Removing the 185kmh speed limiter

[mickeyduck]

Ever since hitting the limiter at Hampton downs I've been curious as to how you get a J-spec AW to do more than 185kmh

Ade, who founded this club and had a track AW as well as a road one, told me you remove a certain screw from the back of the instrument cluster, but she couldn't remember which one.

I've just managed to score a NZ spec instrument cluster which reads up to 240kmh and have had a quick look at the back of it. Sure enough you can see there is a screw, a circuit, and two bridged connectors on the 185kmh version, which aren't there on the 240kmh one. So as I understand it you could remove the screw from a J-spec AW instrument cluster and thereafter your AW would be able to get up to 240kmh (on a race track, eh).

Ade recalls that when you have removed that screw your AW will go the whole hog, but after going beyond 185 you usually get the check light coming on because the ECU has got confused. Doesn't hurt anything, just requires resetting the thing to make the light go away.

Anyway here's the photo showing the 185kmh cluster at top, the 240kmh cluster below (I need to go refit the actual speedo part of it).

If you're into racing an AW and try this, feel free to post any further info and verify whether I got this right or not. Cheers.

EDIT / CORRECTION some time later: the screw to remove is the one labeled RS (restrict speed) near the speedo cable attachment. Not the one pointed to by the arrow in the earlier pic above. The photo below shows the RS screw which can be pulled to disable the speed sensor signal and therefore eliminate the 180kmh speed cut on J-spec AW's. Note also this has an effect upon how a 4AGZE runs (read on).

[Benckj]

I'm curious about this too especially if it can be done on an SW20. Somehow I don't think its that simple especially on those cars which have an electronic speedo.

[*84vvt]

The ECU requires a SPEED signal, the signal is the purple with white stripe wire from the dash to the ECU
if you slow or decrease the number of "pules" say from 4 to 2 then the ECU only sees half the "speed"
This will keep the ECU happy and give you the higher top speed.
All you need to know about the Toyota ECU is here
http://www.autoshop101.com/" onclick="window.open(this.href);return false;
A must read if you ask me .

[Reuban]

My black SW had the speedo signal signal wire cut right behind the dash. Went fine, could get right up near the end of the 240k speedo.
Looking at the bgb speed signal comes from dash cluster whether cable or electric speedo,(Havn't looked at the really late model BGB) maybe signal is created/converted there and sent to the ECU.
Unless its an auto i don't know if it needs speed signal at all.
Another good reason to go aftermarket EMS

[optional]

If the signal for the speed limiter is the purple/white wire then the removal of one screw would work. Not the one you show in the photo though.
I just had a look at my car which has no dash in and the purple/white wire goes to screw at the lower right side of the speedo (at about 4 o'clock).
Removing that screw would indeed disable the speed signal if the purple \/white wire is the correct one. Makes sense and Ade would know what she is talking about.
Keith

[mickeyduck]

If the signal for the speed limiter is the purple/white wire then the removal of one screw would work. Not the one you show in the photo though.
I just had a look at my car which has no dash in and the purple/white wire goes to screw at the lower right side of the speedo (at about 4 o'clock).
Removing that screw would indeed disable the speed signal if the purple \/white wire is the correct one. Makes sense and Ade would know what she is talking about.
Keith

I'm thinking you may well be correct. That screw is marked "R.S." if I'm looking at the same one, which might stand for "restrict speed"...?

That one would be my bet for that reason, except I then went looking for differences in the circuitry which from the looks has probably put me crook. So maybe the "R.S." screw is the limiter and the other one is the annoying 105kmh bell?

Just to clarify, Ade told me there was a screw to remove but she couldn't remember which one it was. All I can say is if she said that's all there is to it then I have no reason to doubt it.

As I've not managed to test this particular theory myself, please feel free to post here which one it actually does turn out to be if you do manage to get it sussed (anyone).

I might try this in my (currently broken) AW when I get it back on the road. Meanwhile I'm probably going to fit my running AW with a 240kmh speedo this weekend, while replacing its broken cable.

Thanks for the info folks. It'd be fun to nail this particular thing. Having been bouncing off the limiter around Hamptons...

