The LHD Digidash Bible

Pyro15D

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With all the talk about digital dashes and how everyone else in the world gets them but us in the States, this should hopefully turn out to be a good thread. A couple months ago, I, like many others before me, decided to attempt the project on my own. My goals with this were to find a way to install an originally RHD MKIII digital dash into my LHD car (obviously). Along the way I wanted to figure out what digi dash sensors I HAVE to run to make the digital dash work, what tach signals work, if there were suitable cross-reference sensors that would work, and finally to dispel all the false “facts” about what works and what doesn’t. Now, to give you a bit of background, I’m not an engineer. I am a lowly enlisted avionics technician for the Navy so what I have figured out may not necessarily be the best way. In fact, it most likely isn’t, but I did this on a kitchen table and dryer with no specialized tools and it worked for me so as always YMMV!
Before you tackle this project, I would like to give credit to a few people and websites who helped me out along the way.
For the translated version of the Japanese wiring diagram:
http://www.supraforums.com.au/forum/topic/41157-diy-mkii-analogue-digital-dash-conversion-vice-versa/
For the initial pinout for the digital dash (I changed a few things but it was mostly accurate for my dash):
http://www.clickdesign.co.uk/supradupra/html/digi_dash_connections.html
For the inspiration for me to tackle the project, Stretch’s digidash thread. Just reading it gave me quite a few ideas on how I should tackle my own project, so his thread was invaluable:
http://www.supramania.com/forums/showthread.php?12183-Stretch-s-Digidash-thread
I would also like to thank Suzy for all she did. Now, even though she didn’t directly help me out, her translated wiring diagrams were very much appreciated and helped me decipher the inaccuracies of the wiring diagrams and pinouts.
I would also like to thank Faye for hooking me up with a new gauge cluster glass. You rock!
Anyway, let’s get started!
*You will need a digital gauge cluster (duh). The gauge cluster I bought was the one with both “Turbo” and “Oil” meters on the left side. The part number was 83010-1B474. There is another digital cluster that does not have the oil pressure meter. Maybe that is for the JZ or 1G motor. I don’t know, I’m not that familiar with those motors in these cars. That one might work, you just won’t have oil pressure readings.
*LHD analog dash skeleton. What I mean is you don’t need the gauges or any of the electrical stuff, just the plastic shell and front glass. Hopefully you don’t have any attachment to this, because you will be hacking the backshell up with a dremel tool.
Digital speedometer sensor (I will get into this later)
Digital fuel level sensor (again, I will talk more on this later)
18 pin connector (hopefully on the back of the dash when you get it, if not, don’t despair)
20 pin connector (same as above)
12 pin connector (same again)
*Dremel tool
*Soldering Iron
*Multimeter (if you don’t have one of these by now, you should probably not own a MKIII)
*Black paint (I used gloss black VHT with primer)
*Duct tape, Masking tape, Electrical tape
*Heat Shrink
*Basic hand tools

