I just finished my 6 speed swap in my Formula. But for some reason this SGI-5 is giving me fits. I wired it up just like was posted on here, using out 3. Take the car for a spin and as soon as I get moving, the speedometer just goes pegged at 150. So I **** with it and try all types of different wiring setups and dip switch setups. Basically come to the conclusion that my speedo is either pegged, or dead and a throw a light.

So...first off. Car is an 88 but has been converted to SD. I left the buffer box in place and just changed it in the tune to read through the box. I know the SGI-5 is getting a signal, the light flashes green when I am moving.

What ppm am I looking for here. I am under the impression that I need 2000ppm since I am still running through the buffer box. Then whats the oc and ac in the SGI-5 directions?

I am just lost on wtf I need to do here. I jacked with it for like 3 hours wiring it every way possible I could think via the directions. But then I have heard their directions are wrong?

When I wire it so the sensor ground is connected to the other wire going back to the ecm, the speedo is pegged. When I ground the sensor ground the speedo is dead and remains dead no matter how i wire it?

I just want to get this thing buttoned up so I can move on.

 

Which version of the box are you using i.e. 5a, 5c? AFAIK unless
you had a TBI originally then there isn't a buffer box.

With your SD setup you're using a computer from a 90-92? If so then originally for an SD car both vss wires go to the computer at ports 910; 99 with yellow wire at 910 and purple at 99.

If the box is getting a signal then I would try wiring 2 outputs and tapping directly into those two wires, or since they were already run to the trans just put them into the output ports on the box.

Don't wire anything to the speedo itself just to the computer and it will do the rest.

 

Theres a buffer box. I pulled it down. Its right by the ecm. Little yellow box that says buffer box on it. The yellow and purple wires go into it on one plug, then theres another plug with about 5 or 6 wires. My car is a L98 car.

I have the newest version, the SGI-5 C.

The wires go into SD ecm at B10 and B9......dont they? Thats not what I am trying to accomplish though. I want to get it to work through the buffer box, so I dont have to change the tune.

 

So if both vss wires go into the buffer box, do two more wires out of it go into ports B10 and B9?(yes B10 and B9 couldn't tell they were B's on the diagram)

I would wire the 2 wires from the buffer box into the outputs on the SGI box and see if that solves the problem.

 

The buffer box distributes the signal to everything else the way I take it. So I would have to find where all the wires that leave the buffer box go into the ecm. I dont think the buffer box has anything to do with it all. Everything was fine before I did the swap. I mainly just need to figure out how to work the SGI-5, how to wire it, and what out I need etc.

 

Anyone else....?

 

The SGI box has a power wire( I used an ignition wire for power)
a ground, a signal wire and a signal ground.

The t56 vss wires both send a signal so it doesn't matter which you use for a signal ground or a signal.

I did a little searching and it says that with a car with an electric speedo to begin with use output 3 on the box, connect the original yellow wire from the original vss plug, and ground the original purple wire from the original vss plug.

 

Thats exactly what I did. And for some reason the speedo just pegs and 150 as soon as a take off. Cant figure out wtf is going on.

 

If I were you I would try plugging both of the original wires into the outputs on the sgi box, and see what happens then.

What other wiring combos have you tried? Also kind of a dumb question but on the box do you have the outputs your using switched on? (I would think so since the speedo is doing something, but just to be sure)

 

I tried the other wire, the purple wire. It wasnt as bad, but it still eventually pegged the speedo once i got moving prob 15-20 mph. What do you mean have the outputs switched on. Theres only four switches. Input type, sensitivity, output type and Cal Range. Thats one of my biggest questions is what is on and off on those switches.

 

It's been a while since I wired up mine but as I recall there was an input for power, ground, sensor sig, sensor ground, then there was like 5 outputs and next to those there were little on off switches for each one of those. Then there were 2 switches up and down to adjust the ppm.

For my application I used an autometer speedo so all my calibration was done through the speedo. I believe for a car with an original electric speedo you have to calibrate through the box, and the way that most members I have heard of doing it by driving on the highway behind a friend at a set speed and then use the up down switches till the speedo is calibrated.

The reason that your speedo is pegging out when you are barely moving is the t56 puts out a 40,000ppm(I think) and I believe your original trans put out between 2000-4000ppm. so when you are barely moving it sends out a huge amount of ppm and the car thinks it is hauling ***. So calibration through the box should solve the issue.

This should fix it, sorry I didn't think of that sooner, but as I said it has been a while since I have had to mess with one of these things.

 

I'm just curious but did you get it working?

 

Nope still cant figure it out. I havent mess with it a ton. Basically what I did figure out is that if I switch to the purple wire, and have it on out 3, its not as bad. It also get interference when the car is idling. When I rev the car the speedo just to like 80mph. My next thing to try is to twist the signal wire and ground wire together. It says in the directions that will kill the interference. But I still have not solved this issue.

 

This seems to be a common problem with this unit. My experience is when I first hooked it up and tuned it in [only took several miles IIRC] but the idle at times runs the rpms up [surging] and the speedo runs as in motion. I've moved wires, ran shielded cable, built filters, bought filters and finally gave up. The mph and odometer seems very correct though. The mile posts on the interstate are a good judge AFAIK......... As we speak I'm building a 3.42 rear which I can get a GM VSS gear for as they made a 3.42 with TPI and 5 speed in 91-92. So after that I hope for no more of this shet.......................