tachometer

[V6'er]

Yes, I know what you have. I'm saying that you can easily mod your Turbo tach with a pot for the needle sweep, which is Gain.

However, if the redline on the 3VZ is 6600 like Wikipedia says, then I'd use the Turbo tach. Because I have a 1MZ, and most tachs I've modified are for 6250-redline motors, I recommend sticking with the N/A tach for those.

Again, in your case, a pot will make it much easier. You have to trace the cluster signal path so that you know which signal is the Tach lead from the rear of the car. You can do this by leaving the front lens and the tach out of the cluster, then put it back in and measure things with a voltmeter. (Black probe to GND.) Or, if that writeup has things identified well enough, there you go. You can extend the tach wires out of the cluster (be careful!) to adjust it in the car.

Bear in mind however, that the writeup simplifies things too much. In your case, you need to calibrate the tach gain, and using one frequency won't work. What you will need is a running car and tach or scantool to veryify the tach with.

[Spektrewing386]

but wont i have to replace other resistors with the turbo board? as in the writeup (using a 22k ohm isstead of 43k ohm.... but 3vz already has proper resistors)

[V6'er]

If the 3VZ uses an ignition-coil-derived TACH signal, they it's the same as the MR2 motors, so no, you don't change that resistor.

[Spektrewing386]

then how come you have to change resistors when using the n/a tach board? as in the writeup

[V6'er]

The resistor changes for a 1MZ, as that ECU puts out a 12 Volt signal. If the writeup says something else, it's wrong.

[Spektrewing386]

ahhh, the writeup did not specify the engine or i didnt remember




so anyone know the location of the resistor i must replace with a pot?

[Dance_Business]

I am sooo loving my current digital after reading this. I also will switch to the EMSPowered digital cluster when it is done. Their digital boost guage fits right in the cluster with NO MODS, and so will all the other parts(fuel, oil temp, oil pressure, wideband afr, etc).

[Spektrewing386]

so anyone know which resistor I replace with the potometer thing?

[V6'er]

I'd have to go out to the shop and get a pic to show you, but I've been too busy, sorry. However, I did point out that all you need to do is measure it with a meter when the cluster is apart but still connected.

[Spektrewing386]

could i compare each resistor from the v6 board to the i4 board and see which resistor is the black sheep?


thats the only change between the 3vz tach and the 3sgte tach is that 1 resistor right?

[V6'er]

Hold the tach facing away from you in the normal vertical position, with the three screw holes in a pattern to the left. Looking at the back of the circuit board, the resistor you need to change is in the upper right corner.

[Spektrewing386]

so thats like the only difference between the 4cy tach and the v6 tach when they both take their readings from the ignition coil?

what about the whole 4 pulses vs 6 pulses a rev, that 1 resistor is what handles that along with the sweep?

[V6'er]

Sweep IS gain. One resistor.

[Spektrewing386]

so i think my dad's friend might have a tach i can match mine against,
but my physics 2 lab has a function generator that i may be able to use.

if i use a function generator:
what should the voltage be?
square wave, sine wave, or trianlge wave?

[V6'er]

It's not likely to put out enough voltage, you need about 20V peak to peak minimum.

[Spektrewing386]

i think thats doable with the ones we have.


but ill just try to use my mr2 as the function generator lol

[Spektrewing386]

wait, i just realized i have a 3vz tach with me lol, ill just temp wire that in parallel to the one im adjusting... bingo



but the resistor you say to change, they are the same on both the v6 one and the i4 one... does that matter? The only thing different about the 2 circuits is the 2 resistors next to the 10 microfarad capacitor.

i also think thats the one sengk replaced in his writeup aswell, the 2nd largest one.

[MR2 Drifter]

This may be a bit off topic...but I need help installing a shift light

and i'm suppose to connect it to the negative side of the ignition coil...and it seems like you guys know what your talking about so do you guys know where it's at or the wire that leads up to the gauge cluster that its connected to?

[V6'er]

Originally Posted by Spektrewing386

...but the resistor you say to change, they are the same on both the v6 one and the i4 one... does that matter? The only thing different about the 2 circuits is the 2 resistors next to the 10 microfarad capacitor.

i also think thats the one sengk replaced in his writeup aswell, the 2nd largest one.

Well, I guess I was in a hurry when I told you that, because that's the input range resistor.

It's the 1/4W resistor on the right edge next to the cap, running vertically. (Hold it like I said before.)

[Spektrewing386]

thats what i was thinking.



well its not pretty, but its functional:




i used the soddering iron to melt the hot glue in there too.