Miata Fuel Gauge set up

[Shelbygs]

I am working on setting up a 1996 miata to the RC Pro. I am having an issue getting the fuel gauge reading on the RC. My issue must be with the configuration. Does anyone have all of the settings for the miata?

[Shelbygs]

http://www.electro-tech-online.com/atta ... jpg.87686/

I came across this chart with what appears to be the voltage calculations I was seeking. I will try to use these to set up the gauge. If this is correct, I would assume that I do not need to use a resistor and to wire directly to the RCP like a temp gauge. I wi post what I find

[Shelbygs]

Well it took some time but I figured how to get it to work. I had the right settings, it was the dashboard Fuel Level gauge that required to be removed and re-installed. I was getting the readings in the dashboard green font screen, just not in the dashboard gauge screen. When I removed and re-installed it works. Now for the configuration to set up a Miata Gauge:
Miata fuel sending unit reads 5v empty; 0v full. Tank is 12.9 gallons.. It is a little more because of fill valve, but I used the factory spec for tank capacity.


Volts 0 | 1.25 | 2.5 | 3.75 | 5
Scaled 12.9 | 9.68 | 6.45 | 3.22 | 0
Channel is Fuel Level
Sample rate 1Hz
Mapped is checked

Press on the gear icon and set the Custom Channel
Name Fuel Level
Units Gallons
Precision 0
Min / Max 0 / 13

[brentp]

Thanks! I got the Fuel Level calibration added here:

https://wiki.autosportlabs.com/Mazda_Miata

[Bryan@UnderbiteRacing]

Hi -

Could you please let me know where you made the wiring connection for your fuel gauge? I'm looking at pulling the dash cluster in my '99 Spec Miata and this is one functionality I would miss.

Thanks,
Bryan

[cj9694]

Well it took some time but I figured how to get it to work. I had the right settings, it was the dashboard Fuel Level gauge that required to be removed and re-installed. I was getting the readings in the dashboard green font screen, just not in the dashboard gauge screen. When I removed and re-installed it works. Now for the configuration to set up a Miata Gauge:
Miata fuel sending unit reads 5v empty; 0v full. Tank is 12.9 gallons.. It is a little more because of fill valve, but I used the factory spec for tank capacity.


Volts 0 | 1.25 | 2.5 | 3.75 | 5
Scaled 12.9 | 9.68 | 6.45 | 3.22 | 0
Channel is Fuel Level
Sample rate 1Hz
Mapped is checked

Press on the gear icon and set the Custom Channel

Name Fuel Level
Units Gallons
Precision 0
Min / Max 0 / 13

Will this work with the OBD1 Miata ecu?

[brentp]

I believe this is a function of the sender gauge's resistance, and it feeds directly to the dashboard gauge. The ECU should actually not be aware of the current fuel level.

Best would be to tap into the fuel gauge sender wire and calibrate as suggested to see if you get the expected reading.

[cj9694]

So basically just pull from the leads that are going into the back gauge cluster?

[brentp]

Yes, it should be a single wire to tap to one of the analog inputs. What I would do first is measure the voltage of the wire you expect with a meter to see if the voltage matches the value in the table provided for the % full your tank currently is.

[cj9694]

awesome, thanks for the clarification.

[Shiftlink]

Following up on this, most guys aren't running stock instruments. In this case a voltage divider to the sensor will work fine with a custom calibration, correct? Just double check ground to make sure everything is happy.

[brentp]

A good rule of thumb is to run a voltage divider with the same resistance as the sweep of the sensor. So, if the fuel level sensor is 200 ohms, get a ~200ohm resistor. When the tank is full, the voltage reading should be 2.5v, when using a 5v reference.

The sensor curve may not be linear, so you'll need to measure voltages on the divider for empty, 1/4, 1/2, 3/4 and full, and then plot that into the analog sensor input window.

Hope this helps!