bodilx6 Posted May 8, 2009 Share Posted May 8, 2009 Just got myself a TRD speedo installed. The pointer had been taken off and was therefore incorrectly positioned. I've calibrated it by diving 62mph after a Racelogic Performance Box and placed the speedo accordingly. Result is that the speedo is completely accurate at 62mph but at lower speeds it shows too high mph and at higher speeds it shows to slow a speed. It's a relative difference, so I I drive 120mph, It shows roughly 8mph too little an at fx 20 it shows 5-6mph too much. How do I go about getting this working in the whole sprectre? Link to comment Share on other sites More sharing options...
NeoFuture Posted May 8, 2009 Share Posted May 8, 2009 change the size of your wheels Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 8, 2009 Share Posted May 8, 2009 It may not match the diff ratio your car has. See why I was reluctant to fit it ? Not sure how the speedo is matched to diff ratios, some are adjustable internally. Pete Betts at Thor Racing used to make an adjustable speedo converter that allowed ou to trim things. Not sure if he's stopped making these now though. Do you know EXACTLY what car it was made for? Link to comment Share on other sites More sharing options...
Supradan Posted May 8, 2009 Share Posted May 8, 2009 Dont drive over 62mph:d Link to comment Share on other sites More sharing options...
bodilx6 Posted May 8, 2009 Author Share Posted May 8, 2009 change the size of your wheels They are very close to stock circumference. Dont drive over 62mph:d Hehe, gonna be hard since I'm leaving for The Ring on Friday.. It may not match the diff ratio your car has. See why I was reluctant to fit it ? Not sure how the speedo is matched to diff ratios, some are adjustable internally. Pete Betts at Thor Racing used to make an adjustable speedo converter that allowed ou to trim things. Not sure if he's stopped making these now though. Do you know EXACTLY what car it was made for? Yeah I do. I just assumed it was for the soop. Bought from Paul Whiffin. I think it was from his own car. Fits very nicely. Thor racing has both mechinical and electronic speedo converters. I was just thinking this was a cheap fix for my mph speedo. Little did I know then.. Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 8, 2009 Share Posted May 8, 2009 It may well be for a Supra, but for one with a different axle gear ratio to the one you have. I bet if you look at the EPC there are LOTS of different speedo heads listed. Link to comment Share on other sites More sharing options...
bodilx6 Posted May 8, 2009 Author Share Posted May 8, 2009 Must be then.. Only solution is to get a speedo converter then? Link to comment Share on other sites More sharing options...
Homer Posted May 8, 2009 Share Posted May 8, 2009 I bet if you look at the EPC there are LOTS of different speedo heads listed. The instrument cluster is only available as an entire unit, but the part numbers are different per spec (there are a lot of them!) A variable speedo convertor is needed. The THOR ones used to be, but not sure if they are available any more. Link to comment Share on other sites More sharing options...
paul mac Posted May 8, 2009 Share Posted May 8, 2009 it sounds like you have a zero and span error and some linearity issues just for good measure, this is about as bad as it gets, at work we would just bin a gauge displaying these errors as its just too time consuming to fix, to the best of my knowledge there is no means of adjusting errors like this on the speedo Link to comment Share on other sites More sharing options...
Soaruss Posted May 8, 2009 Share Posted May 8, 2009 A variable speedo convertor is needed. The THOR ones used to be, but not sure if they are available any more. Yes they are. I have just bought one and had it fitted. My speedo is still out though by about 7mph over reading at all speeds even after adjusting the converter (small dial inside). Anyone know what can be causing this?? http://www.thor-racing.co.uk/DSC+TSD_Combined-DSC+TSD.asp Link to comment Share on other sites More sharing options...
Homer Posted May 8, 2009 Share Posted May 8, 2009 Anyone know what can be causing this?? What size rear wheels and tyres do you have fitted? The gear and tyre size calculator posted last week will help show the difference. Link to comment Share on other sites More sharing options...
Soaruss Posted May 8, 2009 Share Posted May 8, 2009 I have 265/30/19 on the rear but surely it shouldnt be out by 7mph. Do you have a link to the gear and tyre size calculator?? What size did a 93 Jspec TT come with?? Link to comment Share on other sites More sharing options...
bodilx6 Posted May 9, 2009 Author Share Posted May 9, 2009 (edited) 245/50-16 But I'm running 245/35-18 which is a bit smaller than stock specs. The misreading cannot be due to that in my case since i have a difference in misreading across the scale and not a set percentage. If you have a constant 7mph, wouldn't it just be easiest to move the needle at bit at speed? Edited May 9, 2009 by bodilx6 (see edit history) Link to comment Share on other sites More sharing options...
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