Poor mans electronic speedo conversion

supwicha

Veteran Member
Feb 23, 2014
185
Victorville, CA
80sz said:
Can you put stock pointer on new spedo? Looks nice

Well there's more involved than that. My LT1 conversion now runs, still need to do drive-line work and some other electrical. Once tested and working, I'll do a full write-up on the procedure. But in a nut shell, you'll need the electronic stepper motor and a driver to make it function. More than likely, you'll need the PCB from the donor cluster you choose.

The stock pointer from my attempt is designed for a smaller pintle shaft diameter and does not directly mount. You could disassemble the needle and mount it to the base of the needle from your donor parts I suppose. I think for my purpose, I'll repaint in an attempt to get it to match for now.
 
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supwicha

Veteran Member
Feb 23, 2014
185
Victorville, CA
Update:
I now have all instruments working except for the speedometer. I was able to add a pin to the A13 connector of my caprice PCM to drive the original '78 tachometer and it works great.

I stumbled on a way to reset the electronic odometer from the Aveo speedometer to Zero. Now since I cannot program it (this cluster requires OBD2 in the vehicle to program), I'm thinking I'll use a signal generator to advance the odometer on the bench. Most clusters use a DC square wave signal with an amplitude of about 5VDC. Depending on the capability of the Aveo cluster, I could use a simple signal generator and on the bench feed this to the VSS circuit of the speedometer and bump it to 350-400 HZ and advance the odometer relatively quickly. Kind of a backwards approach, plus it will probably take a few days to advance it to 80,000 miles to match the car, but heck on the bench I have nothing but time. . .
 

supwicha

Veteran Member
Feb 23, 2014
185
Victorville, CA
cvhu said:
supwicha is correct the accuracy is off by 10kms but i am working on a way to fix it

A couple ideas on this as I'll too have to deal with it. In looking at the .BIN file of the PCM, there are parameters to account for gear ratios and tire size, so hopefully that will be all.

Alternatively, you could possibly build a buffer using the very popular standard 555 timer to read your current VSS signal (square wave), and either increase it or decrease it, just an idea. Would cost less than $10 to build and would be about the size of a 9V alkaline battery.
 

cvhu

Member
Jan 18, 2012
97
sarnia, ontario, canada
i did get a VSSB/DRAC from a 95 gm truck, i did all calculations for the jumpers to correct the km's per hour just have to repin the jumpers wire it up and see if it works as soon as i find some spare time
 

supwicha

Veteran Member
Feb 23, 2014
185
Victorville, CA
cvhu said:
i did get a VSSB/DRAC from a 95 gm truck, i did all calculations for the jumpers to correct the km's per hour just have to repin the jumpers wire it up and see if it works as soon as i find some spare time

Can you post a picture of your work in progress / parts?
 

cvhu

Member
Jan 18, 2012
97
sarnia, ontario, canada
not to much to see but here you go

speedometer installed in my cluster


speedometer hooked up and running, odometer reads and counts km's


here is the VSSB, still need to set all jumpers for my calculations and wire it up to the car


this is a temp wiring job to see it all workin


video of it working
 

supwicha

Veteran Member
Feb 23, 2014
185
Victorville, CA
Nice work, question: Help me understand why you are not using the signal from the Vss straight from the pcm and doing the speedometer calibration adjustment through the pcm, why are you using the extra module? Thanks for sharing your progress!
 

cvhu

Member
Jan 18, 2012
97
sarnia, ontario, canada
i dont have any way of calibrating the speedo thru the pcm without sending pcm away or buying a programmer to do it, if u have a way and would like to share that would be great, i sent my pcm out last year and had it reprogrammed with all the mods i have done, also its just to see i could get this speedo to work and be fairly accurate
 

hogg

Veteran Member
Dec 29, 2000
3,200
pegram,tn.,cheatam
I would like to here more of this , and with out the elect. turms,,,pcm,vss,vssb,,, Just all the parts i would need from another car to make all gauages work ? back to the top
 




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