Very simple, because the D gear is a fool mode, for novices to use, high-speed full use of S gear is not the real old driver, do you know how the old driver opens at high speed? In fact, it is also necessary to divide into models, AT, DCT and CVT are not the same. If you don't understand, high fuel consumption is a trivial matter, and it is easy to hurt the gearbox if you don't get it right.
In the end what gear, in the end how to open the fuel saving, S gear, D gear what are the advantages, but also really need to systematically understand the basic knowledge of the engine, gearbox, I strive to use the most simple language to explain to everyone.
The first thing to know is what the gearbox has changed? It does not change the speed of the car, but the speed of the engine. The fuel car must be matched with a gearbox, and the tram is not used, why is this? To use a figurative analogy: the engine is born disabled, so it needs to be on crutches, and this pair of crutches is the gearbox.
The first disability of the engine is called low torsion deficiency. To put it bluntly, when the number of revolutions is low, it is impossible to provide enough torque (understood as force) to the wheel, and when learning to drive, the clutch is faster and the ignition is turned off. That is, the torque is not enough, the torque provided by the engine at this time is not enough to drive the vehicle, and the clutch is lifted, the engine and the wheel form a rigid connection, the car does not move, the engine can not move, so it is extinguished. Why is it good to order foot oil? To the oil engine to pull up the speed, the torque is large enough, do not like to turn off.
The second disability is the narrow range of revolutions, and the general engine is the red line area of seven or eight thousand revolutions, which can rarely reach 10,000 revolutions. We don't have to think about fuel consumption, if there is no gearbox, in order to start up, you can only use a gear ratio of gears - how fast can you drive the fastest with a gear? You step on 8000 rpm, which is 50Km to the head (different models have different gear ratios, there are differences). Do you want a car with a top speed of 50km per hour? Can't get on the highway.
So the problem is: the same speed of 50Km per hour, you can also do 1 gear 8000 rpm, 2 gear 5000 rpm can also do, 3 gear 3000 rpm can also do, 4 gear 2000 rpm can also do, 5 gear 1500 rpm can also do. How many gears do you use to open? At this point, everyone should also understand that the engine speed is proportional to the number of fuel injections, and the higher the number of revolutions, the more fuel injections per unit time, the more fuel is theoretically expensive. First of all, the first and second gears are excluded, 8000 rpm, 5000 rpm, in addition to high fuel consumption has no benefits.
Save three gears, let's speak directly according to the speed, 1500 rpm, 2000 rpm and 3000 rpm. Isn't 1500 rpm the most fuel efficient? not necessarily! It also depends on the economic conditions of the engine. Because if the speed is too low, it will lead to insufficient combustion of gasoline, the combustion efficiency will decrease, not only is it not fuel-efficient, but it is also more likely to produce carbon deposits. General engines, most of the economic rpm is about 2000 rpm, so 3000 rpm is certainly not the most fuel-efficient, but 1500 rpm and 2000 rpm, in the end which fuel saving, is really not necessarily.
Because in addition to the speed, the economic working conditions also include a power output range, for example, 2.0T between 25-50Kw, 1.5T in the 16-35Kw range. If you have a uniform speed of 1500 rpm and the output power is only 7Kw, it is better to increase the speed of the car and keep the output at the engine around 2000 rpm. The engine 30Kw, 2000 rpm (2.0T for example), is the most fuel-efficient working condition of your car, and the tube is several gears.
The maximum speed limit of the continental high-speed is 120Km, and the SUV may exceed the economic power output range because of the high wind resistance coefficient and the large wind impact area, so sometimes it is slightly lower than 120Km to be more fuel-efficient (compared to its own engine to see the output power), the car wind resistance is smaller, and the problem is not big.
Capable friends can look at the above thermal efficiency distribution map, the horizontal axis is the number of revolutions, the vertical axis is the torque, and a line with numbers is the thermal efficiency. As can be seen from the figure above, the thermal efficiency is very low at low torque output. When we are driving at a uniform speed, the vehicle resists wind resistance and rolling resistance to do work, wind resistance, rolling resistance is certain, then our speed is certain, we can think that the output power is unchanged. And the power = torque X rpm / 9550, the highest thermal efficiency of 40% of the above figure, that point, about 2400 rpm, output power 42.7Kw. Looking at the 39% range range, starting from 1600 rpm to 3200 rpm, the output power is roughly calculated according to the corresponding torque from 22Kw to 42.7Kw. It can be seen that the efficient range of this engine is relatively wide and will be more fuel-efficient. But to make it work efficiently, at least don't let the number of revolutions fall below 1600 revolutions.
