Just posted this in Members' Rides but it's pertinent here also.

If you got a JDM gauge cluster with your clip, or just bought the cluster to have the tach, you can convert the stock Japanese 180 KPH cluster to read in MPH with the addition of a resistor and some fiddling with a potentiometer on the back. The procedure is detailed here: 180 mph speedo how-to (http://www.zeroyon.com/index/content/view/20/47/)

Since I don't have soldering equipment or experience I asked a buddy (thanks Eric) to actually solder the resistor in for me. He did a great job and made it easily removable if necessary.

As nearly as I can tell the speedo seems pretty accurate. I pegged it on 60 and had my wife time our travel between two mile markers on the interstate. The time was within a second or two of a minute, which is pretty much as it should be. Supposedly the mod also converts the odometer but I haven't tried to measure it yet and it seems to turn over more quickly than it should.

FYI, there's a company called LS Automotive that sells 180 MPH speedos for S13 that actually say MPH on the face instead of KPH. I have no idea whether they've just done the same thing as above and added a new face, or if theirs is more accurate (they advertise that it's calibrated) but theirs is a minimum of $100 at their ebay store; mine cost a few cents for the resistor and a favor from a friend.

End result:
http://www.sr20forum.com/img/data/500/medium/p5150022.JPG

(they advertise that it's calibrated) but theirs is a minimum of $100 at their ebay store; mine cost a few cents for the resistor and a favor from a friend.


Very curious about this in the long run. I saw this stuff on freshalloy.com a while ago. I think it's great to be able to do this. Also interested in your thoughts of reading the gauge for MPH when the KPH is actually pretty close tight in spacing.

I don't have any trouble reading it - it's just that each big tick mark is 10 mph now instead of 5, so on the highway I just park it between 60 and the next mark and I know I'm good. In town I don't look at the speedo that often, especially in traffic. If it becomes too much of a problem I'll just pop the USDM speedo in there.

The other thing I like is that there's only one ring of hash marks on this speedometer, whereas the US speedo has two rings (mph around the edge and kph closer to the center). The JDM unit looks less cluttered IMO. I resisted the temptation to color the needles red, though I might do it in the future.

What would you use to color them red. That would be like a VW dial then. I like that BTW.

I'd just do what the B13 guys used to do (though I never did) and use a Sharpie marker. Don't know if there are any pics left around here of a setup like that.

made it sticky, though it was good info :-)

That is very cool, I wonder if a similar thing could be done with a b chassis gauge. I want a speedo that measures higher than 150mph...

A bit of an update:

If the odometer is reading in miles, then I'm getting REALLY good mileage. I'm 90% sure without doing the math that it's still reading in kilometers, and I'm talking about both the trip odometer and the main odo.

YMMV.

me and my brother did this mod and i absolutely love it! we didnt mess with the odometer but i know it is correctly reading miles (just use the mile markers on the interstate).

Awesome, I keep pegging 110 and wondering.

I swapped the JDM Km/h with the USDM mph and everything is accurate it connected it up fine. It is only a myth of the USDM mph assembly not working with the JDM cluster.So I have mph with the sr20's rpm side

I did the conversion too, but there are a lot of people out there that can't do it or are afraid to try, so I posted stuff on other 240sx based forums that I would do it for them for a reasonable fee.
I also am working on complete face overlays, so I can modify the stock KA gauge to make it more simple for people.
Plus, you can add any logo you want since the decal covers the whole face.
It makes a very custom look!

Just got my engine running again in my new chassis and over the past few weeks have been reassembling the rest of the car. Today I spent a few hours fooling with the gauge clusters.
As stated above, the JDM speedo modified with the resistor read accurately in MPH. However, the JDM odometer continued to read in kilometers even though the Zeroyon writeup said it would change over. I verified this not only by timing how long it took to turn over at 60 mph (should have been one minute) but by watching the odo and comparing it to the mile markers on the highway. We have markers every 1/10 mile (my tax dollars at work :rolleyes: ) and by 3/10 it was clear that the odo was moving too fast. When the ones column rolled over at 6/10 I knew it was still reading kilometers.

My findings are as follows:
1. The JDM and USDM analog odometers are interchangeable. Either one will screw into either gauge cluster and will plug into either speedometer. The wires going to the odometer motor match colors and pin locations on both.

2. The USDM (don't know about JDM) digital cluster odometer will NOT go into the analog clusters. It screws in but the motor plug is different. After this whole experiment was over I figured you could probably switch the motors (see below for reasoning) but I didn't try it.

3. The gearing on the JDM and USDM analog odometers is different. The number of teeth on the drive gears is visibly not the same, even without counting. The colors of the gears are different too - one is blue, the other black, though I don't remember which is which.

4. The gearing on the USDM digital cluster odo and USDM analog cluster odo appear to be the same. They're also the same color.

5. The gear coming out of all three motors is the same. This is why I think you could probably swap the motors.

End result - I stuck both the modified JDM speedo and the JDM 7500 redline tach into a USDM analog cluster and voila, I had a working 180 mph speedo and an accurate odometer reading in miles. Then I just pulled the odo back out, took it apart and rolled it to the correct mileage for the chassis (matching the disfunctional digital cluster I took out of the car) and took it for a test drive.

Note - if you're going to take your odo apart to match it like I did, be careful as hell. Very easy to have little gears going everywhere.

I have a JDM Digital cluster and it really sucks! It's in kph and it dings over 107 kph ... I think that kile 65 mph or so ... I cant stand it! I want to know it I find a USDM one can I just change the speedo part in it. I did find one at a junk yard but the display didnt work..

Um... the speedo part should have a button on it for you to press to change from KPH to MPH.

Also, the ding is controlled by a potentiometer in the back of the gauge, IIRC.

just turn the knob up for the dinger.

have it come on when u hit like 120mph or something.

my other question is, if you do this, how do you get the car to go faster than 115mph with the KA or the SR? I know the JDM SRs are supposedly limited to 112mph or something, but is there someway to get rid of the speed governor? I would like to see how far my KA will go.

You'll have to take out the speed sensor wire IIRC for that to work.

Best just to get a ROM tune or the Greddy/HKS speed cut remover box thingie.

I hit speed cut with the SR in 4th gear around 6700-6800rpm, so still a lot of room to go.

Um... the speedo part should have a button on it for you to press to change from KPH to MPH.

Also, the ding is controlled by a potentiometer in the back of the gauge, IIRC.

No, The JDM cluster dont change just the USDM changes. I was just going to change the diplay part out but the USDM cluster dont work.

1. Get USDM gauge cluster.
2. Take tach out of JDM cluster.
3. Put JDM tach in USDM cluster.

Now you have the speedo you want, an odometer that reads in miles, and the right tach for the SR.

You may have to give up on the digital cluster and go analog. The digital units are notoriously unreliable. This is widely known, and these issues could have been found through searching.

That was my plan kinda.... I was taking the Speedo and swaping them! it's all the same ***.... but my USDM dont work.... I have to find another!