# Tachometer signal help....



## DIYguy (Sep 18, 2008)

Perhaps someone has info or experience with driving a factory tachometer in a 97 Mazda or Ford Ranger? At this point, I would be happy finding out the number of pulses per ICE revolution to drive the factory tach. I need this for the controller supplier to match my application. 

Any other information regarding the type of signal would be most appreciated also... even though I am not quite there yet. 

I did some searches and found some good tidbits... but not what I need yet. 

Thanks in advance. 

Gary


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## RKM (Jun 9, 2008)

Gary,

Mind if I add a request for the same info for a '96 Miata? I'll be addressing the same issue shortly. I suspect the answer may be the same.

Thanks.

Rob


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## DIYguy (Sep 18, 2008)

Hey Rob,

Can't wait for your build thread.... I think ur about due to start soon?

Hopefully Jimdear2 or others may chime in on this thread. I don't wan't to make the wrong assumption as it seems that the PCM conditions these signals on some cars including changing the number of pulses.

Gary


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## Jimdear2 (Oct 12, 2008)

DIYguy said:


> Perhaps someone has info or experience with driving a factory tachometer in a 97 Mazda or Ford Ranger? At this point, I would be happy finding out the number of pulses per ICE revolution to drive the factory tach. I need this for the controller supplier to match my application.
> 
> Any other information regarding the type of signal would be most appreciated also... even though I am not quite there yet.
> 
> ...


Gary,

I looked up the wiring diagrams for the 97 B series and found no clear indications in the documents about what the pulse count should be. Although the troubleshooting section does identify that the tach does count pulses.

It has been years since I stuck my head under the hood of a Mazda B series so I am guessing on some of this.

I'm pretty sure (guessing) your vehicle used a distributorless, waste spark ignition system i.e. one coil drove two spark plugs, one coil for each pair of cylinders (except that weird 2.7 liter four cylinder with two sepsrate ignition systems). 

If that is the case the system would need two hall sender pulses per electric motor revolution (all waste spark systems use a 2 pulse count) to get correct readings to the tach. 

Note also that some waste spark systems had all of the coils packaged into one module so it was hard to tell, but if there is no distributor on the engine and each spark plug does not have a separate coil you are probably dealing with a waste spark system.

For a waste spark ignition, you would need to set up your hall sender with two magnets on the motor shaft, 180 degrees apart. We used to attach magnets for aftermarket cruise controls units to shafts with doublesided tape and then a wrap of string tape. This held up pretty well.

When you pull the instrument cluster you should find a T/Y (Tan with yellow stripe) in the C214 plug (it is the largest plugs). That is the tach signal wire from the ECU. By the diagram it is the only wire in the plug with a empty position on each side of it.

Your hall sender output would go to this wire.

Another possible way to discover the pulse count is to take a frequency meter to the tach test point on the left fender by the upper shock mount of a still ICE powered vehicle, read the frequency in hertz for a specific RPM and do the math.

A last back door method would be go to a tach manufacturers website and see if there is a listing for your vehicle (try VDO). Most generic aftermarket tachs for 4, 6 and 8 cylinder engines are steppermotor types that count pulses from the ignition system. For distributor type systems you get 2 pulses per revolution for a four cylinder, 3 pulses for a six cylinder and 4 pulses for an eight cylinder. As I previously stated all waste spark system use a two pulse per revolution no mater what the cylinder count.

Be sure to determine if your hall sender set up is going to require a pull up resister to generate the correct square wave pulses. 

Hope this helps,
Jim


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## tinkeringgreg (Mar 27, 2008)

I'm not sure about the mazda in particular but as a rule most 4 cycle engines produce a tach pulse twice per revolution for a four cylinder or three times for a six cilinder. As long as you keep that pulse count going to the tachometer it should work. I am using a geartooth speed sensor which is triggered by two steel screws 180 degrees apart on the aluminum fan blade of a forklift motor in my honda civic EV conversion. I hope this helps.

Greg


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## tj4fa (May 25, 2008)

I haven't done it yet to my '91 Ranger, but Keith Mercill who has an '89 Ranger at the EVAlbum.com website has e-mailed me how he did his.

We both had 2.3L 4 Cylinder engines installed previous to the conversion. 

