Ultragauge DTE incorrect
 

So where does the ultragauge get it's DTE and Level Gallons reading from?

My in dash fuel gauge is at the bottom edge of the red line, long after the low level light came on, and my UG is showing I have 4.0 gallons left.

I have it set up as a 24.6 Gal tank and always zero it at fillup but, have never really paid much attention to the DTE reading before. Or have never noticed it being way off like that.

I did just find and fix a tiny pinhole leak that was in the fuel line back by the frame above the evap canister. Could it have sprayed almost 4 gallons out over the course of a tank and made the calculations incorrect for the UG?

Does the UG make it's calculations for the fuel level at the engine and not at the tank to determine how much is supposed to be left in the tank?

Yes, the UG will not read the tank level, you have to update it manually when you fill up. When you first set it up, it asks you how big the tank is in gallons. It will then try to figure out how much is left in the tank, your mpg, etc. basing it off data collected from other senors in the system. Its an estimate.

This is from the ultragauge website: "UltraGauge is a MPG calculator, MPG meter. fuel consumption calculator, fuel mileage calculator and MPG gauge which calculates miles per gallon and the metric equivalent."

The fact the it uses the word "calculator" so many times makes me think that it uses things like RPM, MPH, HP, Torque, etc.. to estimate things like instant MPG, and distance/time till empty.

Maybe the fuel leak threw it off? I have the leak fixed now so will see what it does next round.
thanks

Yea I zero it when filling up and have the tank size set at 24.6 gallons so, doesn't seem like it would miss it that far.... by 3 or 4 gallons.
thanks

It works like the DTE gauge that many cars have built in. The system knows how much fuel it thinks it has injected, that is used along with speed data to calculate mpg. If you know mpg and the fuel tank size, DTE is a simple calculation.

It is quite possible than the gauge reads empty when there are 3 gallons left. Fill it up and see.

Yea if the gauge said it is empty and I had 3 gallons left that would be good. But if the UG says I have 3 gallons left when I really have no gallons left, that would be bad..

I know I could figure it all up manually but, that's the job of the UG, my job is to drive and glance at the UG for information.

If that's the case (having several unusable gallons left in the tank) then DTE and level gallons (gallons left) on the UG could get you in trouble if you had to rely on it as an indicator of how much actual fuel and miles you have left.

I ran it out a few years ago and the needle was just barely touching the bottom of the red line on the dash gauge. That's about where it is now and the UG is saying I still have almost 4 gallons and 50 miles left. I would say garbage in garbage out but, my UG is set up at 24.6 gallons and I zeroed it at fillup.

I am trying to run it completely out again. It was almost on empty anyway and I need to change out some old fuel lines and want it as empty as I can get without draining it. Should be getting close. I've been running it at home charging A/C, checking temps and other stuff. I'll see what the in dash gauge reads and the UG says I have left when it runs out completely sitting on level ground.

When I'm done I will put 5 gallons in, that I have here, go to the chevron right up the street and top it off, total those gallons added to the 5 gallon and see how many gallons it takes to fill up from empty. Then I will subtract that total from 24.6 gallons to see how many unusable gallons are left in the tank when it's to the point where it will not pick up any more fuel.

Then, after doing those calculations if I determine it still has 2 gallons or 3 gallons in the tank when it runs out as in really runs out, I will adjust my tank size in my UG to 22.6 or 21.6 or whatever 24.6 minus the gallons that are left in the tank when it runs out. That way when I look down at the UG and it says 12.5 miles DTE or 1 gallon left I know it really means 12.5 miles DTE and 1 gallon left. And not 50 miles DTE and 4 gallons left and then run out 12.5 miles later with 3 gallons of unusable fuel left in the tank.

I usually fill my tank completely and then fill it again when the light comes on, but if I find myself low on fuel and not near a store it would be good to be able to rely on the UG to tell me exactly how many actual miles and usable gallons I have before I'm walking.

Seems like sitting on level ground it should not run out till it's down to less than a gallon? Not with 3 or 4 gallons still in the tank. I am hoping that calculation is not right and is wrong due to the fuel leak I had. I'll probably run a few tanks through and see how it goes and tweak it from there. I have never used my UG for that in the past and only checked my MPG and temps with it.

I'll work it out, I just wasn't sure how the UG made those calculations, now I know it doesn't read from an in tank sender. It may be off too because I have been sitting idling on some of this tank and not moving? but i figure it meters the fuel sent to the injectors so should take the fuel used idling into account with it's calculations also?

thanks

You need to calibrate it to your ACTUAL speed and Distance traveled to get an accurate reading.

If you've got a smart phone, or GPS, then run it and watch your MPH and Miles traveled compared to your Speedometer/Odometer. They are likely off a bit. You'll need to do it a few times to get a good average of how far it's off.

In the UltraGauge menus, there's an option to calibrate the Odometer Distance Traveled and Actual Distance Traveled. If you don't do that, then your MPG, DTE, etc is not accurate. Even after that, it's still a guess, but at least it's MUCH closer.

I don't remember the exact amount I had to change mine, seems like it was .017 or something like that. After putting on Larger tires, I had to do it again, but in the opposite direction.

Thanks for reminding me..... you know I think I forgot to do that. I remember reading about it, but don't think I ever actually did it.

I'm such a space case! probably not!

I'll do that and see how it goes.

thanks again

When you get it calibrated correctly, your UltraGauge and your GPS will read the same speed at all speeds. It's kinda nice having it working right. It also helps to avoid speeding tickets when you've oversized your tires.