ECU and Dashboard

My speed source is ECU speed sensor. There is always a slightly less deference between RealDash speed readings and car dashboard , 3-5 miles caused to be caught by speed cam if I only check RealDash speedometer.
Is there anyway to calibrate the RealDash speed reading or adding a correction factor to match the speed ?
Thank you.

Pretty much all manufacturer clusters add some into ‘real’ speed that comes from the ECU. I think on some countries this is mandated by government.

If you really worry that you would be speeding, compare ECU speed with GPS speed value to make sure.

There are ways to add correction to this. Either make a modified XML for your connection and add multiplier to conversion, or edit the speed gauge, go to the gauge math and add something like =V*1.05.

Thank you very much for your reply. Not sure about XML modification. The speed reading is always less than car’s clusters by 3-5 miles, let’s say 3 miles. I always get blinking by speed monitors on, for example, 30 miles roads, even I drive 28 MPH, unless I pay attention to my cluster to reduce the speed to 30, that time, the Realdash displays 27 MPH. I double-checked my settings; my vehicle speed source is ECU speed sensor, I also changed it to GPS, and I got 3 miles less than the cluster.
Will be so appreciated to find a way to add +3 to the value.


How are you connected to your car? (OBD2, CAN, Aftermarket ECU?)

Thank you for your swift reply.
I am connected via OBD2.

You could take the default OBD2 XML from our GitHub:

And modify line:

<command send="010d" skipCount="0" targetId="81" units="km/h" conversion="V*1.03"></command>

Then import this XML file into your connection settings.

Another option is to edit the dashboard you are using:

  • Enter into edit mode
  • Select all gauges that display speed
  • Go to Look’n Feel->Special->Gauge Math’
  • Enter formula: =V*1.03
  • Exit Look’n Feel and save the dashboard.

Thank you so much, that’s a great help.
The formula I used was v+3 as the difference is constant 3. I get on my RealDash speed value 3 when I stop but at least I am safe now.

Again, thanks for your help.

Just multiply to get to “0” when you stop.
You need “V*1.111” to get to 30 at 27.