How to get your Tach to work with modern ECU signals

Russell

Club Member
This is a guide to show how I converted my Current sensing tach to work with an ecu or other voltage sending ignitions that cars may have been converted to.

As a bit of background to start with, I am converting my 1975 260z 2+2 to 1JZ and although I have a thread running for that, there isn’t a huge amount of accurate info in the internet for how to achieve this.

The engine bay will look anything but standard but I want to keep the 70’s feel inside the car and the dials are a big part of that

I will do this in a few sections as I’m writing it on my phone.

I have used this setup so read through this first. If you are good at electronics it’s all you need, if you aren’t. Read on so you can see how it works in an S30.
http://www.dinoplex.org/tachoconversion/

It should be very similar for all years as we are replacing everything except the dial coil itself.
It would likely be possible to bring a broken tacho back to life as long as the coil is intact.

You can’t buy the circuit board directly. I found an online service that made them although they have a minimum qty of 10 so I now have 9 spares (8 when I have made Dans).
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All of the components can be purchased on www.farnell.com

First step is to identify all of the components and where they need to go on the board, paying attention to polarities on capacitors and diodes specifically.

Then “tin” all of the pads. This involves adding a small amount of solder to each pad so that the solder will flow easily when heat is applied. These are sensitive components and a lot of heat will damage them.

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When soldering, go slow and start from the middle. Don’t linger with the soldering iron or you will damage things.
This is a very small board so a bit of an eye test and not a job for shaky hands.
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Snip the ends of the components and it should look something like this.

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Russell

Club Member
You then need to strip your tacho down and remove the middle board.
That can go in the bin.
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Now connect the wires up. On mine the main coil wires are black and white. White is negative and Black is positive.
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I wired it back into the original input posts.
For the signal wire, I took the induction loop or whatever it’s called out and wired it straight into the post.

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Make sure the wires won’t catch the mechanism and you can put it back together.


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Russell

Club Member
Nearly done but now you need to calibrate it.

Follow the guide on the link based on a Smiths tacho and whatever signal method you use.
Get a signal generator and set the correct frequency
Adjusting the pot on the board fine tunes it.
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Then make sure it reads min and max accurately.
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Success!

Secure the board in a way that prevents anything shorting or rattling. I am going to make a bracket I think but not done that yet.

Put it all back together and from the outside you would never know anything has changed!
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I haven’t buttoned mine up yet as I have some more technology going into it before it goes into the car.

I hope that’s useful to others that have tach issues.



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Ped

Club Member
Really good job! Very cool, no one will ever know it has been done, except the person who matters... the owner!
 

datsfun

Club Member
This may sound obvious but there is a market out there for plug n play tacho's. You may want to test this by offering an "exchange programme" etc ?

Great job BTW.
 

Fairlineguy

Club Member
Nice stuff
Wsh I knew that could be done when I converted mine to work with the rb25 ecu output
Ended up using a tach match box .
Have to say it works just fine as it replicates the inductive loop signal
 

Russell

Club Member
This may sound obvious but there is a market out there for plug n play tacho's. You may want to test this by offering an "exchange programme" etc ?

Great job BTW.



I might do a few if people want them and there is enough profit to cover my time.
They are fairly time consuming and not being a business I wouldn’t be able to warrant them or have spares incase I damage something.

Anyone have any broken ones the want to donate?


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jonbills

Membership Secretary
Site Administrator
I think pmac has a couple he won’t want much for.
I expect I’ll need a solution for my car when I’ve installed the Nodiz, although I might take the opportunity to find one that goes to 10k, which probably means a switch to a modern tacho.
 
I think pmac has a couple he won’t want much for.
I expect I’ll need a solution for my car when I’ve installed the Nodiz, although I might take the opportunity to find one that goes to 10k, which probably means a switch to a modern tacho.

surely you'll want a ps30 one?:)
 

IbanezDan51

Well-Known Forum User
Great write up Russel.

Just so everyone knows I used this with my old LS1 and it worked great although the signal output being an 8 pot made calibration a little more difficult and wasn’t perfectly accurate but fine for what I was doing.

There is already a guy that makes something similar on Ebay (spydar I think?) and offers a nice frequency tuning option using a 3.5mm aux jack.

Dan
 

johnymd

Club Member
Great work Russell.

I need a solution for my V8. The current option is to use a Bluetooth OBD11 adaptor and view all the engine parameters on an old ipad or iPhone. It would be nice to get the zed tacho and speedo working though. My mate (ECU man) seams to think its a doddle to get an inductive loop tacho working with an ecu output but I've not put him to the test yet. May be interested in purchasing a couple of boards and having a play.
 

Russell

Club Member
Great work Russell.

