I installed the tach adapt this morning in the '79 turbo. It fixed the problem. I tried 2 '75 tachs, one was modified to 10,000 rpm, and they both worked. Saved me a lot of grief, thanks Bob.

Hi,
Does anyone know if a 77 tach will work with MegaSquirt and Ford EDIS?
Obviously anything can be made to work but I'm wondering if I should shoot for a particular tach for this application. It will be going in a 78 SC so I will be needing a tach without the center button to match my other gauges.

Hi,

I'm hooking up MS 2 + EDIS to a 79 SC and from what I can tell pin 2 from the EDIS should drive the tach. Here is a link to what was reported.

http://forums.pelicanparts.com/porsche-911-technical-forum/572759-another-itb-megasquirt-edis-setup-experience.html

Paul

What signal does Megasquirt output to drive the tach?

Hi
Help,,,, We have a 74 911 that has an XDI ignition conversion and has been switched over to Webbers . It has a XDI tach amp on it and the tach reads an easy double what it should .
Getting a return call from XDI has been sporadic at best . So I thought I would ask here before I start changing things .

Any thoughts or comments ?

Thanks

Brian

I had a broken tach, electrics busted. Removed all of them and found out that the "meter" part is actually a 10mA current meter. I made a prototype from Arduino microcontroller that gets a pulse from from ignition unit and outputs "current" to the tachometer and voila, it works. Just needed some calibration stuff, but now its fine. No more malfunctioning old parts.

Using Arduino, it would be super easy to integrate an RPM dependent shift light LED, as well. Pretty cool.

So what would be the correct tach ...
 

For my 71 T with a 3 pin CDI? I have a 73 tach that doesn't work, and a couple pre-69 tachs that don't work...numbers please? I am guessing that my purple black trigger wire is ok, as the car runs fine. Me thinks I have just been trying tachs that are not compatible with the electronics in the car. Seems like a lot was going on with changes in engine compartment electronics between 1969 and 1973.

Speedo

Lars, the right tach is a 71 tach made after October, 1970-- look at the stamped date on the back. Of course the pre-69 tachs require the intermediate unit, which is hard to find. The 73 tach should work, if it doesn't then something is either wrong with it or the wiring.

The only change as far as the tach goes is the changeover from the intermediate unit which was used in 1969 and 1970 to not using it anymore after October, 1970.

black/purple to points and to /1 or "c" on back of tach. that's it. If the wires to the speed switch are shorted or screwed up that can be causing the problem (and maybe keep the car from running)

Tach vs 3.2 DME - alert
 

alert on 3.2 conversion cars

914World.com - The fastest growing online 914 community!

"... Steve said the reason we were blowing ecu's is because we were mixing the ecu's with a non 3.2 tach."

A question for the Gurus
 

Will it harm a 6 pin CDI to run the tach off the coil?

I have a '71 that I just installed a '78 motor into along with its 6 pin CDI and distributor.

My '71's tach was hooked up to the coil originally and my car has the "intermediate unit".

If I hook up my tach as before, meaning to the coil, (not to TD on the CDI) my tach works.

This is not how the 6 pin CDI was originally wired, so am I putting extra stress on the 6 pin CDI? Or am I good to go?

Thanks,

^ You should be fine with that arrangement.

Thanks, that is good to know. This may be the best solution for those with '69-'71 cars doing upgrades. I am glad that I can use my '71's E tach.

I have a spare 911 tacho that I don't know if it works or not. My car is a February 1972 2.4S.

How can I wire up the spare tacho to test it, can I do this from the engine bay, what and where will I find the correct wires to connect to ?

This thread was very helpful to me it solving a Tach issue, I didn't have the TD tacho that was required for my 81 3.0 engine. Great info.

Hey all

Am I right or wrong in thinking that I can put an 86 tachometer in my 81 SC? I see they use the same signal, if I can would it be a strait swap?

Thanks

No idea if it still is of interest, but I my 1987 3.2 Targa (G50, US spec) there was a 911.641.301.05 tach. Had a white sticker on the side with the text "Anschluss an Bosch HKZ-anlage Klemme C (Unterbrecher)

This is the version with the "shift up light"

I have replaced it with the ROW version of this tacho without the shift up light.

On the version I removed all but one terminal on the plug had a prong. On the one I use now, there are a lot less prongs present in the plug.

I have pictures of the original one of you want them.

A friend asked me to test a Tach dated 8.71(metal date) and 9.71(purple stamp date). I tried it with my tach wiring (1976 911S) and saw no movement of the Tach with the engine running. This makes sense based on the above due to impedence mismatch. Is there a way to test the Tach short of finding a 71 car?

Here are pics of the tach. It may be a good tach but how do I tell? Ohm-meter check?
There is glue residue from a sticker on the side but no information there.
http://forums.pelicanparts.com/uploa...1538416150.JPG
http://forums.pelicanparts.com/uploa...1538416150.JPG

I know it's been a long time, hopefully you rec'd a answer to your bouncing tach issue. A bouncing tach usually indicates your points are bad or not adjusted properly.

Good luck -

Hoping someone can help!
I have 74 911 2.7 engine with a crane fireball xr700 ignition with matching coil. The tach is from a 76 911s

This was done by the previous owner, My tach is 1000-1500 rpm higher than it should be.

Does this sound like I need a tach adapter? what is comparable with a Crane fireball xr700. Are the MSD ones interchangeable? with crane devices?