Is it scientific to distinguish automobile "wading ability" by vehicle type?

Recently, strong convective weather has appeared frequently, and heavy rain and strong wind have brought a test to the "wading ability" of cars.

How to wade safely by car? The answer to this question depends on driving skills and knowledge of vehicle "hardware".

On the premise that the water level is not too deep, wading can often pass normally as long as it does not turn off the fire halfway.

Because the engine can continuously output power without water, at the same time, the high pressure generated by exhaust can easily squeeze the water injected into the pipeline out of the car.

There is nothing wrong with the powertrain, transmission system and running system. What's wrong with the car except that it's a little rusty?

1. "Deep" Wade

The intake height of the engine determines the limit.

As mentioned earlier, the limit of wading for fuel vehicles is "no water enters the engine", so how does water enter the engine?

You should know that the engine of an oil-powered car is a piston reciprocating cycle internal combustion engine. The basis of this machine is that oxygen in the air is mixed with fuel oil, and kinetic energy is converted through oxidation-reduction reaction (combustion) of hydrocarbons.

Oxygen comes from air, and air must be inhaled to ensure the normal operation of internal combustion engine.

Knowledge point 1: piston reciprocating cycle!

When the piston goes up, the compressed air generates high-temperature evaporated fuel, and when it goes down, the driving force generated by combustion pushes the piston to drive the crankshaft to run (do work).

The total volume of the engine cylinder is subtracted from the volume swept by the piston from the bottom dead center to the top dead center, and the remaining ultra-small space is the so-called "combustion chamber", and the ratio of the total volume to the combustion chamber is called the compression ratio.

It's hard to feel how little space there is for words. Look at the picture below.

Knowledge point 2: Air inlet clearance from the ground!

The air inlet of the internal combustion engine is generally located at the upper part of the middle net, which is actually commonly known as the "air intake grille".

Most of the air inlets are flat (duckbill-shaped), and there will be a group of air filters in the pipeline, which will then communicate with the combustion chamber through the throttle.

When a car wades, the water level must not be close to (below) the height of the air intake, because the moving car will emit "waves", especially when it meets a car, which is equivalent to taking water to fill the air intake.

Therefore, about 20 cm from the vertical height of the air inlet is considered as the wading limit.

Important: Not all models with high bodies will have high air intakes. The air intake of many cars is only designed at the highest position in the net, while the air intake of some SUVs and even pickup trucks is even lower.

This is why there are all kinds of models in the stagnant water section. We should not be blind and confident in the models.

Therefore, if you want to know the wading limit capacity of the vehicle, you can only know it by actually measuring the height.

However, the "successful wading" without turning off the fire may not hurt the car, and there is no sign that the gearbox will start to water.

2. The gearbox determines the limit

The vertical height of gearbox is lower than that of engine, regardless of front drive, rear drive or four-wheel drive!

AT/DCT/AMT/CVT, the four mainstream models of automobile equipment, all produce high temperature during operation.

Whether it is a gear set or a bevel gear steel belt, gearbox oil (oil lubricant) is needed for lubrication and heat dissipation during operation.

High temperature will cause the expansion of oil and internal air, which will increase the internal stress of the shell. The only way not to destroy the structural strength of the shell is "ventilation"!

The function of gearbox exhaust hole is "constant pressure", which can squeeze out high-temperature air to achieve internal pressure balance and suck in low-temperature air for filling.

Only in this way can the gearbox have a long service life, but it still brings a problem-the wading ability is reduced.

Although the vent hole will have a waterproof cap, it will still cause water to enter the box when soaking and wading; When rainwater turns into sewage, it will contain various components and be more acidic.

This water will inevitably react with the engine oil, and as a result, the engine oil will slowly "emulsify" into a paste, thus losing the lubrication ability of the gear.

Key points: the gearbox is a machine that does not need the reciprocating motion of the piston, and its function is only to amplify the power output by the engine through different gear combinations.

Therefore, this machine will not "stall" even if it is flooded, and it is difficult to find the wear caused by the initial water inflow. It is not until the gearbox oil is "burnt", which forms a great driving resistance and leads to the deterioration of automobile power that the gearbox can be repaired.

Therefore, the limit height of the car should be based on the gearbox ventilation cap, and the limit must be appropriately reduced.

abstract

It is always wrong to distinguish the wading limit of a car by its model. If a car can drive without wading, it should try to avoid it. If it can't avoid it, it is necessary to measure the water depth.

Assuming that the car stalls when wading, the engine must not be restarted at this time, otherwise the connecting rod will be broken by starting the motor to drive the flywheel, which will cause car damage and water-related insurance refusal.

The correct way is to leave the vehicle (escape) in time, notify the insurance company and take photos to collect evidence, and wait for the vehicle maintenance or scrapping compensation.