I need a solution for my V8. The current option is to use a Bluetooth OBD11 adaptor and view all the engine parameters on an old ipad or iPhone. It would be nice to get the zed tacho and speedo working though. My mate (ECU man) seams to think its a doddle to get an inductive loop tacho working with an ecu output but I've not put him to the test yet. May be interested in purchasing a couple of boards and having a play.

You can have one John, as you offered me the y-pipe for free I couldnt charge you for one of these.
I need to arrange collecting that from you at some point.

As Dan says, it will work with a V8, just using different resistors.
 

Russell

Club Member
I have been asked by a few members now to put one of these together for them. Although happy to do so, I need a tach in order for me to test and calibrate them.
Not taking mine apart now its done.

If anyone has any spare ones, regardless of how functional they are I would be interested in a couple.

I would be able to offer a bit of an exchange service to members as it seems quote a few have different engine and ECU combinations and would like their original tach's to work.
Could put LED lights in them etc. while they are out of the car if required.
 

dinoplex.org

New Forum User
I might do a few if people want them and there is enough profit to cover my time.
They are fairly time consuming and not being a business I wouldn’t be able to warrant them or have spares incase I damage something.

Excellent work, looks really nice! BTW, it's faster if you do 10+ in a batch and start installing the same component on each board, then forward to the next part. The only critical part in sourcing is C1 which needs to be an NP0 to avoid thermal drifting.
You can change the calibration range for different engines by adjusting R1.

If you want to produce those and sell them to others, be my guest! :D

Best,
Adrian
 

Russell

Club Member
Excellent work, looks really nice! BTW, it's faster if you do 10+ in a batch and start installing the same component on each board, then forward to the next part. The only critical part in sourcing is C1 which needs to be an NP0 to avoid thermal drifting.
You can change the calibration range for different engines by adjusting R1.

If you want to produce those and sell them to others, be my guest! :D

Best,
Adrian

Thanks Adrian,

I didn't have NP0 capacitor for C1 in mine and really struggling to find one on Farnell and RS components with the correct specifications.
Mine doesn't have one so may have issues when it gets hot.

I'm more interested in helping out others and giving back to the Z community than making money on this.
Everyone I have ever met or spoken to with a Z have been nothing but helpful and generous so hoping to help others!
 

Russell

Club Member
Thanks Adrian,

I didn't have NP0 capacitor for C1 in mine and really struggling to find one on Farnell and RS components with the correct specifications.
Mine doesn't have one so may have issues when it gets hot.

I'm more interested in helping out others and giving back to the Z community than making money on this.
Everyone I have ever met or spoken to with a Z have been nothing but helpful and generous so hoping to help others!

Scratch that! The Capacitors I have used are C0G so I should be good...
 

Woody928

Events Officer
Staff member
Club Member
I have been asked by a few members now to put one of these together for them. Although happy to do so, I need a tach in order for me to test and calibrate them.
Not taking mine apart now its done.

If anyone has any spare ones, regardless of how functional they are I would be interested in a couple.

I would be able to offer a bit of an exchange service to members as it seems quote a few have different engine and ECU combinations and would like their original tach's to work.
Could put LED lights in them etc. while they are out of the car if required.

I've just managed to have a read of this, looks like a cracking idea. It would be great to get the rev counter working accurately and consistently. I’ve still got the tach adaptor but slightly reluctant to fit as it’s another box to hide and seems like a slight cheat. I know you have big plans for little gadgets in yours and can see how it comes together now albeit well beyond my skill/knowledge level.

I’d be quite interested in one of these for my car if you were willing to help out, I’ve seen some old units on ebay for not outrageous money. I provisionally don’t mind sponsoring one and being a guinea pig if your happy to put the time in. Would be for an L series engine which I imagine would be a lot of the demand. Let me know what you think? :thumbs:
 

Russell

Club Member
I've just managed to have a read of this, looks like a cracking idea. It would be great to get the rev counter working accurately and consistently. I’ve still got the tach adaptor but slightly reluctant to fit as it’s another box to hide and seems like a slight cheat. I know you have big plans for little gadgets in yours and can see how it comes together now albeit well beyond my skill/knowledge level.

I’d be quite interested in one of these for my car if you were willing to help out, I’ve seen some old units on ebay for not outrageous money. I provisionally don’t mind sponsoring one and being a guinea pig if your happy to put the time in. Would be for an L series engine which I imagine would be a lot of the demand. Let me know what you think? :thumbs:

Yeah no worries Mark, is it due into Iain's for any work in the near future? Could do it for you while its there.

Failing that, it doesn't take a huge amount of time to do so you could just get your Tach to me and I will do it for you.
 
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