dustovich

Hello fellow S4 owners,
I am in the process of building/programming a digital lcd boost gauge/voltmeter/trip computer/etc/etc that fits in the hole in the gauge cluster where the original '92 one was. I have found some of the specs on the sensors for the car but am missing some. I am wondering if anybody else knows the calibrations on some of the sensors, this would be really helpful. The ones I am looking for right now are:

--Gala speed sensor - how many times does it pulse per km/wheel rotation??
--manifold/input air temperature - what reading (v) for temperature
--fuel consumption signal -- I have no information on this one

My goal is to have the following information available on the screen eventually:
--map 250kpa/300kpa sensors (converted to whatever units)
--voltmeter (missing on s4)
--manifold air temp
--fuel consumption l/100km (or other units)
--total km travelled/avg/max speed
--fuel pressure (with additional sender unit)
--anything else I can think of in the future

If anybody has any ideas to make it better, let me know. I am still in basic development, but it should be pretty cool when I am finished, and not hard to reproduce if someone else wants one . Help is much appreciated.

--Dustin

UrS4boy

Don't want to kill your enthusiasm but...

http://www.efiexpress.com/catalog/pr...products_id=58

Google TDS-1 and TDS-X

Sorry

dustovich

Oh don't worry, I am quite well aware of the TDS-1, but I have not seen the TDS-X and cannot find anything on google. This addon is good, but it lacks screen real estate and flexibility, and it costs $$$$$$$. I can build my own which can show multiple sensors/inputs simultaneously and costs around 1/6th the price for me to build. My goal is to imitate the '92 one, in the same spot.

It won't be hard for me to measure the signals myself, but if someone else has already done it it would save me some time.

UrS4boy

Some IAT info:

The G42 IAT is connected to the ECU via pin T44/55 with a brown striped blue wire (BR/BL). A digital multimeter can be used to measure the resistance of the two-pin device G42 intake air sensor with the connector harness removed. With the engine OFF long enough to cool sufficiently, at an ambient air temperature of 20 degrees, a value of 450-650 ohms should be measured across G42.

From SJM Autotechnik, via S2central.net:

UrS4boy

Some Vehicle speed sensor info:

The signal should be on Pin 50/55 of the ECU connector, white wire with a blue stripe:

50/55- Road Speed signal output (input?) to Instrument Cluster-G21-W/BL-signal also goes to Automatic Climate Control Head Channel 17 - which you can read out speed as well AND the UrS4 lockable rear differential controller (under the rear seat so it can dis-engage the rear diff lock at 15 mph (25 kph))



The road speed sensor is Hall effect sensor that looks like this:



I am not sure what causes the pulses (I can't see anything specific in the parts diagram below). I suggest safely jacking the left front wheel off the ground, putting the transmission in neutral, turning the ignition on to "run" (not start) and with your multimeter connected (somehow) to the two wires connected to the sensor, rotate the wheel 360 deg while counting the pulses. Could be difficult.

UrS4boy

Fuel consumption signal:

ECU Pin 31/55- Fuel consumption signal for trip computer - BL/BK - Note: only used in N.America on 92 spec cars.



This blue with black stripe wire can be accessed in the passenger side kick panel (access by the first 3 steps in this ECU removal DIY: http://12v.org/urs/JimmyPribblesECURemovalProcedure.pdf)

The connector is in the red connector behind the orange and gray connectors. The blue/black fuel wire is in the middle of the back row in T6c/5. (There is a blue/black wire in the Gray T6d connector but it is for the Low Oil Pressure warning in the AutoCheck.) The wire is there (in the red connector) because it is set up to go to the 92 spec trip computer, like the Boost signal Yellow/Blue wire in the grey connector. (My next post)

UrS4boy

Boost signal:

32/55-Output to Trip Computer Boost Pressure Gauge - Y/BL - Note: only used in N.America on 92 spec cars



This yellow with blue stripe boost signal wire can be accessed in the passenger side kick panel (access by the first 3 steps in this ECU removal DIY: http://12v.org/urs/JimmyPribblesECURemovalProcedure.pdf)

The wire is in the grey connector beside the orange connectors in this connector rack. The wire is there because it is set up to go to the 92 spec trip computer (and they never changed the harnesses after 92)

dustovich

Thanks for the info. For the vehicle speed sensor it look like part 8 is what gives it the speed. And by the picture it has 4 nicks in it, so it should pulse 4 times per rotation. But we will see in testing soon.

UrS4boy

Good catch on item 8 and the four notches. Sounds about right. The Vehicle speed signal is available in the red connector behind the orange and grey connectors in the Connector Stn 2 photos I have shown. It is a Brown/Red (0.5) wire in position 1 of 6 (one of the corners of the red connector).

dustovich

Actually, we are all wrong about the speed sensor. Every revolution it pulses to 10 volts 8 times per revolution. Or every 1/8th a turn. So the standard oe tire size of 225/50-16 has a circumference of 78.06 inches or 1982.7mm. So between cycles you will have travelled 247.8mm or 9.75".

Visualized below as a square wave:

10v _ _ _ _ _ _ _ _
| | | | | | | | | | | | | | | |
0v |____| |____| |____| |____| |____| |____| |____| |____|
deg 0 45 90 135 180 225 270 315 360
in 0 9.75 19.5 29.25 39 48.75 58.5 68.25 78
cm 0 24.78 49.56 74.34 99.12 123.9 148.68 173.46 198.24

If we divide it out there are 4035.5 pulses/km. So now we know the distance measurement, now for speed. 1 km/h would be 4035 / 60 / 60 = 1.120972 hz and 100 km/h would be