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Old 08-20-2008, 01:16 PM   #531 (permalink)
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For the VSS, heres what Ive found with many of my GM manuals. It appears most late 80s and early 90s models with electronic speedometer use 4000 pulses per mile going to the speedometer head and cruise control. For the earlier models with cable driven speedometer, it appears many use 2000 pulses per mile coming from the VSS buffer behind the cluster.

Not sure how to cleanly put this into the wiki page. Maybe its just the really new GM models that use 10000 pulses per mile?

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Old 08-20-2008, 03:12 PM   #532 (permalink)
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Quote:
Originally Posted by markr-nc View Post
I guess the Eclipse falls in with the Metro with a nervous speed readout. It jumps around 2 to 3 miles per hour when holding steady speed.
We took a trip in the saturn and the instant speed readout for version 0.70 is very smooth. I have to get the portable scope working or borrow one.
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Old 08-20-2008, 03:26 PM   #533 (permalink)
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I can put the invertor in the car and scope it with a small Snap On scope. I really hadn't thought about doing it. Should be able to do it this evening.

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Old 08-20-2008, 03:29 PM   #534 (permalink)
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Old 08-20-2008, 05:05 PM   #535 (permalink)
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scope picture of speed sensor

this was at about 19-20 mph. shows the signal is 4.9 volts in amplitude. I didn't see any glitches in it, but I haven't driven it very far. faster didn't change the signal except I have to shorten the view time. Didn't drive it very far, just up and down the block without getting run over.

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Old 08-20-2008, 05:09 PM   #536 (permalink)
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The instantaneous speed is determined by the distance between the peaks. Can I ask you to zoom in a bit and see if the "wavelengths" seem consistent at a given speed?

edit: Without getting run over?
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Old 08-20-2008, 05:13 PM   #537 (permalink)
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I didn't know how that picture would look on the page so I re-saved it as a jpg and sized it down some from the original but this should be easier to see.
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Old 08-20-2008, 05:16 PM   #538 (permalink)
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I meant when you display the data on the scope, can you scale it so there are like 3 or 4 peaks and valleys displayed?
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Old 08-20-2008, 07:22 PM   #539 (permalink)
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I understood, just had to deal with end of day customers. Just got to go down the street again. This at 50 mph. Looks like all the same spacing to me.

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Old 08-20-2008, 08:04 PM   #540 (permalink)
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Well, it isn't conclusive with parallax and all, but without precise values on exactly when those verticals occur, it looks like the signal itself might be wonkey (lot of slop in the speed signal on these cars?!?)

if I simply use paintbrush zoomed in and visually compare the widths, there does seem to be a noticable variance. Maybe I need a certain number of pulses or something? Maybe the vss cam has multiple lobes and they aren't terribly precise? Other thoughts?



I suppose I could lift a wheel and hook up a buzzer to the vss line and see...

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