The four cylinder engines had 8 spark plugs (2 for each cylinder) and from his e-mail the original ICE setup appears to have sent two pulses to the factory tach for each engine rpm.

So for the 4 cylinder Ranger's for our year/engine, it looks like all we need is one pickup which generates two pulses per revolution of the electric motor.

Keith uses a glass reed switch and one magnet as shown in the photo below to generate the pulse through the Ranger's tach sensor wire. 

His '89 Ranger wiring harness tach signal wire is color-coded DK Green/Yellow Stripe where for my '91 Ranger the wire is color-coded Tan/Yellow stripe that I traced from the back of the factory tach to the connector on the driver's side fenderwell.

Keith said his glass reed switch/magnet setup had gone over 6000 miles without a problem and cost <$10 to make.

I have purchased a nylon shaft collar and intend on drilling a small hole and expoxying a small rare earth magnet into it that I bought from Radio Shack to generate the pulse. I will likely buy a glass reed switch and complete the setup like Keith did in the photos below:








Nylon Shaft Collar from smallparts.com for $6.38 plus shipping to slip over the outside of my ADC FB-4001A tailshaft. 








Glass Reed Switch Keith purchased from allelectronics.com for about 65 cents.

*RI-25*
¨15mm
¨20W
¨Automotive, Industrial


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## PatricioIN (Jun 13, 2008)

tj4fa said:


> I haven't done it yet to my '91 Ranger, but Keith Mercill who has an '89 Ranger at the EVAlbum.com website has e-mailed me how he did his.
> 
> We both had 2.3L 4 Cylinder engines installed previous to the conversion.
> 
> ...


tj4fa - 

This looks like a cheap and simple setup.. not sure if it will work with my '98 zx2 as the signal goes through the PCU. I will have to investigate that. My question: if you need 2 signals per revolution, how does only one magnet work?? ...excuse my electrical ignorance!!


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## tj4fa (May 25, 2008)

PatricioIN said:


> tj4fa -
> 
> This looks like a cheap and simple setup.. not sure if it will work with my '98 zx2 as the signal goes through the PCU. I will have to investigate that. My question: if you need 2 signals per revolution, how does only one magnet work?? ...excuse my electrical ignorance!!


Patrick,

Here is what Keith Mercill who did the tach setup said in his e-mail:

"*...I also had a 4 cyl. engine (with 8 spark plugs), and used just one magnet. For some reason it pulses the reed switch two times for each revolution..."*

From this thread at a Ford Explorer/Ranger Forum, one member there said:

http://www.explorerforum.com/forums/showthread.php?t=223270

"*If you use the factory tan/yellow tach wire, the PCM will put out the correct pulse frequency for your 4-cylinder, regardless of whether it has 4 or 8 plugs. *
*
Then all you have to do is setup the tach for a 4 cylinder per the tach manufacturer's instructions. The most common aftermarket automotive tachs can be configured for 4, 6 or 8 cylinder engines.*" 

Now since I pulled the EEIC computer and harness out when I did my conversion, I may not get the two-pulses per (motor) revolution. If that's the case, I plan on using two magnets drilled into the collar installed 180 degrees apart from each other.

Terry


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## tj4fa (May 25, 2008)

Gee Patrick there's a guy on a ZX2 forum asking for the same info you are. 

http://www.teamzx2.com/showthread.php?p=169188


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## DIYguy (Sep 18, 2008)

Thank you everyone.

Jim, would it be of any help to look up a 97 Ranger? It is really a Ford with different sheet metal. 

My truck being a B4000 is a 4.0 litre V6 pushrod engine. There was an overhead cam model also according to my manual. Mine has one set of plugs only and one large coil with a feed for each plug wire. There is one sensor on the front of the crank picking up teeth. I wonder if I could use this original sensor....??

TXDJ, nice pics thank you. This will be helpful.


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## Jimdear2 (Oct 12, 2008)

DIYguy said:


> Thank you everyone.
> 
> Jim, would it be of any help to look up a 97 Ranger? It is really a Ford with different sheet metal.
> 
> ...


 
DIYguy

I have a lot of trouble accessing older Ford information, I can do it but it takes a bit of time. I think though, that the Mazord B series data I posted will probably fit your Fordza Ranger needs.

