Vss divisor information

[Tunedperformance]

I was wondering if any one has messed around with vss divisor setting on $8d or $DA2 or DA3. I have change the $8d to optical to run off of buffers and drac's but have never messed with the divisor. Is there a formula for a higher rear end ratio to calibrate the vss to run slower. I am trying to help a guy out and do not have the vehicle here for testing the values.

[Six_Shooter]

In $8D, you wouldn't use the VSS divisor to adjust for gear ratio changes, you would use the Vehicle SPeed Sensor Instrument Cluster Panel Pulse Divisor located at 0x14.

[Tunedperformance]

Sorry six shooter That is the vss divisor I had meant to state the Vehicle SPeed Sensor Instrument Cluster Panel Pulse Divisor.

[Tunedperformance]

I figured out the answer, sweeeeeeet ;)

[EagleMark]

So your not going to tell us?

I don't know if it is accurate for $8D but there is one in the $EE info thread...

[Tunedperformance]

pm sent

[JeepsAndGuns]

Working on $8D too, the other VSS scaler (0X15), can that be changed to match a non stock VSS?
Most stock bins I have seen are 4000 pulses per mile. I assume this means the stock vss is a 4 pulse one? So could this value be changed to 2000 for a 2 pule VSS, or 8000 for a 8 pulse VSS?

[Tunedperformance]

the magnetic vss input can be raised as a magnetic pulse input but not lowered starting at 4k. You can use 2k through a external vss buffer and into a 730 as optical or same thing with a drac

[JeepsAndGuns]

So if I have a 8 pulse hall effect VSS I can use it by simply entering 8000?

[Tunedperformance]

not with a hall effect.

[JeepsAndGuns]

So a hall effect vss is not compatable at all with 8d?

[Tunedperformance]

not that I am aware of. I sent you a pm. As far as I know just magnetic pulse and optical.

[1project2many]

If your Hall effect produces 5V out then it may be usable but it depends on the frequency. The signal could be connected to the optical input but you might not be able to adjust the vehicle speed properly since the optical signal is supposed to be 2000 pulses per mile.

[cmaje72]

I have it set to 8120 on $DA3 for an 8000 PPM sensor. Its right on with my speedo.
Jeeps - its the waggy one and I think it might work for the $8d ecu's. I just went out googling and found this:

Q: How do I tell the ECM I have a magnetic VSS instead of a optical VSS? Change bit 6 of the value at location $8018 to zero.

Its at this site:
http://www.diy-efi.org/gmecm/ecm_info/1227730/qanda.html#q10

So maybe $8d can support both types?

[RobertISaar]

a hall effect SHOULD be able to be used... but you may have to do a little tweak to the wiring first. the hardware in a 7727 wants to see an A/C signal that passes both above and below 0 volts. a normal 2-wire magnetic VSS will do this, hall effect goes from 0-5V(or something along those lines). well, you can make it swing from -2.5 to 2.5 volts using only a single capacitor. something i found out while making my testbench.

and 8D CAN use optical or magnetic, with adjustable PPMs with both. obviously magnetic needs to be at least 4000 pulses per mile for the divider to work correctly, but that's only for the instrument cluster signal.