Engine Intake Charge Management

Hannu Jääskeläinen, Magdi K. Khair

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Abstract: Managing the supply of air and other components of the cylinder’s intake charge to the combustion chamber is an important process to ensure consistent and reliable performance of modern engines. Intake charge management encompasses all aspects that affect the quantity, composition, temperature, pressure, bulk motion and cleanliness of the cylinder’s contents at the start of the heat release period. Details of the intake system, cylinder head and valve train design, pressure boosting technology and charge dilution requirements are all important aspects of intake air management.


Managing the supply of the intake charge up to the start of combustion is a critical aspect of modern engines and can impact emissions, performance and fuel economy. Intake charge management is the process that is used to ensure that the intake charge supplied to the combustion chamber at all operating conditions meets a number of requirements including:

Commonly, elements of this process are referred to as air management. However, the term air management is not clearly defined and can also be misleading as it implies that only airflow needs to be managed. For modern engines, the cylinder contents at the start of combustion can also include diluents such as recirculated exhaust gas and in SI engines, fuel as well. Thus, a term that more accurately incorporates these elements is needed. In this paper, intake charge management is used.

In older diesel engine designs that did not have to meet stringent exhaust emissions requirements, intake charge management systems were in fact air management systems and were relatively straightforward. In some cases, it was sufficient to simply ensure that the air was clean and that the flow capacity of the intake system was adequate to ensure peak torque and power objectives were met. These diesel engines were also commonly design to impart swirl to the air as it entered the combustion chamber to support the fuel injection system in the task of mixing of air and fuel. Typically, no active control of any intake side hardware was required. Even as many engines started to adopt turbochargers and other forms of intake air compression, it was sufficient to simply ensure a proper match between the engine and compressor. Naturally aspirated gasoline SI engines had a throttle plate for load control and had the added complication of premixing air and fuel in the intake system. The intake system would have needed to be designed to ensure that the distribution of air and fuel mixture generated by the carburetor met the design requirements of the engine and that measures were taken to minimize the accumulation of a liquid fuel film in the intake system.

Pressure to lower emissions while maintaining or improving other engine performance parameters required that the intake air properties be better controlled and matched to suit the engine operating condition. This required the introduction more hardware to control these intake air properties. In diesel engines for example, wastegate control on the turbocharger was introduced to enable improved intake air boosting at lower engine speeds and to limit turbine speeds at high engine speeds, valves were introduced to mix some exhaust gas (EGR) into the intake air at some engine operating conditions, turbocharger controls become more complicated to ensure that boost and EGR requirements could be met and higher and higher intake air pressures required that the higher intake air temperatures resulting from compression be limited. All of this added complexity required that more sophisticated control systems with sensors and sophisticated control algorithms be incorporated to ensure everything functions as expected.

There are a number of important aspects of intake charge management including: