Whilst out in my roadster at the weekend, I thought id do a bit of top speed testing. Basically i floored it till the needles stopped moving, all seemed well until a suddenly, the car jolted quite violently. I thought id blown it up so i pulled over and had a look under the bonnet, everything was ok so I started it up and took it easy for a bit. The car was fine so out of curiosity, I got up to speed again, the same thing happened.... Is it because its speed restricted and if so is it only top speed or acceleration as well? (5/00)
Roadsters are limited to 112 MPH (5/00)
If you revved it beyond its limit (where the numbers turn red on the rev counter, varies depending which model you've got), the limiter would come in. I'm sure someone more technical will explain this better. (5/00)
Eunos Roadsters were speed limited from the factory to 112mph. A 1.6 is quite easy to derestrict, a 1.8 is not. (5/00)
Just top speed AFAIK. 1.6 Roadsters (1989-93) are easy to derestrict; take the clocks out, look at the circuit board, speedo side. Where the main bunch of connectors plug in, find the one marked 180 s/w (or something similar). Follow the circuit till you reach the screw. Remove screw, and hey presto, derestricted. If you remove the speedo entirely, you'll see the speed limiter is nothing more than an electrical contact made when the needle reaches 180 kph. Owners who have a UK or US speeo fitted of course have no speed limiter...unless you have a 1.8. The speed limiter on this I believe is wired into the ECU, so no easy solution I know of. (5/00)
But roadsters are quite easy to un-restrict....just undo a screw on the back of the speedo. Or if you replace the KPH speedo with a MPH one, that also de-restricts it. (5/00)

Lets get this straight, people.

All japanese cars (Roadsters included) are limited to 180 Kph (112mph) On earlier Roadsters, its done with a sensor in the speedo. You can disconnect it be removing a particular screw in the back of the instrument panel (circuit board), then you're not limited. Cost zero. With the screw in place, a signal is sent to the ECU to cut the fuel. With the screw removed, the signal doesn't get through, so the fuel doesn't get cut. On later cars, it's apparently not so simple - don't know details. .

This speed limiter has no effect on acceleration, revs or anything else - but at 112 mph the fuel is cut and you don't go any faster. There are two more relevant "limits". Roadster speedos have an internal stop at about 116mph (this is to stop the needle starting going round the dial again). It has no effect on anything, except that you won't see the speed recorded above 116mph - the needle just stops. So no good for boy racer egos. The rev counter will keep on climbing if you've got enough power - and of course in any particular gear there's a direct relationship between speed and revs.

Then there's the rev limiter at 7250 - this is to limit engine speed - the fuel is cut if engine speed reaches 7250 in any gear - rather dramatic but it does no harm. This limiter is not linked in any way to the speed limiter, and it applies on UK cars as well. (5/00)
If I got an aftermarket ECU (like a Superchips one for £165) would this remove the restriction? I'll ask them anyway but is there a cheaper way that's been done by anyone? (3/01)
So where do you want to go that justifies spending around two hundred pounds on removing a restriction to go above 112mph then? :o) The top speed can't be more than about 120mph at the absolute maximum - Autocar only managed a top of 115mph when they tested a 1994 1.8 Eunos (3/01)
1.8 is definitely controlled by ECU .. I have plenty of theories on overcoming it and even recollections of people managing to do it by removing the SST screw from the speedo head .. this may work .. on some Honda's etc they get annoyed when you do this .. totally guess work as to what happens here! (3/01)