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Old 02-16-2008, 10:23 PM   #1
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Default Tach signal with standalone MSI

Just installed an MSI standalone in my 94. Everything is running great but I get no reading on my dash tach. What needs to be done to send the rpm signal to the tach?
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Old 02-16-2008, 11:19 PM   #2
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I thought that in the '94 the tach signal came from the coils? Black/white wire that hits both coils in parallel, then feeds the ECU (2I), the tach (1H), and the diagnostic connector. Your coils have four pin connectors or three pin?
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Old 02-16-2008, 11:35 PM   #3
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they are 4 wire.

with my stock ecu in the car my tach works

with my pnp in the car my tach works

with my MSI installed parallel the tach works

with the MSI installed standalone, no tach
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Old 02-16-2008, 11:40 PM   #4
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ever see the pull up resistor on the 1.6L diagram for cops?

the tach signal needed a 1v power source. When standalone, you'd get no tach signal since you removed the ecu and it was providing that signal....maybe it's the same concept here?
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Old 02-16-2008, 11:43 PM   #5
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yeah did see that when building my COPs. has nobody done a standalone MSI on a 94-95 on this board?
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Old 02-16-2008, 11:52 PM   #6
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not that i can recall, other than the PNP guys.
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Old 02-17-2008, 12:42 AM   #7
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Quote:
Originally Posted by paul View Post
yeah did see that when building my COPs. has nobody done a standalone MSI on a 94-95 on this board?
I have.

You need to create a tach output circut. Takes up one of the outputs. I was researching a way to get around this, I had some leads, but I stopped when I pulled the MS out in september.

I can't recall if it is that the tach is either output straight from the ecu, or if there was a specific resistor that is on the ecu that makes the tach output work.

I don't think I saved anything besides some emails. I remember something about a resistor in the diagnostic terminal (10k ohms?) between 2 pins that was supposed to work, but it didn't work for my standalone.

I was and will be running a custom V2.2 pcb.
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Old 02-17-2008, 12:44 AM   #8
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well that info woulda come in handy before i bought it instead of another PNP. ~$200 in savings wasn't really worth it.
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Old 02-17-2008, 12:46 AM   #9
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I wonder if Jerry or Matt could help...

*cough*
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Old 02-17-2008, 01:44 AM   #10
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well that info woulda come in handy before i bought it instead of another PNP. ~$200 in savings wasn't really worth it.
I didn't say it couldn't be done. The MSPNP is basically the same thing as an MS1, just with all of the R&D done. Obviously they have a fix for it, I am betting they are using an output to drive this circut

http://www.msextra.com/manuals/MS_Ex...l.htm#tachoout

What I don't like about megasquirt personally, is that there are too few outputs to do everything. Then again my total investment is far less then even a V3 kit.

So I can't complain.

If I had the sort of money some people here have invested in their setups, I would go AEM EMS.
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Old 02-17-2008, 06:41 AM   #11
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Quote:
Originally Posted by paul View Post
yeah did see that when building my COPs. has nobody done a standalone MSI on a 94-95 on this board?
*raises hand*

1995.5 with no tach output from the coils factory.



Built that. Simple. Doesn't work yet because I've yet to have any time to locate the exact tach wire in the harness to send the signal to. Shouldn't be that big of a deal, just use a DVM.. One wire on the IG- position in on the Datalink connector under the hood, then one by one test the harness plugs until you find your wire.

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Originally Posted by reddroptop View Post
I didn't say it couldn't be done. The MSPNP is basically the same thing as an MS1, just with all of the R&D done. Obviously they have a fix for it, I am betting they are using an output to drive this circut

http://www.msextra.com/manuals/MS_Ex...l.htm#tachoout

What I don't like about megasquirt personally, is that there are too few outputs to do everything. Then again my total investment is far less then even a V3 kit.

So I can't complain.

If I had the sort of money some people here have invested in their setups, I would go AEM EMS.
I disagree honestly. Including my extras I likely have less than $400.00 invested in the ENTIRE ECU project (including the laptop!) and are more than happy with the results... Plus I built it entirely myself.

Too few outputs?? What the hell are you trying to do? I've run out of things to control with it for the love of god!


That isn't enough for you???
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Old 02-17-2008, 11:21 AM   #12
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Wow this is great to see this thread. I am getting ready to go full standalone and not having a tach could be itneresting. Hopefully we figure something out soon.
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Old 02-17-2008, 11:37 AM   #13
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Paul, I just can't see why the coils wouldn't be providing this signal. Locate the black/white wire that used to go to pin 2I of the ECU. It isn't being grounded out, is it?
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Old 02-17-2008, 11:49 AM   #14
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Pin 2I is blank on the MS connector, just a bare pin, its not grounded out anywhere
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Old 02-17-2008, 12:01 PM   #15
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just to double check i swapped the stock ecu back in and tach is working.
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Old 02-17-2008, 12:35 PM   #16
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Quote:
Originally Posted by Joe Perez View Post
Paul, I just can't see why the coils wouldn't be providing this signal. Locate the black/white wire that used to go to pin 2I of the ECU. It isn't being grounded out, is it?

I'm almost positive it's the same deal with the 1.6Ls and standalone. The b/w tach signal from the coils should have 1V provided to it, else the signal cant power the tach on the dash....

when you remove the ecu from the picture, we dont provide anything through 2I. The easiest way to do this may just be a resistor jumping power and the tach signal in the diagnostic connector box.
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Old 02-17-2008, 12:43 PM   #17
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So Scott When are we going to try on my car?
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Old 02-17-2008, 12:52 PM   #18
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Quote:
Originally Posted by Braineack View Post
I'm almost positive it's the same deal with the 1.6Ls and standalone. The b/w tach signal from the coils should have 1V provided to it, else the signal cant power the tach on the dash....

when you remove the ecu from the picture, we dont provide anything through 2I. The easiest way to do this may just be a resistor jumping power and the tach signal in the diagnostic connector box.
1k? can i just jump it at the harness instead?
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Old 02-17-2008, 02:07 PM   #19
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Quote:
Originally Posted by Braineack View Post
ever see the pull up resistor on the 1.6L diagram for cops?

the tach signal needed a 1v power source. When standalone, you'd get no tach signal since you removed the ecu and it was providing that signal....maybe it's the same concept here?
Yes the '94-'95 is the exact same thing as the '90-'93. The stock ECU does the pull-up. Some wonder why didn't Mazda do the pull-up at the coil packs or at the tach, but IIRC the reason is - along with the pull-up the stock ECU has some primitive misfire detection and lights up the check engine light if it doesn't like the the square wave.

On a '94 with a standalone, if your current coils have the provision to ground a tach wire at every spark fire then all you need is the pull-up resistor. If one has changed the coils with ones without tach support, then he has to do the scheme elesjuan showed above
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Old 02-17-2008, 03:30 PM   #20
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I wonder if i will have an issue using my recently aquired millenia coils with built in ignitors and not being able to get a tach signal?
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