What is powershift？ Advantages and disadvantages of dual clutch gearbox

What is a dual clutch gearbox?

As the name implies, the key technology of dual clutch is dual clutch, that is, there are two clutches, one of which is responsible for odd gears (1st, 3rd, 5th and 7th gears) and the other is responsible for even gears (2nd, 4th and 6th gears). It can be imagined that two manual functions are combined into one and built in a single system, which has no torque converter or planetary gear set. From the gear part, it looks like a manual transmission at first glance, because it has a synchronizer, but the difference is that it uses "double" clutches to control the on-off of engine power. These two automatic clutches, driven by electronic control and hydraulic pressure, can control the operation of two sets of clutches at the same time.

Powershift DCT is different from ordinary automatic transmission system. It is based on manual transmission instead of automatic transmission. Besides the flexibility of manual transmission and the comfort of automatic transmission, it can also provide uninterrupted power output. However, the traditional manual transmission uses a clutch. When shifting gears, the driver must step on the clutch pedal to make the gears in different gears engage, and the power is interrupted during shifting, which makes the output performance intermittent.

At present, more and more models basically use dual-clutch gearbox, which has its own advantages and disadvantages. However, despite the buzz, many car companies still insist on using it. So why do domestic car companies love using dual-clutch gearboxes so much? Let’s take a look at the pros and cons of the dual-clutch gearbox with the car xiaobian.

It is precisely because of this innate advantage that major manufacturers must try their best to overcome technical difficulties and develop their own dual-clutch gearboxes, including their own brands, even if they are faced with many difficulties.

What are the advantages and disadvantages of dual clutch gearbox?

No matter whether you are accelerating or decelerating, you are basically ready to move up and down for you under the clutch, so when you step on the brake, you need to accelerate immediately, step on the accelerator and find acceleration, but there is no power. Similarly, these two conditions will also seriously affect the life of the dual clutch. A good practice is to lift the brakes and slide for a distance, and then start to accelerate the throttle.

Especially in congested roads, it is possible to shift the S gear (when the S gear is in use, the engine speed will be higher, so as to upshift) or switch to the first gear in manual mode, so as to prevent the stop-and-go gear from switching between the first gear and the second gear too frequently and the gearbox from overheating. Try to walk for a while and stop for a while, without semi-linkage crawling. If there are too many people jumping in line, there is nothing to do.

There is also a kind of gearbox, such as Fiat. When you brake to the end, the clutch will not cut off the power, but will always be combined. This is just like the manual gear without stepping on the clutch and still in gear, which will "suppress" the gearbox. Therefore, this kind of gearbox advocates hanging in neutral when you wait for traffic lights or traffic jams for more than 5 seconds. I have such a friend around me. It turned out that he didn’t know that the dual clutch was in this condition, and then he directly scrapped the gearbox. Fortunately, during the warranty period, the manufacturer replaced it for free.

Advantages of powershift

Powershift has the following advantages:

1. Shift gears quickly. Powershift’s shift time is very short, faster than the speed of manual gearbox, less than 0.2 second.

2. save fuel. Powershift can save a lot of fuel because it eliminates the interruption of torque, that is, the power of the engine is always used and always works at the best. Compared with the traditional planetary gear automatic transmission, it is more conducive to improving fuel economy and reducing fuel consumption by about 15%.

3. Comfort. Because the shift speed is fast, every shift of DCT is very smooth, and the sense of frustration is so small that it is difficult for the human body to detect it.

4. There is almost no torque loss during gear shifting.

5. When the high gear is in the preparation state, the upshift speed is extremely fast, reaching an astonishing 8 milliseconds.

6. No matter what the throttle or operation mode is, the shift time can reach at least 600 milliseconds (it takes about 900 milliseconds to shift from odd gear to odd gear, or even gear to even gear, for example, from fifth gear to third gear).

Powershift’s shortcomings

1. Cost. Powershift’s structure is complex, and its manufacturing process requires high requirements, so its cost is relatively high. Therefore, we can see that all the vehicles equipped with powershift are middle and high-end models.

2. Torque problem. Although the dual clutch gearbox can absolutely meet the requirements of ordinary vehicles in terms of tolerable torque, it is still not enough for intense use. Because if it is a dry clutch, it will generate too much heat, while the wet clutch will not have enough friction.

3. Because of the existence of electronic control system and hydraulic system, the efficiency of double clutch gearbox is still not as good as that of traditional manual gearbox, especially the wet double clutch gearbox used to transmit large torque.

4. When the gear to be switched is not in a ready state, the shift time is relatively long, even exceeding 1 second in some cases.

5. The dual clutch gearbox is heavier than the traditional manual gearbox. 6. The reliability of the early dual-clutch gearbox was poor.

With the development of automobile, the shortcomings of dual-clutch gearbox are bound to be less and less, and become more perfect.