Ok, heres the deal guys, my car was originally a 3.1 v-6, i swapped in a 350 TBI, and now my speedo is not hooked up. I bought a 4 out buffer, the one that is yellow from a local junk yard, can i wire this buffer up to my 92 dash and speedo and make it work, or do i need to do something else before it will work ? I know that the buffer is from a 90 firebird, and it has the yellow and purple wires that go to the tranny, the other wires from what i understand are ground, 12v power, and the speedo wire, so if i wire this up, is it going to make my speedo finally work ? Any help will be greatly appreciated guys, i just dont wanna wire all this up and have it not work, Thanks

 

The 3.1L V6 ECM had the VSS buffer built into the 161 TPI ECM, and the TBI ECM uses an external VSS buffer - so the TBI setup should already have a VSS buffer module, if it is complete an functional (the ECM needs the input from the VSS buffer). For the speedo VSS input, you can tap off of the VSS output from the VSS buffer module that goes to the TBI ECM.

 

thanks for the reply Tim, but im afraid im a little lost. I realize that the 3.1 had the vss inside the computer itself, therefore i thought i would need an external buffer in order the get the speedo to work. The original engine and computer were out of an 88 camaro, which had a mechanical speedo, therefore no buffer was needed. I did switch the tranny gear and mechanical unit out for the one that was in the original 3.1 tranny, there was a lead (purple and yellow wires) going toward the unti on the tranny, but were not hooked up on the 88, i hooked them up hoping it would make my speedo work, but it wasnt that easy. So my question is can i use the 4 out buffer i got from a 90 305 TBI firebird and wire it up to my car ? Im sorry if this has been asnwered in the past, but i did a search and didnt come up with any really clear answers, thanks again for helping, and i hope you can answer my questions.

 

Yes, the 88 has the VSS buffer built into the cluster - so to answer your question, yes, the VSS buffer box that you have will work. Connect the two VSS wires to the buffer & connect the output of the buffer to the cluster & the ECM VSS inputs. The buffer module also needs +12 volt ignition power and ground connections.

 

Thanks for clearing things up Tim, you helped alot. So from what i understand the purple and yellow wires go to the harness coming from the tranny, then the pink w/ black stripe wire is the 12V, the black wire is the ground, and then the green wire is the wire which connects to the speedo, is this correct ? The other two wires on the buffer i believe arent going to be used on my car, these are brown, and the other is red, if you think this is correct let me know, or tell me if there is additional wiring i need to do. Again, thanks alot for helping me out with this issue, when it comes to wiring im not very knowledgable, so i appreciate any and all the help.

 

I have a similar problem, and am in just about the same place. After the connections are made from the tranny to the buffer and power/grounds are made to the buffer, which wires in the dash harness need to be conected to the buffer? Are these the only other connections that are needed? I have a 90 Firebird that has an '89 Camaro TPI engine harness in it. The trans is a T56 so the output from that is the same, but will the cruise work too? The car was originally a 305 TBI. Thanks, Rob.

 

The VSS buffer module wire color functions are as follows:

'92 TBI setup:
Brown: VSS out to ECM & cluster
Red: VSS out to cruise control
Pink / Black: Ignition power
Black: Ground
Purple: VSS input (VSS on transmission)
Yellow: VSS input (VSS on transmission)

'84 Berlinetta setup:
Green: VSS out to ECM, cluster, cruise control
Pink / Black: Ignition power
Black: Ground
Purple: VSS input (VSS on transmission)
Yellow: VSS input (VSS on transmission)

 

Hey Tim,..


Where can I get a "Pulse Mask" circiut so that I can install a V-6 dash into my V8 car and get the proper reading from the Tachometer ????


I saw something from an aftermarket supplier - but it was priced around $80 and that seems to be WAY to steep for something like this !

Thanx in advance !

 

John, Never completed the pulse mask design - been on the back burner - my Berlinetta still has the V6 tach in it with a V8 driving it & just reads high.....I am working on a speedo recalibration circuit for my '92 Z that uses a frequency to voltage converter chip & a voltage to frequency converter chip that could be used for the tach circuit as well. Hopefully I'll get around to completing it soon - the last project I did was a wide band O2 sensor circuit - got the basic circuit design from diy-efi.org - well worth the time & effort - got me into the 11's......I'll let you know when I finish the F to V / V to F circuit.

 

I am in dire need for something now to resolve the tach issue now !!!!

In the past I would always just read the numeric tach display to get a good idea where I was in the RPM band,..... but since I installed the aftermarket speedo inside the berlinetta dash I can no longer see that odometer / tachometer readout and will be forced to use the bar graph tach.

The car is getting a T56 installed in it and it's really important for me to have the tach visible and not flashing at 4400 RPM !!!

I'm sure you can relate !

 

If you want, I can send you the schematic for the pulse mask curcuit - haven't tested it, yet, but it is fairly simple & should work.

 

I probably can't do anything with it - but I know a few people that know electronics pretty well and they could probably figure it out !!

I'll take it !!!!


P.S. It going to be interesting to see how my 350HP berlinetta with 3.70- gears and T56 runs compared to my 95Z making about 300HP with a T56 and (soon to be installed) 4.11's !!

 

ttt

 

Here's a sheet showing some cluster pinouts.

 

Tim, how did you make out with the WB circuit? Was it close to what was posted on the diy-efi site or did you need to make changes?

Thanks,

RBob.

 

The WB ckt has been working great. I made a few small changes to the circuit I pulled from the web and added an additional stage to the circuit that allows the output of the WB to be routed to the ECM NB O2 input for data logging. The added circuit scales the output voltage to the 0 - 1 volt range for 10:1 to 14:1 afr range and routes the scaled WB output to the ECM O2 input @ WOT & routes the NB O2 sensor output to the ECM O2 input @ part throttle. I use an Auto Xray to grab the data, dump it into an Excel spread sheet, & graph afr vs RPM. I also built a 30 LED bargraph readout for realtime afr viewing. The WB output reads right @ 14.7:1 (stoich) in closed loop mode @ cruise - pretty cool! Something else that was kind of cool - as I leaned the afr out to about 12.8:1 from like 10:1, the stock ign would not reliably light (the engine missed @ WOT) the mixture above about 4500 rpm - with the Jacobs ign installed it ran fine at the leaned out afr - shows the weakness of the stk ign above 4500 rpm, or so.

 

Sounds like the WB has worked out well. Logging through the ECM does make it easier to use. I've been using a WB for about a year now and it is truely the cat's meow when it comes to tuning.

Interesting about the ignition dropping out. Not something I would have expected.

RBob.

 

John, here's the V6 to V8 tach converter circuit. It essentially masks one out of every 4 pulses. I haven't tested it out yet, but should work.