# Digital to analog tach signal converter



## 1.8TsyncroB3 (Mar 7, 2001)

There was some discussion a while back about building one. Has anyone successfully done so, and would they be willing to share the details?
I already know of the Momentum unit, and I believe that there are other suppliers also selling a unit for $150 USD. I'd rather have the fun of building my own, and saving a few $$.


[Modified by 1.8TsyncroB3, 12:25 PM 2-21-2003]


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## PAGTI91 (Jul 3, 2001)

*Re: Digital to analog tach signal converter (1.8TsyncroB3)*

Give any good EE the input and output signals and he can draw on a napkin what you need. Problem is getting the signals...you need a scope. Wish I had one but they are $$ 
Until someone with a scope hooks us up with the signal info for 1.8T's VR's and OBD2 ABA's we will never know... 


[Modified by PAGTI91, 1:17 PM 2-21-2003]


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## slow2dr (Mar 2, 2002)

*Re: Digital to analog tach signal converter (PAGTI91)*

[Modified by slow2dr, 3:50 AM 2-22-2003]


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## mrkrad (Nov 9, 2000)

*Re: Digital to analog tach signal converter (slow2dr)*

http://www.t-r-j.com/Auto/Tach/tachometer.htm 
most of the circuit there is simply the led stage drivers, you can probably chunk most (3914) of that and take the raw output from the lm2907 to accomplish your task


[Modified by mrkrad, 7:15 PM 2-21-2003]


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## Veedubgti (Mar 5, 2001)

*Re: Digital to analog tach signal converter (1.8TsyncroB3)*

Les, I'm running and MSD tach adapter. P/N 8920 I believe. Available at SummitRacing.com for about $45.00
http://store.summitracing.com/partdetail.asp?part=9197


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## splitmeister (Aug 9, 2001)

*Re: Digital to analog tach signal converter (PAGTI91)*

OBD2 ABAs do not need a signal converter.


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## slow2dr (Mar 2, 2002)

*Re: Digital to analog tach signal converter (Veedubgti)*

[Modified by slow2dr, 3:50 AM 2-22-2003]


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## Veedubgti (Mar 5, 2001)

*Re: Digital to analog tach signal converter (slow2dr)*

.



[Modified by Veedubgti, 10:56 PM 2-21-2003]


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## Veedubgti (Mar 5, 2001)

*Re: Digital to analog tach signal converter (Veedubgti)*

.


[Modified by Veedubgti, 10:56 PM 2-21-2003]


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## PAGTI91 (Jul 3, 2001)

*Re: Digital to analog tach signal converter (splitmeister)*

quote:[HR][/HR]OBD2 ABAs do not need a signal converter. [HR][/HR]​it depends what setup you have...sometimes they do need them...their are ways around it but my point is that the signal from the ECU is different than the square wave coming from the distributor like on the old systems...

have a nice day...


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## mrkrad (Nov 9, 2000)

*Re: Digital to analog tach signal converter (PAGTI91)*

obd-2 ecu's count rpm via the crank tooth , more accurate, so it has to generate the rpm signal based on that and generates the output to the cluster, let the computer do the work, its more accurate than simple analog circuitry.
A pic might work for this job too.


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## 1.8TsyncroB3 (Mar 7, 2001)

*Re: Digital to analog tach signal converter (Veedubgti)*

quote:[HR][/HR]Les, I'm running and MSD tach adapter. P/N 8920 I believe. Available at SummitRacing.com for about $45.00
http://store.summitracing.com/partdetail.asp?part=9197 [HR][/HR]​
Are you running the factory ECU? I'd like to know the details on wiring it up.


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## 1.8TsyncroB3 (Mar 7, 2001)

*Re: Digital to analog tach signal converter (mrkrad)*

quote:[HR][/HR] http://www.t-r-j.com/Auto/Tach/tachometer.htm 
most of the circuit there is simply the led stage drivers, you can probably chunk most (3914) of that and take the raw output from the lm2907 to accomplish your task

[Modified by mrkrad, 7:15 PM 2-21-2003][HR][/HR]​
I've also got some circuitry data from a guy who made some custom tach signal generators for his diesel. The circuitry look similar to what you've provided. I'll have todo some testing once the engine is running.


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## Veedubgti (Mar 5, 2001)

*Re: Digital to analog tach signal converter (1.8TsyncroB3)*

quote:[HR][/HR]Les, I'm running and MSD tach adapter. P/N 8920 I believe. Available at SummitRacing.com for about $45.00
http://store.summitracing.com/partdetail.asp?part=9197 

Are you running the factory ECU? I'd like to know the details on wiring it up.[HR][/HR]​Les, I am running the factory ECU. The MSD tach adapter is a piece of cake to wire up. There are 4 wires coming out of the box. One goes to a ground source, one goes to a key on (15) source, one goes to tach signal out of ECU, and one goes to the tach.


