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Ishii and I are trying to get to the bottom of this issue. There are too many "works" and "Doesn't work" responses. I have 3 tachs and last night we tried many different resistors and jumpers. Nothing worked. I have lots of test equipment.

What I am not sure of is whether any of the tachs I have are really NA or TT. I suspect one is a NA just because there are several resistors on the board that are different to the others. There is really no part # other than the I/C has a different PN. But no Toyota # that can show for sure if it is a NA or not.

What would be awesome, is if anyone has NA tach laying around where they can take a real good detail shot of the board. Then I can compare the layout and IC # on it.

If there is a way to definitively do a "how-to" knowing it is the correct way, I can do this.

So basically, the NA reads the tach signal off the igniter directly, or high voltage. The TT reads it from the ECU which is a lower level voltage signal. Hence why resistors appear to work for some. So the NA tach might have a larger resistor, like the 43K whereas the TT has like a 23k. Jumping it makes no sense at all. And probably would lead to premature tach failure.

I know I can make it work NP with a $90 Dakota Digital interface, but I want to see if I can do it with resistance changes.

So ya, a picture of the NA tach board would be awesome.

Stu
Hey Stu, I'll be doing my Auto to Manual swap this month and am getting rid of the auto NA tach, do you want to swing by and grab it? That way you'll know exactly what you're working with. I'm right up the street from you on Finn Hill. I'll let you know when I pull it out if you want it.
 

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Look for something like "high" or "low" for output setting. One is NA and one is TT
That makes sense...so if i was to put my na tach back in it would probably read correct with that tach? The aem basically has like its own converter in other words??
 

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That makes sense...so if i was to put my na tach back in it would probably read correct with that tach? The aem basically has like its own converter in other words??
Most stand alone have PIDs that you can select to Drive it "HIGH" or "LOW" but I know nothing about AEM. I *heard* from others that there is a cell for the tach where you can change it to either depending on what type of tach. And yes, for a test, I would drop your NA tach in there just to confirm...worth a try.

Stu
 

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Hey Stu, I'll be doing my Auto to Manual swap this month and am getting rid of the auto NA tach, do you want to swing by and grab it? That way you'll know exactly what you're working with. I'm right up the street from you on Finn Hill. I'll let you know when I pull it out if you want it.
I do not need anymore NA tachs lol!. I just sold off the 3 I had. But I might be able to use it for parts, or you can sell if for like $50 maybe.
 

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Most stand alone have PIDs that you can select to Drive it "HIGH" or "LOW" but I know nothing about AEM. I *heard* from others that there is a cell for the tach where you can change it to either depending on what type of tach. And yes, for a test, I would drop your NA tach in there just to confirm...worth a try.

Stu
I will give it a shot and see what happens
 

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So can I do this reversed for a TT 6 speed tach backwards to a NA tach? It seems like I should be able to. Right?
 

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There used to be a write up here. All you needed to do was to bridge two wires together and the stock N/A tach worked on the TT. I have tried to find that writeup but no luck. So I had to find a replacement tach for my friends swap.

On the other hand

I have a Auto TT Tach FS. LOL $50 Shipped.
Thanks for the info!
 

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In the last month or so I have done LED upgrades to cars that have NA tachs in there TT cars. All have that resistor jumped. But being inquisitive, I ask them how are they getting there tachs to work. Everyone of them are using stand a lone ECUs. So this is how these work. I think when some say this wire jumping works and some say it doesn't is they do not offer all of the equation. Yes you can get it to work with a stand a lone because you can tell the it to send a Hi or Low driving output. NA run on a 12v signal and TT runs on ECU 5v.

Some day I will spend more time figuring out how to modify a NA tach for a TT car with stock ECU. But for now, I just use a Dakota Digital converter.
 

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Hey Stu, I'll be doing my Auto to Manual swap this month and am getting rid of the auto NA tach, do you want to swing by and grab it? That way you'll know exactly what you're working with. I'm right up the street from you on Finn Hill. I'll let you know when I pull it out if you want it.
I didn't read your post real close...I live in Finn hill as well...need to hook up sometime! Who is doing your swap? FYI I keep seeing a black MKiV around Finn Hill Jr High...this you?
 

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My car is na-t with na wire harness and has an aristo ecu. Still have distributor. Runs perfect. Jumped resistor and tach working great so far.
Out of curiosity, are you using the VVTI DH61/DS62 igniter?

I am thinking the NA tach might work fine with the resistor jumped IF you are running the VVTI igniter(using the stock na harness wired up like in Ali's TT ECU mod thread), but it might not work that way with the stock TT non VVTI igniter? Maybe I am way off base here, just a thought.
 

