I have a 91 Z/28 that had a factory 305TPI.. I swapped the old engine out and built a 383 TPI and replaced the factory wiring with this new Fitech ultimate TPI... I am having two problems;
1) I cannot seem to get the speedometer to work. Apparently the 91's didn't have the vss buffer box, I've tried wiring the speedo output from the Fitech directly to the speedo cluster input wire.. Still nothing, has anyone on here had any experience with this system on a 91 Camaro ?
2) I connected the tach output wire to the white wire coming into the dash connector and it doesn't work either...
Fitech is absolutely no help with this...

 

I have one in my 92. The tach works fine for me but that's because the ecm has nothing to do with it. Wire straight from the coil to D6 on the C100 sends it to the tach.

I have no direct solution for the speedo. My problem is the same, hooked it up, it does nothing. My car formerly had a buffer box, I may need to reinstall that or get a Dakota Digital box. My other issue is the interface doesn't show my speed either. So maybe it has a failure or wire issue. It's not my vss since it worked before the swap. I haven't gotten back into the garage this spring but if I find the solution, I'll post it here.

 

I bought the Dakota digital sgi 100bt to get my speedo to work. I took the signal directly from the vss (spliced the wire). Works like it should

 

Oh interesting, I thought the non-buffer VSS setups were only in the V6s! If your car did indeed come without a buffer box, then the VSS signal would have been processed and sent to your gauge via the ECU. If you had to pull the factory ECU out for the FiTech install, then your gauge wouldn't be getting the right signal anymore. Dakota Digital box is probably going to be your best bet.
Not surprised to hear FiTech won't help, a friend of mine has been having pretty similar issues trying to get FiTech to work on their 383 TPI motor over the last year or so, customer service has been pretty much useless.... from what I hear, they automatically assume it's for an LS, doesn't seem like many (if any) of the techs are familiar with TPI

 

3.1L and 90-92 tpi has a Vss buffer it’s not an external box but incorporated in the 1227730 ecm unlike tbi that uses a buffer box and i think 88-89 tpi maf as well .

 

Interesting! I knew about the 3.1 since I recently tuned the Road Speed Constant/ IP Pulse Divider for my trans swap, but I wasn't aware about the 90s '7730 TPIs using this feature as well. Pretty cool!

 

Thanks for the info, the tach is back .. The speedo works on my interface... Guess I'm gonna need the Dakota digital box to get it to work, I plugged the old vss wires into the transmission and nothing... Thanks for the help...

 

I hooked mine up to a '92 K2500 so my experience is a little different but I had these problems. Changing the 'from cal' settings to 'On' and 'fromcal' allowed me to get outputs on the wires, and my Speedometer started working. I think I had the FiTech output going straight into the speedometer and not through the factory converter box thing that the vss originally went to.

Tech support helped me with the above but they gave up on me with the tach output from the ecm. I ended up wiring the white wire off the coil straight to the tach and it worked just fine.