How can i modify my speedometer?

[crazy_driver]

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.html


I 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

[N TYPE]

You're welcome

[crazy_driver]

i have the same wheels, what i need to change is the scale not the imput. Thanks

[Towger]

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 spelling
Edit 2: Changed low to high!

[zapta]

You're welcome

Found the schematic here

http://archive.siliconchip.com.au/static/images/articles/i1081/108157_3mg.jpg

What kind of signal is it?

(I am working on a similar concept for linbus signals).

[N TYPE]

You're welcome

Found the schematic here

http://archive.siliconchip.com.au/static/images/articles/i1081/108157_3mg.jpg

What kind of signal is it?

(I am working on a similar concept for linbus signals).

It's normally a square wave pulse.. with varying frequency.

[N TYPE]

It may be easier/more convenient to just get the speed sensor from the GTI and swap it over.

[crazy_driver]

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.

[zapta]

It's normally a square wave pulse.. with varying frequency.

Does the same signal also drives the odometer?

[Excavatoree]

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.

Can 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. 

[crazy_driver]

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 front
http://3.bp.blogspot.com/-gVovNBbvgkg/UjYQqt_vXlI/AAAAAAAAAsQ/ESSTZx34HTE/s1600/front_h.JPG

the 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

[macboy]

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 low.

Edit: Crap spelling

Care to cite a reference for this claim?

[magic smell]

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.

[dr_p]

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 low.

Edit: Crap spelling

Care to cite a reference for this claim?

http://en.wikipedia.org/wiki/Speedometer#Error

[Rerouter]

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)