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The mkiv Supra Owners Club

Speed Limit Defender, SLD

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Speed delimiter


Also known as:

Speed Limit Defender (SLD)

Speedo convertor


What is it?

The Japanese import verion of the Supra is limited to 180km/h, which is 112mph. The SLD bypasses this limit so that you can go faster than 112mph. It usually also serves the function of converting your speedo so that it reads in mph rather than kph (and the odometer counts up in miles).



You can go faster - woohoo!

Your speedo reads in mph

Your odometer counts up in miles



A good SLD has no cons. This is because it takes the input from the vehicle speed sensor and sends three outputs. One output is unchanged and it goes to systems like the speed sensitive power steering and the active spoiler etc. A second output is scaled so that it reads mph instead of kph - this goes to the speedo and the odometer. A third scaled output goes to the ECU and this is clamped at around 179mph, which stops the ECU from ever engaging the speed limiter function. If the SLD doesn’t have this third output, the limiter will kick in at 180mph instead of 180kph.


A crap SLD has various cons. Usually it's electrical-quality related, a lot of problems are caused by poor construction or wiring as the ECU starts seeing a zero speed signal. The main problem with poor SLDs though is if it acts as a speedo convertor as well. Usually they emit only a scaled Vehicle Speed Sensor output to everything, meaning all the speed-dependant systems like the power steering and active spoiler (and especially the autobox!) get an incorrect speed signal and behave eratically.

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  • 1 year later...
Guest SupraTTAeroMatt



Have recently bought an imported Supra and seem to be having problems that seem associated with the SLD. First of all it seems to be limited at approx 122mph???? Also some basic electrics appear to be suffering (Electric Mirrors/Active Spoiler/Stereo folding mechanism). Any tips on whether this may be to do with the SLD or not/where to get a decent one.



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Without a SLD the Supra is limited to 112mph (112 mph = 180 kph)

With a SLD fitted it's limited to 180mph.


To test for a faulty SLD simply remove it.

Good quality SLDs are available from Thor Racing

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mine tops out at around 125 too. also when i fold in the electric wing mirrors the speedo goes crazy, managed to get 200mph indicated speed :)


With regards to the 'topping out' speed, this probably means your speedo is out by a bit, as is mine. Mine appears to go off the scale (which only goes up to 115mph, and then a bit more before hitting 'the wall', so pos due to aftermarket wheels, which sometimes mess the speedo up if you go up a size or 3, and if like mine yours has been converted to mph from kph this could also affect it.

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  • 1 year later...
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im also having problems that sound related, when i put the car into to drive after reversing out of the drive suddenly (according to the speedo) im doing 120mph! lol. same problem when putting the car into park!

Any idea what delimiter you've got fitted?

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i don't honestly know it came on the car, suppose im gonna have to rip the dash out to find out?!

AFAIK, the only way you can delimit the car (ignore the khmph conversion for now) is to get at pin 2 on the ECU. As that's easier to get to and less hassle than ripping the dash out, I'd have a sneeky peek there on the off chance someone fitted the conversion & delimit chip down there. It's a long shot but you're not investing much time & effort so worth a go - if it's not there, you can attempt to follow the wire to the chip. Take some photos and we can have a go at seeing what's what. :)

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pulled back the carpet in the footwell last nite and can find absolutely no evidence of any cables etc being cut and connected. could it be fitted elsewhere?

The chip could in theory be fitted anywhere, but from what I've experienced the most usual places are:

  • behind the dash (like mine);
  • under the dash (for easier access if for some reason you wanted to get at it);
  • under the gear surround (again easy access as that's a 1 minute job to remove);
    ...or sometimes...
  • near the ECU

...but like I say I don't know of any other way of tricking the ECU (i.e. bypassing the 180kph speed limiter) without getting at pin 2, so I'd expect to see some wiring chopped & altered there.


However I'm no expert on ECUs (or anything for that matter lol), I just fitted my delimter/convertor & took pics to try and help others - so maybe someone with more technical knowledge can shine a light. Ian C, Matt Harwood spring to mind and I'm sure there are others - maybe drop them a 'pretty please can you offer advice' PM?

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  • 8 years later...
  • 3 years later...

sorry to bump an old thread - if i already have a mph converter but it doesn't do the delimit - can i fit an SLD aswell or will it interfere?


Edit: I currently have the speed m8 converter . Is this a delimiter too?

Edited by tayr (see edit history)
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