Anyone figured out 4cyl to 6cyl tach yet?

[curbsurfer253]

Has anyone figured out how to mod the tach output from 4cyl to 6cyl yet?

[frosted flakes]

yup use the stock tach just open it up and turn the screw fully clockwise i believe and its alot closer. (still a few hundred rpms off but close enough)

Tony

[NISMO_RB25]

I went to a junkyard and found a tack out of a V6 nissan. pulled the face off and put on mine, then I adjusted it.

Do a little searching on here, because there are easier ways, I just didn't know about them at the time.

[goofynick6]

I'm still working on it, been busy, but I should have it in a week or two..

[NISMO_RB25]

do you mean turning the tach adjustment? That I have done while it was running.

[NISMO_RB25]

I got you. You could do that but the real problem is how the tack reads the signal. Basically you can't get it to read correctly because it sees a signal 1.5 instead of one. So you may get it to read correctly at Idle, but it will be going up at 1.5 from there, so you will peg the tack out before you actually reach the true redline of the motor.

A modification needs to be either made to the signal coming in from the motor, or you have to use a tach that can read the signal.

Do a little searching, because someone posted a how too. Something to do with bringing up a resister on the back of the tach to correct the signal and allow it to read correctly.

You can also send it off to Mckinney to have them make it work for you, but I don't know how much it cost.

[Wulfgang]

I disagree a bit with the naysayers. I was able to calibrate my S14 tach using the pot on the back of the tach. My tach now reads correctly at 1000 rpm, 2000 rpm, 3000 rpm, all the way to 7000 rpm. I didn't check 8000 rpm. And by "correctly" I mean that it is not visibly off.

I calibrated it by connecting a frequency counter directly to the ECU output.

Btw, the pull-up resistor is only needed for the S13. Search for details.

[NISMO_RB25]

good point Wulfgang. I am only familiar with the S13 tach.

[curbsurfer253]

Hey wulfgang, could you be a little more specific with materials needed and the steps to calibrate it? how do you know that yours is properly calibrated? do you have a rev/speed meter. thanks for the input, now i'm going to have to try this.

[Wulfgang]

The ECU outputs a variable duty cycle variable frequency signal to the tach. It is essentially an inverted dwell signal with a constant pulse width (thus the duty cycle varies with frequency). Anyway, all you need is the frequency. Almost all good multimeters now read frequency, so you can just use one of those.

Take out your cluster and take off the gauge face cover. Then unscrew the three screws in the back of the cluster that hold your tach and remove the tach. You will see the little potentiometer that everyone is talking about on the back side of the tach. It will have a little green or orange knob with a slot for a small flathead screwdriver in it. This is the adjustment.

Now you need to find the tach signal, which is on the back of the gauge cluster. The three screws that you removed connect the tach unit to three traces on the back of the cluster. The traces are labeled, so you can see which trace is the actual signal and which are + and -. Connect your frequency counter between the tach signal and the -.

Converting rpm to Hz is easy. Hz are in pulses per second and rpm are in revs per minute. So:

Hz = (rpm/60) x 3 pules per rev

Or just Hz = rpm/20 for our inline-6.

Now just adjust the potentiometer so that your tach reads correctly. You may want to rig up some jumpers so that you can read and adjust your tach without having to re-install it into the cluster; if not, your stuck with having to adjust it, install it, test it, remove it, adjust it, install it, test it, remove, etc.

[goofynick6]

Amazing...I love this guy!

[lyon23]

we have to nick I don't know where we'll be with out him.. i'm about to go and remove the rb tach of my cluster and put the ka back on. Does the speedometer have to be working so the tach can worK? Or will it be fine as long as there is a signal?

[goofynick6]

I tried this yesterday and it didn't work for me. I got a 1.6 KHz reading, so 1600 Hz...then I divided it by 20 to get the RPM's..and well it obviously didn't work. Not sure what I was doing wrong, but any pointers would be great.

NIck

[Wulfgang]

1.6kHz! Yeah, that's really revving it up..... um... 32,000 rpm.

Ok, I don't really know what the problem is, but it looks like your frequency counter is maybe picking up too much noise. What are you using to measure frequency?

If it is really noise (if your frequency counter is working properly) then maybe you need to give it a better ground or possibly filter the tach signal... maybe put it through a ferrite bead. Try to get a good ground first.

I used a Craftsman multimeter and got a solid reading, but I forget what the model number is.

[goofynick6]

I used my buddy's $200 Craftsmen multimeter...haha. So we have that the same, I went from the "TAM" spot to the center "GND" to get my reading...should I try from the TAM to a chassis ground? Then multiply what I get by 20?

