it mounted to the engine mount as a potential source of failure. So I'd planned to put it on the firewall with a heat shield between the gascolator and the engine driven fuel pump with a teflon/SS line from the cube to the engine pump, all uphill.

On the other hand, when I opened the package yesterday, the instructions from EI said that it HAS to go between the "last fuel pump" (i.e. the engine pump) and the carburator, otherwise it may lead to vapor lock and inaccurate readings.

I can live with iffy readings, but vapor lock got my attention.

How has everyone with a non-fuel injected set up done it, and how well did it work?
 
Red Cube

I mounted mine on the engine mount with Adel clamps between engine driven fuel pump and carburetor. Works well.
 
I have mine in the cockpit after the electric pump. It works OK, but the flow jumps around a bit. The totals are always very close. My son mounted his on the firewall and ran a hose from the fuel pump to the red cube and then from the red cube to the carburetor. His is more stable than mine.
 
Before I switched to fuel injection, I had the Red Cube mounted on the cold side of the firewall just a few inches down stream of the Facet pump. It worked perfectly.

I made custom bracket that was riveted to the firewall. The bracket was angled so that the output was slightly higher than the input.

At some point along the way, I learned that it should have been mounted closer to the carb. However, since it worked fine, I did not move it.
 
On taking ownership of our preloved RV9A I found the unit was flopping around between the gascolator and mech pump not mounted to anything particular, sitting vertically. FF indications were terrible, and every time I selected the aux pump on it would spike to a large number.

Following the instructions to the tee I attached it to the lower left engine mount (just prior to the carby and after the mech pump) on-top a rubber standoff.

Happens to sit just over the left cowl louvre which would no doubt provide additional cooling air to the conventional cowl.

Indications are now rock solid with no change to FF reading when the aux pump is selected on.
 
Here is my Red Cube

The cube mounted between the fuel lines pretty much just sits there. The mounting plate just stabilizes it.
I was asked how long those fuel line are and it appears from my pictures that I took while installing them they are about (hose only without fittings) 7” long. I’d make one and then see if it fit both locations. One might be 6.5”

ACtC-3eBIAwWw-1x4XCLfA9QUx_aIZb7GhIirZ9FBZReEaSrJP7_DjBf2h5zyUuiZMq7n1FWUWEYrYFJ81wF_OWwaXful60xJ4Oz8SB5Yhftc1Ns4QOR6g5seM9zROLTg9dspxZ1ERlgRMwvCqsrP-lvbY0zxQ=w449-h598-no


ACtC-3e4UHXiCBVf-xY2ebwozr1vFuJ9m8JsII-02IlcIXfB9X9ubfndN5m9Ej7rZDmbbs6lILg1SUXZT4zI7nhX7KuZ152sOiVafnFO4N-kc_2F-gM-9mUUXDJmlT9Xl6i46lOl9YIb8pl8HyftPnruVNmnYw=w449-h598-no
 
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Instructions for install

I had recent conversation with The manufacturer regarding how important it is to have the wire lead vertical. Bottom line they said if the output is above the input and the wires are slightly up, there may be a slight degradation of accuracy and service life expectancy due the fact, apparently, the impeller bearings are optimized for vertical shaft orientation. That said, my -3 is perfectly oriented per instructions and performance is stabil at 220 hours. My -4 is a little wire out up, stay tuned for conclusions.
 
I have the red cube mounted between the electric fuel pump and the engine driven fuel pump on my carbureted RV4, inside the cabin on the cold side of the firewall. I know this is not the geometry that is suggested by the manufacturer, but there is literally no room in my engine compartment between the engine pump and carburetor to install it. If my only choice was that, I wouldn?t be able to have a fuel flow indication. As it is, it works well where it is, and my fuel flow calculations in my EFIS are spot on, so my location works for me.
 
Various places to locate the cube----under cylinder#4 and near the lower dynafocal cup usually works well.

Tom
 
Mine is mounted between the lower arms of the engine mount, and between the gascolator and the mechanically-driven pump. In use, when the electric pump is running the flow reads high but that's only for a small percentage of the time the engine is running. My receipt at the pump always matches the "amount used" showing in my totalizer (MGL) so I don't think the error introduced by its location is affecting accuracy. With the electric pump off, readings are stable and appear accurate.
 
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