Intake Manifold, Functions and Working

Introduction

The Intake System of any automobile serves a major role in producing power. It plays a key role in the engine’s power and torque. Previously we have discussed how an engine works and what are the major requirements of any engine to produce the power. The engine produces power by combusting air and fuel mixture and a heat source, and today we shall discuss the component responsible for passing air into the engine ie The Intake Manifold.

Intake Manifold can be defined as a series of tubes that are attached forming a single body and placed overhead of engine head, The air enters the engine passing through the air filter then through the throttle body and then finally paving its way into the intake manifold.

As the air enters the intake manifold it is passed through a series of sensors that are located to determine various components of air coming in, for example, its density, oxygen amount, moisture and various other characteristics that are very important for achieving proper air-fuel mixture and hence highly optimized engine performance.

The intake manifold consists of mainly 2 components ie Plenum and the runners.

The plenum is the large cavity at the top of the manifold and runners are individual tubes running each to the cylinder head.

Working

The design of the intake manifold is very important for achieving good volumetric efficiency.

Abrupt contours in an intake manifold result in pressure drops and som of the fuel droplets in spark-ignition engines form pools in the interior part of intake manifolds surface which results in the uneven air-fuel mixture to enter for combustion. High-performance cars use manifolds with smooth contours for increased volumetric efficiency.

Moreover, the design of manifold uses Helmholtz Resonance in which first, the air flows at considerable speed through the open valve. When the valve closes, the air that has not entered the valve yet still has a lot of momentum and compresses against the valve, creating an area of high pressure. This high-pressure air begins to equalize with lower-pressure air in the manifold. Due to air’s inertia, the equalization will tend to oscillate, At first, the air in the runner will be at a lower pressure than the manifold. The air in the manifold then tries to equalize back into the runner, and the oscillation repeats. This process occurs at the speed of sound, and in most manifolds travels up and down the runner many times before the valve opens again.

VARIABLE LENGTH INTAKE MANIFOLDS

Intake manifold nowadays is built quite advanced as automotive components. Variable-length intake manifolds allow the amount of air being sent into the engine to change depending on its needs. This is similar in effect to other technological advances like variable cam profiles and cylinder deactivation, both of which help maintain power and increase efficiency.

Hence, the intake manifold is quite complicated by design but has a simple function to just let pass the fresh air.