Abstract: A method of monitoring exhaust gas flow through an exhaust system of an internal combustion engine comprising the steps of generating a flow efficiency value (KE), comparing the flow efficiency value to a reference efficiency value, and if the reference efficiency value is exceed by a predetermined amount, then setting a flow fault indicator flag. In one aspect of the invention, the flow efficiency value is generated as a ratio of the magnitude of the exhaust gas flow restriction, and the mass flux through the engine. The magnitude of the exhaust gas flow restriction is represented by the pressure drop across the exhaust system, and the mass flux through the engine is determined as a function of the mass airflow rate and exhaust gas density. The resulting flow efficiency value (KE) is a non-dimensional parameter that characterizes the level of restriction in the exhaust system independent of the engine operating conditions.

Abstract: A system and method of normalizing an emissions threshold catalytic brick 302 without a mileage accumulation step is used to evaluate an on-board diagnostics for an exhaust system. The method comprises normalizing a emissions threshold catalytic brick 302 by placing the emissions threshold catalytic brick 302 in a exhaust gas circulation oven, such as a retort chamber 300, immediately after an oven-aging and chemical aging process wherein the emissions threshold catalytic brick 302 is saturated with a exhaust gas at a predetermined rate and at a predetermined temperature for a specified period of time based upon the characteristics desired for the emissions threshold catalytic brick. Additionally, a method for evaluating on-board diagnostics of an exhaust system using an emissions threshold catalytic brick 302 based upon the characteristics of the exhaust system that it will be placed in is also contemplated.