Initially, Bronkhorst supplied a set of ten mass flow controllers (EL-FLOW Prestige), for supplying components into the artificial exhaust gas composition. This to simulate a certain working point. Each specific flow controller is meant for a component that may be present in the car exhaust gas (N2, O2, CO, CO2, NO, hydrocarbons, sulphur compounds etc.) These individually generated gas flows enter a mixing chamber, and when the flow is stable, it is fed to the lambda probe.
With the EL-FLOW Prestige devices it is possible to incorporate small amounts of gas into the exhaust gas mixture. Several ranges were used, and the mass flow controllers were calibrated from 9 millilitres per minute to 20 litres (N2 gas) per minute.
In a later stage, a second set of ten EL-FLOW Prestige mass flow controllers was supplied, to simulate another working point in parallel. While the lambda probe was tested using an exhaust gas composition from the first train, the composition of the second train was premixed in the second mixing chamber. This made it possible to changeover from one working point to another, by physically (dis)connecting each of the mixing chambers from the lambda probe, saving time.
This solution was chosen because of high flexibility, and because of high accuracy. The setup needed to be flexible, as the real working points (compositions) do indeed vary. But also to be prepared for different compositions in the future if compositions or engine effectiveness may change..