Thanks! I think I am close right now, but I seem to be hitting a rev-limiter at 7,000..so either my tach is off or something is causing an early revlimiter.

NIck

[Wulfgang]

That's a little early. I think I hit mine closer to 8000 rpm... maybe like 7700 or so? Can't remember.

I hooked my meter up with the positive probe stuck into the back of the ECU plug on the tach output pin and with an alligator clip to a nearby metal bracket or something.

[Carl H]

i know on the rb20 efi harness there is a jumper that you can tap off of the tach signal for diagnostic purposes.perhaps if you remove the tach and then hook it up there it would be easier to calibrate.i was going to hook up my e-01 and set my tach that way.

[240sxed]

Can this be acomplished by hooking up the original tach to a spliced wire and reading both at the same time...and twist the sucker untill its right?

[goofynick6]

Can this be acomplished by hooking up the original tach to a spliced wire and reading both at the same time...and twist the sucker untill its right?

Yep, I used a Nissan Multichecker and set mine that way and now it's within 50rpms or so.

Nick

[intrexin]

i know on the rb20 efi harness there is a jumper that you can tap off of the tach signal for diagnostic purposes.perhaps if you remove the tach and then hook it up there it would be easier to calibrate.i was going to hook up my e-01 and set my tach that way.

Which wire is it i'm having problems getting a tach signal on my car the one on the ecu dosn't want to give my anything. Maybe seeing if i have anything there will give me a better idea of where to track it down

sorry for hijacking didn't think it was worth it to make a new thread

[s14 2510's]

I got a apexi decs flat tac problem solved. I hope you figure out how to calibrate the stock one.

[240sxed]

Yep, I used a Nissan Multichecker and set mine that way and now it's within 50rpms or so.

Nick

I mean, does it work if I use the R33 Cluster and the S14 Cluster to kinda , "cross calibrate?"

And whats the nissan multichecker? is it a nissan diagnostic tool u plug into some sort of port?

[goofynick6]

A multichecker is a little display you wire in that can show timing, a rough a/f ratio, maf voltage, rpms, etc. I sold it after I got my use out of it.

I'd just grab a tach from someone, like an autometer unit, or an safc or anything, take the tach signal coming into the back of the cluster, tap it in and then monitor both and calibrate them...the screw on the back of the cluster is VERY sensitive to minor adjustments.

Nick

[240sxed]

Hmmmm... r33 tach it is.

[240sxed]

ok so i couldn't figure out the wires on the r33 tach so i borrowed my friends autometer one

here are some directions on the s14:

1. get yourself an autometer tach or something like that, just borrow it whatever it takes.

2. make sure your tach is connected to your stock cluster, however it'll be reading 1.5xrpms at what you're really at.

3. take 6 screws out from under the steeringwheel on the plastic piece covering the key hole/wipers / signal.

4. once all 6 screws are out, the 2 plastic pieces should just pop out, it may require a tiny bit of love. Also take out the little plastic piece which covers the area round your key hole.

5. there are 2 screws located where your cluster is, just look up, and they're hiding under there.

6. Pull that piece out, beware there are 2 harnesses for your dimmer and cruise control, unplug them.

7. undo 3 screws, 1 on the right on the bottom of the cluster, 1 on the left, and 1 on the upper part in the center.

8. Pull the dash out, there are 3 connectors/harness to remove first before it all comes out.

9. Use a flathead or your fingernail to undo the black clips on the back of the cluster, theres probably about 6 of um.

10. pull the gauge cluster bezel away from the actual gauges.

11. Unscrew 4 screws directly behind the speedometer (not TACH), take the speedo out carefully don't hit bend or screw with anything else.

12. there should be a little white box with a screw on it, hiding behind the tach (behind where your white/black gauge face is) this is your adjustment.

13. turn your car on after reconnecting the 3 harnesses, compare your autometer with what your tach is showing. Turn the screw to match to the correct rpms.

14. make sure you put your 4 screws in firm, or else your tach will not read.

15. do everything backwards.

16. enjoy not hitting the bottom of your gauge cluster when trying to hit redline. Make yourself glad that you didn't have to send the tach to lsautomotive for something so simple! And if you don't know how to work that frequency converter like me this is a simiple solution =D

[gawdzilla]

cool writeup, thanks. i'll prolly end up doing this against my pfc instead of the autometer tach.

[240sxed]

glad it helped, sorry no pics.

[swwifty]

does anyone know if it is possible to do this with the s13 cluster? Or is this only possible on the s14?

[240sxed]

does your s13 tach read 1.5 x what its suposed to? or read at all?

[swwifty]

nothing at all.