We have reached an understanding with many people about the hot car. If conditions permit, idling the engine for a period of time before going on the road can reduce the wear degree of the powertrain. However, the warm-up time should not be too long, because it will have an impact on the environment, the fuel economy is not good enough, and the engine is more likely to form carbon deposits due to too much mixed gas. Let's take these as the price of getting warm air, but you may ask, why can the air conditioner outlet blow out cold air after pressing the air conditioner cooling button, but the warm air has to wait for us for so long?
This question is easy to explain. The refrigeration function of air conditioning system depends on air conditioning compressor and refrigerant, that is to say, air conditioning refrigeration is a relatively independent mechanism, while air conditioning warm air strongly depends on the heat generated by the engine. In order to improve the quality of their cars, some high-end cars have added parking heating function (the owner of this device can add it later, but in the near future, this seemingly stable relationship will definitely be broken after the popularization of electric vehicles (the warm air is provided by an independent heating mechanism).
How is the heat of the cooling system transferred to the car?
We are all familiar with the radiator water tank in the front of the car, but what we don't know is that there is a small radiator hidden inside the dashboard in the car, called the warm air box.
The working principle and structure of the warm air water tank are the same as those of the radiator at the front of the car. Both of them expand the heat dissipation surface area through the scales on the surface of the radiator and dissipate heat through the passing airflow. However, the significance of their existence is essentially different. Warm air box is a device that provides heat source for air conditioning warm air. When the fan is turned on, the heat on the surface of the warm air tank is blown out immediately, and the air with heat is sent to the corresponding air outlet along the air conditioning pipeline.
Why is the water temperature in your car rising so slowly?
The thermostat was removed.
In summer, car owners who suffer from high engine water temperature hope that the water temperature can rise slowly, especially those vehicles that are in poor condition. In order to completely achieve the relief effect, some car owners simply remove the thermostat and keep the engine cooling system in a state of large circulation, but this method obviously treats the symptoms rather than the root cause. In winter, the side effects began to appear.
Without the control of the thermostat, the cooling system will always be in a state of large cycle, and the thermal efficiency of the engine can not be guaranteed, so the water temperature rises slowly. In the case of sound structure, when the engine is just started, using thermostat to realize the small circulation state of coolant can help the engine water temperature reach the optimal working temperature as soon as possible. When the water temperature tends to the optimal working temperature, the thermostat is opened, and then the cooling liquid circulates greatly, and the radiator in the front water tank of the engine is used to maintain the optimal temperature state.
The thermostat has poor performance.
It is extreme and tiny to delay the rising speed of water temperature by removing the thermostat. More car owners still want to keep the original structure of the engine. However, when you feel that the water temperature rises slower than before, it may be that there is something wrong with the thermostat.
What causes the high water temperature? Because the thermostat can't be fully opened, the coolant circulation is not smooth, which eventually leads to the high water temperature of the engine. However, the slow rise of water temperature caused by the thermostat is just the opposite. If the thermostat is not closed correctly, the coolant that should flow in the small circulation state will jump into the large circulation pipeline. In this state, the rising speed of water temperature will be affected to some extent. In other words, the greater the gap between the thermostats, the less likely the water temperature will rise.
processing method
Perfecting the function of thermostat is the most effective. However, in order to save trouble, some car owners simply cover the air intake grille to reduce the heat emitted by the radiator at the front of the car and raise the water temperature as soon as possible.
Some improper operations can also lead to slow water temperature rise or poor heating effect.
Need to remind everyone that if you turn on the air conditioning warm air function, it will slow down to the speed of water temperature rise. The defogging function of windshield can automatically activate the refrigeration function of air conditioner, which will inevitably have a certain impact on the supply of warm air.
Insufficient warm air is a good cure for "disease"
It stands to reason that the infrastructure of warm air supply is more stable than the refrigeration system of air conditioning, and it is not easy to have insufficient warm air after the engine water temperature reaches the normal working temperature. However, this is not the case in the actual car use process.
