History of MembersPage/MarcellGal/PowerAndTraction/SpeedoMeter
Older Newer
2011-06-15 14:03:02 . . . . 3e44be11.adsl.enternet.hu [1uF for the 2k7 pullup for the gerabox speedo reed-relay sensor]
2010-03-23 22:13:54 . . . . MembersPage/MarcellGal [wheelspeed]
2010-03-23 15:30:33 . . . . MembersPage/MarcellGal [PS2 wheelspeed cable works]
2007-06-18 08:36:32 . . . . MembersPage/MarcellGal [space in URL corrected to proper format]
2007-05-26 15:16:43 . . . . MembersPage/MarcellGal [speedometer notes]


Changes by last author:

Changed:
I plugged in [PS2 wheelspeed cable] to the PS2 connector of my old 3B ECU with (using 2 wires: pin2,3 of 3pin injector connector for the audi transmission side)

* it just works. Need to calibrate for correct kp/h value though.

Overview

The dash wheelspeed has been junk since I have the car, mostly ~0 (showing some activity but showing usually much lower than real speed), later speedo's been staying at 0 permanently.

Now I have the VEMS v3 ECU logging the wheelspeed to SD-card, and [Display-only Round] showing the ECU wheelspeed in digital format

* among other runtime data, the wheelspeed is sent over the RS232 in [AIM format], besides wheelspeed: lambda, MAP and EGT are also displayed in my setup (using 2 display-only rounds).

Changed:
Making small vemstune ini change so the descriptor is available (under the GPS group, although this comes from ECU, not from GPS).
----

Wheelspeed Sensors overview - some more info below

Changed:
Anyone knows the correct setting for the speedsensor calibration for kp/h (I have factory tires on 15" rims) ? Or the number of pulses per wheelrot ? 8 or 9 ?
Audi-200 (1989) has at least 5 wheelspeed sensors:

* transmission front-left shaft (3-pin AMP connector, but only 2 pins used with a reed-relay between pin2,3).

* 4 high-pulsecount ABS sensors (VR ?)

I plugged in [PS2 wheelspeed cable] to the PS2 connector of my old 3B ECU with (using 2 wires: pin2,3 of 3pin injector connector for the audi transmission side)

* it worked the first time

** calibration: 112 Hz (at 100 kp/h) with only rising edge: 27.7 m/s / (112 1/s) = 0.248 m (sounds like 8 pulses: 0.63m*pi / 8). Verification needed.

* After the winter the ECU-wheelspeed showed mostly 0 or 255.

** We suspected firmware problem first (fw was upgraded a few times), but on bench all was perfect.

** We installed a 1uF SMD (0805 size) capacitor in the DSUB9 of the wheelspeed-cable between the Base and Emitter of the BC817 (sot323 SMD) NPN transistor.

** Soldering was easy: there was provision for a 0805 component. The 1uF * 2k7 input pullup = 2.7msec which limits the max freq to appr 350 Hz ~315km/h (the top-speed is below 290km/h anyway). 220 nF was almost enough, but there was still some noise. The 1uF seemed to fix it perfectly.

----

Calibration

Anyone knows the number of pulses per wheelrot ? 8 or 9 ?

Changed:
It would be much easier to mount a round device and display precisely calibrated digital wheelspeed on it, than sorting out this mess around the speedo gauge in the dash.
Brainstorming
Added:
Gearbox wheelspeed sender ("geber" in German :-)