Inlet manifold

1961 Ferrari 250 TR 61 Spyder Fantuzzi engine

Manly 1919 Fig 133 Fordson intake

Manifold comparison

Lower-intake-manifold

Inlet manifold or intake manifold is a component of an internal combustion engine that supplies the fuel/air mixture to the cylinders. The design and function of the inlet manifold are crucial for the engine's performance, efficiency, and emissions. The manifold typically consists of a series of tubes or passages that distribute the air or air/fuel mixture from the throttle body to the individual cylinders. In some engines, the manifold can also serve as a mount for the fuel injectors.

Design and Function

The design of the inlet manifold can significantly influence the performance of an engine. It must efficiently distribute the air or air/fuel mixture to each cylinder, ensuring that each receives an equal amount of the mixture. This distribution is critical for the engine's smooth operation and optimal performance. The manifold's design, including its length, diameter, and shape of the passages, can affect the engine's power and torque characteristics.

In addition to distribution, the inlet manifold can also affect the engine's air charge temperature. Cooler air is denser and can lead to a more efficient combustion process. Some manifolds are designed with features to help cool the incoming air, or they may be made from materials that help reduce heat transfer from the engine.

Modern engines may use variable length intake manifold (VLIM) technology, which can change the length of the intake tract depending on engine speed and load. This technology helps optimize performance and efficiency across a broader range of operating conditions.

Materials

Inlet manifolds can be made from various materials, including aluminum, cast iron, and composite materials. Aluminum manifolds are lightweight and have good thermal properties, which can help reduce heat transfer to the air/fuel mixture. Cast iron manifolds are very durable but heavier and can retain more heat. Composite materials, such as plastics, are used in modern engines for their light weight and low heat conductivity, which helps keep the air charge cooler.

Maintenance and Issues

Over time, inlet manifolds can develop issues such as leaks, cracks, or buildup of deposits, which can affect engine performance and efficiency. Leaks in the manifold can lead to an incorrect air/fuel ratio, causing the engine to run lean or rich. This can result in reduced power, increased emissions, and potential damage to the engine. Regular inspection and maintenance are important to ensure the manifold is in good condition and functioning properly.

Environmental Impact

The design and operation of the inlet manifold can also have an impact on the engine's emissions. Efficient distribution of the air/fuel mixture and maintaining a cooler air charge can help improve combustion efficiency, reducing harmful emissions. Advances in manifold design and materials continue to contribute to cleaner and more efficient engines.