If you get a dash with no connectors, all is not lost. We have those connectors on our cars already, and I think I would be safe to assume that many other Japanese cars have those same connectors. Just spend some time in junkyards! The 18 pin connector is the same as the 18 pin connector for the theft deterrent system and cruise control as well as the H1 harness connector. The 20 pin connector is the same as the wire harness joining connector O1 (http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=31). The 12 pin connector is the same as the one on the A/C amplifier. Anyway now that that is done let’s move on to building the dash.
Now, I wish I could show you pictures throughout the build, but the SD card on my camera isn’t living up to the “secure” part of its name and lost all my pictures. What worked for me was to hack up both backshells for the dash. All you really want left for the analog one is the outside portion to mount the glass and screw the dash into the stock mounting holes and a spot for you to put your stock clock. Now, be careful with skeletal remains of the backshell. It is very fragile without all the support of the rest of the plastic and WILL break on you if you aren’t careful. It would be a good idea to screw the front glass to it to give it some structural rigidity.
Moving onto the digital backshell, what worked for me was to cut the back out of the plastic that the gauges mount to. What you want when you are done is one piece that holds the main board with speedo, fuel, odometer, and coolant temp gauges. The other plastic piece is the one that the tems and oil and turbo pressure gauges mount to. Before I did this, I used a sharpie and a ruler to make straight lines and figure out the best spots to cut. Remember, to cut is permanent!
Now, after you have accomplished this, you should have the analog dash skeleton with front glass mounted to it face down and the two plastic pieces with gauges mounted to them. What you are going to do next is lay the gauge assemblies down over the skeleton. You may want to use stacked washers or spacers of some sort to hold the gauge faces between 3/8” to 7/16” away from the closest part of the glass. Don’t go too far away from the glass, because you want the cluster to be as shallow as possible. Look at the depth of the old cluster. The digital one is a bit deeper than the analog one, but you really don’t want to go too deep, otherwise it won’t fit! In case you don’t know, the glass is concave (or convex, depending on how you’re looking at it) so place your spacers on the middle of the glass. After you are happy with the placement of everything, place reference marks on the plastic pieces to make sure they don’t move around while you fiberglass it all together.
On the subject of fiberglassing, I’m pretty new with this. I fiberglassed the cluster together with the gauges still mounted inside. That being said, the resin is nasty stuff and will flow everywhere. It’s like honey. What I did was covered the connectors and everything I didn’t want covered in fiberglass with duct tape. Not the most aesthetically pleasing thing to do, but hey, it worked for me! After the fiberglass cured (took mine around 12 hours till I felt comfortable to gently handle it) I used sharp razor blades to make my cutouts for the connector openings and such. One thing I would like to add, do not fiberglass over the gauge glass. You are most likely going to get some resin dripping onto the gauge glass and will want to replace it with new stuff. Thankfully Toyota still carries them and they are reasonably priced.
Now that you have it physically ready, now would be a good time to trial fit it in the car. Do this with the gauge glass on, since that is what you’re aligning everything to. As long as everything fits, now we can work on the wiring. You will have to extend the 4 connectors from the main display to the tems display by 24 inches. It is pretty easy. With wiring, it doesn’t take much longer to do it right, so get yourself some heat shrink and soldering stuff and extend them that way. When extending wires, use the “Western Union Splice” method. It works really well and is actually quite strong. You can find info on it here http://en.wikipedia.org/wiki/Western_Union_splice . Here is a picture of how I did the harness extension (I didn’t do the door warning light harness yet, that’s why there are only 3 connectors instead of 4):
20140219_214031_zps2491c0cd.jpg
Now at this point, you have a digital cluster that doesn’t look very pretty. There is a tinted piece of acrylic on one of the layers of the digital dash that is used as a vacuum fluorescent display (VFD) filter. You are going to want to separate that from the framework holding it on. Be careful, it is somewhat brittle and you can crack it. I’m looking into sourcing sheets of the VFD filter acrylic, but so far, I’m coming up with nothing. If anyone knows where to get it, let me know! Anyway, after you have the filter separated from the frame, you will be left with a bunch of adhesive residue. I ended up using a very sharp razor blade to get the adhesive stuff off (while being careful not to scratch the acrylic) then used Windex to take care of the rest. It isn’t the best, but at least it worked!
Next, we have to tackle the indicator lights below the dash that house the turn signals, charging light, high beam, etc. I just used a dremel tool and cut out that whole section, then routed the harness to the connector on the main board. Fit it in there to that it looks nice, then glue it in place. When that is done, you should have something that roughly looks like this:
20140219_203150_zpscee8fdc4.jpg
Now fit the analog dash’s clock in the spot to the right of the odometer. From left to right on the bottom of the dash, you should have your section of indicator lights, the odometer, and the clock. If you have all the gauges, clock, indicator lights, odometer in there and they look nice, fit the front glass back on. This would be a good time to put on a factory fresh new front glass. The part number for that is: 83138-1B190 and is still readily available. Take a dry erase marker and outline the gauges, clock, indicator panel and odometer. Remove the glass and mask on the inside of the glass and paint it with a good black spray paint that adheres well to plastic. After you are done with that, take a break and enjoy a delicious beer.
When you are done with your tasty beverage, remove the masking tape and fit the glass over the dash. Hopefully it all looks nice. If not, well bummer. I’m going to assume that it looks nice though. Now you get to install the acrylic filter in the dash, formerly adhesive side up. You might want to put a couple dabs of hot glue on it to prevent it from sliding around. After that is mounted, install the glass for the last time. When you are done, it should look like this:
20140219_214056_zpsac41a74d.jpg
Pretty sweet, isn’t it? Now is a good time to remove the vents from your old dash and put them on the new dash. No, the JDM dash vents won’t work. They technically do snap into place but the angles are wrong, so you have to use the USDM vents. Also, the screw holes on the vents will not line up with anything. Thankfully the vents snap into place on the glass so you don’t have to worry about that. After you are done with that, admire your work and the transition from your old analog dash to the new digital dash:
20140219_214319_zpsbdf9b4ff.jpg

Next post, wiring it up!
 
