Almost all modern cars have on-board computers, but what are these systems and how do they work?
The first electronic on-board computer came out in 1978 and was installed in the Cadillac Seville. Mechanical systems had previously existed, but the Seville’s ability to calculate its own fuel economy and allow the driver to input the number of miles to their destination was a novel idea.
Car on-board computers have since evolved and become more sophisticated (especially in electric cars), but the principle behind them has remained the same. Here we explain what an on-board computer is, how it works and what kind of information you can reasonably expect from one.
What do onboard computers do?
As the old saying goes, an on-board computer does what it says on the tin: it calculates data associated with a trip.
There are five main areas that an on-board computer provides information about:
- fuel consumption
Each of these four areas contains layers of information, and while exactly what an on-board computer reads will vary from car to car, here’s what you can reasonably expect:
On-board computers show you how long you have been on the road since you started your journey. When connected to the sat nav, they can also tell you how much longer you have to drive to reach your destination.
As you can imagine, this will tell you how the car drove.
This will give you the average speed the car was traveling at.
This generally gives two readings: your car’s average fuel economy and instantaneous fuel economy – meaning how much mpg the car is making from one moment to the next, so you can see how different the conditions are (e.g. hills, speed, how aggressive you are). with the accelerator pedal) affect fuel consumption.
This tells you how far you can go before your fuel tank runs out. While the range figure generally decreases as the journey progresses and the fuel tank is empty, the range figure can actually increase if you start a city trip and then head out onto open roads where efficiency is better, as the calculations show will vary based on driving style over the course of the journey.
On-board computer: Trip A and Trip B
Many trip computers provide information for three “trips”: Trip A, Trip B, and Since Reset.
This allows all of the above information to be measured separately and in parallel over three time periods. You can reset each trip individually or all at once.
As an example, you can use Trip A to determine how far, how fast, and how efficiently the car goes on each tank of fuel, and reset Trip A each time you fill up the tank.
But you might also want to see if a new route to work takes less time, is more economical, or is faster than your usual route. So you can reset Trip B to determine this while Trip A keeps running in the background until the next time you need to refuel.
As for the “since reset” information, many people never touch it, which means it can show how far, fast, and efficiently the car has traveled since it left the factory (or possibly since the battery was last removed). became).
Also note that if you make a series of short trips (e.g. picking up the kids from school, going to the supermarket, going to soccer practice), these trips are often treated as a single car trip, which is usually resets to a new “ride” after the car has been off for about four hours.
Trip computer for electric cars
Perhaps the biggest change in the world of onboard computers has been brought about by the advent of electric cars.
An electric vehicle’s on-board computer will normally show you all of the above information, plus the electrical equivalent of fuel consumption: instead of miles per gallon, you will be shown miles per kilowatt hour (e.g. if you have a 100kWh battery and the car is doing 3 miles per kWh gives you 300 miles per charge – see more info here.)
In addition, many electric vehicles will sync their battery range with the sat nav and calculate how far you can go on one charge and where to stop to recharge when going on a long drive.
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