Gas tank dimensions and profile

[EcomilerChristopher]

Anyone have exact gas tank dimensions and profiles?

[Ryland]

What do you plan to do with that info?

[EcomilerChristopher]

Just get a better idea on how accurate the fuel gauge is. Not that I can really do much with it anyways but it was an interesting thought.

Newer vehicles have digital readouts on how much fuel is left while it's somewhat more of an estimation for needle readers. The needle moves faster in some places more than others.

[RobertSmalls]

Both old and new gas gauges rely on the fuel tank level sensor, which consists of an angle sensor and a float. You can read voltages directly from it, and come up with a pretty good guess as to how much gas is in the tank. It will vary when the gas sloshes around, or if you're cornering, or on anything but perfectly level ground.

Obviously, gas tank geometry is different for different cars. If you really want to calibrate your level sensor voltage vs. volume of fuel in the tank, I don't see any option other than draining the tank, then adding carefully measured amounts of fuel while recording voltage. That's a lot of work, and you might be unimpressed with the accuracy anyway.

P.S. you should create a Garage entry for your car so we can see what you're driving.

[vtec-e]

I've never tried to do something like that but if it's any use: My fuel gauge has 8 bars on it. When i burn off the top two my tank is approximately half empty. I don't know how linear it is below that but it drops quicker than the top two.
When i'm filling up and i let the pump trip out normally and fill no more, the gauge will start dropping more or less straight away. Which tells me that's the way the system is designed. Then you get guys like us filling to the brim and we are in a situation where the needle doesn't move for ages until we burn off the fuel that went above the fuel gauge, so to speak.

ollie

[MetroMPG]

Originally Posted by RobertSmalls

If you really want to calibrate your level sensor voltage vs. volume of fuel in the tank, I don't see any option other than draining the tank, then adding carefully measured amounts of fuel while recording voltage. That's a lot of work, and you might be unimpressed with the accuracy anyway.

krousdb did this - calibrated his fuel level sender's voltage - when he was driving his pre-ODBII del Sol, and he actually managed to get decent accuracy from it. To the point that when parking the car back at home at the end of each day, he was able to make decent estimates of his trip MPG (fairly long trip, though).

It's something I'd do if I didn't have access to either a ScanGauge or MPGuino.

[Bicycle Bob]

It does not have to take a long time to calibrate a gauge. When I got my Metro, I carried a gas can and ran it below "Empty" as far as I dared (140km) This carries some risk of disturbing sediment, though. Now, I'd just go to a not-busy self-service gas station, probably with a friend to help, with the guage on "E." From there, we'd mark the guage at every gallon or 5l as measured by the pump. Subtract the total fill from the rated capacity to find out how much lies below "E," but it is not all accessable.

Given the guage response time, a friend may not really speed this up. You may want to do the initial marking on a strip of tape, and then move it up or down slightly to put zero where you want it.

[bestclimb]

Things sloshing around the bottom of your tank is why you have a fuel filter. If there is enough to clog your filter, I would rather do it in a controlled environment when I am expecting it may happen than when I am out on the road somewhere far from easy support.

[EcomilerChristopher]

I suppose it would be more trouble than it's worth. My fuel gauge only has a full / half full and an empty line.

However I did find out, that my fuel light comes on when there's roughly 6-7L of fuel left in the tank (for most people that's about 50 to 100 km left). Also my gauge at halfway = 20L left on my 45.1 L fuel capacity (I just happen to reach halfway so I filled up with gas and figured it out that way - a somewhat crude way of figuring it out but it did the job) probably +/- 2 litres or so.

Didn't know about the voltages though and thanks for that, might be helpful for me if I do any mods.