I've fitted a 'chip' behind the speedo head to convert from km to mph but its failed the sva reading to slow. It's a 98 STI4 RA Limited, does this need a special type?

Please help cause I want it on the road!

Darren i also had a problem with my speed delimiter/convertor when my car went for its SVA test.

The tester told me that it was under reading by 4 mph and they told me that they would have to replace it and retest the car.
After they had changed the unit they retested it and it was doing exactly the same under reading by about 4 mph. It turned out to be that while testing the car they didn't set the rolling road correctly to the width of the car which meant that the passenger front wheel wasn't making good contact with the RR.
I pointed this out to them to which after they readjusted the RR mph reading were over by about 3 mph which was acceptable.

I did point out to them that they had charged me for a convertor which didn't need replacing but they just fobbed me off saying that the old one was faulty.
Aparntantly this is a well known i've been told.


The only thing is though mine is fitted above the gearbox inline with the speed sensor, so maybe you do have a different type?


Mel.