Pulled this post from another thread cause I didn't won't to interrupt the discussion. I know this question is a little off couse for 3rd Gen but FSC seems to have moved on newer problems, whereas, a lot of you guys are still tuned in to the older rides. Would appreciate any info.

Quote:

Originally Posted by dimented24x7

Sweet... I found the last set of TOS inputs. These work exactly the same as the TOS input thats driven off of the buffer box on pin F12, but are instead driven by an AC signal. The address in the ram is $3FC6 for the pulse accumulator and $3FF8 for the counter and pins F4 and F5 are the sinusoidal inputs. Not only can I FINALLY have a stable VSS signal rather then the usless bouncy one from the stock cable driven VSS, but it also makes using a MAF and e-trans possible. The only change needed is to just use the alternate set of inputs and tap ahead of the buffer box for the VSS.

dimented or anybody else,

Could you elaborate a little more on this setup.

With my setup (7747 ecm, 87 PU) and speedo cable driven optical sensor, am having a lot of trouble synchronizing my speed vs ecm, speedometer & gps. My gps says I’m running about 4 mph lower than speedo and 14 mph below ecm readout. As you can imagine, this is causing problems tuning, shift points, etc.

Not sure what ecm you’re running but will these code changes work with mine? Do you eliminate the vss buffer box? If so, what are the codes that need to be made. What other code or setup changes need to be made?

Thanks,
Buddy

 

Most calibrations have a setting that adjusts the pulses per minute which will adjust the speed computed by the ECM; but does not affect the speedo reading.

I found a minor difference between my speedo & ECM when I first started tuning years ago on my SD TPI. And by making a minor adjusting the "pulses per minute" constant for the VSS, I was able to syncronize the Speedo & ECM exactly. Unfortunately, if the speedo is still off, then you must look at changing your speedo gears.

 

The gps also gives you the distance as the crow flys
hills and corners will give incorrect speeds