Let’s take stock of some misunderstandings about fuel consumption

This may be the most serious misunderstanding among Chinese people, and it is rarely corrected. The best efficiency range of a general household gasoline engine under high load conditions is between 2500-3200 rpm. For Chinese people who drive manual cars for daily driving, the 2000 shift gear is also suitable. It takes into account fuel consumption and noise, but even if rapid acceleration is required, It is common to upshift at 2000 rpm, causing the speed to drop to the inefficient range below 2000 rpm after the upshift. Instead, oil needs to be replenished due to poor power. The correct shift should be to shift gears after 3000 rpm. At this time, the speed drops. At 2300-2400 rpm, it saves fuel.

In fact, when overtaking at high speed and with a large displacement, the general speed can be kept in the efficient range and save fuel. Small displacement only has advantages at overall speed and low speed. Generally speaking, with the same engine technology, a moderate displacement is the most fuel-efficient. This moderate displacement is 1.8-2.0 for compact cars (1.5 and 1.6 may be good for some models. This is a new situation that only appeared in some new cars that were replaced in 2014. It is also a technical recommendation. The new 1.6 and 1.5 engines The power has reached the level of the previous 1.8 engine), and for mid-level cars 9 is 2.0-2.5. The turbo can be a little smaller than this. A displacement that is too small actually causes the engine to work beyond optimal working conditions many times, which in turn consumes more fuel. The first thing that has the biggest impact on the fuel consumption of traditional power vehicles is the vehicle weight, the second is the aerodynamic Q characteristics, for example, a tall and square SUV will consume fuel, the third is the technical level of the gearbox and engine, and the last is the displacement.
Sometimes, user data does reflect that in compact cars, 1.6 displacement is more fuel-efficient than 1.8 and 2.0, and in mid-size cars, 2.0 is more fuel-efficient than 2.4 and 2.5. However, this is often due to drivers with small-displacement engines. The car uses less power. Even if the power is not enough, it is not willing to use a large accelerator due to fuel consumption and noise.

A car of a smaller class is generally lighter than a car of a larger class. At low speeds, because the main resistance is rolling resistance, which is greatly affected by the weight of the car, it does have a fuel consumption advantage. However, cars in the next class usually have lower gearbox and engine technology. In addition, because the body is short and space must be ensured, the most streamlined design cannot be made. The wind resistance is large when driving at medium and high speeds, which is not conducive to fuel economy. At the same time, the engine configuration of small cars is too low, which leads to an increase in fuel consumption more than that of large cars. The above situation is particularly obvious between small cars and compact cars. In fact, compact cars generally have no higher fuel consumption than small cars. To some extent, even when driving in cities where small cars have a greater advantage, some compact cars are still more fuel-efficient than some small cars.

This sentence was correct in the early days of automatic transmission development. Compared with the 4AT, the traditional 5MT has more gears, and the speed is easier to control in the efficient range. In addition, there is no loss caused by the torque converter 9, and it is indeed more fuel-efficient in general. However, modern automatic transmissions can already be almost the same as manual transmissions or even more fuel-efficient than manual transmissions by improving the shifting procedures, adding gears, etc. The CVT, because the transmission ratio can be changed continuously, and the dual-clutch transmission, "because the shift interval is extremely short and the transmission efficiency is extremely high, can basically be more fuel-efficient than the manual transmission. In addition, even a manual transmission with lower fuel consumption in principle In the hands of a novice who is not good at grasping the clutch and gear shifting timing, it may also consume more fuel than an automatic transmission.

This statement is not entirely wrong. For high-end cars, if you want to pursue additional power, compared with increasing the displacement and the number of cylinders, it is generally more fuel-efficient to increase the turbine without changing the displacement. Its principle is equivalent to that when you don't need so much power, the engine is an ordinary naturally aspirated engine with a moderate displacement, so there is no fuel consumption of a large displacement. At the same time, the weight of the engine can also be reduced, and with a large displacement It is quite obvious to measure the weight of the engine itself.
But for family cars, especially compact and small family cars, they may not be more fuel-efficient. Why? When a small-displacement engine is running at a medium speed on a fast road or is completely blocked and creeping at low speeds, the turbine does not intervene. The air intake volume is smaller than that of a naturally aspirated engine with a larger displacement, which can save fuel. Normally, When driving on highways and fast roads, the turbocharged 9 model is more fuel-efficient. However, on ordinary urban roads with many traffic lights, or when the expressway is semi-congested or not blocked, if you frequently decelerate and then accelerate, the impact of turbo lag will be greater (the turbine of a high-horsepower turbocharged car can remain uninterrupted at this time), and the accelerator is pressed The power comes up after a while, which will greatly increase fuel consumption; when the turbine remains involved during high-speed cruising, fuel consumption will also be slightly higher. Generally speaking, the fuel consumption of naturally aspirated engines is similar (the fuel consumption of some Volkswagen 1.4T+dsg cars is mainly due to the gearbox and lightweight design). But it is also a four-cylinder engine, compared with turbocharging The cost of naturally aspirated engines is actually higher, and maintenance and repairs are more expensive. At the same time, they also have disadvantages in smoothness and quietness, so they are not highly recommended.