Abstract:
Methods and systems are provided for regulating air flow through a charge air cooler. In one example, an air flow regulating element may be positioned in a tank of the charge air cooler, the air flow regulating element including a cylindrical barrel valve rotatable about a rotational axis to adjust air flow through cooling tubes in the charge air cooler. A position of the barrel valve may be based on a mass air flow rate and/or a temperature at an outlet of the charge air cooler.
Abstract:
Methods and systems are provided for determining changes in a flow area of an exhaust gas recirculation (EGR) valve for EGR flow estimates due to a change in temperature difference between a stem and body of the EGR valve. In one example, a method includes adjusting an EGR valve based on an estimate of EGR flow, the EGR flow estimated based on a pressure difference across the EGR valve and an adjusted valve flow area. The adjusted valve flow area may be based on the temperature difference between the stem and body of the EGR valve.
Abstract:
Methods and systems are provided for expediting purging of LP-EGR from an air intake system during conditions of decreasing engine load. During a tip-out, an EGR valve is closed while the engine is shifted to a VDE mode of operation to improve engine tolerance to EGR at lower engine loads and until the EGR is sufficiently purged. A non-VDE mode is resumed if higher engine loads are restored, else, a deceleration fuel shut-off mode is selected if the tip-out continues to zero load.
Abstract:
Methods and systems are provided for controlling LP-EGR flow in a variable displacement engine. In one example, a method may include providing a higher fixed LP-EGR percentage relative to a total intake air flow during a VDE mode, and providing a lower fixed EGR percentage relative to the total intake air flow during a non-VDE mode. Further, during a tip-out when operating in the VDE mode at a load below a threshold, transitioning out of the VDE mode after transitioning the LP-EGR from the higher fixed percentage to the lower fixed percentage.
Abstract:
Methods and systems are provided for reducing exhaust energy delivered to a turbine of a turbine-generator coupled to a split exhaust engine system in order to reduce turbine over-speed conditions and/or to reduce a generator output. In one example, a method may include retarding a first timing of a first exhaust valve utilized to deliver a blowdown portion of exhaust energy to the turbine, and/or advancing a second timing of a second exhaust valve utilized to deliver a scavenging portion of exhaust energy to an exhaust catalyst in response to a turbine speed greater than a threshold speed.
Abstract:
Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor during selected engine no-fueling conditions. The learned zero point is used to infer EGR flow and accordingly adjust EGR valve control. In addition, EGR valve leakage is diagnosed based on the zero point learned during a DFSO adaptation relative to a zero point learned during an idle adaptation.
Abstract:
Methods and systems are provided for using compressor recirculation flow via a venturi to enhance low pressure EGR flow. The opening of a compressor recirculation valve can be adjusted based on EGR flow demand to recirculate cooled compressed air through a venturi while generating vacuum for drawing EGR. The approach allows for concurrent EGR control and surge control.
Abstract:
Methods and systems are provided for adjusting charge motion control devices coupled to a series of cylinders organized into cylinder groups, one of the cylinder groups including a dedicated EGR cylinder group wherein the cylinders are the only engine cylinder routing exhaust to an engine intake. In one example, a first cylinder group may be a dedicated cylinder group recirculating exhaust to the intake manifold while a second cylinder group may be a non-dedicated cylinder group routing exhaust to a turbine. A method may include adjusting a first charge motion control device coupled to the first cylinder group and a second charge motion control device coupled to the second cylinder group to vary a charge motion level between the first and second cylinder groups.
Abstract:
Methods and systems are provided for reducing EGR estimation errors during lean engine operating conditions. During lean engine operation, EGR is disabled if the estimated exhaust air-fuel ratio becomes leaner than a lean threshold. The lean threshold is adjusted based on an upper limit of EGR errors that may be tolerated by the engine at a given engine speed and load.
Abstract:
Methods and systems are provided for expediting EGR purging in a hybrid vehicle during transient operations, such as tip-out to lower load conditions. In response to decreasing engine torque demand, engine fueling is disabled and a motor is used to spin the engine unfueled until a desired LP-EGR rate is achieved. Alternatively, engine operation is maintained with EGR disabled until the desired LP-EGR rate is achieved, and the excess engine torque generated is stored in a system battery.