[Malcolm]

Probably the best way to remove the limiter, which will work (AFAIK) for all manual MR2s, (not sure, but it's possible automatics need an accurate speed signal to function correctly), is to install a frequency divider in line with the speed signal to the ECU. The wire should be purple/white stripe on everything from the AW11 to Gen 2 SW20s, then from Gen 3 it is an orange wire. Check the appropriate wiring diagram and confirm for yourself before cutting the wrong wire and blaming me

So you need a frequency divisor IC, such as this one from Jaycar http://www.jaycar.com/productView.asp?ID=ZC4024" onclick="window.open(this.href);return false;
I would also suggest getting a suitable socket (http://www.jaycar.com/productView.asp?ID=PI6454" onclick="window.open(this.href);return false;), and probably some veroboard to attach your wires to (or just solder to the legs of the socket if you want...) (http://www.jaycar.com/productView.asp?ID=HP9540" onclick="window.open(this.href);return false;)

Have a look at the last page of the datasheet for the IC to see how the pins are numbered. All you need to do is:
Cut the speed signal wire that goes from the speedo to the ECU. Connect side that comes from speedo to pin #1
Connect speed signal to ECU to pin #12
Connect pin #14 to a 5V power supply, there should be at least one of these coming out from the ECU (TPS, MAP, AFM and most other engine sensors with 3-pin connectors run off 5V, on a Gen 3 this is a red wire, pin #1 on the 16 pin ECU connector)
Connect pins #2 and #7 to ground

The result is that the pulsed signal being sent to the ECU is halved, so instead of a speed cut at 180kmh you get one at 360. If that's not high enough you can connect to a different pin on the IC, but I'd be very surprised if anyone can get an MR2 going that fast on the stock ECU!

[Alsw20]

AW doing 240km/h?

[Redmist]

AW doing 240km/h?

They have been known to out drive a 180km speedo.
Being able to see 200km at a glance is a bonus.

[Grrrrrrr!]

And there area a couple of 3sgte powered AWs around.. they might hit 240.. not sure how stable they'd be at that speed tho!

[85AW20v]

.... and the other one is the annoying 105kmh bell?

When you take out the 105km bell, make sure you put the 2 screws back in as they act as earths for a few other parts of the circuit board.

See ya
Simon

[optional]

The bell on mine was "removed" merely by cutting the wire from the screw (I think it is a yellow wire). It is all still in place.
Now I may be paranoid, or maybe just old but the speed warning may be a useful feature. I am sure that we have all received ticket for excessive speed when we were just cruising and did not really mean to be exceeding the speed limit. This is now an expensive lapse in concentration!
Since my instrument cluster is currently out I am going to re-instate the speed warning, with an added feature. I have a circuit that I used on another car which, at the touch of a button will disable the warning for as long as you are above the speed limit, plus another preset time ( say 2 minutes). This allow you to pass a line of traffic and then settle back down to the speed limit without the annoying ding, ding, ding but still warns you when you don't want tickets.
This, or alternatively a simple switch to break the circuit to the bell when you want to be an idiot, or when you are playing on the track, seems to be a better option: the best of both worlds perhaps.
The only issue I have is where to hide the button. After what I have spent restoring the thing I want it as original as possible.

[mickeyduck]

AW doing 240km/h?

I've read here and there that a supercharger can get to about 140mph which is getting pretty jolly close (240kmh = 150mph)

The n.a. AW's top out somewhat earlier apparently due to lesser torque etc.

I guess next time I'm at Hamptons or something maybe I'll find out? We'll see...

Finally fitted the 240kmh speedo to Stripe this arvo, and I left that RS screw out so we'll see what comes of it.

As for AW stability Lee... I find the thing tends to hunker down more and more the faster you go. More speed = more stability it seems. At least that's been my experience up to 185kmh. Though I do think adding a vent in the bonnet for the radiator like in an F308 or F328 makes lots of sense. Anyway, back to the topic at hand...

[mickeyduck]

OK a wee update, some time later.

As I posted here earlier I fitted the 240kmh speedo to my AW SC with the RS screw removed, thus providing the ECU with no speed sensor signal. I discovered this made the engine idle at 1200rpm instead of 800rpm, prevented it revving beyond 7000rpm whereas it usually went to 7500rpm, and made it run rich and use a lot more gas. So I pulled it out again and put the 180kmh original cluster back in.

A couple of years later I have a different AW SC and Malcolm has been immensely helpful and fitted the 240kmh speedo with a frequency divider as described in his post just earlier on this thread. The wiring was done only on the speedo (no cutting the loom) so that the speedo can be fitted to any AW SC to eliminate the J-spec 180kmh speed cut. Here is a link to the build of the thing in case anyone is looking for more info. And eventually I expect I'll be able to explain how it worked out too.

http://mr2.org.nz/phpbb3/viewtopic.php? ... 96#p133096

[MR2GUY]

I never knew the AW had a limiter, i've definitely been over 190...