First off let me thank knate from freshalloy for his kph conversion thread because that pointed me in the right direction although this is a little different.

Now most of us run z32 trannys via the mazworx kit, on ka's sr's and vh's like me in our s14s and as you know the speedometer doesnt read right, actually very high ie 50mph is like 120, as a result i havent had a speedometer for over 2 years and it has realy irrated me.

Now you could probably spend the money and buy the dakota digital converter or you can do these few easy steps that are free and get the same result.

First step is to take the speedometer out of the cluster.



now you turn it around and look at the circuit board on the top you will see the letters ADJ with numbers, these are the adjustments.

Now unfortunatly i did not take pictures before i started, but the circled portions are what is soldered from the factory.



This is the tricky part, given what diff you are running and your tire size it can change the percentages of where it needs to be.

My setup is j30 (3.90) rear with 18s out back, most 18 tires are 25.2-25.6 inch diameter so this should cover all popular non stretch sizes

what you need to do is solder pin 9 together, bridge the gap so to say and desolder pin 7, open the gap. As shown in the rear picture.

This got me exact on my car tested up to 100mph.



Now thru the miracle of mathmagic, i was able to come with a combo that should get you close for a stock application 205/55/16 with a 4.08 rear diff, it should be plus or minus 2 % ( ie at 100mph you could either really be going 98 or 102)

You still need to solder switch 9 and 6 and still desolder switch 7



Im still working on the odometer, still reads twice as high but im sure theres a fix for that as well. Ill update it when i get it sorted.

Cool beans, it took me about 3 hours to do mine last year.

I'm interested in you odometer fix. I think it will come down to using the Dakota Digital unit and put the solder joints back to the way they were. I can't wait to see your results though.

i went with the dakota unit because at least on the Q, taking the dash is out is an hour job each way.. And I can easily adjust to any rear end of tire size I'm using...

Its under $100 and it basically lets you do anything you want to correct your speedo and odometer in one stop.

Hey thats pretty sweet! s13's don't need that (I think) as mine would read pretty close to accurate. It would just fluctuate on the actual working part sometimes. Sometimes it would, others it wouldnt. I'm banking on the actual sensor being bad though.

NEW AND IMPROVED METHOD

SUCCESS!!!!!!

In my trial and error aproach, i found the right circuit to put a resistor to fix the odometer. The only problem was apparently it reduces the signal BEFORE it goes to the speedometer so after that odometer would read right less than 4 percent off ie (travel 100 miles and odometer will show 103.6 miles) , and the speedometer was decreased by half. So all the adjustment i did up in the first post was cancelled out.

Here is the new and improved method.

Assuming of course you are starting off with a usdm speedometer that reads in mph. Desolder all switch joints EXCEPT number 7. This will take care of the speedometer.

Now here is the tricky part, you need to aquire either a resistor from another cluster ( the circled one in the picture) or aquire a new 6.8k ohm surface mount resistor ( should cost no more than .50 cents). And solder it where i show in the picture the j2 solder.

This will fix both speedometer and odometer. If you have another spare speedometer or circuit you can just swap it over, thats what i did.. best part it was free.

Heres the pic



also from knates thread on freshalloy the adjustment ranges

ADJ 9: -49.4%ADJ 8: -24.7%ADJ 7: -12.4%ADJ 6: -6.2%ADJ 5: -3.1%ADJ 4: -1.5%ADJ 3: -0.8%ADJ 2: -0.4%ADJ 1: -0.2%ADJ 0: -0.1%

Not only that since i had it apart i readjusted the odometer and now have the lowest mileage s14 in the united states lol.


Modified by gs14racer at 8:43 PM 1/13/2010

awesome.

Great post. Quality information.

Where can I get that Resistor from?

Pretty nice that you have 30 miles on the trip meter, but 0 on the odometer...

You think that would show up on a carfax?

some states no longer go by the odometer reading...and i doubt jerry is going to be selling that car any time soon.

lol, im never ever selling the car, as a matter of fact i got offered 25k for it a few weeks ago and turned it down...

jerry i have a few questions for you regarding this topic, as well i purchased some of these resistors so if anyone needs one hit me up and i'll mail them out. i have 4 left!
the main question i have is regarding the gearing, i have a N/A 300zx vlsd with 4.08 ratio and i was just wanting to double check with you on installion of the chip. the 4.08 ratio is the same as stock so all i should need to do is solder in the resistor? correct? i shouldn't need to solder any of the adjustment solder joints? thanks man!

you need to put in the resistor and de-solder all adjustments except number 7. Thats for a 4.08

thanks jerry you are the man

no prob, since doing this as of yesterday, i have hit 2640 miles on my car, all though i figure it has closer to ten thousand as i have had it for quite some time before doing this.

How did you do the math, so that the rest of us can figure out our own modifications? Great thread; very useful information.

hey jerry i just now got a chance to check my speedo and it shows to be off by about 8-10 mph. when i first take off the needle doesn't move then slowly creeps up. then going down the road pacing with my buddy, he's doing 35 and my car shows 25-27mph. after playing with the %'s on knates thread that you posted im thinking i need to solder switch joint 8 instead of 7? just wondering if you have any suggestions? thanks

yes just play with the percentages. I had another car with a similar issue but it was off by about 4-5 mph. I guess every cluster is potentially a little different. It should get you in the ball park at least.

So...... I have a 6 cyl tach... In a s13 with a rb25 and the speedo actually reads super low.... Like when I'm doing 60 it says I'm doing like 30.... Ideas?