Fuel Control Unit – RV-14 Build

Fuel flow test

Posted on April 25, 2026 by Neal

Today I tested the fuel system for the first time, running the electrical fuel pump and testing fuel flow. Everything worked well, and I was happy to see no obvious leaks.

I started by disconnecting the fuel line leading into the fuel servo, and redirected it into a large measuring jug. Then I poured approximately three gallons of gas into the left fuel tank, and turned the fuel selector to the left tank. I wanted to make sure I had fuel in the fuel pump before starting it the first time, so I used the shop vac and some clear tubing to prime the system – drawing fuel through the fuel lines, all the way to the fuel servo.

I powered up the panel and switched on the pump, and was happy to see fuel flowing into the jug. I ran the pump for a minute and measured 92 fluid ounces pumped, which translates to 43.125 gallons per hour. I repeated the test on the right tank, measuring 94 ounces pumped, about 44 gallons per hour. During the second test the fuel flow gauge was measuring 43.7 gallons per hour, which is very close to the amount I measured.

I repeated the test in a level flight attitude, and then tested for unusable fuel. With the plane in a level attitude, I pumped all the fuel out of the tank, and then drained the leftover fuel from the fuel tank drain port. I measured 6 ounces of unusable fuel per tank, for a total of 12 ounces.

Note the fuel flow of 43.8 G/H. Fuel PSI is low at just 1.5, but I expect that is because the fuel line is simply draining into a jug

Disconnected fuel line pouring fuel into a jug

Left tank test results after a minute of pumping fuel

Total unusable fuel left, just 12 ounces

Blast tubes

Posted on April 25, 2026 by Neal

Today I added a couple more blast tubes to cool the battery, and the voltage regulator on the back of the alternator. I also reconfigured the fuel lines in the engine compartment and moved the fuel flow sensor to the engine mount.

The Earth-X battery gets a lot hotter than the standard battery, and benefits from a blast tube to direct cool air at the battery while in flight. I used a length of 1 inch SCAT tube, some hose clamps, and an aluminum flange to make the blast tube. I used a step drill to upsize the hole to the right size. I also added a lock washer on the back side of the flange, along with RTV to make it secure to the baffling.

I had bought a 3D printed fitting for the back of the alternator that directs air at the voltage regulator, but never installed it. Today I mounted it and hooked it up with a blast tube from the air inlet ramp on the right side of the engine compartment. Lots of RTV, another lock washer, hose clamps, and it was done.

Then I moved onto the fuel lines. I had previously loosened some of the fuel lines to test that my new routing would work. By switching the fuel lines either side of the fuel flow sensor, the sensor moves aft several inches, placing it right above one of the engine mount struts. Today I removed some of the old fittings, added new ones to streamline to fuel line routing, and mounted the red cube to the engine mount. It’ll be much more stable, and cooler, in this location, which should hopefully make for a longer useful life.

Battery blast tube, forward side of baffling

Back side of the baffling showing the new blast tube

Blast tube directed at the battery. The safety wire is holding the tube steady while a blob of RTV dries

Voltage regulator blast tube entry on the air ramp

Under side of the blast tube flange on the air ramp

The 3-D printed fitting for the back of the alternator. Note, this is high-temp material with Carbon fiber blended in

The new location for the Red Cube (fuel flow sensor)

The fuel lines aft of the fuel flow sensor. I removed the 45 degree fitting from the red cube inlet, as this is not ideal. The straight fitting I replaced it with will allow for a smoother flow of fuel, and is actually the recommended configuration by the manufacturer. A single adel clamp is holding the sensor.

Snorkel fitting

Posted on August 31, 2024 by Neal

With the fuel controller in place, I was able to test fit the snorkel. Unfortunately I ran into an interference issue, but after some further investigation I found this is a known issue. I ordered a new oil return line for the #2 cylinder from Aircraft Specialty, as they have solved the problem by making a custom tube that doesn’t protrude as far forward. Kit #13 from their firewall forward hose kits: https://www.aircraftspecialty.com/rv-14.html

I also heard back from Airflow Performance, and they sent a doc that has some useful RV-14-specific install info, and confirmed I needed to order a gasket. $2 gasket, and $10 of shipping, it should be here in a couple of days.

RV-14 Mixture Throttle cable pictures.docx Download

The snorkel resting in position as an initial test

The interference issue with the oil return line. The snorkel needs to move aft about 1/4 inch to line up. Rather than restricting the oil flow by modifying the fibreglsss, a new oil return line solves the problem.

Some people have reported interference with the starter solenoid, will have to see how it goes once this is in it’s final location

Fuel controller

Posted on August 28, 2024 by Neal

Tonight I unpacked the fuel controller and installed it on the engine. This required some research, as there isn’t any documentation from the Lycoming or Airflow Performance in the box. I found some help on Vansairforce, and was able to find the Airflow Performance manual. I ended up emailing them anyway, because I don’t have a gasket in the box.

For now I installed the unit using the temporary nuts to hold it in place, so I can test fit the snorkel.