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Fuel Tank Reading on G3X

design4p

Active Member
Hi,

I understand with a full tank of fuel it will take a little flight time for the fuel quantity to be seen to be reducing on the G3X screen due to the dihedral of the wing and position of the sensor.

Just wondering at what quantity point should the reduction be viewed on screen.

It is a little disconcerting to see a full tank for quite some flight time.

Any comments most welcome.

John
 
Fuel remaining

The Fuel Remaining data field which gets data from the fuel flow sensor is the best way to get info on your fuel until the Fuel Gauges start to show a change.

On my 7A, fuel gauge readings start to get accurate at 16 gallons per tank. I like to cross check Gauge Fuel with Fuel Remaining while in flight.
 
Fuel quantity

You put 24 gallons in tank and sender generally reads full at about 18 gallons. So you will burn off about 6+ gallons before your sender will start to read.



RV 14A 140507 flying
Donation paid 2020
 
+1 for what Rick is saying. With a correctly calibrated fuel totalizer you can see total fuel, fuel used, fuel remaining within 1/10 of a gallon of actual quantity. Why rely on a known “inaccurate” fuel quantity gauge for fuel quantity information then?
 
config

+1 for what Rick is saying. With a correctly calibrated fuel totalizer you can see total fuel, fuel used, fuel remaining within 1/10 of a gallon of actual quantity. Why rely on a known “inaccurate” fuel quantity gauge for fuel quantity information then?

So i assume you have the fuel tanks float senders on a gauge readout on the G3X. Do you also have a gauge readout for the totalizer, or is that just displayed as numbers somewhere?

Just curious how y'all display this info?
 
So i assume you have the fuel tanks float senders on a gauge readout on the G3X. Do you also have a gauge readout for the totalizer, or is that just displayed as numbers somewhere?

Just curious how y'all display this info?
The G3X engine display will show remaining fuel, and all other pertinent fuel information on the screen from the totalizer not as a gauge but as number displays. One thing about fuel totalizers to keep in mind. They do require the user to input the total amount of fuel in the tanks at each fill up. So, with that in mind it is not like a float sender fuel quantity gauge where there is no active management of the system. The user does have to manage it at each fill up. However, if you have driven a car in the past 30 years that keeps track of your fuel mileage, distance to empty, etc., it is no different than how one manages those systems in a car.
 
if only

Man, I really wish i would have put an extra fuel sender in the outer tank closeout rib. I was soooo close to doing this, but had just sealed the tanks up and didn't want to contaminate tanks with debris cutting a hole for sender. Should have done it; then my fuel gauges would have been accurate.
 
We played around with calibration on my friends -8, and settled on15.5 gals. as the first reading below full.
Totally agree that a properly calibrated fuel computer is the best solution.
 
My -8 reads the last 16 gallons in the wing tanks, which is all I need them to read. The totalizer takes care of the rest of my fuel burn information.
 
Nice to have, but . . . .

Man, I really wish i would have put an extra fuel sender in the outer tank closeout rib. I was soooo close to doing this, but had just sealed the tanks up and didn't want to contaminate tanks with debris cutting a hole for sender. Should have done it; then my fuel gauges would have been accurate.

I have plenty of things to do rather than monitoring a full tank. Right tank (RV7) becomes accurate at about 14 gal and the left about 12 gal using a generous (2 gal) margin for each. I have a dip stick that is accurate within 1/2 gal (actually + qt) and adding both tanks it is well within 1/2 gal compared to the totalizer. Also, I don't know exactly how much my tanks really hold in spite of trying to measure. Each tank alert is set to 7 gal and that is really accurate. Verified many times.

A good place monitor "fuel remaining" on a busy panel is the selectable data bar along the top of the G3X display. I put it there on a critical long cross country, otherwise rely on the 7 gal alert and monitor fuel used against predicted at waypoints. FF helps this.
 
Initial Reading

I'm getting a true reading 20 gals and less each tank and normally burn down to 5 gals each tank so 2 1/2+ hours of flight time which is all the bladder I have anyway. I thought about installing sensors in the outboard side of my tanks and glad I did not. I am a little surprised the 10's reading is that low but will find out when the 10 I'm building is calibrated. I still don't think I will install outside tank sensors. The fuel flow sensor on the EFII is extremely accurate and I can get amounts in each tank remaining from the beginning.
 
Man, I really wish i would have put an extra fuel sender in the outer tank closeout rib. I was soooo close to doing this, but had just sealed the tanks up and didn't want to contaminate tanks with debris cutting a hole for sender. Should have done it; then my fuel gauges would have been accurate.

How would you wire this to read accurately?
 
Never done the math

How would you wire this to read accurately?

So I think if there is enough data points, the fuel level verses voltage curve does not need to be linear. Therefore, the G3X can be fully calibrate over its fuel level range with a non linear fuel level sensor(s).

There are two ways, one is to put the sensors in parallel and have the G3X calibrate that value. It will be about half the normally full scale value, but the G3X should be OK with that.

When i was contemplating this, i was planning on re wiring the outboard sensor to be isolated from ground and then put the sensors in series. But I didn't get the whole design worked out before my tanks were done and I was past that stage.

Knowing what I know now, which isn't much, I would run the sensors in parallel, and make sure the sensors both increase or both decrease in resistance as the tanks are filled. I believe that means the outboard sensor has to be the opposite side's. For example, the outboard right tank sensor has to be the left side inboard variety. JMHO, YMMV
 
My -14 reads full until about 20 gal a side (5gal from full) before the senders are moving. I check for full before takeoff so I know it's actually full and to be honest, I really care about accuracy when the fuel starts getting down towards my personal limit, not so much until then.
 
I calibrated my -9A equipped with a G3X Touch system using the "add one gallon at a time" method. The calibration value for both tanks remained the same starting at the 15 gallon level up to the 18 gallon full level.
This was identical to when I had Van's analog fuel gages, i.e. the gages read full until the fuel level actually drops below 15 gallons.
 
I agree

My -14 reads full until about 20 gal a side (5gal from full) before the senders are moving. I check for full before takeoff so I know it's actually full and to be honest, I really care about accuracy when the fuel starts getting down towards my personal limit, not so much until then.

I agree with all of the above. I was going to put senders in the outboard ribs while building, but didnt. But with the G3x and totalizer, I dont think I will miss it. My thinking has jumped forward 50 years since I built my tanks.
 
If

If you are still building the tanks, you can put a single capacitance sensor from the bottom root rib to the top outboard rib in the tank. It with allow accurate readings from full to empty…no need to use two sensors for each tank in this case…
 
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