How To: Z32 Tachometer Recalibration for VH45DE

[SuperHatch]

This is long overdue as I did this quite some time ago, I'm just now getting around to doing a how-to. This is very similar to any 240 recalibration for a RB or other 6 cylinder engines, and this process should also work for the VH in an S-chassis car.

Start off by removing your dash cluster, use the FSM, I didn't take pictures of these steps. If you're good enough to put a VH in your Z, you should be able to do this without instructions anyway...



Take apart the cluster, you need to remove some screws and clips as shown below...



Disassembled cluster:



Tachometer:



To remove the tach from the cluster, remove three screws in the following locations. The screws are already removed in this image. You can also remove the oil pressure gauge for clearance if you'd like... You'll need the three screws from the oil pressure gauge later if you don't have a stock of spare screws.



Tach out:



You'll see on the side of the tach there is a small potentiometer that is used for adjustment, DO NOT TOUCH at this time.



You'll need to get three short pieces of wire (12" each), three ring terminals, and three butt connectors and make three leads. You'll use these to connect the tach to the cluster as shown... Double and Triple check that you have the wires in the correct spots!









Once this is done, install the half disassembled cluster into the car and start it up, verify that the gauges all work. See video below (18MB)

http://www.godspeed-racing.com...6.avi

Now this is the tricky part. You need to let the engine warm up, and then hold the RPMs at 4000RPM on the Gauge. While holding the engine at 4000RPM, turn the pot until the gauge reads 3000RPM. The pot is sensitive, it doesn't take much!

!!!!!!!! DO NOT CHANGE ACTUAL ENGINE RPM WHILE DOING THIS!!!!!!!!!

If you successfully do this the tach will now read correctly for a V8 signal. Of course a better way to do this is to use a timing light that displays RPM or a consult port on a laptop and adjust to match. Some people on this forum don't have tools like that, so the above method will work, but if you screw it up you'll NEED a timing light or consult to get it right. If you do use a timing light or consult, adjust it at a higher RPM, like 3000 engine revs to have a better calibration than at idle.

Note: If doing this in a 240SX, hold engine at 4000RPM and turn down to 2000RPM.
Modified by SuperHatch at 3:52 PM 5/27/2009

[newbissan-tech]

hey man i tried watching the vid and it opens a page that looks like hairoglyphics! is the site down?

[SuperHatch]

hey man i tried watching the vid and it opens a page that looks like hairoglyphics! is the site down?

Did you try right click, save as?

[newbissan-tech]

sweet man i did that and it worked, one more question what is the drum, i'm kind of lost, and you lost me there, is it the potentiometer? thanks for the info!

[elwesso]

do you know of any way to adjust a speedo other than changing the pinion gears?

[newbissan-tech]

elwesso have you seen the dakota digital device that mazworx puts in the swap kits? outside of that i don't have a clue!

[SuperHatch]

do you know of any way to adjust a speedo other than changing the pinion gears?

The speedo has the same pot on it, but its adjustment range is limited. You can also solder additional resistors in series or parallel with it to get additional range. If you did the same wire method on the speedo and drove next to someone who has a correct speedo you could see if your potentiometer has enough range first.

Also, if you are attempting to make an adjustment for having 4.08 gears out of a GTR, just get a speedo sensor out of an NA auto Z, should bolt right in and is calibrated for that ratio.

[SuperHatch]

sweet man i did that and it worked, one more question what is the drum, i'm kind of lost, and you lost me there, is it the potentiometer? thanks for the info!

I don't think I ever said the word "drum" in my post. In this picture...



The white part that is circled actually has a small flat head screw adjuster on it, it's just washed out from the flash and you can't see it. Trust me, it's there.

[newbissan-tech]

sorry i meant pot and i gotcha now, great info sir!

[elwesso]

The speedo has the same pot on it, but its adjustment range is limited. You can also solder additional resistors in series or parallel with it to get additional range. If you did the same wire method on the speedo and drove next to someone who has a correct speedo you could see if your potentiometer has enough range first.

Also, if you are attempting to make an adjustment for having 4.08 gears out of a GTR, just get a speedo sensor out of an NA auto Z, should bolt right in and is calibrated for that ratio.

Im actually going backwards.. Ive got a N/A 5 speed in my Q45 but ive got the 3.54 diff.. So I cant use the TT speedo sensor since its got a smaller diameter pinion gear.

I will try to adjust it with the pot though... Thanks!

[T45]

Good writeup but it seems a lot different than what I did. I just removed covers, reinstalled speedo and ran the engine while turning the potentiometer. I didn't pull the tach out of the assy at all. Worked great using the consult.

[shauno]

Hey mate, good write-up, will need this soon myself.

Any idea how this works? Is the potentiometer just a multiplier based on the pulses the engine is sending?

[T45]

I'm not sure, I believe it to be a variable resistance type potentiometer (is there any other kind?). Not sure what value it changes, all I know is that it works.