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Time-resolved concentrations of formaldehyde and acetaldehyde in the exhaust gas have been investigated during transient motor operation, such as sudden change of speed and load, misfiring and switching off the fuel mixture control. To this purpose, a new laser mass spectrometer has been applied which is capable of measuring the concentrations of individual exhaust compounds with 1 ppm sensitivity at a sampling rate of 50 Hz corresponding to a sampling period of 20 ms. At sudden speed changes, high concentrations of aldehydes are observed, in particular during the phase of decreasing speed, i.e. after closing the throttle valve.

A new multicomponent exhaust gas analyzer has been applied to investigate the time-resolved concentrations of the aromatic hydrocarbon exhaust components benzene, toluene, xylene, trimethyl benzene under dynamic engine operation, such as sudden change of speed and load, misfiring and switching off the fuel mixture control. The analyzer consisting of a compact laser mass spectrometer is capable of measuring the concentrations of the individual aromatic hydrocarbon compounds simultaneously with 1 ppm sensitivity at a sampling rate of 50 Hz corresponding to a sampling period of 20 ms. High concentration peaks are observed for these substances at instationary motor operation. However, whereas the real-time concentrations of toluene, xylene, and trimethyl benzene show equal dependence on motor speed and load a different behavior has been observed for benzene even during the emission phase of single combustion cycles.

A sensitive laser mass spectrometer has been developed for fast multicomponent automotive exhaust analyses. The system is particularly appropriate for working at dynamic motor test stands and provides the following features: Detection of all individual organic and inorganic exhaust constituents with 1 ppm sensitivity Simultaneous detection of up to 12 selectable exhaust compounds with a measurement rate of up to 100 Hz 2 ms time precision relative to the motor phase - Ruggedness for operation at engine test facilities This system has been used at a motor test facility to investigate the emissions of aromatic hydrocarbons benzene, toluene, xylene, and of nitrogen oxide in stationary and dynamic engine operation. These measurements demonstrate some of the capabilities of the analysis system to obtain fundamental information about the combustion processes and about processes in the exhaust pipe.

A new analytical method for the automobile industry has been developed using a pulsed tunable laser system and a Reflectron time-of-flight mass spectrometer. The goal was to achieve the following conditions: High time resolution (〈100ms), high sensitivity (down to 1 ppm), high accuracy (10%) and applicability to most exhaust emission components. The main problem is the large number of components with very different and fast varying concentrations. For a preliminary list of 25 exhaust emission components, all necessary parameters have been determined. First results obtained from a real exhaust gas sample will be presented.