Abstract: Systems and methods for operating an internal combustion engine that includes an oxygen sensor are described. In one example, a voltage that is applied to a heating element of an oxygen sensor is integrated to determine a resistance of the heating element. The resistance of the heating element is the basis for adjusting voltage applied to the heating element during subsequent engine starts.

Abstract: Methods and systems are provided for a battery supplying power to an exhaust oxygen sensor heater. In one example, a method may include estimating a power delivered to the heater during heating of the sensor and in response to a power delivered from a battery being lower than a threshold, adjusting a battery charging strategy prior to an immediately subsequent engine start.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual transient and steady-state noise sources to an engine background noise level. The contributions of the transient and steady-state individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be determined via adjusting timing of a knock window or timing of the individual noise sources.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system. The method and system may increase opportunities to learn one or more engine knock background noise levels via changing poppet valve timing and/or fuel injection timing. The method and system may also improve knock detection if knock sensor degradation is suspected.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.

Abstract: Methods and systems are provided for warming vehicle tires prior to a vehicle launch event. In one example, a method may include, in response to an initiation of a burn out event while locking non-driven wheel brakes, adjusting a spinning of driven wheels based on vehicle performance parameters measured during a previous vehicle launch. In this way, a vehicle controller may control the tire warming to increase tire traction while reducing tire wear.

Abstract: Methods and systems are provided for adjust spark timing based on ambient humidity and transient tip-in parameters. In one example, a method may include, during a tip-in, retarding spark timing based on each of ambient humidity, peak air charge, and rate of change of air charge. As such, the spark timing retard may be higher at lower humidity levels, and the spark timing retard may be lower at higher humidity levels.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual transient and steady-state noise sources to an engine background noise level. The contributions of the transient and steady-state individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders. The contributions of individual noise sources may be determined when engine cylinders are deactivated.

Abstract: Systems and methods for operating an engine that includes a compression ratio linkage for adjusting engine compression ratio are described. The systems and methods provide different ways of changing a compression ratio of an engine based on forecast or anticipated engine operating conditions. In one example, the forecast or anticipated engine operating conditions may include a forecast or anticipated transmission gear shift.

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 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 estimating an actual compression ratio of an engine cylinder based on the electric current applied to an actuator of the associated variable compression ratio mechanism. The compression ratio is estimated as a function of both a value and a location, relative to cylinder piston position, of a peak holding current applied by an electric motor on the actuator to maintain the actuator at a commanded compression ratio setting. In this way, the vehicle control system may more accurately infer the current actual compression ratio of each cylinder.

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 adjusting engine compression ratio (CR) and spark timing to attain particulate filter (PF) regeneration temperature. In one example, a method may include, in response to PF load reaching a threshold and PF temperature being lower than the PF regeneration temperature, lowering the CR and then selectively adjusting spark timing based on an estimated residual gas fraction (RGF) at the lower CR.

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: Systems and methods for operating an engine that includes a compression ratio linkage for adjusting engine compression ratio are described. The systems and methods provide different ways of diagnosing the presence or absence of engine misfire in response to engine operating regions that may be more or less prone to torsional engine crankshaft vibration. In one example, engine misfire may be determined responsive to force applied to an engine compression ratio changing linkage.

Abstract: Methods and systems are provided for adjusting a compression ratio of a variable compression ratio (VCR) engine during engine shutdown. In one example, a method (or system) may include actuating a VCR mechanism from a higher compression ratio setting to a lower compression ratio setting after a last combustion event and before the engine spins down to rest. In this way, engine shake, for example, due to piston bounce-back, may be reduced.

Abstract: Methods and systems are provided for adjusting engine compression ratio (CR) and spark timing to attain particulate filter (PF) regeneration temperature. In one example, a method may include, in response to PF load reaching a threshold and PF temperature being lower than the PF regeneration temperature, lowering the CR and then selectively adjusting spark timing based on an estimated residual gas fraction (RGF) at the lower CR.