Vehicle Speed (VSS1) ≠ Car's Digital Speed Display


The speed shown on my Suzuki Swift Sport dashboard display is roughly 2-3 mph higher than the actual speed (according to GPS). I know this is normal to prevent accidental speeding due to fitting new wheels, etc.

However, the speed outputted from the OBD2 port is different and is actually much closer to GPS speed.

I want the speed within RealDash to match the car’s displayed speed. Is there a way of adjusting RealDash?

In these cases your vehicle probably sends multiple replys for vehicle speed request. For example, the ECU sends its value, transmission sends its and instrument cluster sends its own. These really can be 3 different speed values.

When RealDash receives multiple replys for single value, it just uses the first one. This is for performance reasons. While in theory you could make a custom XML that reads the speed from a specified control unit by using filtering, it is quite complicated to get working.

Thanks for the explanation. Is there any easy way to adjust what speed is displayed on the RealDash dashboard? If I could add 2 mph that would fix the discrepancy.

(I was wondering whether input mapping would allow this somehow.)

Adding 2 would show 2 when standing still.

You could use Gauge Math to scale the value:

  • Go to edit mode and select the speed gauge
  • Go to ‘Look’n Feel->Special’ and set Gauge Math to V*1.02, which adds 2 percent to the value.

Problem with this approach is that you need to do this for all dashboards you use.

You could also modify the default OBD2 connection XML file, which is here:

RealDash-extras/OBD2/realdash_obd2.xml at master · janimm/RealDash-extras (

The line:

<command send="010d" skipCount="0" targetId="81" units="km/h"></command>

Could be modified to:

<command send="010d" skipCount="0" targetId="81" units="km/h" conversion="V*1.02"></command>

Thanks, I’ll try the dashboard edit because I’m only using the one anyway. :slight_smile:

Can you please tell me why the calculated gear uses “Master speed”? What exactly is that? Does that uses VSS1? (I set the gear ratios correctly and the gear number is shown correctly.)

“Master Speed” refers to the speed source set in ‘Settings->Units & Values->Vehicle Speed Source’.

After my last post I did change that setting and my speed (mapped to VSS1) and gear stopped working. I just wondered if “master speed” is mapped to VSS1.

Is your map location updating? Maybe there is no location permission given to RealDash.