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Pyro15D

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Now the fun part…Wiring. The way I did this was I just added the new connectors to the old harness like they did here http://www.supraforums.com.au/forum/topic/41157-diy-mkii-analogue-digital-dash-conversion-vice-versa/ so that I could easily swap back to the analog dash if I wanted to. Unfortunately for my case however, many colors don’t just cross directly over. This, I’m hoping is my biggest help to you all out there. I have looked at every schematic I can find for the various digital dashes and all of them have errors, even the pinout for the digital dash wasn’t completely right. What I have here is the most accurate analog to digital diagram out there for the 86.5-88 Supra. This works and is correct. If you use it correctly, it should work for you too. I’m not sure if they changed the wire colors for the 89 and up cars, but you can swap analog dashes between them without incident, so the pinouts should be the same at least. I say again though, your mileage may vary. Anyway, without further ado, here you go in PDF form:
View attachment Digital Dash Conversion info.pdf

Here is the updated wiring diragram. This is 100% accurate with how my gauge cluster works. I am looking into alternative sources for the dimmer, since it is a different one than the analog ones use. It has a function to disable the the panel dimmer while keeping the rest of the dash lights on (useful during dawn and dusk).
Mk3SupraDigitalDashWiring_zps84800775.jpg

Now, there are a few things I’ve noticed. Here are a couple pictures comparing the guts of the analog and digital fuel senders:
20140218_163721_zps924ebb5b.jpg
20140218_163708_zpsb5cb8dc2.jpg
20140213_163255_zps49732a70.jpg
What I’ve noticed is the total resistance of both of them is very similar. The pinout is slightly different and more importantly, there are only 2 wires that drive the analog gauge. That being said, it wouldn’t take too much to modify your standard sender to work with the digital cluster. I will get into modifying that later.
Now, vehicle speed sensors; the white one the digital dash uses is no more than an optical encoder. The dash only needs to see 5 volt pulses on it in order to work, which means you can use an optical sensor or hall effect sensor. The inside of the stock optical sensor looks like this:
20140214_122209_zps5f211dc9.jpg
20140213_162627_zpsdc70a9af.jpg
20140213_162640_zps43e078fc.jpg
It is a 20-slot wheel. If this were to be modified to run a 12-slot wheel, then it would display the numbers in MPH vs Km/H. You would have to change the legends to light up correctly (which the clickdesign website talks about) but if you did both of those things, you would show the correct speed in the correct measurement. The sensor itself is just an optical slot sensor, which can be bought at Radio Shack for $3. The other chip on the board is just a voltage regulator since the LED for the sensor can’t take more than around 2.8 volts and the power going to it from the dash is 5 volts. Another option is to just get an electronic kph to mph speedo converter. These require 4 wires to be connected (switched 12v, GND, input, output) and then you should be good to go. I tried the marlin crawler VSS and although it worked, it only puts out 4 pulses per revolution.
As far as the other sensors, the stock 7mgte oil pressure, coolant temp, and boost pressure sensors worked just fine. The stock boost pressure sensor pegs the display at around 7 psi. I am currently at 20 psi, so when I’m driving hard, that gauge is pretty useless. Since it runs on a standard 5v signal though, you can adapt pretty much any MAP sensor to make it work. For applications up to 22 psi, the MPX4250 2.5 bar map sensor that comes stock on Megasquirt could work. Running that would make the display illuminate all bars when the boost hits ~20 psi. If you are running more boost, just find a map sensor that maxes out at the boost you are wanting. The GM 2-bar MAP (pn: 16040609) is good to 14.3psi max boost, the GM 3-bar MAP (pn: 16137039) is good to 29.7 psi max boost pressure. Looking at the Voltage/kpa scale of the stock boost sensor vs the aftermarket units however, I would recommend the 3-bar MAP. The voltage at 100 Kpa for the stock sensor is 1.55v. The voltage for the 2-bar at 100 Kpa is 2.45V, so it will indicate a bit high on the display. The voltage for the 3-bar MAP at 100 Kpa is 1.6v. Anyway, hopefully this is enough info for you all to get started. With any luck, you'll be able to be driving around with his in front of you:
20140220_120758_zpsf076b32d.jpg
 
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BabylonDown

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Holy Sh*...... That looks fantastic. I can't imagine the work it took to do that.

So, when are you going to start selling these to the public? ;)
 

Silver MK3

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Wow, nice write up and great job on the project!

You have any more pictures or maybe a video of all the gauges moving?
Also, if you don't mind me asking how much did this whole project run you approximately?
 