Therefore, at high speed, the most fuel-efficient way is to keep your engine in economic conditions, use D gear or S gear, or even manual mode, and keep the number of revolutions. If your car has only 1500 revolutions at high speed 120Km, it is really not as good as the whole S gear, which is equivalent to manually reducing one gear. Fuel consumption will not increase, but the power will be stronger.
In addition to the most economical conditions for fuel saving, the engine also has a maximum power rpm and a maximum torque rpm, which can be simply understood as the most energetic state. Keeping the engine in the range of maximum torque revolutions and close to the maximum power revolutions, its power performance is the best. Taking the EA888 low-power version equipped with the Volkswagen Tanyue 330 as an example, its maximum torque range is 1500-4000 rpm, which means that the number of revolutions can provide maximum torque in this range. The maximum power rpm is 4100 rpm - 6000 rpm, when the horsepower is the greatest. If it is manual transmission, this engine you will shift gears above 4000 rpm, the power is the strongest, this is S gear, sport mode.
Of course, the adjustment of car companies is not necessarily so violent, because the sport mode will pay the price of fuel consumption, and the engine rotation is high and noisy, and the driving experience is not good. Some car companies also give you an S+ or something, or S gear + performance mode. It doesn't matter, the main difference is the shift logic. S gear downshift will be more positive, upshift will be more lagging.
In addition, some models will also have feedback in terms of steering wheel power, if you use S gear, the default into the sport mode, the steering wheel will become harder, but also more accurate, the virtual position is smaller. Some suspensions equipped with variable damping will also stiffen the suspension to provide better lateral support.
Back to the question itself, is there a benefit to using S gears at high speed? Yes! More power, cleaner overtaking, which is equivalent to indirectly improving vehicle safety. If it is a variable damping suspension, the high-speed pavement is better, the comfort is not a problem, the suspension is harder, and the support is better when the direction is sharply hit in the unexpected situation. The disadvantage is that fuel consumption is more likely to increase.
However, it also depends on the specific model, some cars, if you have a uniform speed of 120Km, there is no difference between the D gear S gear, there is only a point of throttle, one does not downshift, one actively downshifts.
There is also the gearbox, AT do not care, double clutch if the total run high speed, do not always uniform speed, appropriate switch gear, to avoid the same set of gears excessive wear (involving the failure rate after ten years) CVT try not to use S gear, you have to be it daddy, be careful to wait.
The old driver drives, no one will be the whole S block, unless it is two bottles of fuel treasure before refueling, pull up the number of revolutions in order to clear the carbon. More than 3000 rpm, open for two or three hours continuously, is very helpful for carbon deposition cleaning. The time is short, 1500 turns stop and go, plus is useless.
How does the old driver drive at high speed? The automatic block is like a manual gear! Want to overtake, S gear, run at a constant speed, look at the number of revolutions to change D gear, and even sometimes deliberately use snow mode, sand mode to use different modes of gear shift logic to combine speed control engine rotation. I am now driving a BYD Tang generation, it is really like opening a manual gear, the power is low to charge, the city is not fast, then use the sand mode, high-speed want to clear the carbon, use the sports mode. In order to start smoothly in the city, I use pure electric snow mode, 70Km hybrid ECO mode, and even deceleration on high speed, I will manually cut pure electric loose throttle to make full use of kinetic energy recovery.
The so-called old driver can do more subtle operations under the premise of ensuring safety, and pursue driving pleasure and more extreme fuel consumption. My old Don, known as the Oil Tiger, can prescribe a minimum of 5 starts with fuel consumption. Therefore, what D gear, S block, is not static, no matter what you do, there is no brain there is a simple way to D gear to go around the world, but also there are a variety of need to think, need to operate the advanced experience, it depends on how everyone chooses.