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Any fix for this tach issue yet? I'm pretty much stumped. So here's my setup,
Just recently bought this (already project) car to fix up and keep

1996 N/A auto, converted to
Aftermarket GTE engine harness
2jzgte engine with v160
Car Is running off AEM series 2

I have another 1994 Supra N/A 5 speed. So I took the tach from that and installed it to the 96 N/A auto
Did 51k resistor mod, Still didn't work.
Did continuity test from cluster tach input connector C12 pin 13, to igniter input connector E9 pin 1, and also Body connector II1 pin 29. All have continuity.
I was unable to check the data link connector 1 because this aftermarket harness doesn't have one.
I went on to check ecu connector E10 pin 16a (ls7 tach output) and found that there was not a wire coming out of it. So I installed a pin and spliced it into Body connector II1 pin 29. still no go
Also installed a pin into ecu connector E10 pin 38a (ls7 spare tacho) still no go. There is voltage coming out of both ecu connector E10 pin 38a and 16a but I do not have an oscilloscope to really read/see whats going on.
All I have left is what others have mentioned and do a 22k resistor instead of the 51k or just go dakota digital
 

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Stock Twins King
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Any fix for this tach issue yet? I'm pretty much stumped. So here's my setup,
Just recently bought this (already project) car to fix up and keep

1996 N/A auto, converted to
Aftermarket GTE engine harness
2jzgte engine with v160
Car Is running off AEM series 2

I have another 1994 Supra N/A 5 speed. So I took the tach from that and installed it to the 96 N/A auto
Did 51k resistor mod, Still didn't work.
Did continuity test from cluster tach input connector C12 pin 13, to igniter input connector E9 pin 1, and also Body connector II1 pin 29. All have continuity.
I was unable to check the data link connector 1 because this aftermarket harness doesn't have one.
I went on to check ecu connector E10 pin 16a (ls7 tach output) and found that there was not a wire coming out of it. So I installed a pin and spliced it into Body connector II1 pin 29. still no go
Also installed a pin into ecu connector E10 pin 38a (ls7 spare tacho) still no go. There is voltage coming out of both ecu connector E10 pin 38a and 16a but I do not have an oscilloscope to really read/see whats going on.
All I have left is what others have mentioned and do a 22k resistor instead of the 51k or just go dakota digital
I have tried a ton of NA tach modifications with no results yet to get them to work on TT. The reason for the resistor thing is that NA tachs are driven on 12v feed whereas TT are driven off the ECU 5v signal. If I have more spare time I will eventually figure this out. It could be that the Integrated I/C chip is the cause as they are different.

I have heard tho....that AEM and other stand alone people get the NA tachs to work fine by going into the software and change how you "drive" the tach..LO or HI...one being 5v the other 12v. Might want to look into this.

Stu
 

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I have tried a ton of NA tach modifications with no results yet to get them to work on TT. The reason for the resistor thing is that NA tachs are driven on 12v feed whereas TT are driven off the ECU 5v signal. If I have more spare time I will eventually figure this out. It could be that the Integrated I/C chip is the cause as they are different.

I have heard tho....that AEM and other stand alone people get the NA tachs to work fine by going into the software and change how you "drive" the tach..LO or HI...one being 5v the other 12v. Might want to look into this.

Stu
Thanks for the info Stu, I tried toying around with the tacho options on the aem software but still no go. If I were to use the tach output from E10 pin 16a (ls7 tach output) and use the dakota digital, it should work then right? Is this what you use to make it work? If so which output from the dakota do you use?
(standard output to tachometer / high voltage output for some tachometers / jumper to HI VOLT output for some
early Toyota tachometers)
 

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Thanks for the info Stu, I tried toying around with the tacho options on the aem software but still no go. If I were to use the tach output from E10 pin 16a (ls7 tach output) and use the dakota digital, it should work then right? Is this what you use to make it work? If so which output from the dakota do you use?
(standard output to tachometer / high voltage output for some tachometers / jumper to HI VOLT output for some
early Toyota tachometers)
If you post in the MKIV section asking AEM users how they are getting there NA tachs to work I am sure you will get answers. I know for a fact this works as I have done many cluster upgrades that have NA tachs in TT converted cars and they all say there tachs work fine.

As far as the DD, you use Output 1 (Input is a single option) DIP switch is off-on-off-on
 

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I'm trying to remember what I did on my last NA. I feel like I jumped the resistor and it worked.

On the car I am building now I have replaced the resistor with a 24K resistor, I hope that gets it working. I wonder if there is any difference between an Auto and manual tach. My last one was a manual and this one is auto
 

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OK finally after years of F'ng around I finally got a NA tach to work in a TT car. I won't go into details on how I isolated this, but the key was getting the exact size resistor to replace the 43K NA one. Range was 980-1040 ohms. Oddly, just installing a 24K TT resistor didn't work which really confused me. I think because there are a few other resistors that are different, but by using this 1K resistor, the R/C network functions in TT mode.



It has been confirmed as working as it should in a TT car.
 
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