Pyro15D

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Thanks! The project cost me a couple months and maybe $800 in parts. The first gauge cluster was damaged in shipping so I had to fork out more money for another one. FML. Oh, I have a few videos of it going. I'm in my phone though and don't know how to post videos via tapatalk. Here is a pic earlier today though.


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Silver MK3

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Thanks! The project cost me a couple months and maybe $800 in parts. The first gauge cluster was damaged in shipping so I had to fork out more money for another one. FML. Oh, I have a few videos of it going. I'm in my phone though and don't know how to post videos via tapatalk. Here is a pic earlier today though.


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That sucks about the broken one. So probably about $500 if you only have to buy one, that's about what I was expecting. It looks so cool, I'd love to see the videos when you get a chance to upload them.
 

Pyro15D

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Thanks a bunch! This is a few months of research coupled with me being really bored at work... I really want to see someone else make one of these for themselves. That would really be awesome!
 

Pyro15D

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I'm working on modifying the stock fuel sender so that you guys don't have to acquire the elusive blue topped sender.

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Silver MK3

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Thanks a bunch! This is a few months of research coupled with me being really bored at work... I really want to see someone else make one of these for themselves. That would really be awesome!
Thanks for the video, I bet its cool watching the gauges move so quickly as you drive. I'm contemplating one for my car, I always thought the digital dashes from that era were cool. Since my car is N/A though I would probably end up with an unused gauge and electronics kinda scare me. :)
 

Pyro15D

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Yeah, as far as the tach signal goes, the dash will read all the turbo motors correctly. The tach signal for the N/A motors is different though and I haven't done enough research to see how different it is and whether or not it can be made to work. I'll post the info on here though if I find anything out.

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Pyro15D

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Here is a video driving. As like before, this was recorded with the cell phone so the sound sucks.
[video=youtube;PLTx3eNLb5g]https://www.youtube.com/watch?v=PLTx3eNLb5g&feature=youtube_gdata_player[/video]
 

Pyro15D

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Yeah it is. I'm trying to work out the most economically feasible way to convert it.

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Doat

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I remember reading something about the connectors on the back of the circuit that changes it to MPH along with the other stuff I think it was in Stretch's thread
 

Bmettie

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^I was just about to mention that, IIRC it was as simple as switching some wires, the conversion is done internally.
Did you do anything to carry over the gauge idents, "temp", "Oil Pres", "Fuel" etc? I cant tell. Whats the difference between the 2 fuel sending units? Different resistance sweep? Either way good work.
 

MightyAl

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Yeah I changed the one I installed to mph. That was like 8 years ago. It was put in a usdm car that was converted to rhd.

I applaud your work and commitment to the project.
 

Pyro15D

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Hey thanks! For your conversion did you use an electronic speedo converter to give you the correct readout after you changed the legends?
 

Pyro15D

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I haven't figured out a pretty way to carry those over yet. I need to meet someone who does silkscreen printing. That would be the best option I think.

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Grizzly

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My congatulations to this verry clean build !
I´m from Germany and doing the same. Did you get rid of the stick at 180Km/h problem ?
I purchased my Dash from Knight Rider ( Peter ) he is also a MKIII driver. He started this project long years ago. He drove with the dash allready but his buid was not as clean as yours. I will really follow this thread !
 

Pyro15D

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Thanks a bunch! I haven't tackled the 180km/h issue yet. I just bought an electronic km/h to mph converter so the numbers will read out in mph. I also have to cut and solder the traces on the board to illuminate the correct legends.

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reydio

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Wow, Awesome work!! props to you. You got some major skills, great job!!
 

Pyro15D

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Hey thanks! I'm heading back home now from a weekend of snowmobiling in the mountains. Next I'll be showing how to make the old analog fuel sender work with the new dash.

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jetjock

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Well done. Although not all that difficult engineering-wise it's nice to see someone take on that project and then do a great write-up for the benefit of others. My hat's off of you Sir...
 

Pyro15D

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Well a small update. I figured out the part numbers for the 3 connectors for the digidash. They are made by Yazaki and are part of their 2.3mm terminal line of connectors. The 12 pin connector is 7123-1210; the 18-pin is 7283-1180; the 20-pin is 7283-1200. Now sourcing those might prove difficult. Digikey doesn't seem to have them. I'll have to do more research.

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Faye

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Awwwww!!! You're so very welcome!! This is such a good write-up, I feel like I could almost do it myself!!!

...

...


...



...

almost.... :-/
 

Doat

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I only wish there were more pics and details on how to do some of the things like a full walk through lol. I would attempt this myself but I don't feel confident enough unless I had more info and pics. I am more of a visual person.