Just another site to show a simple pulse generator system that people use on single cylinder engines, very simple to understand.
http://www.pullmapa.com/Command_Tips_and_Tricks/command_automotive_tach_hook_up.htm

The pulse count I think you will need for the Mazda B series and Ford Ranger Tachs is going to be 2 pulses. One nice thing, if two isn't enough just add pulses untill you get it right . 

You can check rpm accuracy by checking road speed against tire diameter and gear ratios to get the RPM. There are many calculators on line to figure that.

Have fun,
Jim


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## DIYguy (Sep 18, 2008)

Jimdear2 said:


> DIYguy
> 
> I have a lot of trouble accessing older Ford information, I can do it but it takes a bit of time. I think though, that the Mazord B series data I posted will probably fit your Fordza Ranger needs.
> 
> ...


Thank you Jim! I appreciate your time and efforts very much. This has been very helpful for me. We use hundreds of proximity sensors at work every year (or at least we use to). I can get a smaller PNP 12 volt DC prox gratis, from an old stock not required bin.

edit, we have a hand held RPM meter as well. 

Cheers,
Gary


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## 85Turbo (Jun 27, 2008)

sorry to drag up an old thread......

i need info on how i might get the factory tacho to read correctly in a suzuki swift / geo metro 3 cylinder......

being a 3 cylinder, does that ,mean the tacho is expecting 1.5 pulses per rev ?
doesn't seem possible (half a pulse) you either have a pulse, or you don't ?
anyone here know how this might work ?

Jason.


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## Jimdear2 (Oct 12, 2008)

85Turbo said:


> sorry to drag up an old thread......
> 
> i need info on how i might get the factory tacho to read correctly in a suzuki swift / geo metro 3 cylinder......
> 
> ...


 
Describe the ignition system. Is it a distributor and coil or three separate coils fired by the ecu. I'll look at the OEM site and see what I can find as soon as you give me a year.

Jim


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## 85Turbo (Jun 27, 2008)

it's an old carby version, with no ecu at all.
single coil, with a standard rotor button type distributor.

the car is a 1990 model.
this car is old school all the way.....

i suppose worst case scenario, i could get a dash from a 4 cylinder variant...
that might make things a little easier....

Jason.


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## Jimdear2 (Oct 12, 2008)

85Turbo said:


> it's an old carby version, with no ecu at all.
> single coil, with a standard rotor button type distributor.
> 
> the car is a 1990 model.
> ...


 
Jason,

Nothing I can get my hands on now goes back past 1995. What I did find is that in 1995 (which also used a distributor), the tach was driven by the ECU which got a signal from a crankshaft position sensor. The ECU sent a signal to the tach through pin 8 (brown wire) of the 16 pin connector on the back of the instrument cluster.

Even back in the early 90's they had ignition control ECUs that used crank sensors. My best guess is your tach needs a 2 pulse signal. See below for a way to check. 

It also might just have used a crank sensor to do nothing else but drive the tach.

Since I don't have the exact wiring diagram for your model try googeling around to see what you can find. If you can't find anything, what I would try is isolating the wire that drives the tach (you should be able to trace that on the instrument cluster circuit board). The tach will have connections to + and - 12 volt traces and then a trace will lead to a connector that goes off to ??? That is the signal input.

Try connecting that wire to a pulse generator output. You can mock up a pulse generator using a drill motor, a prox sensor, a bolt, a strip of metal and a battery. Check the threads for how to build one, a number of people have done this. (A "how to" might be a good WIKI). Don't forget the tach also has to be powered by the vehicle 12 volt system (turn on the ignition) when you are checking.

If the tach works at all with the pulse generator, your golden. If you know the RPM of the drill motor you can figure if you need 2, 3 or 4 pulses to make the tach match the drill motor RPM. You then need to make up the needed pulse generator and mount it to your motor.

Have fun checking,


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## 85Turbo (Jun 27, 2008)

thanks for your help...

i will post my results.

Jason


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## atzi (Jun 26, 2008)

85Turbo said:


> sorry to drag up an old thread......
> 
> i need info on how i might get the factory tacho to read correctly in a suzuki swift / geo metro 3 cylinder......
> 
> ...


Most older models had one pulse per revolution. On a 98 Saturn for example the PCM sends 6 pulses per revolution even though the original engines were 4 cylinders.






















see http://saturn.lynnautorepair.com/node/326


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