Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be determined via two filters that are constructed in parallel. Output of the two filters may be the basis for determining the presence or absence of engine knock.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Fuel injection timing and cylinder firing patterns may be adjusted to maintain engine background noise levels so that the presence or absence of engine knock may be more reliably detected. Further, select variable engine displacement modes may be avoided so that engine background noise level changes may be reduced to improve engine knock detection.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are deactivated to determine the presence or absence of engine knock. Additionally, engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are reactivated such that the engine operates with all cylinder combusting so that the possibility of indicating knock when knock is not present may be avoided.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine background noise levels for detecting engine knock may be the basis for determining whether or not the engine is operating in a cylinder deactivation mode. Further, select variable engine displacement modes may be avoided so that engine background noise level changes may be reduced to improve engine knock detection.

Abstract: Methods and systems are provided for accurately determining the composition of a knock control fluid using sensors already present in the engine system. An intake or an exhaust oxygen sensor is used to estimate the water and the alcohol content of a knock control fluid that is direct injected into an engine cylinder responsive to an indication of abnormal combustion. A change in the pumping current of the oxygen sensor due to the water content of the knock control fluid is distinguished from a change in the pumping current of the oxygen sensor due to the alcohol content of the knock control fluid.

Abstract: Methods and systems for diagnosing operation of a compression ratio adjusting mechanism are described. In one example, an output of a pressure sensor is sampled and an assessment of the engine's present compression ratio is made after adjusting sampling of the output. Engine operation may be adjusted responsive to whether or not degradation of the compression ratio adjusting mechanism is indicated.

Abstract: Methods and systems are provided for determining a dilution of recirculated gases, including blowthrough air, combusted exhaust gas, and fuel vapor, in a split exhaust engine. In one example, the dilution rate may be calculated using a steady state model based on temperature measurements from an intake region of the engine. The steady state model may be further used in combination with a feedforward model adapted to estimate engine dilution during engine transients as a correction factor.

Abstract: Methods and systems are provided for determining a dilution of recirculated gases, including blowthrough air, combusted exhaust gas, and fuel vapor, in a split exhaust engine. In one example, the dilution rate may be calculated using a feedforward model that includes determining a pressure differential across a region in an intake passage, mapped engine parameters such as gas temperature, and exhaust valve timing. Engine operations such as spark advance and fuel injection may be adjusted according to the modeled rate to reduce engine knock and improve combustion efficiency.

Abstract: A vehicle control method includes, by a controller, while an engine is auto-stopped and an electric parking brake is engaged, auto-starting the engine without releasing the electric parking brake responsive to application of an accelerator pedal less than a predefined amount, and auto-starting the engine and releasing the electric parking brake responsive to application of the accelerator pedal greater than the predefined amount. The method also includes comprising auto-stopping the engine and engaging the electric parking brake responsive to vehicle speed being less than a predefined threshold speed.

Abstract: Methods and systems are provided for accurately determining the composition of a knock control fluid using sensors already present in the engine system. An intake or an exhaust oxygen sensor is used to estimate the water and the alcohol content of a knock control fluid that is direct injected into an engine cylinder responsive to an indication of abnormal combustion. A change in the pumping current of the oxygen sensor due to the water content of the knock control fluid is distinguished from a change in the pumping current of the oxygen sensor due to the alcohol content of the knock control fluid.

Abstract: Examples are provided for estimating an amount of fuel in an engine oil and an effect of the fuel on a gas sensor. In one example, an apparatus may include an analyzer to analyze an engine fluid and a computing device operably coupled to the analyzer, the computing device storing non-transitory instructions executable to determine fuel dilution in engine oil based on speciation of hydrocarbons in fuel in the engine oil determined based on output received from the analyzer.

Abstract: A method of controlling a stop-start vehicle includes, in response to an engine being in an auto-stopped condition and a signal indicative of a driver exiting the vehicle, maintaining the engine in the auto-stopped condition. The method additionally includes securing vehicle wheels against rotation and reducing a convenience feature power consumption.

