Intake and exhaust system

4.10.1 Intake system

This system consists of several elements that provide air supply to the intake ports of the cylinder head It also carries the burden of cleaning the air, which mainly contains dust, dirt and sand.

Figure 4.41 Elements of air intake system.

Thus, the entire air intake system consists of the following elements:

• air intake;
• air filter body with filter cartridge;
• air duct (-s);
• throttle blade;
• receiver (not always);
• intake manifold;
• systems of additional (interim) air cooling, in case if the car has a supercharging system.

Note
Figure 4.41 indicates no elements of the intermediate air cooling system.

Let's consider each element separately.

4.10.2 Air intake

Often, this is a plastic part designed, as you might guess from its name, to "intake air". It is most often located as close as possible to the front of the engine compartment, usually above the radiator (an example of an air intake is shown in Figure 4.41). This detail is vital, especially in case if the car belongs to the class of off-road vehicles that are operated in harsh off-road conditions that include wading through streams and rivers.

But, regardless of the class and operating conditions of the car, manufacturers try to install the air intake higher - farther from road dirt and dust.

4.10.3 Air filter 

This is one of the simplest and at the same time irreplaceable car parts. Purpose of the air filter is cleaning from dirt and dust particles the air that comes from outside. In case if there was no filter, then the foreign particles that get inside would turn into "sandpaper", regularly tearing the cylinder face (we explained this in the section "Description of the Layout of the Basic Engine"). We should not explain what does this "processing" lead to. A schematic representation of the air filter body is shown in Figure 4.41.

4.10.5 Throttle valve

Throttle blade is a device, which regulates the amount of air entering the engine cylinders. The throttle blade in the body is shown in Figure 4.42. If assembled, it is a body in the form of a tube with a damper mounted on an axis inside it. By means of a cable, the damper is connected to the accelerator ("gas") pedal. When you press the accelerator pedal, the cable moves and turns the damper at some angle. Accordingly, more air starts flowing through the open damper, the electronics "gives the command" - and the power system starts supplying more fuel.

Figure 4.42 Appearance of throttle blade.

Note
A more detailed description of the operation of the power supply system is given in the section "Power Supply System of Modern Engines".

4.10.6 Receiver

The receiver is designed to accumulate a certain amount of purified air in front of the intake manifold and more evenly supply it to the cylinders. An example of a receiver is shown in Figure 4.41.

4.10.7 Intake manifold

The intake manifold (Figure 4.41) is an intermediary between the air pipes and the cylinder head. Fuel injectors are also installed in it in case if the vehicle is equipped with a port fuel injection system. Sometimes, depending on the design, a throttle blade is installed directly on the intake manifold.

4.10.8 Additional (intermediate) air cooling system

This system is designed for cooling the air, which is pumped by the compressor (if installed) and directed into the engine cylinders. This is done with one goal - to increase the degree of filling the cylinder by increasing the air density due to cooling. This system includes air ducts that connect the compressor to the throttle blade, in which an air or liquid-cooled radiator is mounted in series.

Note
The degree of filling of the cylinder is characterized by the filling ratio, which is equal to the ratio of the volume of the incoming air to the volume of the cylinder.

Note
In order to increase engine power and torque, one of two types of compressors is often installed on car engines: powered and turbochargers. The first type of compressor is driven directly from the crankshaft through a drive belt, chain or gears. There are many compressors of this type. The turbocharger consists of two parts - a turbine and a compressor. They are mounted on the same shaft. The turbine spins up the flow of exhaust gases, along with it the compressor spins up, pumping an additional amount of air into the cylinders.

4.10.9 Exhaust system

The exhaust system is necessary for removing exhaust gases and reduce noise while they are exhausted (or exhausted into the atmosphere, if scientifically). It consists of an exhaust manifold and an exhaust pipe. In order to improve environmental performance in modern engines, a catalytic converter is additionally installed between the exhaust manifold and the exhaust pipe.

Figure 4.43 Exhaust system.

4.10.10 An exhaust manifold

The exhaust manifold (schematically shown in Figure 4.43) is a part, which is installed directly on the cylinder head and designed to redirect exhaust gases further into the exhaust pipe.

This element of the exhaust system gets very hot, that’s why in modern cars it is covered with a thermal insulating cover. The exhaust manifold can have different shapes. It can be manufactured in different ways and represent a cast part or a set of pipes (see Figure 4.44) of the same length, bent into bizarre shapes (in everyday life it is often called a "spider"). This is done in order to improve the removal of exhaust gases from one cylinder due to the vacuum, which is created by the exhaust of gases from another (the next according to the "stroke").

Figure 4.44 Engine with exhaust manifold, which consists of pipes.

4.10.11 Catalytic converter

A catalytic converter is a device, which is designed for "burning out" unburned fuel contained in exhaust gases and "removing" some of the harmful substances. We will not go into the details of the chemical processes that take place inside this device, just say that the installation of this device has significantly reduced the emissions of harmful substances contained in the exhaust gases.

Note
Basically, the service life of the catalytic converter is the same as that of the vehicle. However, in domestic operating conditions, when using low-quality fuel, to which leaded additives are added contrary to the norms, the special porous filling of the catalyst is destroyed. This leads to a deterioration in the operation of the engine as a whole. In some cases, particles of a collapsing working element fall into the cylinders, which leads to the failure of the piston group.

4.10.12 Exhaust pipe

The exhaust pipe (Figures 4.43 and 4.45) is a pipe, which consists of several sections, in the intervals of which mufflers are installed.

Figure 4.45 Exhaust pipe assembly.

The fact is that the combustion of the air-fuel mixture in the engine cylinder occurs so quickly that an almost explosion is obtained. And as soon as the exhaust valve opens, the sound starts propagating from the exhaust channel in the engine block head through the exhaust manifold into the exhaust pipe. In order to eliminate the rumble and noise, mufflers were invented, which, although they take away some of the engine's power, they do it exclusively with good intentions - so that the engine's operation is as invisible as possible.