How can i modify my speedometer? - Page 1
Forum section: electronics / beginners

author: crazy_driver
author_rank: Contributor
timestamp: January 29, 2014, 01:52:27 pm
content: I need some help to try to calibrate a speedometer so i can change the face and put one with 260km/h.Bigger pictures here:http://mk1tdi.blogspot.pt/2013/09/golf-mk1-gti-instrument-cluster.htmlI have one from a 1.9 diesel ibiza 200km/h (1994) and one from a ibiza GTI 240 km/h (1995) found on ebay.Both are K=3853 IMP/KM and both circuits have the same reference, only one letter and two different numbers on the vdo chip.The 93S06 should be the chip to change the settings right?The circuit only has 3 conections, +12v, signal and ground. The 4th is not conected on the cluster and the +12v has condensers in the circuit that i used on the new circuit and it works fine.Thanks

author: N TYPE
author_rank: Regular Contributor
timestamp: January 29, 2014, 02:47:04 pm
content: You're welcome

author: crazy_driver
author_rank: Contributor
timestamp: January 29, 2014, 04:05:32 pm
content: i have the same wheels, what i need to change is the scale not the imput. Thanks

author: Towger
author_rank: Super Contributor
timestamp: January 29, 2014, 05:06:06 pm
content: The speedos in Europe are calibrated about 10% too low, in order to take into account people changing the wheel size. I believe this is done as the car manufacturers can be held responsible if the speed is displayed too high.Edit 1: Crap spellingEdit 2: Changed low to high!

author: zapta
author_rank: Super Contributor
timestamp: January 29, 2014, 05:32:42 pm
content: Quote from: N TYPE on January 29, 2014, 02:47:04 pmFound the schematic herehttp://archive.siliconchip.com.au/static/images/articles/i1081/108157_3mg.jpgWhat kind of signal is it?(I am working on a similar concept for linbus signals).

author: N TYPE
author_rank: Regular Contributor
timestamp: January 30, 2014, 02:44:11 pm
content: Quote from: zapta on January 29, 2014, 05:32:42 pmIt's normally a square wave pulse.. with varying frequency.

author: N TYPE
author_rank: Regular Contributor
timestamp: January 30, 2014, 02:55:36 pm
content: It may be easier/more convenient to just get the speed sensor from the GTI and swap it over.

author: crazy_driver
author_rank: Contributor
timestamp: January 30, 2014, 03:00:26 pm
content: i have both speedometers, the sensor is the same and the speedometers look the same on the inside so something sould be making a different scale so that one shows maximum 200 and the other one 240, but maintaining the same signal from the gearbox sensor so that the odometer doesn't read more than it travels.

author: zapta
author_rank: Super Contributor
timestamp: January 30, 2014, 05:15:38 pm
content: Quote from: N TYPE on January 30, 2014, 02:44:11 pmDoes the same signal also drives the odometer?

author: Excavatoree
author_rank: Frequent Contributor
timestamp: January 30, 2014, 05:23:37 pm
content: Quote from: crazy_driver on January 30, 2014, 03:00:26 pmCan you find the data sheets from the ICs in the cluster? The VDO brand clusters used on some Ford and Chrysler vehicles in the US use a common IC that has a resistor divider that sets a "divide by" ratio. My "police car" cluster had a trim pot, but the "civilian" cluster used two resistors. Yours may have a similar feature.If not, the idea presented above, using an aftermarket divider/multipler, is your best bet.

author: crazy_driver
author_rank: Contributor
timestamp: January 31, 2014, 12:44:59 am
content: the same signal from the gearbox hall sensor drives odometer and speedometer, so if i modify the signal the odometer will register too much travel.i'm a noob so all i know about electronics is by playing a little with this stuff.the motorolla sc7812op chip is on the fronthttp://3.bp.blogspot.com/-gVovNBbvgkg/UjYQqt_vXlI/AAAAAAAAAsQ/ESSTZx34HTE/s1600/front_h.JPGthe 93s06 on the back maybe could have the info i need?http://1.bp.blogspot.com/-c1a0S2ebO_A/UjYQpxwvpII/AAAAAAAAAsI/7bN2MVBChR0/s1600/back_h.JPG

author: macboy
author_rank: Super Contributor
timestamp: February 04, 2014, 05:32:54 pm
content: Quote from: Towger on January 29, 2014, 05:06:06 pmCare to cite a reference for this claim?

author: magic smell
author_rank: Newbie
timestamp: February 04, 2014, 06:50:18 pm
content: Yust swap the complete cluster and it will work yust fine. I had made the same with golf, i put in 1,1 gasoline the cluster from gti.

author: dr_p
author_rank: Frequent Contributor
timestamp: February 05, 2014, 12:30:04 pm
content: Quote from: macboy on February 04, 2014, 05:32:54 pmhttp://en.wikipedia.org/wiki/Speedometer#Error

author: Rerouter
author_rank: Super Contributor
timestamp: February 05, 2014, 12:39:05 pm
content: Unless that eeprom stores the calibration factor i am not seeing any easy way for you to accomplish this with both the pointer and speedometer reading accuratly,sometimes the air coil driver has a span adjustment, but i do not recognize this circuit, though i see no other purpose for that micro / eeprom on there other than that and possible an odometer reading mirror (to tell if it has been changed) read off the contents you may find the K in plain DEC,as far as factory calibration goes to reply to the above poster, higer Utes regularly come new from the dealer 23% fast, (My company occasionally fits correction boxes)