Emissions control based on the status of one or more after treatment devices

摘要

A method or control system to calibrate engine out NOx emissions 18 from a diesel engine 10 comprising deriving the status of one or more after treatment devices such as a diesel particulate filter (DPF), a selective catalytic reduction catalyst (SCR), or a lean NOx trap (LNT); and controlling one or more engine parameters to increase or decrease engine out NOx 18 emissions based on the status of the or each after treatment device 14. Deriving the status of the after treatment devices may include measuring or estimating fuel penalty levels, sulphur poisoning, levels of fuel in oil, storage efficiency of a NOx storage device, additive reservoir levels and/or emissions of carbon monoxide or hydrocarbon products. The invention provides a method of prolonging the working life of some or all of the after treatment devices whilst still meeting emissions targets.