Abstract: Methods and systems are provided for characterizing aged fuel, which loses volatility over time. In one example, a method may include estimating a fuel vapor pressure during an engine cold start using a pre-determined fuel distillation curve and adjusting one or more combustion parameters based on the estimated fuel vapor pressure. Because the fuel vapor pressure directly relates to the fuel volatility, adjusting the one or more combustion parameters based on the estimated fuel vapor pressure may reduce aged fuel-related engine performance degradation, such as hesitation and emissions during cold start.

Abstract: Sensors in a vehicle detect execution of a sign language symbol. The sign language symbol invokes a vehicle interface function. In some embodiments, the sign language symbol is an ASL sign. Sensors include three-dimensional optical, ultrasonic, or other sensors. The locations of targets (fingertips, knuckles, palm, etc.) are detected in the individual outputs of the sensors. The locations of targets determined from the outputs of multiple sensors may be associated with one another and filtered, such as using an RBMCDA algorithm and Kalman filtering. The system may be calibrated to detect each symbol by measuring the target locations with the user executing the each symbol.

Abstract: Methods and systems are provided for adjusting engine operation based on estimated vaporized and condensed portions of water injected during a water injection event. In one example, a method may include injecting an amount of water into the intake manifold in response to engine conditions and inferring vaporized and condensed portions of the injected water based on the injected amount and a change in manifold temperature following the injection. Further, the method may include adjusting water injection and engine operating parameters in response the evaporated and/or condensed portion of water.

Abstract: Methods and systems are provided for accurately determining the composition of a knock control fluid using sensors already present in the engine system. An intake or an exhaust oxygen sensor is used to estimate the water and the alcohol content of a knock control fluid that is direct injected into an engine cylinder responsive to an indication of abnormal combustion. A change in the pumping current of the oxygen sensor due to the water content of the knock control fluid is distinguished from a change in the pumping current of the oxygen sensor due to the alcohol content of the knock control fluid.

Abstract: Methods and systems are provided for conducting measurements of relative humidity using an ultrasonic sensor. In one example, a plurality of ultrasonic signals having different frequencies are transmitted from a single sensor, and attenuation values of reflected signals are determined only for those signals determined to have the same transit time from transmission to receipt, and where frequency of the plurality of ultrasonic signals may be changed responsive to an indication that the signals may be below a signal-to-noise threshold. In this way, by determining a difference between attenuation values between pairs of signals, where the signals comprise different frequencies and where the signals comprise the same transit times, relative humidity may be accurately determined.

Abstract: Methods and systems for diagnosing operation of a compression ratio adjusting mechanism are described. In one example, an output of a pressure sensor is sampled and an assessment of the engine's present compression ratio is made after adjusting sampling of the output. Engine operation may be adjusted responsive to whether or not degradation of the compression ratio adjusting mechanism is indicated.

Abstract: Methods and systems are provided for accurately determining the composition of a knock control fluid using sensors already present in the engine system. An intake or an exhaust oxygen sensor is used to estimate the water and the alcohol content of a knock control fluid that is direct injected into an engine cylinder responsive to an indication of abnormal combustion. A change in the pumping current of the oxygen sensor due to the water content of the knock control fluid is distinguished from a change in the pumping current of the oxygen sensor due to the alcohol content of the knock control fluid.

Abstract: Methods and systems are provided for conducting measurements of relative humidity via the use of an ultrasonic sensor. In one example, the ultrasonic sensor for conducting the relative humidity measurement is selected from a plurality of ultrasonic sensors positioned at various locations on the vehicle, and where the selecting is accomplished in some examples via the use of one or more onboard cameras configured to identify suitable objects that are stationary with respect to the vehicle. In this way, robustness and accuracy of relative humidity measurements may be improved, lifetime of individual ultrasonic sensors may be extended, and vehicle operating conditions that depend on accurate relative humidity measurements may be improved.