fuel sensor ~ obd2

[j12piprius]

How difficult would it be to connect the fuel sensor to obd2?

I'm interested to get more accurate fuel tank readings with the ultragauge.

As the fuel tank empties, a float drops and slides a moving contact along a resistor, called a potentiometer, increasing its resistance. The dashboard indicator displays the amount of electrical current flowing through the sending unit on a gauge. The potentiometer should read 2-5 ohms when empty and 105-108 when full.

[MetroMPG]

Interesting question. Usually it's the guys with pre-OBD-II vehicles that are looking for more accurate ways to measure fuel used at the tank.

I don't know anything about fiddling with OBD-II. I'd be surprised if you could feed a new sensor into the system and then have the gauge read it though.

But I think you'd be able to buy or make a higher resolution digital gauge easily enough. You'd just have to calibrate it against an actual fill (done in measured increments) for accuracy.

[j12piprius]

Originally Posted by MetroMPG

I think you'd be able to buy or make a higher resolution digital gauge easily enough. You'd just have to calibrate it against an actual fill (done in measured increments) for accuracy.

That would be good, but shouldn't a new gauge adjust from the sensor in the tank?

[MetroMPG]

I assume you'd be going for a display with high resolution (eg. a % readout or 20 "bars" vs analog).

By "calibrate" I mean you could measure exactly how much fuel each bar represents. I don't think the float/resistor gives you a linear progression from full to empty.

[MetroMPG]

PS: what's your reason for wanting more resolution from your gauge?

[j12piprius]

Yes, high resolution.

My reason is for greater accuracy, verification of how many gallons to fill up, and a double check of fill ups from different stations.

[Xist]

My understanding is that people with lean burn install an MPGuino.

[D.O.G.]

Most float type fuel tank level sensors aren't designed to be super accurate, so it throws out whatever display you use.

In a typical rectangular tank, climbing/descending a hill, cornering, road camber, how warm/cold the fuel in the tank is and probably lots of other outside influences will effect the displayed fuel level.
Some type of damping device is usually used to smooth out the reading, but they aren't perfect and will give false readings at times.

An MPGuino is pretty accurate, but even that ignores variations in fuel pressure and temperature, dirty or worn injectors, fuel leaks, etc.

This is why most guys recommend only filling from one particular pump at one particular petrol station at a regular time of day. Even then, there are just too many variables to rely on one tank's result, you have to average results over time.

[2000mc]

I think the fuel level sensor will already be reading its maximum value after filling at a pump that turns off a bit early, so the exact sensor reading won't help to determine how complete of a fill you are truly getting

[oldtamiyaphile]

I too would love an accurate fuel gauge.

At it's simplest, you can simply connect a voltmeter to the factory gauge, X volts means full, Y volts means empty. You could use an Arduino to translate this to actual litres/gallons.

However, as stated already, this would be of limited value as there's still fuel in the tank when the sender reads zero and you can always fill past full.

I've often thought about adding a camera inside the tank for visual confirmation, you could even add a tide stick inside with markings. Only way I can think of to have complete accuracy.

I once nearly ran out of fuel because I put too much faith in my MPGuino, luckily I was at the top of a hill when it began to sputter, and there was a petrol station at the bottom.