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.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.