Understanding the working principles of the mechanisms hidden under the hood and in the nodes of the body is the foundation for anyone who plans to connect their lives with the car. A competent driver or a novice mechanic should not rely only on intuition when the Check Engine light goes on or a foreign knock appears in the suspension. That is why the test on the device of the car has become the standard of qualification testing in driving schools and specialized colleges around the world.
The modern car is a complex set of mechanical, electrical and electronic systems that require deep study. Internal combustion engine converts thermal energy into mechanical energy, but this process depends on dozens of concomitant factors: the quality of the mixture, the angle of ignition advance and the state of the exhaust system. Mistakes in diagnosis can cost the owner huge amounts, so regular self-checking through specialized questionnaires is the best way to keep knowledge in good shape.
In this article, we will discuss the key nodes of the machine, paying attention to those aspects that most often cause difficulties in passing exams. We will go from crank-and-wheel mechanism to complex electronic control systems so that you can confidently answer any question of a technician.
Basics of the internal combustion engine
The heart of any vehicle is the engine, and it is from it that the study of the technical part begins. The crank-shaking mechanism (CSM) is used to convert the reciprocal movement of porn into the rotational movement of the crankshaft. Without this fundamental process, the car simply wouldn’t be able to budge, remaining a motionless piece of metal.
The most important parameter that is often found in tests is the degree of compression. This is the ratio of the total volume of the cylinder to the volume of the combustion chamber. For gasoline engines, this figure usually varies, whereas diesel units require significantly higher pressure to ignite the fuel.
- 🔧 The piston performs four strokes: intake, compression, stroke and release.
- ⚙️ The gas distribution mechanism (GRM) synchronizes the opening of the valves with the movement of the porn.
- 🔥 The ignition system provides a spark at a strictly defined point in time.
- 🌡️ The cooling system maintains the optimal temperature mode of the engine.
⚠️ Attention: Never try to adjust the heat gaps of the valves on a hot engine, as the metal expands when heated and you will get incorrect data, which will cause the valves to burn out.
Particular attention is paid to the lubrication system. Oil not only reduces friction between rubbing parts, but also removes heat and also removes wear products. Oil pump creates the necessary pressure by driving the liquid through filters and channels in the cylinder block. If the pressure drops, a red indicator lights up on the dashboard, requiring immediate stop.
Transmission and torque transmission
Once the engine has generated energy, it must be transferred to the wheels. It's what he's doing. transmission, which includes a clutch, gearbox, driveshaft (on rear-wheel drive cars), main gearbox and differential. The main task of this unit is to change the magnitude and direction of torque transmitted from the engine to the driving wheels.
The clutch is used for short-term separation of the engine from the transmission, which is necessary for gear shifting or stopping the car without stopping the engine. In modern cars, robotic boxes or variators are increasingly found, the principle of operation of which differs from classical mechanics.
| Type of PPC | Principle of work | Feature |
|---|---|---|
| Mechanical (MIP) | Manual gear shifting | High reliability and maintainability |
| Automatic (ATM) | Hydrotransformer and planetary series | Comfort but complicated repairs |
| CVT (CVT) | Change in the diameter of pulleys by belts | No fixed transmissions |
| Robot (DCT/DSG) | Two clutches and electronic control | Switching speed and economy |
Differential allows the driving wheels to rotate at different speeds, which is critical when cornering. Without this mechanism, the inner wheel would be towed, and the outer one could not turn at the desired speed, which would lead to rapid wear of the tires and breakage of the semiaxles.
When passing tests, remember: on front-wheel drive cars, the gearbox and main gearbox are often combined into one unit, called a transaxel.
Chassis and control system
The chassis ensures smoothness and stability of the car on the road. The main elements here are suspension, wheels and tires. Suspension It can be dependent or independent, and it is the type of suspension that largely determines the nature of the car's handling.
Steering allows the driver to set the direction of travel. In modern machines, hydro- or electric power steering (GUR / EUR) is widely used, which facilitates the rotation of the wheels. Faults in this system, such as a backlash or pump hum, are frequent topics for exam questions.
- 🚗 Levers and Silentblocks extinguish vibrations from the road surface.
- 🛑 The braking system uses hydraulic pressure to press the pads.
- 🌀 The shock absorbers control the vibrations of the suspension springs.
- 🎯 The steering rack converts the rotation of the shaft into the rotation of the wheels.
