Page 287 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Chapter 2.5

Ford Motor Co. - Ford France SA - Ford Werke AG - Ford

Motor Co. Canada - Ford Motor Co. Ltd.

The method of W09420738 (1994) is applied when the engine operates in a cruising or steady
state mode and comprises the following steps:
1) operating the engine in a cruising or steady state mode
2) perturbing the air/fuel ratio of the engine to increase hydrocarbons and carbon monoxide of
the exhaust gases without causing engine misfire i.e. by enriching the air/hel mixture by 5
to 10 percent above stoichiometry for a duration between 10 and 30 seconds. This is
sufficient to cause a readily sensed temperature increase without affecting the output
power and torque of the engine
3) adding air to the exhaust gases prior to their reaching the catalytic converter
4) monitoring changes in the temperature of the exhaust gases in response to this perturbation
by
a) measuring the rise in average temperature of the catalytic converter after
the lapse of at least one time interval following the step change of the
constituents of the exhaust gases, or
b) measuring the rate of rise of the average temperature of the catalytic
converter after the lapse of at least one time interval following the step
change of the constituents of the exhaust gases, or
c) comparing the temperature at different volume elements of the catalytic
converter spaced from one another in the direction of flow of the exhaust
gases after the lapse of at least one time interval following the step
change of the constituents of the exhaust gases

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