C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

electronic speedo fix

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Old May 2, 2007 | 04:44 PM
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Default electronic speedo fix

For those that have corrected their speedometers electronically, I have a question about which wire to use on my '86.

Do I use the yellow or purple (going off memory on the colors down there) coming off the VSS? Can I tap into the wires at the dash, or does it have to be before the ECM?

BTW, the unit is a dakota digital...older style with the dip switches. Does anyone have instructions for this thing they can scan and send to me? All I can find on the DD website is instructions for the newer model.

Chris

Last edited by okinawa86vette; May 2, 2007 at 04:50 PM.
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Old May 2, 2007 | 04:54 PM
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This thread may help:

http://forums.corvetteforum.com/show...Dakota+digital

Sorry, I don't remember which connector is which on the cluster.

Also, I've got the revision A instructions at home, I can scan them tomorrow. Or if you have specific questions I can answer tonight.

Last edited by tequilaboy; May 2, 2007 at 04:58 PM.
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Old May 2, 2007 | 05:33 PM
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I think I'm more confused about which wire to tap into since I don't have my C4 shop manuals anymore to check which wire is D11 etc. Did you by any chance take pics last time you were in there?

Although now I know I can do it at the dash cluster.

I just checked and the one that's in there is an SGI-5 rev A.

I managed to find the instructions online...DD still had them up, I just had to rename the pdf file for the rev C to A and it came up.

Thank you

Chris
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Old May 2, 2007 | 05:40 PM
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Ok, after looking over the instructions, it seems that this is how to hook it up...please correct me if I'm off here...

PWR gets a 12V accessory wire
GND is...wait for it...ground
Sig In is the yellow wire coming from the VSS
Out 1 is the other side of the yellow wire going to the gauge cluster

The rest are left open, right?

http://www.dakotadigital.com/pdf/sgi-5a.pdf

I found a dash diagnosis site that has the pinouts and it looks like the yellow wire you spoke of in the other post is the one on the bigger connector.

Hopefully this thing'll wire up easy enough....

Chris

Last edited by okinawa86vette; May 2, 2007 at 05:50 PM.
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Old May 2, 2007 | 08:08 PM
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It is easy. Sounds like you got it figured out.

I finally found my instructions after some digging.

As far as set-up goes, I used application #2 for a low speed 4-8k ppm signal.

My current cal ratio setting for 3.73 gears is 0.810 (based on the original drive and driven vss gearing for 3.07).

I've run different settings between 0.826 and 0.810 depending upon my tires.

Just set the dip switches accordingly for your ratio swap and you should be fine.
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Old May 2, 2007 | 10:45 PM
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Cool, it worked perfect first time out.

One of the previous owners did a T5 swap, so the speedo was just about double off....at 65, it read 125mph. I'm also pretty sure it has 3.45 gears in it, so that doesn't help.

I think the ratio I used was .516 and it matched up when I had a friend pace me in my pickup first try.

Thanks for the help. I was not looking forward since I had one on my 88 a few years ago and I couldn't ever get it to work. I finally gave up and bought speedo gears. I figured I'd have a hard time finding gears considering how off the speedo was on this one.

Chris
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