If you'd like to upgrade your current stock speedometer for a more modern digital unit, you are going to do some work under the bonnet. This is because your speedometer is attached to your car battery. This task can be done, even if you don't know much about cars, but the process does require some time and concentration.
Turn off your car and open the bonnet. Disconnect the cables from the terminals on your battery.
Remove the dashboard panel on your car, according to the maintenance manual. Slide the current speedometer out of its compartment. Use the tip a flathead screwdriver to shimmy the speedometer out, if you can't remove it with your fingers.
Unplug the cables from the ports on the back of the current speedometer. If they don't unplug, cut the wires near the ports. Note the different colours of the speedometer wires, and which ports they connect to on the back of the speedometer. Set the old speedometer aside.
Plug the wires into the back of the digital speedometer or, if they don't plug in, strip about a half inch of insulation off the end of each wire.
Solder the wires into the ports. Let the solder harden and wrap the exposed wiring in electrical tape.
Fit the new speedometer into the compartment in the dash. If it is too large, use a drill with a 3 3/8-inch bit, to create more space in the compartment.
Connect a metal clamp to the studs on the back of the digital speedometer and clamp the unit to the rear of the dash, to secure it.
Reconnect the battery cables in your car.
Turn on your engine while holding the "Function" button on the front of the digital speedometer. The unit will now enter calibration mode.
Press the "Function" button on the front of the unit, to scroll through the calibration options . Stop on the option you would like to select. Use the controls on the front of the speedometer to set the options according to your preferences, and the instruction manual.