RT Dash2 fuel sensor wiring

[skydragon]

I'm just in the process of fitting a Race technology Dash2 to my seven and am trying to work out the correct wiring for the fuel tank level sender.

 

I'm guessing I should use a 1k resistor in series with the voltage feed to the sender, using the +5v reference voltage, instead of the car's 12v supply.

 

Anyone else been down this path who can remember what/how they did this?

 

Thanks

[Harry Flatters]

This might help a bit.

 

*arrowright*Harry 'Haka' Flatters - 263bhp of VX joy *arrowright*

AKA Steve Mell - Su77on Se7ener

[rgrigsby]

Yes that's pretty much what we do on my car, I can't remeber exactly how it was definetly something along those lines.

 

Cheers

 

Rob G

 

[skydragon]

Thanks for the link Harry

 

I've worked out the resistance values and hence voltage lookup tables for the sensors on my car (oil and water temps) apart from the fuel level sender, hence my question.

 

In this BC post here there is some info as to the resitance scaling on the CC fuel level sensor which I'm going to use as a starting point.

[skydragon]

Rob, Can you remember what value you entred in to the Dash2 for setting the speedo calibration?

 

Can you also remember whether you had to add a pull-up resistor to the std CC speedo drive sensor, or whether this wire just connected straight into the Dash2 speedo input?

 

Edited by - skydragon on 13 Dec 2010 12:16:17

[rgrigsby]

Unfortunatly I don't have the standard CC speedo drive so I can't help on that, I'm using sensors on the wheels instead. Here are my numbers for the fuel sensor vs voltage. However I had a small hiccup with mine as it turns out I calibrated with fairly flat battery so it over reads a bit.

 

0.09 4

0.09 6

0.11 8

0.15 10

0.2 12

0.25 14

0.29 16

0.34 18

0.4 20

0.47 22

0.51 24

0.58 26

0.65 28

0.69 30

0.76 32

0.77 34

 

Cheers

 

Rob G

 

[Roger Ford]

Wouldn't those values depend on what pull-up resistor you used?

[skydragon]

Wouldn't those values depend on what pull-up resistor you used?

Yes.

 

I 'think' I've got the info together I need now. I just hope the values I've guessed for the fuel sensor are close enough and I don't end up having to drain the tank and refill to measure the various resistance readings...

 

I calibrated with fairly flat battery

why didn't you use the 5v regulated refernce voltage, which avoids the main 12v battery voltage variations affacting sensor readings? 😬 😬

[Rattie]

BTW, the RT forums are quite useful and RT's tech support are very handy chaps.

RT sensor forum

 

Martyn

^_R300GRR

[skydragon]

For those who've fitted a DASH2 into a seven, how did you end up mounting the display to give the best viewing angle, for the LCD display?

 

In my car, with my seating position, the display is a good 20-30 degrees away from the optimum viewing angle, when it's mounted flat against the dash panel. I'm going to have to mount the display so that the top of the display is tilted away from the dash panel by quite a bit....not a problem making up some spacers and doing this I guess, but I'm curious how others have done this?

[skydragon]

Ok, now I've fitted my Dash2 and got it all working/calibrated, here's some info which might help others in future.

 

(I bought the Dash2, the oil pressure sensor and the 4xbutton switches for the Dash2 menu controls from Race Technology and the Carbon Dash Panel and Carbon sheet from Carbon Mods I replaced all the switches with new ones from CC. I chose to keep the std CC switches as I didn't want the added complexity/reliability of using R500 type switches and relays.

 

The Dash2 comes with a built in +5v reference source (older models use an external +5v regulator to give the ref voltage...whatever you do, use this reference voltage to feed all your sensors with (except the speedo sensor as noted below)...don't use your car's main +12v supply as this voltage will change dependant on whether the engine is running or not and in turn this will cause errors in your display readings.

 

Firstly - LCD panel viewing angle... Since you have to view the Dash2 display from above the zero axis of the display to get a clear high-contrast display, for me, it meant mounting the Dash2 in the carbon dash panel, rather than on it (where the mounting angle is not good for best viewing). I ended up making up a carbon mounting tray using 1mm carbon sheet and mounting this in a cut-out I made in the carbon dash. Have a look at This piccie here and you'll see what I mean

 

Speedo - I used the standard CC gearbox speedo sensor and wired the car's +12v voltage (not the +5v ref voltage in this case) to the light green wire (going to the speedo sensor) and took the return red/blue wire from the speedo sensor to ground via a 600 ohm resistor. The Dash 2 speedo input was taken from the point where the resistor and red/blue wire meet. I haven't calibrated the speedo display accurately yet, but a pulse per mile of approx 8750 on the Dash2 seems to be close as a starting point.

 

Fuel - I took the green/black wire from the fuel level sender and took it to the +5v reference voltage via a 300 ohm resistor. Using one of the Dash2 analogue channels I used the point where the green/black wire and the 300 ohm resitor meet.

 

I drained my fuel tank and refilled whilst measuring and used the following voltages/levels to programme the Dash2 using the config software.

 

Fuel Voltage (using a 300ohm resistor and a +5v reference voltage)

0L 2.08v

4L 2.03v

5L 1.86v

8L 1.1v

12L 0.9v

16L 0.7v

20L 0.55v

Full (40L?) 0.17v

 

For oil temp and water temp I used stack temp sensors that I already had fitted on the car (the std stack water temp 0-150degC temp sensor I think called a ST746)

 

Using a 1kohm pull up resistor from one side of the temp sensor to the +5v reference voltage, I measured the following and used this to programme the Dash2 via the config software

 

Temp (degC) Voltage

0 4.867v

45 4.091v

60 3.571v

70 3.3v

80 2.967v

90 2.619v

94 2.50v

96 2.368v

98 2.297v

100 2.222v

105 1.951v

110 1.622v

 

I tapped off the full beam wiring near the fusebox for the Dash2 full beam signal.

 

I used the black/white wire on the back of the rpm gauge for the 'engine speed' input to Dash2. I didn't use any pull-up resistor on this wire.

 

All other signals I took from the switch wiring loom.

 

Hope this helps.

 

 

 

1.6 K Series EU3, 2003, with DVA K05 and a few other goodies...

website here