My Westfield MX5

90° angle for speedo cable

frank — Mon, 16 Apr 2012 18:10:16 +0000

Those of you who used a NA (Mk1) donor, will have found that the speedo cable makes a very sharp bend at the transmission. Every single car that I know of ended up with a broken cable because of this. The only solution is to make a hole in the body to feed the cable through or use the NB (Mk2) cluster with its electrical drive gear (it’s a direct swap against the mechanical drive gear).

However, there is a much easier solution. The mazda gearbox has a metric M22-1.5 thread as do old 80′s and 90′s Toyota’s. Most (all?) RWD Toyota’s used a 90° angled drive to prevent this problem. The part is a straight fit for the Mazda transmission!

The original Toyota P/N is 83770-30070 and it is meanwhile superceeded by P/N 83770-22100.


View at Picasa M22x1.5 90° adapter Toyota P/N 83770-30070, replaced by P/N 83770-22100	View at Picasa M22x1.5 90° adapter Toyota P/N 83770-30070, replaced by P/N 83770-22100

Cluster installed

frank — Wed, 21 Mar 2012 19:31:32 +0000


View at Picasa	View at Picasa	View at Picasa

Installed the S2000 cluster today. I used a powdercoated piece of aluminium sheet that I cut out and painted satin black. This went fairly well and looks a lot better than the MX5 cluster.


View at Picasa Luckely, I can still see the most important part of the tacho, but I'd like to see more of the odo.	View at Picasa Mission accomplished. I can see everything.

Before and after pics


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I’m not too fond of that amber color so I’m going to change it to something else. I haven’t yet decided which color to use, probably blue or multicolor.

More pics in the S2000 album.

New headlights

frank — Fri, 09 Mar 2012 20:09:53 +0000


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Remember those yellow headlights we used to see years ago? They were introduced in France in 1936 and were required until 1993. They now are no longer required but they’re still approved in Belgium. I’ve always liked them, so when I came across a set of NOS (New Old Stock) on Ebay, I just had to have them! A bit expensive, but very rare nowadays.

Resetting the odometer

frank — Thu, 08 Mar 2012 19:54:40 +0000


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My cluster has 143K kms and my car only has 12K so I need to adjust the odo. I have a programmer to modify the code in the cluster, but I’m hesitant to try it. I wouldn’t be the first one to brick the cluster. The easy solution is to just turn it forward to 12K. The maximum frequency that the cluster can handle is 24kHz, which corresponds to about 900km/h. At that speed, it takes over 44 days to turn it over to 12K.
Mmm… Anyway, here’s a schematic that works fine.

If you use a 12V source, use a voltage divider at the output to reduce the voltage to 5V because the speedo wants a 3-5V input.

SpeedoHealer V4 installed

frank — Mon, 05 Mar 2012 19:37:15 +0000

It arrived today and was very easy to install. Only 4 wires (gnd, +12V, speed in and speed out). It took about 30 mins to install and finally the speedo indicates the correct speed. I should have gone for a Speedohealer from the start. So, if you plan on doing the same thing, don’t start messing and buy this immediately. It’ll same you a lot of time and swearing .

Next is the installation of the cluster in the car.

SpeedoHealer V4

frank — Sat, 25 Feb 2012 01:54:26 +0000

Well, ain’t that a bummer. After going for my first testdrive, it turns out that my speedo is reading about 20% slow compared to my gps. I could only do a short drive, but it immediately was very clear that the speedo is off.

This means that the transmission is sending out 4000 ppm, not 4800 like I assumed. I’ll have to use a 39 multiplier, something Jean’s board can’t do, so I’ll have to look for an other solution.

I could program a pic to do the conversion, but this project has already taken too much of my time. I’ve been messing about with VR circuits, voltage dividers and PWM converter circuits for too long. I don’t want to spend several days designing a pic based circuit, building and testing it, buying a programmer to progam the pic etc. So, I decided to take the easy and fast route and ordered a SpeedoHealer V4 today. 78€ well spent .

got it working

frank — Wed, 22 Feb 2012 18:21:21 +0000

Finally got it right. The speedo is working!


View at Picasa I was sending a 9V signal into my PWM converter that can only handle 5.3V … luckely I had 2 chips

Turns out I was feeding my circuit with a too high signal. The circuit can only handle 5V and I was sending 9V in it (oscilloscope was set to ~AC in this pic).


23.8Hz = 28km/u as indicated by TunerStudio" width="200" height="149" class="shashinThumbnailImage" id="shashinThumbnailImage_20" /> View at Picasa Speed conversion. Red is 5.6V input, blue is 5V output (freq x32). The chip can only handle 5.3V, so I need to lower the input a bit. 23.8Hz = 28km/u as indicated by TunerStudio


View at Picasa Perfect! 5V square wave in (red trace) and 5V square wave out with x32 frequency

After modifying the signal to 5.6V, it was working perfectly, but I didn’t want to take the risk of blowing up the chip, so I reduced it to 5V exactly.

Partial success

frank — Sun, 12 Feb 2012 19:27:49 +0000


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I got the speedo working with a PWM signal generated by a generic output from the Megasquirt. I then send this signal through a PWM converter with a 32 multiplier. This generates a 499Hz signal that indicates a speed of 18km/u, what corresponds with what I calculated. It was kinda cool to see the odo ticking forward. I let the car run for 8.8km . The speedo should be spot on .
Unfortunately, I didn’t get it working in the car yet. My transmission generates an AC signal that I convert to a square wave and send to the PWM converter. Although it works with my self generated signal, it doesn’t work with the signal coming out of my VR converter. It looks ok on the oscilloscope though. I’m a bit puzzled, but I’m sure I’ll figure it out eventually.

Speedo is working after all

frank — Sun, 29 Jan 2012 19:28:47 +0000

Decided to take another look at the speedo today. Turns out I forgot to solder the wire for the VSS signal. After soldering in that last wire, the speedo works. It indicates 3 km/h, not much, but at least I now know the speedo is working.

Accidently deleted all pictures :(

frank — Mon, 23 Jan 2012 21:36:35 +0000

Did an update of a WordPress plugin yesterday and I didn’t think it was necessary to take a backup of the database. I was wrong. The update deleted all columns in the database, so all links to the pictures are gone. I spent about 5 hours yesterday and today putting back the correct links. I had to look up all my pages and posts in google cache, figure out which pictures I had used, find them back in about 55 albums and correct the links. Not fun. I think I have another 2 or 3 hours work left to get everything back in order.