Whether the coolant can reach the warm air tank smoothly and circulate fully in it is the key. From the pipeline leading to the warm air tank, it can be seen that although the warm air tank is a part of the cooling system, it is not a necessary component in the cooling liquid circulation system, that is, even if the cooling liquid does not pass through the warm air tank, it is not easy to cause too much influence on the circulation of the cooling system (sometimes, the warm air tank still acts as a radiator). In order to improve the thermal efficiency of the engine, some high-end brands specially installed electric control valves on the pipeline of the heater box. When the water temperature rises or the passengers in the car need warm air, the valve will open and the coolant will enter the warm air tank, thus improving the thermal efficiency of the engine.
Besides the electronic control valve, the gas in the cooling pipeline will also hinder the circulation of coolant. Of course, this has little effect on the circulation of coolant in the engine cooling system (although the circulation will not be greatly affected, it may lead to the increase of water temperature in the system), but if the gas gathers in the warm air water tank and related pipelines, it is difficult for coolant to circulate here, and the supply of warm air for air conditioning is naturally insufficient.
In this case, you can go to the repair shop for the exhaust cooling system. But this is on the premise that the cooling system and the warm air tank are intact, because from past experience, when the warm air tank is damaged, the coolant leaks and the gas may enter from the damaged place (this is not very certain, after all, the reasons for the gas in the cooling system are more complicated).
But sometimes, the owner is not easy to notice the water leakage. Because, if the damage point is small, the degree of coolant leakage will not be serious. Because the pressure in this part is not high, the cooling liquid remaining on the surface of the warm air tank and solidified may only block the damaged point, which will not cause serious shortage of cooling liquid and alarm. As the owner, there is no textual research.
What should I do if the heater water tank leaks? (Serious coolant leakage)
Replacing the damaged heater water tank is the most direct way, but usually the whole instrument panel needs to be removed, which is a big project in terms of cost and time consumption.
Can I not change it? Yes, on the premise of giving up the warm air function of the air conditioner, the specific method is to directly connect the two inlet and outlet pipes of the warm air tank, so that the coolant leading to the warm air tank can directly flow back to the engine cooling system from the sewer pipe. However, I don't recommend you to repair it in this way. There are some hidden dangers, but there is no way out.
Duct valve failure
If the valve used to switch the air duct fails, it will also lead to abnormal heating, especially for automatic air conditioning, because the button on the air conditioning control panel corresponds to the valve motor. For example, you want the wind to blow only from the air outlet of the dashboard, or you want warm air to reach your feet directly. These are all controlled by valves in the air duct. Similarly, if the valve used to control the warm air duct fails (motor failure or mechanical transmission structure failure), even if the warm air tank has generated heat and the fan works normally, the blocked warm air will not be blown out from the air outlet of the air conditioner.
This situation can also occur on manual air conditioners. The control lever or knob on the control panel controls the air duct valve through the cable. If the transmission mechanism is damaged (mostly joint damage and cable breakage), the above problems will also occur. The owner can judge such problems by the feel of the control lever and knob on the operation panel.
What can the engine do for air conditioning heater?
Having said that, if the engine can't reach the working temperature as soon as possible, there is no way to talk about air conditioning and warm air. Is this caused by the engine?
When the engine is started, the engine computer determines the state of each cylinder by collecting the position information of crankshaft and camshaft as the basis for fuel injection and ignition. After knowing which cylinder to inject fuel into, the fuel injection quantity should be adjusted next, and the water temperature signal plays a key role in this link. After obtaining the temperature signal of the coolant in the cooling system, the engine computer compares this value with the working condition pulse diagram, and then the engine runs at a higher speed in the idle state, thus accelerating the temperature rise of the coolant. By the way, the failure of the water temperature sensor may also cause the engine to fail to start.
