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In closed evaporation control systems, the purging air flow through the active carbon canister is mixed with the intake air flow. In order to avoid degradation of the λ control and the pollution emission levels, the purged hydrocarbons must be evenly distributed among the cylinders and mixed as thoroughly as possible with the intake air. Based on the purge charactisctics of standard carbon canisters and on the HC levels in a fully charged carbon canister, and using a 4-cylinder sixteen-valve engine, the operating frequency of the canister purge valve and the inlet point of the purge flow into the intake manifold were varied, using n-butane as the hydrocarbon. The measurements taken for HC emissions and the voltages of the lambda probes in the exhaust manifold showed that the inlet point, the valve operating frequency and the microdosing behavior of the valve significantly affect mixture and engine's HC emissions.

In closed crankcase ventilation systems, the oil-loaded blow-by is fed back into the intake air. Due to the incomplete combustion of the oil, it produces higher particle and hydrocarbon emissions, a reduced catalytic converter lifetime, and deposits in the intake manifold. A survey of state-of-the-art ventilation systems is given. The procedures for measuring the ventilation aerosol on the engine and the requisite measuring instruments, especially for determining the particle size distribution, are described. The results of the measurements prove the usually unsatisfactory separation efficiency of the production parts. A significant increase in separation efficiencies can be obtained by using nonwovens. To optimize the construction concerned, several measurements with varied separation parameters of the nonwovens were conducted on an oil mist test bench.