Fuel level display

Samueljon
Posts: 7
Joined: Sat Jul 04, 2020 3:09 pm

Fuel level display

Postby Samueljon » Mon Apr 18, 2022 5:23 pm

Evening all,

I finally got round to sorting the fuel level reading on my dash2

The dash seems to read roughly right but I’ve added an extra 20 litres and the dash doesn’t seem to show it? Do I have to do the whole table up to a full tank?

Cheers for your help

Sam

Greg Amy
Posts: 42
Joined: Sun Dec 11, 2005 2:59 pm

Re: Fuel level display

Postby Greg Amy » Mon Apr 18, 2022 9:00 pm

How did you add 20 liters?

What are you using for a level sender?
Greg Amy
FastTech Limited, http://www.fasttechlimited.com/
Data Acquisition, Driver Consultation

Samueljon
Posts: 7
Joined: Sat Jul 04, 2020 3:09 pm

Re: Fuel level display

Postby Samueljon » Tue Apr 19, 2022 5:47 am

Morning,

I’m using the standard Nissan 200sx fuel sender with a Haltech signal conditioner

I filled the last 20 litres straight out the Jerry can rather than decanting it into a 5L can

Cheers
Sam

Greg Amy
Posts: 42
Joined: Sun Dec 11, 2005 2:59 pm

Re: Fuel level display

Postby Greg Amy » Tue Apr 19, 2022 8:53 pm

Any time I'm using a generic sensor - such as the stock sender with a pull-up resistor like the Haltech - then I calibrate the whole thing myself.

- Config the dash to show bare voltage output
- Empty the tank
- Add in a small known quantity of fuel, such as a gallon or liter
- Let the system settle and note the voltage
- Repeat until the tank is full

From there you can input the volts-versus-quantity into the DASH2 config. Note that stock sender outputs are rarely linear, given non-rectangular shapes of most stock fuell tanks.

If you've already done that, and the system stops showing a change after a certain level, then you've likely reached the extent of the sender's capabilities (or its travel limts). Alternatively, you may need a different pull-up resistor.

For example, in my first-gen MR2 the workshop manual resistance for the stock fuel sender is 3 on a full tank and 110 on an empty tank. I used a 20A pull up resistor with the 5V input on my Dash2Pro, giving me 0.644V output when full and 4.221V when empty. I calibrated it into the DASH as percentage of the tank versus gallons.

Of course, the vagaries of a stock fuel tank and sender are such that these are simple guidelines for whether or not I need to add fuel for a session. I'd never count on that gauge for an important decision like whether or not to take another lap or run out of fuel...

If you have any question on it, remove the sender, ground it to the car, and see if it works within the full travel of the sender.
Greg Amy
FastTech Limited, http://www.fasttechlimited.com/
Data Acquisition, Driver Consultation


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