puggy Posted November 20, 2021 Share Posted November 20, 2021 I bought the car a few years back and immediately noticed that the speedo was out. Basically, 30mph (true speed) reads 36mph on the speedo, 60mpg reads 69mph on the speedo, 70mph reads 79mph on the speedo, etc. I have had it reset twice but it has made no difference. Anyone had a similar issue or any ideas what’s wrong and how to fix it? Quote Link to comment Share on other sites More sharing options...
puggy Posted November 20, 2021 Author Share Posted November 20, 2021 Sorry, forgot to add, it’s a J-spec NA auto. Quote Link to comment Share on other sites More sharing options...
m12aak Posted November 20, 2021 Share Posted November 20, 2021 My speedo is off by about 6mph at motorway speeds (75/76 is 70mph gps). As the tacho is front and centre I always just drive off revs, so 3200rpm indicated in 5th is 70mph gps. By 'reset' what do you mean exactly? Has the converter been recalibrated? I think getting another converter & having it properly calibrated should sort that out. It seems odd that at 30 it's 6mph off and not 12mph off at 60 (mine seems to scale with the speed), makes me think the converter is malfunctioning or some sort of scaling is wrong. Both of mine came with the converters already fitted and I haven't needed to touch them (long may that be the case!), so I have no idea how they're plumbed in or what converters have been used. They both use the OE kmh dials too. Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted November 20, 2021 Share Posted November 20, 2021 Do you have a speedo convertor fitted? Quote Link to comment Share on other sites More sharing options...
puggy Posted November 21, 2021 Author Share Posted November 21, 2021 3 hours ago, Swampy442 said: Do you have a speedo convertor fitted? I’m no mechanic so to be honest I have no idea. I have ordered one so I’ll get it fitted and see if it makes a difference. Do you know if you can adjust it whilst driving? i.e. get to say 70mph and manually adjust the needle. Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted November 21, 2021 Share Posted November 21, 2021 No they can't be adjusted, it just converts a signal to the speedo, but cheap ones can cause issues 1 Quote Link to comment Share on other sites More sharing options...
rider Posted November 22, 2021 Share Posted November 22, 2021 You could have a low ratio differential. I changed one of my cars from a 3 stock to 3.55 street differential and that added 20% to the speedometer. I just need to get around to changing the driven gear some time on the old car I did the differential change on. Quote Link to comment Share on other sites More sharing options...
Bender Posted December 7, 2021 Share Posted December 7, 2021 On 11/21/2021 at 2:15 AM, puggy said: Do you know if you can adjust it whilst driving? i.e. get to say 70mph and manually adjust the needle. Of course you can. Take the needle off take gps with you drive up to 80mph/kmh (so it is in the middle) and put needle back. Sorted Quote Link to comment Share on other sites More sharing options...
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