The injection times needed by the engine at different conditions are stored by the ECU in a table of numbers called a look-up table. The ECU determines the engine's load and speed, and uses these two parameters as an index to the table. This table is called the Base Fuel table.

Example: At an engine speed of 4000 rpm and at –20kPa, the relevant number in the table may be 4.35. If the engine approximates -20kPa at 4000 rpm, then the computer will extract the value of 4.35ms from the table as the base injection time. This value is then adjusted to compensate for numerous conditions, such as temperature. The ECU then holds the injectors open for that time on the next injection.

The Ignition Tables work in a similar way, except that it is the ignition advance that is stored in the look-up table instead of the injection time.