An outlet of a sub passage that returns measured gas, which has passed through a flow sensor, from the sub passage to a main passage opens on an outer wall of a housing toward a downstream side in a reference direction. The outer wall of the housing includes a protrusion on the downstream side of the outlet. When the outlet and the protrusion are projected onto a projection plane perpendicular to the reference direction, the outlet and the protrusion partly overlap with each other on the projection plane. A relationship of 1<2<90 is satisfied, where: 1 is assumed to be an angle formed between a direction from an upstream end to a top, and the reference direction; and 2 is assumed to be an angle formed between a direction from a downstream end to the top, and the reference direction.

A sensor system is provided for determining at least one parameter of a fluid medium flowing through a channel structure, e.g., an air mass flow of an internal combustion engine. The sensor system has a sensor housing, e.g., a plug-in sensor that is introduced or can be introduced into a flow tube, in which the channel structure is formed, and at least one sensor chip, situated in the channel structure, for determining the parameter of the fluid medium. The sensor housing has an inlet into the channel structure, oriented opposite a main direction of flow of the fluid medium, and an outlet from the channel structure. The channel structure includes a main channel and a measurement channel. The measurement channel branches off from the main channel. The sensor chip is in the measurement channel. The main channel and the measurement channel discharge together into the outlet from the channel structure.

A method and system for estimating air mass per cylinder of an internal combustion engine is provided. An output signal from a MAF sensor is digitally processed to provide an estimate air mass per cylinder (APC). The system includes the MAF sensor; a data acquisition unit configured to receive an output signal from the MAF sensor and produce a sampled signal having a sampling rate greater than one sample per firing event; a multiple band pass (MBP) filter configured to remove signal components caused by airflow pulsations and oscillations through the MAF sensor; an envelope detector configured to detect the lower and upper envelopes of the MBP filtered signal; a MAF estimator configured to estimate a mass airflow based on the detected lower and upper envelopes; a signal decimator; a low pass filter; and a APC converter to converted the low pass filtered signal into an estimated APC.

An object is to provide a control device that calculates an intake pipe pressure of an engine, in which the humidity of air is measured, and a change in a gas constant due to a change in the total number of moles of air is corrected, to improve the accuracy of the calculation value of the intake pipe pressure.

A control device that controls an engine provided with an air amount measurement unit that measures an air amount passing through a throttle throttle valve provided in an intake passage of the engine, and a humidity measurement unit that measures a humidity of air passing through the throttle throttle valve, includes: an air amount calculation unit that calculates an air amount flowing into a cylinder of the engine based on a measurement result of the air amount measurement unit; and a pressure calculation unit that calculates a pressure of the intake manifold on a downstream side of the throttle throttle valve based on the air amount measured by the air amount measurement unit, the air amount calculated by the air amount calculation unit, and the humidity measured by the humidity measurement unit.

Methods and systems for operating an engine with an electrically driven compressor are described. In one example, output of the electrically driven compressor is adjusted to increase a temperature of an engine so that the engine may be started without glow plugs or with glow plugs that have a lower heat capacity output. Additionally, a position of a recirculation valve may be adjusted to increase the temperature of the engine.

A flow measuring device includes a housing including a bypass passage and a flow sensing chip located in the bypass passage and including a sensing surface portion. A throttle portion that is a part of a flowing passage wall facing a sensing surface portion throttles a cross-sectional area of a bypass passage. A position where the throttle portion starts is referred to as a start point position, and a position of the throttle portion where a distance between a gravity center of the sensing surface portion and the throttle portion is shortest is referred to as an end point position. The start point position and the end point position define an imagination line, and the imagination line and the flowing direction define an angle that is in a range from 0 degrees to 20 degrees.

An air flow rate measuring device for a vehicle measures an air flow rate based on an output value of a sensing unit disposed under an environment in which an air flows. The air flow rate measuring device includes a processor programmed to calculate a standard deviation from sampling data in the output value for at least one cycle of a pulsation waveform of the air, calculate a kurtosis of the pulsation waveform from the output value, estimate the pulsation error that is correlated with the standard deviation and the kurtosis, and correct the air flow rate to mitigate the pulsation error by using the pulsation error.

An air flow rate measuring device measures an air flow rate based on an output value of a sensing unit placed in an environment that allows air to flow therethrough. The air flow rate measuring device includes: an acquisition unit configured to acquire the output value; a storage unit configured to store uneven flow information that indicates an uneven flow state of the air in the environment; a pulsation error correction unit configured to correct the air flow rate by using at least one of the uneven flow information and the output value such that the pulsation error Err in the air flow rate caused by the uneven flow becomes smaller.

Provided is a flow rate measuring device including a connector portion, a main body portion, an internal flow passage, and a flow rate detection element. The internal flow passage includes a main flow passage and a sub-flow passage. The sub-flow passage includes a flow rate detection element-side flow passage and connection flow passages. The main flow passage includes an introduction portion, a small flow passage sectional area portion, and an exit portion. The connection flow passages include an upstream-side connection flow passage and a downstream-side connection flow passage. The main flow passage and the flow rate detection element-side flow passage are formed so as to be symmetric with respect to a plane having a flow direction of the fluid to be measured flowing through the pipe as a normal. The main flow passage has a portion at the plane of symmetry as the small flow passage sectional area portion.

The present invention is one in which an off board Mass Air Flow (MAF) sensor is used to diagnose the internal combustion engine. The MAF sensor is connected to the air induction system of the engine. The sensor is then powered from the vehicles battery. The MAF sensor is designed for lower air flow rates produced from the engine such as; crank, idle, and light load. The sensor creates an output voltage that is proportional to the volumetric air flow of each cylinder entering the engine. This MAF voltage output signal is then used to diagnose engine pumping issues.