Anyone know anything on import speed limiters?

[DanielSan]

Greetings, I've discovered an unbelievably strange problem with my car this weekend. It's a 99 JDM car, speedo has been converted to MPH as its now in the UK. BUT, I noticed this weekend on a 'rolling road' that the speedo gets to 129mph the starts reading backwards to 128,127,126 etc etc but the revs appear to still be rising on the rev counter but very slowly.

[DanielSan]

Not sure if it could be that the car still has the JDM speed limiter on it but is expect that to just hold one speed rather than go up and start coming back down slowly or if it could be an issue with the cluster itself?

I've just checked the ECU and there's nothing attached/wired into it that can take the limiter off (HKS and a couple of other jap companies do them) so I'm really stuck on what the hell is up.

Please dear god help, this is driving me insane.

[civicduty]

Thought the JDM speed limit was 112 mph, from Wiki,

"In 1988, JDM cars were limited by voluntary self-restraints among manufacturers to 280 horsepower (PS) (276 hp) and a top speed of 190 km/h (118.1 mph), limits imposed by the Japan Automobile Manufacturers Association (JAMA) for safety. The horsepower limit was lifted in 2004 but the speed limit of 180 km/h (111.8 mph) remains in effect. Many JDM cars have speedometers that register up to 180 km/h (111.8 mph) (certain Nissans go up to 190 km/h) but all have speed limiters."

HTH

[Krikkit]

Speed coming down with revs rising would suggest an ECU/cluster problem. What car is it?

[DanielSan]

I'm aware if the limit, but take into account the 10% mis-reading speedos are supposed to have, even digital ones like in my s2000.

[Goatboy]

When I discovered the speed limiter in my Impreza many moons ago it was very noticeable. Car essentially slams into the limiter drops revs slows down then rushes back towards it again.

Does not sound like what you are experiencing.

Apart from that I am clueless sorry.

[DanielSan]

Goatboy said:

When I discovered the speed limiter in my Impreza many moons ago it was very noticeable. Car essentially slams into the limiter drops revs slows down then rushes back towards it again.

Does not sound like what you are experiencing.

Apart from that I am clueless sorry.

That's what I thought it should be like. Excellent, one possibility ruled out then from the sounds of it.

[DanielSan]

Bumped for more views.

[so called]

My FTO had a limiter that kicked in at 200km/h (autobahn tested many times).
Just seemed to die for a few seconds and come back at about 190.

[DanielSan]

I'd thought it could be something like that but can't see why the revs would keep increasing, the numbers are moving in keeping with how they are going up on acceleration up to that point, they just then start going backwards after 129.

[Welshwonder]

I'm not sure what kind of de-limiter was used on your car. I've had experience with the ones fitted to Evos where you install it in-line with the speed sensor on the gearbox. It's just spliced in and intercepts the pulses, slowing them down so that KM's become miles. If yours is the same type, I'd just replace that, as it may be failing at higher pulses.

I think some Jap cars had an output off the speedo dial where a signal is sent to the ECU when the needle physically reaches 112mph. I think they can use a couple of different methods though. Try searching the forums to see how your limiter was commonly raised/removed.

Either way, it sounds like there's electronics behaving oddly under stress.

[DanielSan]

Searches so far have found the most common seems to be the HKS Speed Limit Defencer unit, which is basically a small box that sits next to the ECU and wires into 3 wires coming off it. Had a look today and that kind of unit is nowhere to be seen on or near the ECU, other solution seems to be wiring in a resistor either by the ECU or behind the speedo apparently. Definitely something not right, just have a feeling its going to take a lot of fking about to find it.