FIGURE 54-12
An engine equipped with a turbocharger and intake air intercooler.

Turbocharging increases volumetric efficiency (VE) and reduces nitrogen oxides. As a result, more power can be derived from smaller displacement engines with greater fuel economy. It is important to remember that VE is the amount of air taken into the cylinder on the intake stroke, or intake port, opening in relation to the space in the cylinder. Turbochargers act as compressors and pump more air into the cylinder; therefore, through increased airflow, the flow pattern, or swirl, is also improved, combustion efficiency improves, and the engine emissions are lowered. Intake air intercoolers enhance the benefits of the turbocharger by lowering air temperatures entering the combustion chamber Figure 54-12. Cooler air is denser, which means more can enter the combustion chamber by volume. Since the intercooler lowers combustion air temperature, it lowers nitrogen oxide emissions.