Engine Swap Forum

Hello,

   Here's a quick writeup on how to recalibrate your 240sx S14 tachometer for a 6 or 8 (10,12) cylinder engine.  As you may know when you use a larger engine than stock your tach will not read properly.  The tach expects a 4 cylinder pulse from the ignition system and when it gets a 6 cylinder pulse it will read too high.

 

Start by removing your speedometer cluster from the dash (you'll want to drop the steering column down by removing the two 12mm bolts holding it to the dash bar).  Disconnect the 4 plugs from the back of the cluster.  Then use your fingers to press in the small black tabs that are holding the clear plastic face of your cluster to the white backing.  Once that's off flip the cluster over and remove the 3 small gold screws directly behind the tachometer. 

 (this one is out of a 97 Maxima but is very similar to the 240sx setup)

The tachometer will then pull straight out the front.  It looks like this:

Then you need to put together a simple jumper harness made of 3 wires and 6 small ring terminal:

Connect one side of the harness to the back of the cluster.  Hold it on using the 3 small screws and 3 small nuts.  I couldn't come up with any suitable nuts so I made do with some plastic zip ties!

Once you have the harness connected reinstall the cluster and reconnect it's 4 stock connectors.  Then start the engine and watch your laptop's RPM display in MegaTune (if using MegaSquirt) (or if you don't have a laptop borrow someone's aftermarket tach for this process).  You should now be getting a RPM reading on the stock tach but it will be wrong.  While watching your laptop's display turn the small blue screw counter clockwise until the stock tach reads the same as the on in MegaTune display(or your aftermarket tach).

 

Once you get them in sync turn off the car, remove the jumper harness, reinstall the tach, reinstall the speedo cluster and your done. 

As a side note if you are using MegaSquirt with the EDIS ignition system like I am you can use EDIS PIN number 2 for a tach signal, wire it into your main dash plug (M63) on pin 18.  No other mods appear to be necessary.

 

Fred

I vote this guy for Nissan DIY'er of the year...

Did u get a chance to evaluate the 'laziness' of the stock tach or check its calibration closer to redline?

Kurt

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Argh... guess I'll stick w/ the plan...

Well, I only know what I know because of others who've done this kind of thing before me.  I wouldn't be anywhere as far along with this stuff as I am if it weren't for the internet and other's hard work.

I only tested the stock tach up to about 3k RPM or so because I'm too much of a wuss to rev the snot out of my relatively new setup.  It did seem to respond pretty quickly though.

 

Fred

 

Allen for president , lol it cant be worst

where is the blue screw to adjust the tacho?

You'll see it soldered to the tach's little circuit board, can't miss it.

 

Fred

where did you buy those 3 jumper wires with small rings?

I think I got the ring terminals at Radio Shack and the wiring at O'Reilly's.

 

Fred

works in a S13 too.

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92 240sx coupe VQ35de 62-1 1/4mile 11.1@126.6mph

I was woundering for the recal you would need to swap over a ka dohc cluster for the vq if you had a ka24e before right? or would the ka-e tach stillwork and all you need to do is recal it?

It probably works the same but I'm not positive, pop it open and post up some pics of the guts.

 

Fred

im not actually at home so haha i cant

but i will when i get back next week...

i asked becasue i know when you swap the ka24e for a ka24de or sr20det, ect thoughs motors are dohc so the tach doesnt pick up the signals with the sohc cluster, So im asuming that its the same thing with the vq, the only thing throughing me off is that there is 4 cams like you all know.

I Just succesfully adapted the a JDM S14 tach's steppermotor to an S13 tach (CA18DET). It fits flawlessy and just needs some adjustment now. I dont know if the S13 motor could also be used with a transistor switching 12v to the stepper (the 5v tach signal beinbg the trigger). The adjustment on the s13 cluster might be a problem tough. So, for all of you who want to keep the stock cluster, you can just buy the s14 tach motor and put it on the s13.