VSS signal wire for aftermarket speedo?
07-08-2010, 03:30 PM
#1
Racer
Thread Starter
VSS signal wire for aftermarket speedo?
I'm building a Cyberdyne digital dash for my 85. Do I have to tap into the wire coming from the vss at the tranny before it gets to the ecm? I was hoping to tap into the instrument cluster connector but read that the ecm converts the vss signal into mph for the lcd dash to use. The setup for the Cyberdyne speedo is to drive at 50 mph on a level road and push a button. I think this speedo will work with any vss but I'm not sure about the signal coming from the ecm. It doesn't seem like a big deal to tap into the vss signal wire but if I don't have to it would be easier. Any help would be appreciated.
07-08-2010, 05:34 PM
#2
Melting Slicks
Member Since: Jun 1999
Location: Bowling Green KY
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I'm building a Cyberdyne digital dash for my 85. Do I have to tap into the wire coming from the vss at the tranny before it gets to the ecm? I was hoping to tap into the instrument cluster connector but read that the ecm converts the vss signal into mph for the lcd dash to use. The setup for the Cyberdyne speedo is to drive at 50 mph on a level road and push a button. I think this speedo will work with any vss but I'm not sure about the signal coming from the ecm. It doesn't seem like a big deal to tap into the vss signal wire but if I don't have to it would be easier. Any help would be appreciated.
07-08-2010, 07:36 PM
#3
Racer
On 85 - 89 vettes the VSS raw sensor data is sent to the digital cluster, the cluster modifies the signal for the speedo, cruise control (also built into the cluster) and sends it to the ECM. Post 89 the VSS sensor data goes to the PCM and then to the speedo.
(i.e. the '165 ECM gets the signal from the cluster, the '730 ECM (and later) gets the signal from the VSS.
Without the digital cluster (85-89), all you have is the raw sensor data.
From what I understand the sensor sends out a sign wave. The speedo, cruise control and ECM need a square wave at a frequency of 4000 cycles per mile.
If the speedo you have can use a sign wave, then the VSS signal from the cluster wirng harness should work. If it works at all, this should be the case. A lot of cars in the 80's and 90's have the type of VSS the C4 uses (most GM, I think). It would seem that after market "self calibarting" speedo's should handle this.
You're problem may be a bad VSS sensor. Just a theory.
My experience with this stuff:
I got cheap and put the analog cluster from a 92 Camaro RS into my 86. It needed the sign wave to square wave conversion. That gen Camaro had a box to do the conversion. Without the box the speedo didn't work at all, it danced all over the place at any speed.
(i.e. the '165 ECM gets the signal from the cluster, the '730 ECM (and later) gets the signal from the VSS.
Without the digital cluster (85-89), all you have is the raw sensor data.
From what I understand the sensor sends out a sign wave. The speedo, cruise control and ECM need a square wave at a frequency of 4000 cycles per mile.
If the speedo you have can use a sign wave, then the VSS signal from the cluster wirng harness should work. If it works at all, this should be the case. A lot of cars in the 80's and 90's have the type of VSS the C4 uses (most GM, I think). It would seem that after market "self calibarting" speedo's should handle this.
You're problem may be a bad VSS sensor. Just a theory.
My experience with this stuff:
I got cheap and put the analog cluster from a 92 Camaro RS into my 86. It needed the sign wave to square wave conversion. That gen Camaro had a box to do the conversion. Without the box the speedo didn't work at all, it danced all over the place at any speed.
07-09-2010, 07:18 AM
#4
Racer
Thread Starter
Thanks for the info. It explains alot. Mike, how did you tie the Camaro cluster wires into the Corvette instrument cluster harness? I would rather not cut the Vette instrument harness off but I would need something on the end of each instrument wire to be able to plug that wire into the Vette instrument harness plug.
Moon
Got the instruction sheet out for the speedo and it says that it will work with an input range of between 1000 and 200,000 pulses per mile.
Moon
Got the instruction sheet out for the speedo and it says that it will work with an input range of between 1000 and 200,000 pulses per mile.
Last edited by Moon86; 07-09-2010 at 07:20 AM.
07-11-2010, 01:35 AM
#5
Interesting post.....installed a new gauge cluster from Vette Aid, white face Autometers in my 85.......all gauges work wonderfully except the speedo....has an eratic needle at low speeds, but stables out somewhat at hwy. speeds......they even sent me a new speedo....same results after callibration?? could it be callibrated incorrectly causing an eratic needle???
07-11-2010, 05:04 PM
#7
Racer
Thanks for the info. It explains alot. Mike, how did you tie the Camaro cluster wires into the Corvette instrument cluster harness? I would rather not cut the Vette instrument harness off but I would need something on the end of each instrument wire to be able to plug that wire into the Vette instrument harness plug.
http://forums.corvetteforum.com/c4-p...digi-dash.html
Last edited by Mike263; 07-11-2010 at 05:57 PM.
07-11-2010, 05:46 PM
#8
Racer
Thread Starter
After trying every combo involving the ppl and yellow vss wires I couldn't get one peep out of the cyberdyne speedo. Kept giving me the error for no signal. Have to get under the car and check out the vss on the tranny and see if an aftermarket vss, that I know will send the correct signal, will install and fit.
To access the vss wires I clipped them about an inch back from the connector. I doubt if I'll ever hook them back up but I have the option anyway. Mike-- wish I had thought of what you did before I clipped the wires.
856SPEED-- That sucks that you spent all that money and the speedo doesn't work like it should. I canceled my order for the analog gauges after getting backordered twice and finding some Cyberdyne gauges on the shelf from a past project. Should have some pics soon.
Moon
To access the vss wires I clipped them about an inch back from the connector. I doubt if I'll ever hook them back up but I have the option anyway. Mike-- wish I had thought of what you did before I clipped the wires.
856SPEED-- That sucks that you spent all that money and the speedo doesn't work like it should. I canceled my order for the analog gauges after getting backordered twice and finding some Cyberdyne gauges on the shelf from a past project. Should have some pics soon.
Moon
07-12-2010, 07:15 AM
#9
looks great though
no really I am 90% satisfied and 100% satisfied with the customer service end of it.....it is only at low speeds......they are taking care of me however! they call/e-mail me......have to give credit there for sure!
I think its actually something in the calibration (I hope).....we'll see....
