It is the duct through which the air (oxygen) that produces combustion in the engine enters the intake valves through the pipes in the cylinder head.
The manifold is attached to the engine cylinder head using a group of bolts and is what determines the way in which the cylinders are filled.
Intake manifolds are normally made of aluminum or similar materials, as well as highly resistant plastics.
Intake manifold operation
There are 2 types of intake manifolds: conventional and variable intake, the latter being the most common in recent years.
It is located next to the cylinder head to supply air to the combustion chamber so that the mixture of air and fuel for the explosion of the engine is made.
Sometimes it includes an EGR valve and its design and length depends on each engine design based on its needs, since the air supply must be equal and perfect for each cylinder, thus determining the power and consumption of each engine.
Practically the design of the intake manifold is unique for each type of engine, both outside and inside.
Intake manifold types
Fixed conventional intake manifolds
They do not adapt variably to the different engine speeds, but they achieve very high torque at a low number of revolutions or very high power at a high number of revolutions, although they never manage to combine both benefits.
That is why the need arose to design a system that provides efficiency at any engine speed, and thus the variable intake manifold was born.
Today, the conventional manifold is still used in gasoline engines with a carburetor or with a single-point injection system that require a very uniform mixture of gasoline and air, and its characteristic is its simplicity since the cylinder tubes are of equal length. for each of them.
Variable intake manifolds
They allow air to enter the cylinders according to the speed at which the engine is operating at any given moment, thus increasing engine performance.
In general, they are used in engines with four valves per cylinder, thus compensating for the low number of revolutions, these systems being called multipoint injection since in them the fuel injection is carried out through the intake pipe or in the combustion chamber in direct injection systems, always in front of the intake valve, with the intake tubes configured to improve air intake.
The variable intake manifolds also have a system of electronically controlled flaps (butterflies) to channel air through the manifold at low power speeds and through the long section when driving at high speeds.
Possible faults in the intake manifold
In general, the intake manifold does not require any maintenance, and if it breaks it must be replaced, since the most common problems with this important part are usually cracks or breaks that generate air leaks, with a notable increase in consumption and poor performance. non-linear engine due to incorrect mixture.
It may also happen that the joint between the manifold and the cylinder head fails, normally generating very black engine smoke from the exhaust, which is an unequivocal symptom of a problem of this type.
We must not forget that the presence and good functioning of the intake manifold guarantees that the vehicle does not jerk while driving, also ensuring that consumption is not excessive and avoiding decreases in power, which undoubtedly contributes to this part of the engine. a very important mission for its proper functioning.
If any of the breakdowns described above appear, you must prepare for a major economic intervention, mainly due to the difficulty and time required to access it and replace it (it is a generally expensive and complex part to replace).