Function Analysis and Maintenance of Intake Manifold

Function Analysis and Maintenance of Intake Manifold

The intake manifold is the necessary part for air to enter the car engine and plays a key role in the movement of the engine's pistons and cylinders. When the engine is in the intake stroke, the piston moves down to create a vacuum in the cylinder, and the air pressure decreases accordingly, creating a pressure difference with the outside air, allowing air to enter the cylinder. Due to the low temperature at the intake end, composite materials have become a popular intake manifold material. It is light in weight and smooth inside, which can effectively reduce resistance and increase intake efficiency.

The intake manifold is located between the throttle valve and the engine intake valve. The reason why it is called "manifold" is that after the air enters the throttle valve and is buffered by the manifold, the air flow path "divides" here. Corresponding to the number of engine cylinders, for example, there are four channels in a four-cylinder engine, and five channels in a five-cylinder engine, and air is introduced into each cylinder respectively. For a naturally aspirated engine, since the intake manifold is located behind the throttle valve, when the throttle opening of the engine is small, sufficient air cannot be sucked into the cylinder, resulting in high manifold vacuum. When the engine throttle opening is large, the vacuum in the intake manifold will become smaller. Therefore, the fuel injection engine will install a pressure gauge on the intake manifold to supply the ECU to determine the engine load and give an appropriate amount of fuel injection.

Manifold vacuum can be used not only as a pressure signal to determine engine load, but also for many other purposes. For example, braking also needs to be assisted by the vacuum of the engine. When the engine is started, the brake pedal will be much lighter because of the vacuum assistance. There are also some forms of cruiser control that utilize manifold vacuum. Once these vacuum tubes leak or are improperly refitted, it will cause engine control imbalance and affect the braking effect, so try not to make improper refits on the vacuum tubes to maintain driving safety.

The design of the intake manifold is also very knowledgeable. In order to ensure that the combustion conditions of each cylinder of the engine are the same, the length and curvature of the manifold of each cylinder should be the same as possible. Since the engine completes the operation program with 4 strokes, each cylinder of the engine will intake air in a pulsed manner. According to experience, the longer manifold is suitable for low-speed operation, while the shorter manifold is suitable for high-speed operation. Therefore, some models use variable-length intake manifolds, or continuously variable-length intake manifolds, so that the engine can perform better in various speed ranges.

The maintenance of the intake manifold can be cleaned with a combustion chamber cleaning agent. The sequence is generally the combustion chamber, spark plug, throttle valve, and intake port. It is time-consuming to disassemble the intake manifold, and a sleeve extension rod is required. It is recommended to take out the battery to make room, and finally take out the intake manifold. Since the intake manifold does not participate in combustion, there is not much carbon deposit, just spray some cleaning agent for simple cleaning.

However, cleaning the intake manifold is carried out at the same time as cleaning the fuel injectors and other key steps, so learning to clean the intake manifold will also make the carbon deposit cleaning of the entire engine more systematic and comprehensive. For example, removing the intake manifold while soaking the combustion chamber is a very scientific step.
Back to blog