Some Problems in the Improvement of Measurement of Transient Emissions

A numerical technique, aimed to the reconstruction of the analog output of an analyzer during continuous exhaust gas analysis, is presented. To this purpose the system composed by sample line and analyzer is described as a discrete Linear Time Invariant system with Finite Impulse Response. This technique has been tested on the reconstruction of the continuous emission measurements of diluted exhaust, obtained during a driving cycle acted on a chassis dynamometer. A comparison with the results obtained with CVS bag analysis has been made. The air/fuel ratio during the test cycle has been evaluated and compared with the signal of an oxygen sensor. An attempt to evaluate the emission indices in the transients has been also made, comparing the results of reconstructed and non reconstructed signals.