Page 269 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Emitec Gesellschafi fir Emissionstechnologie - Dr. Ing. H.c.F. Porsche AG 251

values with specified desired values for the second operating condition. The second
operating condition can be
a) a coasting operation or
b) an idling operation of the internal-combustion engine.
The ignition of at least one cylinder is switched off temporarily when the engine operates
under coasting or idling condition
3) acting upon the exhaust gas catalytic converter with an exhaust gas pulse which does not
correspond to the second operating condition existing during the second time period and
which produces one of an under or over-stoichiometric engine operation. The pulse is
generated with a brief additional injection of fuel in the cylinders
4) sensing values of at least one first parameter of the exhaust gas train which changes as a
result of the exhaust gas pulse. The parameter can be
a) a temperature measured in the exhaust train or
b) a concentration of the exhaust gases measured by a h sensor
5) forming at least one first parameter difference between a parameter value (e.g. rotational
speed or load) sensed before or while the exhaust gas catalytic converter is acted upon by
the exhaust gas pulse and its value atter the exhaust gas catalytic converter is acted upon by
the exhaust gas pulse, and comparing the first parameter difference with a specified first
desired difference range, and continuing the process if the first parameter difference is
within the first parameter desired difference range
6) comparing the value of the first parameter with a specified desired value and by a
subsequent comparison of the thus determined change with a desired change range