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What to do when driving in the rainy season when the engine gets wet?

  • 发布时间: 2023-07-04

Rainy season driving instructions:

 

1. Automatic start stop when boarding is turned off;

 

2. Do not attempt to ignite again when the vehicle stalls on a waterlogged road section;

 

3. The gearbox may also have water ingress and no performance in a short period of time, resulting in a long emulsification process of the gearbox oil;

 

4. Timely clean the drainage holes on the vehicle body.

 

Many times, prevention is the main focus, avoiding driving to waterlogged roads, taking detours on unclear road sections, and not rushing through if the depth of waterlogging is unclear. I believe everyone is very clear about these. What should we do if we really encounter a vehicle stalling and causing the engine to water in?

 

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First, let's talk about the water ingress process of the engine

 

Because we are in heavy rain or wading conditions, we cannot determine what caused the engine to stall in the car. Therefore, the most reliable way is to stop thinking about the engine and rely on external forces to move the vehicle to a safe place. If you insist on restarting the engine, then we need to continue to explain possible situations for you. At this point, you must be mentally prepared for potential major repairs in the future.

 

There are many possible reasons why a vehicle stalls after entering water:

 

1. When the engine is running at low speeds, due to the exhaust pipe being in water, the exhaust pressure is too high and is suppressed;

 

2. The air filter is wet and the intake air is insufficient, resulting in stalling (water has not yet entered the manifold);

 

3. The engine may experience a small/large amount of water ingress, resulting in the engine not functioning properly/being damaged and stalling.

 

Will ignition of the engine again after being extinguished in water (with a large amount of water filling the cylinder) cause bending of the connecting rod and more serious consequences?

 

The answer is no! When a vehicle is wading at a slower speed, the accumulation of water entering the cylinder can cause the engine to be suffocated. At this point, there is already water in the cylinder. With conventional thinking, water is incompressible, which will inevitably cause bending of the connecting rod and even damage to the cylinder block. Why do we argue against this?

 

Because in this situation, the engine crankshaft may not be able to rotate at all! At the same time as the engine is suffocated by water, the interior of the cylinder is basically filled with water. Due to the incompressibility of water, there is almost no room for the piston to move up. At this time, even if you turn on the ignition switch, the starter cannot rotate at all, let alone cause damage to the engine. Moreover, in this case, the engine often causes irreversible internal damage due to a large amount of water entering before stalling, and your "secondary ignition" cannot change this fact whether it is successful or not.

 

How are the connecting rods bent? (A small amount of water enters the cylinder and the engine can start "normally")

 

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In many cases, car owners do not know that the engine has already been filled with water, and coincidentally, the water intake is not large enough (enough to meet the engine's starting needs). At the moment of starting, a certain piston moves up to complete the compression work before ignition. Almost at the same time, the intake valve closes, creating a sealed space inside the cylinder. As water is incompressible, when the piston moves up to a certain position, there will be a significant increase in resistance, But the crankshaft pushed by other pistons that are doing work is too rigid to send this piston to the top dead center position.

 

In short, water will not make concessions. In contrast, the connecting rod becomes much more fragile (with slight deformation), and accumulated water will be discharged from the cylinder body with the opening of the exhaust valve when starting. However, the damage it causes to the connecting rod has become a fact. The bent connecting rod invisibly reduces the compression ratio of the cylinder and increases the resistance of the engine to run, so the vehicle will feel less powerful when driving, And the driver may not be aware of what is happening inside the cylinder. From the driver's perspective, he may think that the car's power is insufficient and deliberately press the accelerator pedal deeper, using higher revs to obtain the desired power.

 

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The slight bending of the connecting rod can make the operation of the piston in the cylinder extremely unstable, and excessive rotational speed undoubtedly accelerates its deterioration. At the same time, the fluctuation of the piston in the cylinder can also increase the bending degree of the connecting rod. The larger the bending degree of the connecting rod, the more crazy the piston will swing during operation, until finally, the piston ring is damaged, the cylinder wall is damaged, and the piston is stuck in the cylinder, And the connecting rod may also be unable to withstand tremendous pressure or bend or break, and in more severe cases, the broken connecting rod will directly pierce the cylinder block. Immediately, the engine loses power and the vehicle will stop after a short taxi.

 

The loss assessor of an insurance company will determine whether the damaged vehicle belongs to the deductible category based on this characteristic. On the contrary, we can also safeguard our own interests by understanding some real situations.

 

Why does the engine suck water into the cylinder?

 

The path of engine water intake is basically the same as the path of air intake, so when discussing this issue, it is important to first understand how the engine gasps. Here, you can use a factory provided air intake effect diagram to display it, but you need to consider the blue part as water.

 

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Why is air (water) drawn into the cylinder?

 

This sounds like a philosophical question, indeed, the more fundamental the question, the less easy it is to answer. During the downward phase of the piston, negative pressure will be generated and then released through the intake valve. If you really can't understand it, imagine it as a syringe without a needle. Use your fingers to block one end and forcefully pull the piston push rod, so that you can feel the presence of negative pressure.

 

When the speed is stable, the negative pressure value is almost constant. When the driver presses the accelerator, the swing of the throttle valve will expand the intake throttle area. At this time, the fuel injection amount will also be corrected with the cooperation of the engine computer, and the speed will then increase (the reciprocating motion of the piston will instantly accelerate). At this moment, the negative pressure value will fluctuate significantly. In computer programs, the relationship between them is presented as a function.

 

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Water still faces a choice before being sucked into the cylinder, which cylinder to go to? This is the first choice for water after successfully passing through the air filter and throttle. The fork in the intake manifold leads to each cylinder. Taking a four cylinder engine as an example, although there may not be two cylinders on the intake stroke at the same time, there is a theoretical possibility of a single cylinder entering the water. However, even if the engine is running at idle speed, an engine speed of around 800rpm is sufficient to completely divide the water that flows into the intake manifold in an instant.

 

After the water and fuel blend, they enter the cylinder, which is like a syringe absorbing chemicals. At this time, the combustion chamber has never been filled as fully as it is now, and thus the engine is suffocated.

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