An engine equipped with a turbocharger or supercharger forces a greater volume of air into the cylinder. The power output does not increase until the intake air is burned completely. For this reason, it is necessary to increase the fuel volume to burn the intake air completely. Thus, fuel consumption will increase as the power output is increased.
1. Mechanically controlled type
With a diesel engine, the boost compensator increases the maximum fuel injection volume in accordance with the boost pressure. (Refer to the chapter of the diesel injection pump in the book of diesel engine, for details.)
2. Computer-controlled type
The computer-controlled engine detects the intake air volume with the air flow meter and the intake manifold pressure with the turbo pressure sensor, and increases the maximum fuel injection volume with the engine ECU. (The fuel injection volume is determined by the injection duration.) Although the illustration on the left shows the diesel engine, the fuel injection volume is increased in proportion to the volume of the intake air in a gasoline engine.