Modern car is a complex engineering complex, where each node performs a strictly defined function to ensure movement. In the context of internal combustion engines, whether gasoline or diesel, the term “stream system” is most commonly associated with the organization of movement of gases or liquids. This may include the intake tract, the exhaust gas recirculation system (EGR), and the hydraulic circuits. Understanding exactly how these flows are formed, directed and regulated is key to proper operation and repair.
The main task of any such system is to create optimal conditions for combustion of the fuel-air mixture or effective cooling of the units. Violation of tightness, change in the geometry of channels or failure in the operation of control valves lead to loss of power and increase in fuel consumption. In this article, we will examine in detail the physical principles underlying these mechanisms and look at typical malfunctions.
Physical principles of gases and liquids movement in the ICE
The fundamental basis of any engine is the pressure difference. Flow It always tends from a high-pressure to a low-pressure area, and it is this law of physics that engineers use when designing intake and exhaust manifolds. The speed of the medium depends on the channel cross section and the pressure drop, which is described by Bernoulli's equation. In modern motors, this process is not chaotic, but is strictly controlled by electronics to achieve maximum efficiency in different modes of operation.
The most important parameter is turbulence flow. If air or liquid moves too quietly (laminar flow), the mixing of components is worse, which reduces the efficiency of the engine. Engineers specifically create vortices in the channels of the cylinder head to improve the mixing of fuel with air. However, excessive resistance of the walls of the channels can "strangle" the engine, so finding a balance between speed and volume of the passing medium is the art of the automotive industry.
Particular attention should be paid to the temperature of the environment. Hot gases have a lower density, which requires adjustment of fuel supply. The engine control system (EBU) constantly analyzes data from the mass air flow (MAC) and absolute pressure (AAC) sensors. Based on these indications, the required amount of fuel and the angle of opening of the throttle valve are calculated.
- 🌪️ Turbulence: chaotic movement of particles, necessary for qualitative mixture.
- 📉 Dilution: the reduced pressure state in the intake manifold at idling.
- 🚀 Inertial boost: effect that occurs when a sharp closure of the throttle or the use of tuned lengths of the intake tract.
Intake system device and airflow control
The intake system is the first frontier from which the formation of the cylinder working charge begins. Air, passing through the air filter, is cleaned of dust and enters the air. mass-flower. Further, the flow is regulated by a throttle valve, which changes its position depending on the position of the accelerator pedal. In modern cars, an electronic throttle valve is used, where there is no mechanical connection with the pedal, and control is carried out by an electric motor.
To increase efficiency at different speeds, systems for changing the geometry of the intake tract are used. At low revs, air moves through long channels, which increases the flow rate and improves the filling of the cylinders. At high revs, the flaps switch the flow to short paths, minimizing resistance and allowing the engine to "breathe" fully. This mechanism is often called variable-intake.
Periodic cleaning of the throttle and channels of the intake manifold helps to restore factory idling parameters and remove floating turns.
A critical element is the tightness of the entire system after the air flow sensor. Any crack in the pipe or loose connection leads to the entry of unaccounted air. The ECU is unaware of this additional volume and does not add fuel, which leads to a depletion of the mixture. The engine begins to work unstablely, ignition passes and errors appear on a poor mixture.
| Element of the system | Function | Typical malfunction | Impact on flow |
|---|---|---|---|
| Throttle | Air volume regulation | The damper's on the damper. | Unstable idling |
| Intake manifold | Distribution of mixture | Cracks, sucking. | Depletion of the mixture |
| EGR valve | Gas recycling | Open jamming | Strangulation of the engine |
| Turbocharger | Air injection | Wear of bearings | Loss of boost pressure |
Efficient gas recirculation system (EGR)
One of the most difficult systems to maintain, affecting the flow of gases, is EGR (EGR).Exhaust Gas Recirculation). Its main task is environmental: reducing emissions of nitrogen oxides (NOx) into the atmosphere. The principle of operation is based on the return of part of the exhaust gases back to the intake manifold. Mixing with fresh air, inert gases reduce the combustion temperature in the cylinders, which prevents the formation of harmful compounds.
The EGR valve is controlled by an electronic control unit. In certain modes, for example, with a sharp acceleration or on a cold engine, the valve is completely closed so as not to worsen the dynamics. However, in partial load mode, it opens, allowing the exhaust gas flow to pass through. Over time, a dense soak is formed on the walls of the valve and intake manifold, which can completely block the passage section or, conversely, prevent the valve from closing.
⚠️ Attention: If the EGR valve jams in the open position, the engine will suffocate at idle speeds due to excess exhaust gases in the intake. In this case, software or physical shutdown of the system is often required.
Diagnosing an EGR system is often difficult, as the symptoms of a malfunction may be similar to ignition or fuel system problems. Computer diagnostics shows errors on the pressure sensor or valve position. Mechanical inspection involves removing the element and visual inspection for coking channels.
☑️ Verification of the EGR system
Hydraulic flows: lubrication and cooling system
Not only gases, but also liquids in the car form complex flow systems, on which the life of the engine depends. The lubrication system provides a pressure supply of oil to rubbing vapors. The oil pump creates a primary flow that passes through the filter and is further distributed through the channels of the block and cylinder head. The most important parameter here is the viscosity of the oil and the throughput of the filter elements.
