Well, this has been done before, but instructions were poor. I had a hard time getting it right with what I found on PFF.

The gauge I have is from an 86 Sunbird.

First you have to modify the housing and the tach itself to fit. In the pic you can see the posts where the original tach was fastened are circled. You just need to cut away until the gauge sits close to flush with the top of the housing. There is also a notch in the circular post a bit lower for the circutboard to slide into.

The bulb housing needs to be trimmed too. I used black tape to keep the lights for the tach from shining through and lighting up the blinker area.

Next you have to trim the gauge too. In a pic I will post a little further down you should see the trim area.

Now you have to wire it up and modify the tach to work with a V6 instead of the 4 cylinder it was made for. This was the tricky part for me, I know squat about electronics. Nobody ever posted a pic of the trimmer.

You can see the black line I drew over the trace you need to break/cut. And the trimmer is a 1M. I got it at Radio Shack in a little box with about 10 other resistors for about 5 bucks.
Here you can see another view of the trimmer. The white center rotates to adjust the current.

Hopefully you can see where I soldered the wires for the trimmer on the board. The wire on the right side is soldered on the 3rd prong up from the bottom and the other wire is on the one inbetween the two chips (the chips are on the other side). That was the part I could never see in the pics and it was never explained in detail.

The green wire that goes to the Map sensor is one I can't remember. I connected mine to the wire right at the plug to the ECM. I forget the number in the plug for this wire. It is a green wire, but there are a few of them in the plug. I think I tracked it from the MAP as close as I could to the plug and then used a voltmeter to get it right. Maybe someone can jump in here. I think Jelly2M8 told me where it was once...

You can see I also added a bulb. It's actually really bright right there and I might remove it.

The screws that double as the post on the stock tach and the Sunbird are in completely different places. You can see I just added wires to the posts and soldered them to the back of the cluster in their proper places. Then I covered the inside area with tape incase anything touches them.

[This message has been edited by SCCA FIERO (edited 09-06-2004).]

Now it's time to adjust the new tach. I wired them together and layed them on the floor. It wasn't too hard to do this. I also took some readings at different speeds and did it again with the new tach. It seems to be perfect.

The boost gauge seems to be perfect too. Each break in the bar is 3psi, 15 psi being the max. Here it's 12psi.

Here it is too.

I think Terry ( PFF = TK) is the inventor of this, or maybe Rockcrawl. It sure wasn't me. So give those guys the +s, not me.

Nice photos and a good practical set of detailed pictures for this work . My tach is modified, all I need to do now is get the engine installed. LOL

[This message has been edited by hnthomps (edited 09-06-2004).]

hey! my fiero doesn't tell me when to shift, lol. At what rpm does it tell you to shift? I have never seen that light come on before.

James

nice write-up and excellent mod. a + to you.

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power corrupts. absolute power corrupts absolutely.

Custom Chip Burning | Fiero Engine Conversions | Turbocharging | www.gmtuners.com

Skitime has the same thing in his car.

Nice and clean. Thanks for the post with the pics!

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John DuRette, Custom 85 SE, PFF SUPPORTER

This is a great post. I am planning to do the same thing if I never get around to my swap. Good work.

Very interesting. I hope you were on your way to the gas station because you're out of gas!

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-Matthew
87 GT My transportation
86 GT My headache

It actually had just under half a tank of gas. Ever notice when you hit the gas, the gauge will go to empty, hit the brakes and it will go towards full?

In 2nd gear with 12psi really makes the gauge move.

The shift light should be in every Fiero with a manual tranny. Maybe your bulb is blown out? It usually has to do with the RPM and the vacuum in the manifold. I'm actually wondering why mine is on in the pic. It's not too high in RPMs (the shift light comes on in the redline of the tach no matter what) and I know there's no vacuum in the manifold.

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2002 Utah Region SCCA 1st Place C Street Prepared
Utahfieros.com

Thanks SCCA! I found a tach just like yours in the yard and I'm hanging on to it in case I ever decide to get blown. Bookmarking the write up now.

cool write up and great pics.

but why did you do all that work if you already have a boost gauge?

Or was there another reason it was done other then the boost gauge?

Thanks

SH

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JM / SH

Pick up the bone phone Fred Flinstone and call George Jetson. Get Cable or dsl or something....

[This message has been edited by The Punisher (edited 09-07-2004).]

The shift light comes on to indicate the best time to shift for the best fuel economy. I have an 86SE (V6) and mine usually comes on at about 3000rpm and goes off at about 4000rpm. I suppose if any of us actually used it we might get a few more miles to the gallon! LOL

How about some ideas for those of us who need the 7k redline, but do not have a turbo. Other uses for the boost guage? I know where theres one of these, and Ive been eyeing it for months, but not gotten around to pulling it