How does Dash calculate fuel efficiency?


One of Dash's biggest and best features is that the app automatically calculates your fuel efficiency. But how do we do it?

As you're probably already aware, Dash gets information about your vehicle's ECU from the OBD port. This gives us access to several different sensors which we use to make our calculations.

In addition to speed, there are two main sensors that we use for fuel economy calculations:

  • Mass Airflow: this sensor uses a heated wire to calculate how much air is passing into your engine. In gasoline vehicles, there is a fixed ratio* between air and fuel, so this is usually a very accurate calculation. Diesels need another adjustment but should still work well.
  • Manifold Absolute Pressure: with this sensor, we need to know your vehicle's engine displacement and RPM as well as speed to make the calculation. It might not be quite as accurate, but should still be OK.**
  • Fuel Consumption: a few modern cars will actually report their fuel consumption rate in liters per hour, but we've found this is fairly rare.

And that's basically it - Dash will poll the sensors necessary to make this calculation ever 1-2 seconds so we can make an accurate calculation throughout your drive.


* This is called the "stoichiometric" ratio, which is a chemistry term. Search the term for tons of great background info.

** As a by-product of this, altering the engine displacement for these vehicles will affect your fuel calculations.

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