The engine gas flowing Superflow 600 flowbench at Coltec:-

thumb A flowbench is a device to measure airflow resistance through a mechanical component such as a cylinder head or intake manifold. The result can be expressed as a Coefficient of Discharge of the component or as an airflow rate.
SuperFlow Flowbenches are ratiometric measuring devices. Volumetric flow is determined by the ratio of the pressure drop through the component under test to the pressure drop across a calibrated orifice. This measurement principle ensures results which are independent of atmospheric conditions.
Most Flowbenches can be used in either Intake or Exhaust mode. Virtually every engine component which is in the inlet air or exhaust gas path can be tested and improved on a Flowbench.