The cooling system is also a closed circuit of fluid circulation. Thermostat It plays the role of the main regulator, directing the flow of antifreeze either in a small circle (for rapid warming up), or through the main radiator. Violation of the thermostat or pump leads to local overheating or, conversely, underheating of the engine. Cavitation (collapse of vapor bubbles) in the pump can destroy the impeller and stop circulation.
It is important to understand that air traffic jams in the cooling system are the number one enemy for proper heat exchange. The air entering the system blocks the fluid flow, creating zones where temperatures can rise critically in minutes. The correct procedure for replacing antifreeze always involves removing air from the system.
- 💧 Viscosity: The key parameter of oil, which determines the speed of its passage through the channels.
- 🌡️ Thermostat: valve regulating the temperature of the coolant.
- 🚫 Cavitation: the process of formation and collapse of bubbles, destroying the metal pump.
Diagnosis of flow disorders and typical malfunctions
Identifying problems in gas and liquid supply systems requires an integrated approach. The first sign of malfunction is often a change in the sound accompaniment of the engine. A whistle may indicate air suction or turbine problems, and a gurgle may indicate the presence of air in the cooling system. Modern cars report problems through the lamp Check Engine.
For accurate diagnosis, smoke generators are used, which help to find even microscopic leaks in the intake tract. Smoke supplied under pressure visually shows the place where the tightness is impaired. Pressure gauges connected to the appropriate ports of the system shall be used to check the boost or vacuum pressure.
Hidden Signs of Flow Problems
Often drivers ignore the change in the sound of the exhaust or the appearance of a whistle during acceleration, considering this the norm. However, it is these sounds that first signal the depressurization of the pipes or wear of the bearings of the turbocharger.
Particular attention should be paid to the condition of the catalyst and particulate filter. Their clogging creates back pressure in the exhaust system. The engine becomes difficult to "push out" the exhaust gases, which leads to loss of power and overheating. In severe cases, the hot gases can go in the opposite direction, melting the engine elements.
⚠️ Attention: Operating a car with a clogged catalyst or particulate filter can lead to valve burnout and destruction of the piston group due to a critical increase in temperature and pressure.
Methods of maintenance and recovery of throughput
Regular maintenance is the best way to avoid flow problems. Replacement of the air filter should be carried out strictly according to the regulations, and in dusty conditions - more often. A dirty filter creates high resistance at the intake, causing the engine to operate in enriched mix mode and lose power.
Washing of the intake manifold and throttle valve is a procedure that is desirable to carry out every 40-60 thousand kilometers. Special chemical compositions allow you to dissolve oily soda, which inevitably settles on the walls. For EGR systems and direct-injection diesel intake valves, this procedure is critical.
In hydraulic systems, it is important to monitor the condition of the fluid and the timely replacement of the pump and thermostat. The use of poor-quality antifreeze can lead to corrosion of channels and the formation of deposits that narrow the cross section of the tubes. Flushing of the cooling system before pouring a new antifreeze removes the decay products of the old liquid and rust.
Timely replacement of filters and use of high-quality technical fluids extend the life of air supply and cooling systems by 40-50%.
The influence of chip tuning on flow parameters
Many car owners resort to software improvements in engine performance, known as chip tuning. Changing the ECU program maps allows you to adjust the opening angle of the throttle, the boost pressure and the gas distribution phase. However, increasing power requires the appropriate bandwidth of all systems.
If you programmatically increase the supply of fuel and air, but leave a regular exhaust or a clogged catalyst, the effect will be reversed. The engine will not be able to effectively clean the exhaust gases, which will lead to detonation and overheating. Therefore, serious tuning always begins with an audit of hardware and an assessment of the ability of systems to pass increased volumes of media.
In some cases, it is necessary to install zero resistance sports filters or remove the catalyst (eco-tuning). These measures reduce flow resistance, allowing the engine to rotate more easily at high revs. However, such interventions must be carried out with an understanding of the environmental and resource implications of the motor.
- 💻 Chip tuning: Reprogramming of the ECU to change the parameters of the engine.
- 📈 Boost: The pressure of the boost created by the turbocharger.
- ⚖️ Balance: compliance with the throughput capacity of intake, release and supply of fuel.
How often should I check the EGR system on a diesel car?
It is recommended to carry out visual inspection and computer diagnostics of the EGR system every 30-40 thousand kilometers, especially if the car is operated mainly in urban mode with frequent downtime.
Can I drive with a faulty mass air flow sensor?
You can drive, but the ECU will go into emergency mode, calculating the fuel supply according to averaged tables. This will lead to increased fuel consumption, loss of dynamics and possible failure of the catalyst due to the wrong mixture.
What is the Venturi effect in a carburetor and injector?
This is a physical phenomenon in which in a narrow part of the pipe the flow rate of liquid or gas increases, and the pressure drops. In carburetors, this is used to suck fuel, and in injection systems, DMRV is often built on the principle of measuring the pressure drop.
Why does the turbine whistle when it accelerates?
Whistling may indicate depressurization of the pipes through which air is released under pressure, or wear of the bearings of the turbocharger shaft. Also, a whistling sound can be emitted by a bypass valve (vestgate) when pressure is relieved.