Vacuum Guage and Digital Fuel Gauge

[krousdb]

Originally Posted by SVOboy

Looks like a good tank so far.

I just found a DMM in my basement, think it's my teachers but I wanna hook it up before I return it to make sure I can get the hook up working well for when I buy my own DMM (it's only 9 bucks after all).

Do you have any pictures of how it's wired into the fuel sender thing?

No pics. I would have to take all my trip pieces out to get to it. But you don't need pics. Especially if you don't want to switch between analog and digital guage all of the time. Just locate the fuel pump and sending unit. Access should be from the inside of the car directly on top of your fuel tank. If you can't tell which is which, the fuel pump is the one that buzzes for two seconds when you turn your ignition on. You want the other one which is the sending unit. The sending unit also has smaller gauge wires than the fuel pump.

Once you find the two wires going into the sensor cut both wires, leaving yourself some room to solder them back together if you want to restore the analog gauge. Next, connect the DMM leads to the cut wires that go to the sending unit and set to 200ohm setting. You should be at 2 - 5ohm for a full tank and around 130ohms for an empty tank, according to the 92-95 civic shop manual. I have never had it higher than 110 ohms however.

You should do your own calibration since your fuel tank may be a different size or shape. I started with an empty tank, dead on the "E". I added gas in 1/4 gallon increments, taking a reading afer a few seconds of letting the reading stabilize. When you get close to 10 ohms, it only takes a small squirt to move it an ohm or two. Continue small squirts until a squirt fails to change the reading, this is what I call the full point, because I can duplicate that exact level on each fill, ensuring accurate tank MPG calcs.

Now all of this is based on the 92-95 civic. Refer to your CRX shop manual as there may be differences in locations and sensor range.

And one more thing. Readings between DMM's will vary. If your teacher's is high quality and the ebay is low quality (most likely) then you may see a few ohms difference. The ebay one will be fine, just be sure to calibrate with the ebay DMM.

[SVOboy]

Thanks, I'm pretty sure I know what it is and since I've got no interior getting to it isn't a problem.

[Matt Timion]

Just as an alternative, a digital panel meter might be better than hooking up a DMM to your car. A digital panel meter could easily be made to fit and be more permanent.

And they're rather cheap too.



http://search-desc.ebay.com/Digital-panel-meter_W0QQbsZSearchQQcatrefZC6QQcoactionZcompareQQ coentrypageZsearchQQcopagenumZ1QQfposZ84104QQfromZ R10QQfsooZ2QQfsopZ2QQfstypeZ1QQftrtZ1QQftrvZ1QQfts Z2QQmppfqyZQ28n600Q2cQ20an600Q2cQ20z600Q2cQ20az600 Q2cQ20Q22hondaQ20600Q22Q2cQ20Q22nQ20600Q22Q2cQ20Q2 2zQ20600Q22Q29Q20Q2dcbrQ20Q2dbluetoothQ20Q2dmotoro laQ20Q2dsonyQ20Q2dnorcoldQ20Q2dQQsadisZ200QQsargnZ Q2d1QQsaslcZ2QQsatitleZQ22DigitalQ20panelQ20meterQ 22QQsbrftogZ1QQsofocusZunknown

http://www.action-electronics.com/panelmeters.htm#Digital

I would do this in a heartbeat if someone could convert the readout to be a percentage of the tank left instead of the voltage.

[krousdb]

Originally Posted by Matt Timion

Just as an alternative, a digital panel meter might be better than hooking up a DMM to your car. A digital panel meter could easily be made to fit and be more permanent.

And they're rather cheap too.



http://search-desc.ebay.com/Digital-panel-meter_W0QQbsZSearchQQcatrefZC6QQcoactionZcompareQQ coentrypageZsearchQQcopagenumZ1QQfposZ84104QQfromZ R10QQfsooZ2QQfsopZ2QQfstypeZ1QQftrtZ1QQftrvZ1QQfts Z2QQmppfqyZQ28n600Q2cQ20an600Q2cQ20z600Q2cQ20az600 Q2cQ20Q22hondaQ20600Q22Q2cQ20Q22nQ20600Q22Q2cQ20Q2 2zQ20600Q22Q29Q20Q2dcbrQ20Q2dbluetoothQ20Q2dmotoro laQ20Q2dsonyQ20Q2dnorcoldQ20Q2dQQsadisZ200QQsargnZ Q2d1QQsaslcZ2QQsatitleZQ22DigitalQ20panelQ20meterQ 22QQsbrftogZ1QQsofocusZunknown

http://www.action-electronics.com/panelmeters.htm#Digital

I would do this in a heartbeat if someone could convert the readout to be a percentage of the tank left instead of the voltage.

Problem is that the sensor output is not linear. Yiu would need to set up a lookup table. If that could be done, sign me up for one.

[Matt Timion]

Originally Posted by krousdb

Problem is that the sensor output is not linear. Yiu would need to set up a lookup table. If that could be done, sign me up for one.

Ah, I was under the impression that the output was linear. If it was then the conversion equation would be REALLY easy to do. Assuming 2.6Volts was "full" and 0 volts is "empty, the percentage would just be "(x/2.6)*100," or just "38.46x," where "x" is the voltage.

If it's not linear, however, I have no idea. Perhaps some of the electronics guys on this site want to make a LITTLE extra money and whip something up for us? Huh? Anyone?

[krousdb]

Originally Posted by Matt Timion

Ah, I was under the impression that the output was linear. If it was then the conversion equation would be REALLY easy to do. Assuming 2.6Volts was "full" and 0 volts is "empty, the percentage would just be "(x/2.6)*100," or just "38.46x," where "x" is the voltage.

If it's not linear, however, I have no idea. Perhaps some of the electronics guys on this site want to make a LITTLE extra money and whip something up for us? Huh? Anyone?

Take a look at the chart that was included in the first post. The sensor is quite linear from the full to half tank mark at about 4.8 ohms/gallon. But after that you can see a more of curve. You probably notice this on your analog gauge also.

Lets just keep our fingers crossed that the SuperMID will work with non-toyotas. If so, in addition to showing tank, trip and lifetime MPG, it shows fuel used in the lower right hand corner, and is extremely accurate, as is the ODO after calibration. It takes awhile to get used to the metric display. But just remember to multiply km/L by 2.35 to get MPG. So 50 mpg would be 21 - 22 km/L. The fairly commom 11.9 gal fuel tank is 45L. The 15.9 tank is 60L. Didn't you ever wonder why the odd tank size, well it's not so odd if you convert to liters.

[JanGeo]

The meter should have a calibration but it may be automatic - however all you need to do is go through a pot to adjust the voltage range so full tank reads 100 on the meter. Hell calibrate it to gallons!!

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohm, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohm, 3.675 gallons, 49.4 MPG

OUCH! Running errands sucks. Lots of short trips, but only one cold start. So calculating backwards, my MPG for day 4 was around 38. I hope the WAI didn't cause any of that.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG

Whew! Back over 50. Day 4 reading could have been a fluke.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG
End of day #6, 286 actual miles, 33.8 Ohms, 5.583 gallons, 51.2 MPG
End of day #7, 339 actual miles, 39.1 Ohms, 6.313 gallons, 53.7 MPG

Nice and warm today, 44F in the AM and 55F in the PM