K-factor for fuel flow

[backcountry]

I have a RV-12 ULS with a Garmin G3X system and wonder what K-factor you feel good using.
With a system that measures what’s going out and doesn’t account for what’s coming back is kind of difficult to find a good number. I certainly haven’t come up with anything I feel comfortable with.

 

[sansoneservices]

I don't think k factor alone will help. The volume of the return changes with throttle changes. I could be wrong, somebody will add to this

 

[seagull]

Current K factor/ (divided by) the amount of gas pumped X (times) the amount of gas that the EFFIS says that’s been used. This will be your new K-Factor.
I am currently using 115000.

 

[Mich48041]

My K-Factor is 54000.

 

[seagull]

My K-Factor is 54000.

Mine was giving me bad usage numbers and I kept adjusting the K-factor, it finally settled in at 90000. During the conditional I was doing the fuel return line test and found a blockage in the orifice. After clean it my K went back to normal.

 

[bruceh]

The Dynon Skyview install manual (page 7-97) has some calibration information for fuel flow. Basically, you need to keep track of both how much fuel from the pump you are putting into the tank, and the amount of fuel that the computer "thinks" you filled up with (ie, Actual fuel, vs. Computed fuel used).

Computed fuel divided by Actual fuel times the K factor of the cube (default pulses per gallon is 68000) = the new K factor.
In my case the fuel flow ratio is 1.028 * 68000 = 69912 (new K factor).
Ideally, you want to see that the computed fuel is slightly more than the actual. That way the computer will leave you with some extra gas before it thinks you have run dry.

 

[sansoneservices]

I learned something new from this thread. Like the op I was confused about measuring the RETURN fuel. Thanks for clarifying

 

[HarryL]

Mine is now set to 110000 and seems to be very accurate.

 

[drill_and_buck]

Note, the K factor that you start with will be determined by which fuel flow transducer is installed in your aircraft. It will vary from aircraft to aircraft. You will be able to find the K factor on the the manufacturer's website of the model installed I.E. Floscan, Red Cube, Electronics International, .......

As noted by @bruceh, your EMS documentation (GARMIN, DYNON, AFS, ...) will provide you with the algorithm used to tune the K-factor over it's lifespan to provide you with the accuracy needed.