Multi-cylinder Engine Exhaust Sensor Placement

The exhaust passage system is segmented into multiple independent exhaust passage parts (first exhaust passage part, second exhaust passage part, etc.) that are separately connected to different cylinder groups. This segmentation allows the temperature sensor to be strategically positioned in one specific exhaust passage part where it can accurately measure exhaust gas temperature while remaining accessible for maintenance, rather than requiring installation deep within the cylinder head.

The independent exhaust passage parts serve as intermediary channels that connect the cylinders to the collective exhaust passage. By placing the temperature sensor in one of these intermediary exhaust passage parts, the system achieves both accurate temperature measurement and easy maintenance access, as the sensor is positioned in an intermediate location rather than directly in the cylinder head or final exhaust outlet.

The EGR passage is selectively connected to only some of the independent exhaust passage parts (e.g., first exhaust passage part) rather than all of them. This local quality approach allows the system to recirculate exhaust gas from specific cylinders to achieve effective NOx reduction while avoiding the complexity of connecting all exhaust passages, thus balancing performance with system simplicity.

Instead of connecting the EGR passage to all independent exhaust passage parts, the system implements partial action by connecting it to only the necessary number of passages (first exhaust passage part and potentially second exhaust passage part). This partial connection achieves sufficient NOx reduction efficiency without creating excessive device complexity, following the principle of doing just enough to achieve the desired effect.