fuel flow

[Klimek]

To all the mechanical, electrical, nuclear engineers, physicists, Dr's, lawyers and Indian Chiefs...
I'm finishing my firewall forward and would like to run a fuel flow test. Anyone have an idea what it should be at the aero Injector
inlet? Onex standard gear 15 gallons of fuel, gascolator (well insulated and shielded) with 06 line and fittings. Fuel cap on and 1/4"
vent line.
Thanks!
Frank
ONEX090
90%.90%

[kmacht]

Take a look at AC 90.89A (page 23). It details out how to do the fuel flow test and what the results should be.

http://www.faa.gov/documentLibrary/medi ... 90-89A.pdf

The aircraft needs to be in a certain attitude and configuration when doing the test but for gravity feed systems the formula is (.55 X engine horse power x 1.5) to get pounds of fuel per hour. Divide that by 6 to get gallons per hour. For the 80 hp vw it the fuel flow should be about 11 gallons per hour minimum or for the 120 hp Jabiru it is about 16.5.

Keith
#554

[gammaxy]

I have an Aerovee with Aeroinjector.

With an automotive inline fuel filter and the Floscan fuel flow sensor I measured 12GPH for the last two gallons in my tank at the aeroinjector inlet.

I ended up removing the Floscan while troubleshooting a poor idle after landing. Without it I get 20GPH and no longer have trouble at any power setting. I spent a while adjusting and swapping needles in the aeroinjector, but once I removed the Floscan I was able to set the needle according to the plans and it has worked great ever since.

I'd like to put the Floscan back in, but would first like to know if anyone else is successfully using it and what kind of flow rate they get with it. Right now I'm just happy to have a smooth-running engine.

[Sonerai13]

With an automotive inline fuel filter and the Floscan fuel flow sensor I measured 12GPH for the last two gallons in my tank at the aeroinjector inlet....Without it I get 20GPH and no longer have trouble at any power setting....

Chris,

We have a flowscan on the fuel system in our engine test cell here at Sonex. After discussing your fuel flow issues with you I thought I'd check the flow on our test stand. While the fuel system isn't directly comparable to the system in the Sonex airframe, The numbers ended up comparable to what you found. I measured 22 GPH right out of the tank, through the fuel shutoff valve. Flow measured at the AeroInjector inlet (through the flowscan transducer) was a smidgen over 15 GPH. So the transducer does restrict flow to a measurable degree. Still, 15 GPH is more than enough for an AeroVee engine (We're running a turbo engine on the test stand right now). However, your 12 GPH is still more than the minimum recommended by the FAA's fuel flow AC (150% of the maximum fuel consumption of the engine, which for a normally aspirated AeroVee is around 7 GPH or so), so it should be adequate for your engine.

[GWMotley]

Chris and Joe,
I have essentially the same number with the flow meter installed. I do note that if I try to run a little lean of peak, there is at tendency for the engine to experience sputters from reduced fuel flow especially as I burn off fuel to lower levels in the tank. This is also noticeable during turbulence. My experience leads me to believe that some us experience a lower fuel head pressure. I have even considered a low pressure fuel pump, but If I run the needle and mixture control a little richer, the fuel flow of course increases and the sputters stops. Fortunately, these VWs don't eat much fuel even at a richer than ideal cruise settings.

[mike.smith]

To all the mechanical, electrical, nuclear engineers, physicists, Dr's, lawyers and Indian Chiefs...
I'm finishing my firewall forward and would like to run a fuel flow test. Anyone have an idea what it should be at the aero Injector
inlet? Onex standard gear 15 gallons of fuel, gascolator (well insulated and shielded) with 06 line and fittings. Fuel cap on and 1/4"
vent line.
Thanks!
Frank
ONEX090
90%.90%

http://www.mykitlog.com/users/display_l ... 8790&row=5
http://www.mykitlog.com/users/display_l ... 9395&row=4

[fastj22]

I use a Red Cube flow meter and see 26GPH full and 22GPH near empty disconnected at the inlet to the aerocarb. AN-6 lines and fittings, gascolator.

[lpaaruule]

I haven't had nearly as good of results as others with fuel flow testing.

Since redoing my fuel system to have only gravity feed, I'm lucky to get 13.5 gph with 10 gallons in the tank. Surprisingly, at a 19 deg angle the fuel flow doesn't change much, the fuel level has the most effect. I stopped at 19deg because I was getting nervous that the plane would fall and it was getting hard to push up the ramps.

At a 19 deg incline and 2 gallons in the tank I only get 10.8 GPH. This certainly isn't 1.5 times the fuel flow a Jabiru 3300 can use. I was hoping for around 15 GPH. Ironically, from pictures I've seen, the Jabiru's intake appears to be higher than the AeroVee, making it even harder for the Jabiru to get the fuel it needs.

I'm using AN-6 lines and fittings. From my tank the fuel goes through a red cube sensor, then an inline fuel filter, then a short run to the AeroInjector. The only thing I can think to do to get more fuel flow is remove the red cube sensor. I've checked the fuel filter for debris, and it was clean.

On a side note, I've looked at other builders sites, and believe that some of the testing done is invalid. Some builders will let their fuel line hang down lower than the inlet of the carb, or add a short length of fuel line to reach a bucket. Based on my testing, letting the fuel line hang down even an inch can increase fuel flow by 1 GPH with a half empty tank. It has a siphoning effect.

For example, I added a 5 inch fuel line to the end of my fuel system so the fuel would more easily go into the gas can, and the siphoning effect increased my fuel flow from 13.5gph to 17.7gph. So, any builder that simply disconnects the fuel line from the carb, and lets it hang down from the gascolator would likely get fantastic fuel flow due to the siphoning effect.

At the moment I don't have any idea how to make my fuel system simpler other than removing the red cube sensor.

Anyone else run into this issue with the red cube? BTW, there is a T-fitting before the in-line fuel filter that has a short run of fuel line to remove water and other debris from the system. I did a flow test from that point and the curtis valve flowed 18.6GPH. That's not a fair comparison to the carb fitting though because the curtis valve is approx 7 inches lower than the rest of the system.

If you have a Jabiru 3300, red cube sensor, gravity fed system, and are able to get 15+ GPH with minimal fuel in tank, and measuring the flow rate accurately, please respond with info on how this is done! :-)

[gammaxy]

I think you're correct that some of the other reported flow rates are optimistic due to the problems you mentioned. I also doubt most have tested to 19 degrees.

I haven't tested this but suspect if the red cube was mounted lower in the fuel system you might get a little higher flow rate.

One measurement I never made but wish I had is the flow rate pouring through the carburetor with the throttle full open and the mixture full rich. Maybe if everyone flew Aeroinjectors we wouldn't use the 150% check since we'd all be able to measure pretty much exactly what the actual flow rate is.

[lpaaruule]

I imagine that builders are going to be reluctant to admit they are flying with less than optimal fuel flow. My guess is that there is not a single Sonex out there with a fuel flow meter and Jabiru 3300 that is getting 150% max fuel flow with minimal fuel. My system would probably work fine as-is, but I like to have the odds stacked heavily in my favor.

Still thinking...