Has anyone replaced a 730 ecm with a FAST XFI and had the VSS working? I tried all sorts of wire combinations and I can't get it working any ideas on the wires to use from the XFI harness? I have the VSS harness from FAST with a white,yellow,black,black/wht and my old signal from my 730 VSS input. I'm stumped. And what about the settings in CCOM??? Shaft speed, etc.

 

No suggestions? I guess I'll figure it out and post when it works. I know some GN guys are running XFI's with VSS connected. The pulse rate number in CCom would be helpful for a 2000 PPM VSS.

 

The GN VSS and the '730 VSS are different. The GN being a digital signal with the '730 VSS having a variable voltage/frequency AC sine wave. Then 2000 PPM vs 4000 PPM respectively.

If the XFI is expecting a digital signal best bet is to get a GM '4-out buffer' box. These are found in a bunch of cars: '90-'92 TBI f-body's, and Caprices of around the same vintage. Usually in white or yellow. And has the '4-out buffer' on the label. I think some of the '165 equip'd Firebirds also used them. Can be found under the dash of the cars.

That box will convert the 4000 PPM AC signal to a 2000 PPM digital signal.

RBob.

 

Thanks RBob.Thats way more information than I got from FAST. As soon as I get it working & calibrated I'll post parts & calibration numbers.

 

Got it working, the XFI will accept either an analog or digital signal. Makes things easy. One issue I had was when I removed my old parts, I removed the ground for the VSS. So anyway, I fixed the ground, then I put a drill on the speedo input & turned ign on. My speedo read ~52mph, so in Ccom I used the formula to figure my MPH cal, 26in dia tire, 3.23 gears and XFI's factor gave me 1569. So when I looked at the main dash in the XFI, I saw driveshaft speed, so then I played with driveshaft PPR in sensor rate calibration, I adjusted it until my MPH in the main dash exactly matched what the speedo said. It ended up being 785, but that number will vary depending on your set up.

 

on that buffer box... What are the pinouts from the box? I'm trying to custom wire one, but I don't know which pins do what?

 

I did a bunch of testing and looked up a spec sheet for a similar chip as the one in the VSS buffer and resolved the following:

For the VSS buffer on 1228746 and some 1227165
pin__Color__(function)
1__YEL__(VSS signal)
2__PPL__(VSS reference)

3__PNK/BLK__(Battery)
4__BRN__(GND)
5__RED__(2k ppm: output for cruise control)
6__BRN__(4k ppm: output for speedometer)
7__BLK/WHT__(GND)

To get the speedometer and cruise control to work on a 92 TBI car with a 1227730 ecu (or 1227749):
-remove the VSS buffer
-connect pin 5 from the VSS buffer harness connector to C1 on the 7730ecu
-connect pin 6 from the VSS buffer harness connector to B11 on the 7730


The wires from C1 and B11 go to the C207 connector and connect to NOTHING, so I cut the wires at the C207 so I didn't have to extend them to connect to the VSS buffer connector.