The braking system deserves special attention, as safety depends on it. Disc brakes are more effective at removing heat than drum brakes, so they are more often installed in front or on all wheels of modern cars. ABS (anti-lock system) prevents wheels from locking during emergency braking, allowing you to maintain controllability.
What is a collapse-adventure?
The collapse is the angle of the wheel relative to the vertical. Convergence is the angle between the direction of movement of the car and the plane of rotation of the wheel. Violation of these parameters leads to accelerated wear of rubber and the car to the side.
Electrical equipment and current sources
A modern car is impossible to imagine without electricity. The onboard network powers the starter, ignition system, lighting, multimedia and a variety of sensors. The main sources of current are battery and the generator.
The battery (ACB) provides energy to the starter when the engine starts and feeds consumers with the engine silenced. The generator generates electricity while the engine is running, while charging the battery. The voltage in the network of a serviceable car with the engine running should be in the range of 13.5-14.5 V.
⚠️ Attention: When installing the battery, strictly observe polarity. The mixed plus and minus can instantly disable the generator’s diode bridge and burn electronic control units.
In tests, questions about safety locks and relays are often encountered. The fuse protects the wiring from overload, breaking the chain when the permissible current is exceeded. The relay allows you to control powerful consumers (for example, headlights or a radiator fan) using weak currents supplied by buttons on the panel.
☑️ Diagnostics of Electrics
Safety and environmental systems
Every year, the requirements for the safety and environmental friendliness of cars are growing. New systems are being introduced into the design, such as ESP (Stability Control System), airbags and catalysts. Knowledge of their design is essential to understanding modern standards.
The catalytic converter burns out harmful exhaust gases, turning them into less dangerous compounds. The lambda probe (oxygen sensor) monitors the composition of the mixture and adjusts the engine for maximum cleaning efficiency. Failure of these elements leads to the lamp failure and increased fuel consumption.
Airbags (Airbag) is triggered on impact by a pyropatron that instantly fills the bag with gas. This happens in a fraction of a second, so any interference with the safety system without turning off the battery is strictly prohibited and can result in injuries.
Today’s 40 percent test of a car consists of questions about electronic driver assistance systems and environmental regulations, not just mechanics.
Practical aspects of diagnostics
Theoretical knowledge should be supported by the ability to conduct diagnostics. Modern cars are equipped with a system OBD-II (On-Board Diagnostics), which allows you to read error codes through a special connector. This is the first step in finding a fault.
Diagnosis begins with a visual examination and a survey of the driver. Then check the levels of technical fluids, tire pressure and the condition of external elements. Only then do they move on to instrumental verification methods.
- 👀 Visual inspection for leaks and damage.
- 👂 Listening to the engine and running on hearing.
- 📱 Reading error codes by scanner.
- 📏 Measurement of compression in cylinders and oil pressure.
The ability to correctly interpret the data that is obtained distinguishes the professional from the amateur. For example, triple engines can be caused by both a spark plug and a low compression or air sucker. Tests often model such situations, suggesting that you choose the most likely cause from a list of symptoms.
How often should I change the engine oil?
The replacement interval depends on the type of oil (mineral, semi-synthetics, synthetics), operating conditions and manufacturer's recommendations. On average, for modern synthetic oils, the interval is 10,000-15,000 km, but in difficult urban conditions it is better to reduce it to 7,000-8000 km.
What does black smoke from the exhaust pipe mean?
Black smoke indicates a re-enriched fuel-air mixture. The fuel does not have time to burn completely and flies out in the form of soot. Causes: malfunction of nozzles, problems with air sensors, clogging of the air filter or failures in the operation of the fuel pressure regulator.
Why do you need antifreeze and can you mix it?
Antifreeze not only prevents liquid from freezing in winter, but also increases the boiling point, and also contains additives from corrosion. Mixing antifreezes of different colors and compositions (for example, G11 and G12) is strictly not recommended, as this can lead to precipitation and blockage of the cooling system channels.
Why is the engine knocking?
Knocking can be caused by various reasons: detonation (thumping of fingers), wear of root or rod liners, problems with hydrocompensators or a chain of HRM. The nature of the knocking (frequency, dependence on revs) helps to determine the source of the problem.
How often should I check the brake fluid?
The level of brake fluid should be checked at each TO or once a month visually by tank. The liquid itself is hygroscopic (absorbs moisture), so it is recommended to completely change it every 2 years or 40-60 thousand. mileage, regardless of condition.