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> How to wire the tach on an MSD, can't find the thread for a friend
brant
post Jan 20 2010, 09:45 AM
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A really great member of the teener community called last night
he has done more good things for more people, but last night had a question

It was around trying to get his tach to work on his -6 conversion

I remember many threads about not requiring a MSD tach adapter, but couldn't find them in my searches. Can anyone point me along or offer their knowledge to help out ?

specifics: 2.7/6
CDI died a few months ago. MSD was installed, and car runs well. Tach is now not working however. He is running an MSD optical pick up (white wire) and using the wiring instructions provided. He is not running the tach adapter and it was my belief that it may not be required?

thanks in advance all!

brant
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underthetire
post Jan 20 2010, 09:48 AM
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From what I understand you need it for the VDO tach.
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jcd914
post Jan 20 2010, 10:26 AM
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When Rob and I put a MSD 6A on his 914/4 we tried 2 different MSD tach adapter (neither worked) before we got smart enough to plug the tach straight into the tach output from the MSD 6A unit. The tach adapter are an attempt to condition the voltage pulses thru the coil enough that the tach will read them similar to a point signal.
I don't know if it will be that simple for a 6 cylinder but it was for the 4 cylinder.

Jim
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Kirmizi
post Jan 20 2010, 10:51 AM
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Brant, when I hooked up the MSD in mine, I didn't need the tach adapter.
I used the tach output like jcd and it's been working fine.
Mike
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mightyohm
post Jan 20 2010, 10:56 AM
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Early tach (silver dot) - Need tach adapter, tach is still wired to the trigger (white) wire of the MSD. Tach adapter goes from white wire to ground.

Late tach (black dot) - No tach adapter required. Connect tach to the MSD tach output terminal on the side of the box. Any tach for a 6 that came with CD ignition probably also falls into this category.

This is based on my experience, YMMV.
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ConeDodger
post Jan 20 2010, 10:56 AM
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As Jim said, we used the tach output right off the MSD 6AL box. The only thing I notice that is different is that the tach needle bounces. It was pretty steady in the stock configuration.

Oh, and it was Jim who got smart. I forgot the doggone tach output was even there...
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rick 918-S
post Jan 20 2010, 11:37 AM
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I have a custom tach built inside a 914-4 housing by Mark Surel (Marks914) Here's his web site.

http://www.newvintageusa.com/

I plugged the tach wire directly into the port on the end of the MSD AL6. Works perfect, no adaptor.
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naro914
post Jan 20 2010, 12:21 PM
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I use an Autometer tach, and it's connected directly to the tach output on the MSD.

IIRC, going from a 4 to a 6, the original tach from the 4 will not work with a 6 engine so you need to replace it anyway.
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IronHillRestorations
post Jan 20 2010, 12:50 PM
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If it's a Porsche tach for a six cylinder engine, it will probably need the tach adapter from MSD. Wiring is gray wire from MSD box to tach adapter, then out to the tach via the black/purple wire in the harness.
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campbellcj
post Jan 21 2010, 01:47 AM
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I just did this a couple months ago too - I had no tach reading at all without the adapter. Tach is from a 69 or 70E as I recall. With the adapter it reads fine but bounces a lot. I'm going to send it to NH Speedo shortly and get it refaced to a GT/RSR look, and see what they can do about the bouncing.

Let me know if you need a pic or more specifics on the wiring but the above posts pretty well cover it.
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brant
post Jan 21 2010, 10:02 AM
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Thanks to all of you!

I'll pass along to my friend
thanks a ton
its really great to have multiple actual experiences !

brant
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underthetire
post Jan 21 2010, 10:07 AM
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QUOTE(campbellcj @ Jan 20 2010, 11:47 PM) *

I just did this a couple months ago too - I had no tach reading at all without the adapter. Tach is from a 69 or 70E as I recall. With the adapter it reads fine but bounces a lot. I'm going to send it to NH Speedo shortly and get it refaced to a GT/RSR look, and see what they can do about the bouncing.

Let me know if you need a pic or more specifics on the wiring but the above posts pretty well cover it.



The bouncing can be solved by putting a capacitor in the tach. There is a write up on this site somewhere for it.
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campbellcj
post Jan 21 2010, 11:02 AM
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QUOTE(underthetire @ Jan 21 2010, 08:07 AM) *

The bouncing can be solved by putting a capacitor in the tach. There is a write up on this site somewhere for it.


Cool! I thought I had seen some info on that. Mine needs cosmetic refreshing and the redline moved anyway so I will leave it up to the pros in this case...
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watsonrx13
post Jan 22 2010, 06:37 PM
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Here's a link to my website showing how I hooked up the MSD. This was installed on a rebuilt 2.0 dual weber engine. Here's a link to the wiring diagram I made.

-- Rob
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IronHillRestorations
post Jan 22 2010, 08:10 PM
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Here's the source!

Just enter the model number and download the instructions in pdf.

http://www.msdignition.com/instructiondownload.aspx
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