I installed a set of the Nordskog digital gauges in my camaro and replaced the optical vehicle speed sensor behind the speedometer with a tranny mounted magnetic pickup sensorprovided from Nordskog I was wondering if anybody knew how many pulses per revolution the optical sensor sent to the computer because after I installed the new sensor my speed limiter kicked in at 35 mph? And does snybody know of another sensor I could install to fix this because I really don't want to have to scrounge up a new speedo cable and optical sensor to rig something up that'll work...

 

It would help to answer your question if told us what year and model cat you were working with.

Actually the VSS you took out of the transmission tail housing is not optical but magnetic, and sends electrical (digital)pulses to thePCM to let it know how fast the driveshaft is spinning. ThePCM translates this data to MPH. The computer output, which is also a digital electronic signal, sends 4000 pulses per mile (if the PCM is properly programmed for the tire size and final drive used)toa logic module in the istrument panel which then drives the speedometer. The PCM also uses the VSS data for engine and power train management.

Whatever you replaced the VSS with, either is sending too many pulses per driveshaft revolution to the PCM or may have caused the PCM do go into limp mode.

There are no optical circuits in the instrument panel.

 

If you had a speedo cable there is an optical sensor. A small yellow box on the back of your speedo cluster. I believe it is a 2 pulse sensor.
When I put autometer gauges in my 84 I needed something to replace that sensor and I got a hall effect unit to hook to the cable.
Rodger at Speedometer services knows this stuff well.
www.speedometersolutions.com 414-463-6660
I told him I was installing autometer and I needed a cable and something to replace that thingy and he knew exactly what I was in need of.

 

Sorry its an 89 rs with cruise controland the optical sensor is located behind the speedometer and reads flats on the speedometer cable, the flat spots reflect the light from an L.E.D. to an photocell which sends a signal to the computer in the form of a pulse, Im guessing there is two flat spots so it sends two pulses per speedo cable revolution... but the guages I installed are all digital and do not require the speedo cable so I was hoping I could run the guages and the computer off the same sensor... the gauges will work off virtually any sensor because I can recalibrate it, I just need to finda sensorthat sends the right signal to the computer...

 

You also need that signal if you have an automatic trans. The sensor originaly in the car is 2 pulse. I would assume the nordskog sensor works off of pulses. If the question you are asking is how many pulses it works off of then i would suggest asking the manufacture.

 

I have the Nordskog full dash replacement in my 86 frankenstein. The Nordskog speedometer sender factory is set a 8000 ppm (pulse per mile) According to the chilton's/haynes books and some other sources. The camaro uses a 2000ppm system. That little yellow box with the three wires hooked into it sent those puleses to the ECM and to the Cruise Control unit. I have on order from Dakota Digital a universal VSS Buffer. That will take my 8000ppm signal and convert that into 2000ppm for my ECM. Its about $80 for the buffer. Has like 5 outputs for various signals. That unit is the SGI-5. Found here at http://www.dakotadigital.com/index.c...rod/prd126.htm

I like the clean blacked out look of digital gauges but I hate the reliability factor. I just mechanical gauges more so than electrical.
I'm not real happy with nordskog...not very informitive nor do they have the support factor that dakota digital has.

Anyway...good luck and have fun