That's assuming that the output is linear. Do you have reason to believe that it would be linear with the amount of fuel?

 

You could also fill up a gallon at a time and record the value at each gallon, using the pump to meter out a gallon at a time.

Might take a bit of time but would be cool info to have.

 

That's what I was thinking

 

So I ran my tank down fairly close to empty before filling up and logged MUT88 during the fill-up marking off each gallon. Here are the results:

The numbers are all x.4 because I ended up putting 12.6 gallons in the tank, so I figure I started at about 1.4

So, it looks to be linear until about 7 gallons. After that, it's no longer linear.

It also appears to level off at 26 after about 12 gallons. This could be because the float or whatever measures the fuel level is maxed out. I have no evidence of that though apart from the constant MUT88 above 12 gallons.

I don't know how to go about scaling MUT88 to output a meaning number (say # of gallons in the tank), but I'd be happy to help if someone wants to take me through it.

One final thing that I while driving around and monitoring MUT88 was that it moved around quite a bit when accelerating and breaking (even lightly) or when going up and down hills. There's no built in smoothing of the value, so if we wanted that, we'd have to do it on our own. Obviously the stock fuel gauge doesn't move around that much, so there has to be smoothing built in somewhere, but whether it's accessible is another question I guess.

I'm happy to actually give something back to the board as opposed to just leeching (even if it is something somewhat useless)

 

Since the readings seem to level off around 12 gallons, maybe this is the reason the fuel gauge always seems to stay on F for so long then drop off rather quickly.

 

Too bad fuel level is not linear with the MUT value. Would make it easier to log. I'll have to look at how this compares to the scaled value in the ECU.

 

Topping out at 12gal makes perfect sense as I can usually drive about 40 miles (2 gallons or so) before the needle even starts to move.

I would be curious to see if it bottoms out at any point (below a galon or so) as that is where it will really be helpful to be able to log wether you have 1.5 gal or .5 gal.

Perhaps the reason it becomes non linear above about 8-9 gallons, is actually the shape of the tank and not the response of the sensor. Maybe the tank becomes more narrow at the top and so an additonal 1 gallong raises the fuel float more then it would at lower fuel levels. Either way, I think the values below 9 gallons would be more usefull then values above 9 anyway. The only reason to check fuel is when you are in danger of running out.

Nice work by the way.

 

Just thought I would bump this. Have the same idea as the OP about replacing gauge cluster with a touch screen device (probly android tab). Only two things missing that i cant currently log in evoscan is fuel level and oil pressure. Im sure for oil pressure i can use a liner 0-5v sender hooked into an open adc. For the fuel level though id like to use whats already there. BTW im running 96531706.

Did you guys have any luck with the scaled vs raw level data and scaling for evoscan?

 

Wow, never knew we could log fuel level, that's pretty cool. Thanks for bumping this old thread