Methods and systems are provided for detecting air-fuel ratio imbalances across all engine cylinders. In one example, a method (or system) may include indicating cylinder imbalance based on each of the exhaust air-fuel ratio, exhaust manifold pressure, and cylinder torque weighted by a confidence factor, where in the confidence factor is determined based on operating conditions.

An anomaly determination unit includes an EGR amount acquisition section configured to acquire an actual amount of an EGR amount, which is a flow rate of EGR gas; an estimation amount computation section configured to compute an estimated amount of the EGR amount based on a working gas pressure, which is a pressure of working gas in which the EGR gas and intake air are mixed, an EGR temperature, which is a temperature of the EGR gas immediately upstream of an EGR valve, an EGR pressure, which is a pressure of the EGR gas immediately upstream of the EGR valve, and an opening degree instruction value for the EGR valve; and a determination section configured to determine the presence or absence of an anomaly in the EGR valve based on the divergence between the actual amount of the EGR amount and the estimated amount.

Control techniques for a turbocharger of an engine utilize a wastegate valve configured to divert exhaust gas from a turbine of the turbocharger that is rotatably coupled to a compressor of the turbocharger. A controller is utilized to obtain a torque request for the engine, determine a target compressor power based on the engine torque request, determine a normalized target turbine power based on the target compressor power, determine a target position for the wastegate valve based on the normalized target turbine power and a normalized exhaust flow, and actuate the wastegate valve to the target position. Such control techniques involve the actual calculation of much less intermediate parameters, such as target turbine pressure ratio, which results in more efficient calibration and implementation.

Methods and systems are provided for estimating an engine exhaust pressure based on outputs from an exhaust oxygen sensor. In one example, a method may include estimating an exhaust pressure of exhaust gas flowing through an engine exhaust passage based on a difference between a first output of an oxygen sensor disposed in the exhaust passage and a second output of the oxygen sensor and then adjusting engine operation based on the estimated exhaust pressure. As one example, both the first and second outputs may be taken while operating the sensor in a variable voltage mode, after increasing a reference voltage of the oxygen sensor from a lower, first voltage to a higher, second voltage.

Methods and systems are provided for estimating exhaust pressure based on an exhaust air/fuel ratio sensor. In one example, a method may comprise estimating an exhaust pressure based on periodic waveform outputs of an exhaust air/fuel ratio (AFR) sensor, and adjusting at least one engine operating parameter based on the estimated exhaust pressure. The exhaust pressure may be estimated based on one or more of the standard deviation and frequency of the periodic waveform outputs.

A driving device for driving a vehicle includes an internal combustion engine, a feed line for feeding combustion air to the internal combustion engine, a discharge line for discharging exhaust gases from the internal combustion engine, a charge air cooler that is arranged in the feed line for cooling the combustion air, and a recirculation line branching off the discharge line for recirculating the exhaust gas from the discharge line into the feed line. The recirculation line includes a bypass line that the exhaust gas can be fed to the internal combustion engine through the charge air cooler and/or bypassing the charge air cooler.

A variable geometry turbocharger control method and system for an engine air system with a variable geometry turbocharger having adjustable vanes. The method includes monitoring engine parameters; generating engine state estimates using an engine observer model; generating measured engine states based on the monitored engine parameters; computing observer error based on the differences between the measured and modeled engine states; generating model correction factors; and generating commands for adjusting the vane positions of the variable geometry turbocharger. An inverse engine observer model can generate the desired variable geometry turbocharger vane positions. The method can include generating feedback actuator commands in generating the desired variable geometry turbocharger vane positions. The correction factors can include fresh air, EGR and/or turbine mass flow correction factors.

Methods and systems are provided for estimating exhaust pressure based on an exhaust air/fuel ratio sensor. In one example, a method may comprise estimating an exhaust pressure based on periodic waveform outputs of an exhaust air/fuel ratio (AFR) sensor, and adjusting at least one engine operating parameter based on the estimated exhaust pressure. The exhaust pressure may be estimated based on one or more of the standard deviation and frequency of the periodic waveform outputs.

Methods and systems are provided for detecting air-fuel ratio imbalances across all engine cylinders. In one example, a method (or system) may include indicating cylinder imbalance based on each of the exhaust air-fuel ratio, exhaust manifold pressure, and cylinder torque weighted by a confidence factor, where in the confidence factor is determined based on operating conditions.

An engine system and method for improving sampling of a port throttle pressure sensor. In one example, the port throttle pressure sensor is sampled a plurality of times during a cylinder cycle and different engine operating conditions are determined from selected samples. The system and method may improve engine air-fuel control as well as engine diagnostics.