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Dual fuel injection systems, like PFI+DI (port fuel injection + direct injection system) are being increasingly used in gasoline engine applications to increase the engine performance, fuel efficiency and reduce emissions. At a given engine operating condition, the air/fuel error is a function of the fraction of fuel injected by each of the fuel systems. If the fraction of fuel from each of the fuel system is changed at a given operating condition, the fuel system error will change as well making it challenging to learn the fuel system errors. This paper aims at describing the adaptive fueling control algorithm to estimate the fuel error contribution from each individual fuel system. Considering the fuel injection system slope errors to be the significant cause for air-fuel errors, a model structure was developed to calculate the fuel system adaptive correction factor as a function of changing fraction of fueling between the fuel systems.

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.

Engine Mapping is usually performed under nominal conditions which include a humidity level of 8 g/Kg. Customers driving at different humidity conditions (which may range from 1 g/Kg in dry and colder climates and up to 35 g/Kg as in tropical climates) may experience a degraded performance due to the errors in engine torque estimation provided by the ECU. The torque estimation error interacts with many other features that affect drivability, such as the peak performance of the engine, transmission shift quality, etc. This paper extends the investigation in Part-1 by analyzing and quantifying the torque estimation error that may result in certain customer use cases at high humidity conditions, due to the mismatch between calibrated and actual conditions. The analysis is mainly performed for Speed-Density systems (MAP sensor based) but the effect of mass air flow sensor (MAF sensor) based systems is also briefly considered.

Engine Mapping is usually performed under nominal conditions which include a humidity level of 8 g/Kg. Customers driving at different conditions (which may range from 1 g/Kg in colder and dry climates and up to 35 g/Kg as in tropical climates) may experience less-than-optimal engine combustion which results in reduced onroad fuel economy. Humidity has an EGR-equivalent effect, and measuring it will correct the spark timing, mainly at Maximum Brake Torque (MBT) and borderline conditions, and claim back some of those losses. This paper aims at quantifying the small fuel economy benefits associated with on-board humidity measurement for certain customer use cases at high humidity conditions. Dyno data was collected for a Ford 2.3L GTDI engine at three speed load points, and intake air humidity was varied between 20% and 80% relative humidity. The effect of humidity compensation on spark timing, combustion phasing, knock, and consequently on overall engine efficiency was analyzed.

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.

Lean NOx Traps are used to treat the NOx emissions from lean-burn engines by storing the NOx under lean conditions and reducing the NOx during periodic rich excursions. However, sulfur poisons the adsorption sites of the traps. The sulfur can be removed from the NOx trap by operating rich at high temperatures for several minutes. This results in the release of some SO2 but also large quantities of H2S, which is a source of customer dissatisfaction that must be reduced or eliminated. This paper describes the use of a nickel-containing catalyst and air/fuel control to maximize the release of SO2 and minimize the emissions of H2S during the desulfation of a lean NOx trap. We present laboratory and vehicle data with a nickel-containing catalyst located downstream of a lean NOx trap during desulfations of the trap. The nickel effectively reduced the emissions of H2S during the desulfation while improving the robustness to fluctuations in the air/fuel control.