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## 1.8TsyncroB3 (Mar 7, 2001)

*Re: Digital to analog tach signal converter (Veedubgti)*

Thanks for the tip! It sure beats $150 from the "tuners" and at $45, it's not worth my time to experiment with my own circuit.
http://****************.com/smile/emthup.gif


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## Veedubgti (Mar 5, 2001)

*Re: Digital to analog tach signal converter (1.8TsyncroB3)*

Very true!


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## HOVTroll (Jan 10, 2005)

*Re: Digital to analog tach signal converter (Veedubgti)*

Would that converter be very similar for a 94 2.0 swap into a 90' jetta coupe? I need to find a signal converter for my tach.. I definatly new to wiring is it a hard install?
Cheers


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## need_a_VR6 (May 19, 1999)

*Re: Digital to analog tach signal converter (UBER1.8t)*


_Quote, originally posted by *UBER1.8t* »_Would that converter be very similar for a 94 2.0 swap into a 90' jetta coupe? I need to find a signal converter for my tach.. I definatly new to wiring is it a hard install?
Cheers 

All you have to do there is wire the coil - (Terminal1) to the tach input on the cluster.


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## Technik Motorsport (Feb 16, 2005)

*Re: Digital to analog tach signal converter (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_
All you have to do there is wire the coil - (Terminal1) to the tach input on the cluster. 

X2 http://****************.com/smile/emthup.gif


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## HOVTroll (Jan 10, 2005)

*Re: Digital to analog tach signal converter (Technik Motorsport)*

Excellent.. Thanks alot.

Cheers


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## mozcar78 (Nov 30, 2003)

*MK1 ABA swap RPM signal converter digital to analog*

Grave Digger..........


Yes i know. I am updating this thread with some current options for anyone looking to grab the RPM signal off the ECU vs the coil post #1 when swapping in an ABA into an mk1 cluster and car. 

http://www.fastforward.ca/signalprocessors/

http://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=8920


http://www.momentummotorparts.com/store/electronics.asp


Spending money for no good reason. opcorn:


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## 134hpvw (Sep 6, 2013)

Sorry to keep this going but I might need something like this on my build.

I know nothing about electrical stuff more than a + or ground.

With that in mind.

I have a 91 passat 16v with digital odometre. V.s.s. and 7000 rpm read out instrument cluster.

I am building a higher revving engine to drop into it. I have sourcex a corrado 16v 8000 rpms read out cluster. That is speedo cable driven . Instead of v.s.s. signal type.

What is my most cost effective way to achive a tach signal for my cruise control to work?.

The engine management will be obd1 aba ecm and harness remapped to 16vg60 standarts.

I want to keep the cruise and multi function display for oil temp. Distance traveled and so on.

Thanks a million for digging this up


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## zaskar (Jan 17, 2000)

134hpvw said:


> Sorry to keep this going but I might need something like this on my build.
> 
> I know nothing about electrical stuff more than a + or ground.
> 
> ...


you probably don't need anything except someone to help you out with wiring. 

it's not something ive done, but im almost 99.5% sure of what im saying,... 

your corrado cluster have a electrical speedsensor in the back, and from the diagram i just looked at, the 90 corrado with mechanical speedo cable, they also took the tach signal from the digifant unit... so basically no worry at all, it's just a matter of making sure you connect the good wire in W-1 in the fusebox. If you need both diagram (mechanical & vss) cluster send me a message I'll print them in pdf and send them to you. you should be fine...


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## 134hpvw (Sep 6, 2013)

Thanks for the offer. I have both bentleys.

I understand that the aba management takes the tach signal from the ecm. That will not change with the cluster swap.

My concern is to have a v.s.s. signal for the onboard computer and cruise computer to work properly. 

So either I find a way to convert the tach signal from the ecm to speed or distance; or buy one of those kits to pick up a speed signal off a cg shaft? And I tegrate that signal into my chassis harness that feeds the m.f.a. and cruise?


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## zaskar (Jan 17, 2000)

134hpvw said:


> Thanks for the offer. I have both bentleys.
> 
> I understand that the aba management takes the tach signal from the ecm. That will not change with the cluster swap.
> 
> ...


I think you don't understand me or I don't understand your problem. 

You'll be fine with the tach signal - Both same input
You'll be fine with Speed - different input, but SAME output (so cruise & MFA will work)

Your speed signal is going out of the cluster t28/7 goes to fusebox in u2/2 and get out of fuse box in W-1 . Same for both cluster. don't worry.... try it before buying anything. you also need to plug the blue/white single wire coming from your motronic management to this W-1, this will give the ecm a speed input.

there's nothing to convert here.


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