Possible A70 Supra Digital Dash 180 km/h Speed limit fix

**Supra Sam** · 06-08-2007, 01:27 PM

Hey guys,

I've been trying to find a solution to the problem of A70 digidashes sticking on 180 km/h.

I currently have SCD on the ECU, which clamps the speed signal from the dash to ECU at 180 km/h, and tricks the dash into thinking its not going faster than 180(keeping in mind its the actual dash signal that limits the speed of the car, not the ECU)

This overcomes the speed limitation issue however it leaves the annoying problem of the dash not showing speeds faster than 180 km/h.

The main solution people seem to offer is to just get an aftermarket speedo, which will be more accurate anyway.
However I'm a little pedantic when it comes to these sorts of things and I like things to work in stock form to my desire.

Anyhow we discussed this on supraforums au, and someone was suggesting that in order to acheive this there is probably a jumper that can be shortened to bypass the speed limiter(kind of like the same thing you would use to flick the dash between KMh and MPH, or the same thing the soarer guys do to fix their digidash speed limit) but no one had any idea how to actually do this.

I searched on US, UK and NZ forums... but the only fixes are baindaid fixes, and no one had found a way to make the dash read any faster than 180km/h.

So I thought, who would have a solution to this.
Then I realised the answer was pretty obvious. Our good friends in Japan.

I sent a couple of hail mary emails, and hoped that A) the jap guys I was emailing spoke english, and B) they had a fix they were willing to share.

Anyhow the guy who I emailed which responded has an awesome race\road car JZA70 which actually has an analogue dash, but the guy seemed to be pretty involved with a70 Supras, so I though what the hey.

Here was his response:

There is a person to whom I executed this in the acquaintance.
The appended image is a resolution of a digital meter.
When the earth is taken from the seventh from the left, it is completion though thinks that wiring has gone out of the center of the image.
It is sure to go well by this if it is the same as the specification of Japan.

See attachment

I love Japlish!

My car is currently off the road due for an engine conversion, so I wont be able to test this for a while, plus I don't trust my soldering skills.

If anyone wants to try this fix, or alternately I have a spare digidash in Sydney, I could lend to someone more skilled to do the soldering. Maybe we can test it on a bench or something!?
Would love to know if this solves the issue once and for all.

Sam

**Endless** · 06-08-2007, 02:17 PM

Awesome find mate, would love to confirm if this works before attempting it on my own dash!

**hamgatan** · 06-08-2007, 02:21 PM

wheres the wire going to though?

interestingly enough when you mention soarer drivers having this issue, do you mean z30 or z20 drivers? i cant say ive clocked that high a speed yet to know..but ill sure want to know if im going any faster than 180...

**Supra Sam** · 06-08-2007, 02:35 PM

Originally Posted by Endless

Awesome find mate, would love to confirm if this works before attempting it on my own dash!

Thanks dude, hopefully I can test it on my spare dash to confirm.

**Supra Sam** · 06-08-2007, 02:39 PM

Originally Posted by hamgatan

wheres the wire going to though?

interestingly enough when you mention soarer drivers having this issue, do you mean z30 or z20 drivers? i cant say ive clocked that high a speed yet to know..but ill sure want to know if im going any faster than 180...

From the explanation that our Japanese friend gives, I'd say the wire is grounded at the other end.

As for the model soarer, not sure, that bit of info was mentioned on a thread on SF au. hang on..... here's what was said :

Originally Posted by LowGuido

schematics = circuit diagrams, pinouts pictures etc.

i know for a fact that the soarer cruise control only works up to 108km/h
but if you open it up and short a particular jumper it will work up to any speed.

judging by picures on this site: http://www.supras.org.nz/techinfo/gl...sassembly.html
it also has the option of displaying miles.

im thinking that somewhere inside there there is a jumper that swaps it to miles, and probably (hopefuly) a jumper that makes it read higher then 180km/h.

Sam

**Endless** · 06-08-2007, 02:51 PM

I know for a fact the Z30's have this same problem, so no doubt the Z20 dash would be the same.

Yeah i'd be thinking that wire is just connected to common ground.

**CrUZida** · 06-08-2007, 03:10 PM

I can't speak for the Z20/A70, but with the Z30 dash the digits are '188', meaning that the first number will never read a '2'.

So I'm not sure if it will stop at 199, or start again at 0, or have a dodgy top half of a 1 where a 2 should be.

I'd presume the A70 and Z20 would be identical to Z30 in this manner.

As for the Soarer being able to do something to stop the cut, thats BS if is it refering to the Z30, coz there have been a few discussions on SoarerCentral, and no one knows how to do it.

**Supra Sam** · 06-08-2007, 03:15 PM

Originally Posted by CrUZida

I can't speak for the Z20/A70, but with the Z30 dash the digits are '188', meaning that the first number will never read a '2'.

So I'm not sure if it will stop at 199, or start again at 0, or have a dodgy top half of a 1 where a 2 should be.

I'd presume the A70 and Z20 would be identical to Z30 in this manner.

As for the Soarer being able to do something to stop the cut, thats BS if is it refering to the Z30, coz there have been a few discussions on SoarerCentral, and no one knows how to do it.

OK, I can confirm for the A70 the first digit has the lights to be able to display the digits : 2 and 3 ie 200+ and 300+ km/h
It also has MPH as well as KMH (even though the digidash was never exported for the a70, so one can assume that theres a way to change from KMH to MPH, and hopefully same goes for the speed limit)

As for what I wrote before, it seems I was mistaken about the speed limit issue being fixed for Soarers, the fix was for being able to use the cruise control faster than 108 km/h.See the quote I put in my second reply.
The point of me mentioning this fact, was to show that the electronics can be modified, by jumping circuits etc I personally don't know much about soarer digidashes.

Sam

**CrUZida** · 06-08-2007, 03:40 PM

It will be interesting to see if changing to MPH will stop the dash at 180, or at ~112.

Wont change speed cut level though.

I have a Jaycar speedo corrector in mine, and I was going to change the reading to MPH if I ever needed it for the drags.
The speedo will still thinks its getting KPH input though, so it would count all the way to 180.

**Supra Sam** · 06-08-2007, 04:28 PM

Originally Posted by CrUZida

It will be interesting to see if changing to MPH will stop the dash at 180, or at ~112.

Wont change speed cut level though.

I have a Jaycar speedo corrector in mine, and I was going to change the reading to MPH if I ever needed it for the drags.
The speedo will still thinks its getting KPH input though, so it would count all the way to 180.

Yeah the A70 guys in the UK use the same method. They use a speedo corrector, and then open the dash cluster and remove the bulb for KM/h, and turn on the MPH bulb.

Its a bandaid fix, and again as you mentioned it will only read to 180.