We find a problem in the picture. Why is the water temperature sensor installed on the side of the engine (near the gearbox)? It seems that every engine is used to being installed there. Why?
The water temperature sensor is responsible for accurately monitoring the temperature change of the engine cooling system. On the one hand, the performance of the water temperature sensor is also very particular about the monitoring position. It is not difficult to see from the schematic diagram of the coolant system that the coolant is circulated in the cylinder and sent to the radiator and heating system. The reason why the water temperature sensor is arranged here is because the coolant passing through the water outlet can reflect the temperature of the cooling system more objectively. If it is arranged in other places, because the local temperature is too high or too low, the water temperature signal inevitably cannot objectively and accurately reflect the temperature state of the engine.
The gearbox should also be warmed up.
I don't know if you realize that the shift point of automatic gearbox (the switching law between gears keeps corresponding relationship with throttle opening, engine speed and vehicle speed) will also be delayed when driving in cold state. Is this related to the low engine water temperature?
To some extent, the low engine water temperature is indirectly related to the lag of shift point of automatic transmission in cold state. First of all, in control, the engine speed is an important signal for the automatic transmission control unit to control the shift timing. According to the working characteristics of high idle cold car, the shift point lags behind. Secondly, the transmission oil temperature is an important signal for the automatic transmission control unit to identify the load, so it is also important to make the transmission oil temperature reach the best working state as soon as possible.
The automatic transmission control unit will also increase the oil temperature without hindering normal driving, and its concept is the same as that of the engine. By delaying the shift point, the transmission mechanism inside the gearbox can get a higher speed to stir the gearbox oil and raise its temperature. When the engine water temperature and the gearbox oil temperature gradually increase, the shift speed of the automatic gearbox will also decrease accordingly, and finally return to the normal shift rhythm.
Idle speed higher than normal working temperature and delay of shift point are beneficial to the engine water temperature rising as soon as possible. However, in the cold state, engine oil may not be able to protect the interior of the power system.
Influence of cold car on lubrication system
Engine lubrication
Finally, talk about the influence of low temperature on lubrication system. The engine computer detects the working state of the engine lubrication system according to the signals provided by the oil level sensor installed in the oil pan (which can partly detect temperature and quality) and the oil pressure sensor installed near the oil filter. In other words, as long as the oil storage capacity is sufficient and the oil pressure pumped by the oil pump is qualified, the lubrication system of the engine can provide good protection for all components in the engine. Is that really the case? A little one-sided.
Although the oil can be transported to the designated place according to the position of oil passage and oil hole, compared with the normal working temperature, under the condition of oil film formation and adhesion, the more viscous oil can not fully meet the lubrication requirements of the engine. Low temperature fluidity is also a parameter of engine oil specification. It is this that will affect the actual lubrication effect in cold state.
Gear box lubrication
Transmission oil will also become sticky due to low temperature, which may be more real for the owner of manual transmission. When the car is cold, the shift lever will feel a little rough, which is different from what we often say. It's like stirring a bowl of honey with chopsticks. When the temperature rises, the shift process will be much smoother. Compared with the cold state, it is like stirring with a chopstick in a glass of water.
In this way, in order to reduce the internal wear of the powertrain in the cold state, the engine speed and speed are not easy to be too high when driving, and it is best to gradually return to the normal driving mode when the water thermometer has an upward trend.
Editor's summary:
It has become one of the key optimization projects for engine engineers to make the engine water temperature reach the normal working temperature as soon as possible. Shortening the hot start time can not only improve the vehicle quality, but also improve the fuel economy. For the majority of car owners, although we can't change anything during the hot car, through understanding, car owners can ensure the thermal efficiency of the engine to the greatest extent, such as ensuring that the thermostat is in good condition, and not turning on the air conditioner and warm air during the hot car. In addition, when the engine water temperature gauge has not risen, don't rotate too fast, and don't forget that the gearbox also needs preheating. (Photo/Wen Li)