Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by f5fstop:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ChevyHighPerformance:
There are speedo recalibrators out there that change the frequency output from your VSS (vehicle speed sensor) to what you need. Some also have a switch to accomodate two differnt size tires (i.e., winter or summer). The speedo box connects or splices in the wires going to the VSS (use to be on the tail of the tranny).
Please explain further. The I/P cluster on the H3 is a dumb cluster. It receives all readouts, except five, from the BCM/PCM via class 2 serial data circuits. There is no input to the cluster from the speed sensor. (Those five readouts are left and right turn signal, seat belt, security, and MIL control.)
There may be aftermarket calibrations out there that change tire sizes, but nothing at GM. If you have a 32 inch tire, and upgrade to a 33 inch tire, the dealer can request, at customer expense, a callibration to change the tire size.
The VSS is located in the tail of the transfer case. </div></BLOCKQUOTE>
The VSS is a reluctor based sensor that produces XX number of pulses per revolution. The output of the VSS looks like a square wave. The speedo recalabrators splice or connect into the VSS wiring (and get power and ground too), measure the VSS frequency, and feed the PCM another frequency scaled from the original. Here is a PCM screen shot of a silverado's speedometer calibration. You can see the the PCM needs tire diamter, final drive gear ratio, VSS pulses per revolution, etc for speedometer calibration. </div></BLOCKQUOTE>
Darn Chevy...I know what a Vehicle Speed Sensor is. http://www.elcova.com/infopop/emoticons/icon_biggrin.gif I was a bit confused on your first posting, thinking you were saying the VSS sends the signal to the cluster.
I would have to look in the parts manual, but I would bet any of the calibrators, used for many GM vehicles, would have connectors that fit.
Do you know anyone who tried one on a vehicle that had stability control? Just curious if it would mess up the stab system since it calculates based upon speed of the vehicle as well as actual wheel speed.
I would assume there is an algorithm that states the speed of the wheels should be at a set range if the vehicle speed is at this range (or something like that). (Sorry if I'm not being too precise, but just left an all day meeting on the H3 cylinder head serviceability issue, and the H3T, and I'm burned out.) </div></BLOCKQUOTE>
My thought was that if I wasn't clear to you, I probably was unclear to a bunch of people too.
The PCMs I've interfaced with don't do the stability stuff so I'm not sure how the H3 does it, but the stability systems I'm vaguely familiar with use capacitive accelerometers to measure three axis movement. Vehicle speed is a player, I'm not sure if the controlled gets it from the data bus or calculates it directly. Is there a differnt program for the ABS and stablity modules for adventure and non-adventure H3's or do just the PCMS get flashed differently?
The LS1 ABS and traction control used wheel sensors for each wheel (except the without traction control, ABS used one sensor to measure the ring gear speed for the rear tires) and made a differential measurement (this wheel is spinning faster than the rest -> it must be slipping -> apply brakes to that wheel and/or cut back on throttle) or (this wheel is decelerating faster than the rest or stopped -> modulate brake pressure to that wheel).