A method for controlling an engine having an exhaust system with a secondary air device.

摘要

The method comprises estimating an air amount introduced into the exhaust from the secondary air device 209. Said estimation based on at least one operating condition (for example a pump voltage, an ambient temperature, an ambient pressure, an exhaust pressure, an engine air flow or an exhaust gas a/f mix). Said estimation may be further based on an adaptive learned parameter. The estimation is then adjusted based on a measured exhaust gas condition and a fuel injected amount injected into the engine based on the adjusted estimation. In an embodiment of the invention a correction to the estimated air amount is based upon the measured exhaust gas condition, a desired gas mixture a/f ratio. The fuel injection amount injected is then based on this correction. In a further embodiment comprising an exhaust gas sensor 80 (for example an exhaust gas oxygen sensor) the engine is operated in a first mode if the sensor 80 is operating, and in a second mode if the sensor 80 is not operating. The system may comprise a catalyst 20 in the engine exhaust, downstream of the sensor 80.