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I have a 1207747 that I have put on 1965 El Camino, i pick up parts from wrecking yard and some i have bought. For the Vss signal used a Hall Effect chip on the drive shaft, this causes my speed in the data log to be off by about 30% high. In the bin files Mph is used in several places, Everything seems to work, other than some fine tuning, which i am in the process. Is there any way to correct this. Any help or thoughts would be helpful.
The ecm expects 2,000 pulses per mile. There is no correction in the software. Some of the early cars with TBI used an electronic module to change the speed signal for the computer. I know that TBI Camaros and the old, square Chevy Caprice are two places to find this converter. I do not know if the converter will work with the square wave signal produced by your Hall effect sensor.
There is another converter that is very popular called a DRAC. It's job is to convert a 40 pulse per revolution sine wave signal to 2,000 or 4,000 pulses per mile for the ecm. It is not appropriate for the square wave produced by the Hall effect sensor.
A correctly calibrated speedometer cable turns at 1,000 revolutions per mile. If you install a sensor on the cable to produce two pulses per revolution then you will provide the correct 2,000 pulses per mile speed signal that the ecm expects. The sensor should produce a square wave signal.
Thanks i was afraid of that, My speedometer is corrected, not sure what to do from here.
Bill
Put a sensor on the cable?
Not sure how i would do that, could you give me some ideas?
I also run into another problem tunerpro rt, trying edit my VE table, i can see it change when i paste to it, it doesn't save, when i look for it.
jagsthatrun sells a sensor that goes inline on the speedo cable. alternatively you could possibly adapt an optic sensor from a eightys camaro/pickup, ect to your existing speedo.
then run the vss buffer for said sensor. we did something similar on a buddies chevelle.(access to a machine shop helped a bunch!)