Continued with the above:
"shifting feeling" of low-temperature cold start vehicle
abnormal. Is
normal?
Some vehicles will feel obvious pauses in the initial stage of acceleration shift after starting the engine at low temperature. How can this be explained? There are two main reasons. In fact, the low-temperature flow performance of transmission oil is poor, and the control and lubrication of the solenoid valve are not at the best state; there are many types of automatic transmissions, and the first thing you need to know is AT and wet dual-clutch transmissions.
AT uses a torque converter to connect the engine and transmission . The torque converter can amplify power, so just understand this; secondly, what you need to know is "low-speed hydraulic transmission ". The torque converter often uses hydraulic transmission when the vehicle speed is less than 10km/h or when it is accelerated in 1 gear, that is, the transmission oil is stirred through the pump wheel, and the oil promotes the turbine through the guide wheel . To put it bluntly, it uses oil to transmit power.
The transmission oil viscosity during low-temperature cold start is high, the flow performance is poor, and the degree of power loss is also relatively large.
This is the key point: It is normal for to feel the power when starting with low temperature cold. The core factor is first of all, the impact of excessive cooling on the engine thermal efficiency, and secondly, the loss of transmission oil viscosity in the torque converter increases.
Moreover, during the oil transmission process, the temperature of the transmission oil will gradually change, and shifting hysteresis may occur during the process of reducing viscosity; at the same time, the gear shift of the AT also requires the participation of transmission oil. The oil in the solenoid valve is transmission oil, which also plays a transmission role in the solenoid valve, which can be defined as "forced oil". So how high the viscosity will inevitably affect the feeling of shifting gears, but so what? In-situ hot cars are wasting fuel and low-efficiency hot cars. The fuel wasted in the process far exceeds the impact of the torque converter on fuel consumption during normal driving; some hysteresis of gear shifting is nothing more than a pause, but the automatic transmission of all fuel vehicles cannot be truly smooth, and the difference is nothing more than obvious and not very obvious. Running in this state does not damage the gearbox.
wet dual clutch transmission is quite special. This dual clutch is actually very similar to a torque converter; the torque converter will be rigidly combined after a slightly higher speed, and the turbine and pump wheel of the torque converter are pushed through the one-way locking clutch to combine, so as to reduce power loss.
The wet dual-clutch transmission has always been rigidly combined with transmission, but there is one special feature.
That is, the wet dual clutch always has "sliding friction", which means there will be slight slippage during normal operation; however, this level is controllable and will not affect the service life of the clutch assembly, and its design life can be comparable to that of the torque converter.
Wet clutch will be lubricated and flow heat dissipated through transmission oil, which is just the core factor that ensures its service life.
The transmission oil viscosity at low temperatures is high, which will also have some impact on the sliding degree of the dual clutch; therefore, the probability of acceleration at low temperatures is that it is a shift hysteresis or abnormal state standard, but it can still ensure the service life of the clutch. As for the gearbox part, of course, there is no need to worry. The transmission oil can reach the best level, but its wide enough service temperature will only fluctuate on the normal, optimal or excellent standard line. Normal standards can achieve standard wear reduction.
What is the applicable temperature range of transmission oil?
Correct answer: ﹣40℃ to 170℃ above zero
If the temperature in your car is lower than minus forty degrees, it is another matter, but there are not many places that will be so low; on the contrary, there are no need to worry in other normal environments; after driving for so many years, from the lowest-end manual transmission car to various automatic transmission cars using AT/DCT/AMT, there is no hotter car on the spot, so there is no problem.
There is only one kind of automatic transmission that is special, that is, "CVT·Currentless Transmission".
The transmission part of , such as transmission, does not need to be interpreted specifically. It uses two types. One is the same torque converter as AT, and the other is the wet multi-piece clutch, which has a long service life and is not affected by temperature.
The special feature is that it does not use gear shifting, but uses "friction transmission".
Two sets of variable angle conical wheels are used to imitate the large and small gears, use the active conical wheel to push the steel belt and push the driven conical wheel to rotate, which is the core part; the conical wheel and steel belt are driven in friction and change the speed ratio , and there is wear during the process.
CVT is different from general automatic transmissions. Its special structure determines that extremely high standards of lubrication must be used to effectively reduce grinding, and the requirements are far beyond the gears of other transmissions. Therefore, in low temperature environments, the vehicle must be heated on site, first heated the engine antifreeze coolant, and then heated the transmission oil with antifreeze , and then the gear shifting operation can be carried out normally. Before this, if you forcefully accelerate, you cannot shift gears. You can only drive at a fixed speed ratio and forcefully at low speed under the premise that the torque converter is not rigidly combined; this will greatly increase fuel consumption and accelerate wear of the engine and gearbox.
Now, the only cars that need to be hot in winter are left with continuously variable transmissions, but they are not representative. After all, only a few car series and a few entry-level cars use it.
The last thing you need to know is the contradiction between the in-situ hot truck and the particulate matter catcher. In-situ hot trucks are definitely asking for trouble for vehicles that meet the national standard 6-b emission standards.
Because the engine's combustion sufficiency is extremely poor before the hot-car water temperature is reached; if the combustion sufficiency is low, the free carbon particles are produced, and the particulate matter will have a great impact on the air quality. Therefore, high-standard emission rules require vehicles to install particulate matter traps. The model used by gasoline engine is called "GPF" and the diesel engine is "DPF".
Its function, as the name suggests, is used to collect particulate matter in the exhaust gas, and then regenerate particulate matter under conditions that meet the standards (high temperature treatment).
The process of heating the vehicle in the place is a process of producing large quantities of particulate matter. If you have the habit of heating the vehicle in the place and commuting mainly on urban roads, then the vehicle can cause serious blockage of the particulate matter trap if it has seven or eight hundred kilometers. There is only one solution for the blocked capture device, that is, drive at medium speed for a long time, so that the temperature of the capture device reaches the temperature of renewable particulate matter, and can be effectively cleaned for about half an hour.
However, family cars generally do not drive like this, so it is easy to cause congestion in the hot car on the spot.
The blockage of the particulate matter trap will cause the exhaust back pressure to increase, the intake becomes difficult, and the engine torque will drop significantly; if the torque drops, the power of the same speed will decrease, and the power reduction will be equal to the slower acceleration and the vehicle speed will decrease; as a result, the speed can only be forced to increase the power to compensate, and the fuel consumption will be high. The clogged catcher will cause the fuel consumption to increase several times. The fuel consumption of ordinary 1.4-2.0T scooters can also soar to more than 30L/100km. The general semi-trailer is the standard.
Still think it is necessary to warm up the car in the spot?
Take a look at the user manual of these cars. It basically states that "try to avoid idle at the same time".
Editor: Tianhe Auto-Auto Science Island
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