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Presented in this paper is an on-line method for estimating the sulfation levels within a lean NOx trap (LNT). Sulfur poisoning plays a major role in the reduction of oxygen and NOx storage capacity in an LNT. Indicators of LNT degradation are LNT NOx absorption efficiency and capacity. The estimation of LNT oxygen and NOx storage capacity is an on-line method of monitoring LNT NOx absorption efficiency and capacity. The estimation provides information regarding the sulfation level of the LNT. This estimate may be used in conjunction with lean burn strategies to initiate an LNT sulfur purging mechanism and maintain maximum fuel economy. In addition, the estimation of LNT oxygen and NOx storage capacity may be used for on-board diagnostics, LNT NOx absorption efficiency estimation, NOx purge fuel estimation, and many other applications.

Low Pressure (LP) Exhaust Gas Recirculation (EGR) promises fuel economy benefits at high loads in turbocharged SI engines as it allows better combustion phasing and reduces the need for fuel enrichment. Precise estimation and control of in-cylinder EGR concentration is crucial to avoiding misfire. Unfortunately, EGR flow rate estimation using an orifice model based on the EGR valve ΔP measurement can be challenging given pressure pulsations, flow reversal and the inherently low pressure differentials across the EGR valve. Using a GT-Power model of a 1.6 L GDI turbocharged engine with LP-EGR, this study investigates the effects of the ΔP sensor gauge-line lengths and measurement noise on LP-EGR estimation accuracy. Gauge-lines can be necessary to protect the ΔP sensor from high exhaust temperatures, but unfortunately can produce acoustic resonance and distort the ΔP signal measured by the sensor.

The automotive industry has been witnessing a major shift towards downsized boosted direct injection engines due to diminishing petroleum reserves and increasingly stringent emission targets. Boosted engines operate at a high mean effective pressure (MEP), resulting in higher in-cylinder pressures and temperatures, effectively leading to increased possibility of abnormal combustion events like knock and pre-ignition. Therefore, the compression ratio and boost pressure in modern engines are restricted, which in-turn limits the engine efficiency and power. To mitigate conditions where the engine is prone to knocking, the engine control system uses spark retard and/or mixture enrichment, which decrease indicated work and increase specific fuel consumption. Several researchers have advocated water injection as an approach to replace or supplement existing knock mitigation techniques.