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Second/Dual Red Cube/Floscan (G3X Touchor Skyview) fuel computation.

R

rjtjrt

Well Known Member
Sorry for the long thread title.
Has anyone installed a second Red Cube (or Floscan) transducer in RV-12 (on return line) so as to get accurate fuel calculation?
I am tempted to get this as it seems the only way to get accurate fuel calculations on the EFIS.
If any have, any tips or hints?
I have G3X Touch.

John
 
The use of a single cube with a k-factor determined by the manual's procedure works fine. No second cube is really "needed." How accurate do you need it to be?
 
Bill

I tried with K factor 68000 set and used 5.1 USG but EFIS Calculated I used 8.7USG. This results in a corrected K value of 107829 as new k factor. Seemed to me far too high to be correct.

I posted this on VAF asking for advice
( http://www.vansairforce.com/community/showthread.php?p=1069069#post1069069 )

Advice is that it is a known issue with RV-12 and due to return fuel line and electric pump on all the time, only way to get accurate fuel calculation in RV-12 is to use a second red cube on fuel return line (G3X Touch has facility to read 2 red cubes and subtract the one on fuel return from other to get true fuel used).

John
 
If the pump is on all the time and the return is a fixed flow amount, you should be able to adjust the single sensor to a K factor that is close enough. As you have found, the number will be much higher due to the return flow. It is what it is.... I would try it and see how it goes, you may have to try several fillups to get it zoned in.

If for some reason the return flow is variable, your gonna have to have 2 cubes to get accuracy.
 
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Refer to my posting from long ago. I just refreshed it to bring it to the top. This technique works extremely well on the D-180. I'm pretty sure the Skyview alao has a RETRN parameter as well.
 
With Skyview 110,000 works very well for me and for others as I recall picking it up in a post here (obviously not Big John's post which applies to D180)
 
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Thanks for the advice.
Will look at trying the k factor we calculated first and see if it gives reasonable accuracy. If not will try Bigjohn's suggestion.
 
You really can't factor in a fixed return with just the K factor.

Imagine the fuel returned is 1 GPH, and the correct K factor is 60,000:

At 1 GPH actual flow (idle), this means your K factor would be 120,000, at 4 GPH (cruise) it would be 75,000, and at 10 GPH (takeoff) it would be 66,000.

You might hit an OK average for the way you operate your plane, but if you calibrate it for 30 minute local cruises, you'll be way off when you do a 3 hour cross country. Maybe it does work well enough, but it's hard for Dynon to support that knowing what errors it does cause and the importance of good fuel quantity information.

The D180 took care of this with a calculated return parameter that subtracted a certain GPH from the flow. This was done because the D180 couldn't handle a second flow sender, and this was better than nothing. Now that SkyView can take two senders, we don't support the calculated return flow. Even the fixed return flow calculation was subject to inaccuracies due to fuel pressure variation and temperature changes.

--Ian @ Dynon
 
Apparently my assumption that the Slyview had a RETRN parameter was incorrect. Thanks for straightening that out Ian. Yes, the D-180 system with the two parameters is imperfect. But if calibrated and refined per the manual, it can be quite accurate on longer flights, which is where you need it. Of course the point can be made, why do you need this function at all when you have redundant visual indicators?
 
What I did years ago - -

First understand, not a lot of traffic in rural Iowa. I knew from experience how much fuel I was using per hour in general. I set mine while flying to where it read the amount that experience said was about right for a given speed. Has worked well for years now. Only advise doing this way in a open area away from traffic.
 
I have two red cubes feeding info to my GRT HX with EIS 4000. I have an ECI fuel injection setup with return fuel lines in my 9A. Not a 12 but similar problems you are facing. The second red cube is expensive but once installed and calibrated my fuel flow reads accurate to within .1 GPH on every flight no matter how long or short, full throttle, idle, high, low. After 6 years of flying I don't miss the extra money spent on it but do enjoy the peace of mind knowing I can rely on the information my instrument is displaying.
 
rjtjrt said:
Sorry for the long thread title.
Has anyone installed a second Red Cube (or Floscan) transducer in RV-12 (on return line) so as to get accurate fuel calculation?
I am tempted to get this as it seems the only way to get accurate fuel calculations on the EFIS.
If any have, any tips or hints?
I have G3X Touch.

John
Click to expand...

John..I'm with you. I'm going to add the second transducer. To me, knowing how much fuel I have is important...along with fact this plane has just about every electronic gizmo known to mankind (well short-of).
 
Ric,

I've always found my float gage to be within a few tenths of a gallon. I calibrated it to read zero on the bottom of the tank so it reaches the mechanical stop at 17 Gal. I fly for an hour before it drops on scale when I top off.


Rich
 
Phantom30 said:
John..I'm with you. I'm going to add the second transducer. To me, knowing how much fuel I have is important...along with fact this plane has just about every electronic gizmo known to mankind (well short-of).
Click to expand...

Ric
Looks to me like that will be a good solution.
Hope you are able to post where you locate it, and any tips about how you go.
John
 
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