Summary: Analysis of the two core factors that determine the fuel consumption of automobiles, and analysis of the embarrassing reasons for fuel saving of MT automobiles.
Mt manual transmission is more fuel-efficient than automatic transmission with the same displacement! This statement is common sense in the dominant stage of MT models, and it seems to be true; The main reason for saving fuel is that the automatic gearbox has a single type, the number of forward gears is relatively small, and the high gear option is only "≤5AT". At the same time, MT models have six speed ratio options.
On the premise of the same displacement as the vehicle type, the transmission ratio width is generally narrow if the number of forward gears is small; And the difference between each speed ratio is relatively large. To put it bluntly, acceleration requires a substantial increase in speed to achieve improvement, and high speed leads to high fuel injection frequency, and fuel consumption is naturally difficult to control.
General standard: Take 4AT gearbox as reference.
First gear 0-20km
Second gear 20-40km
Third gear 40-60 km
Fourth gear ≥60km
The speed difference of each forward gear will be about 20km/h, and the speed can be easily increased to the range of 3000/4000rpm when accelerating; Moreover, after the speed exceeds 60 kilometers per hour, the speed increase depends entirely on speed increase. In this way, the speed of high-speed cruising will be stabilized at around 3500 rpm, and the fuel consumption will naturally be high.
Most people who drive MT cars have the driving habit of "high gear and low speed". In order to save fuel, they can't wait to cruise at the speed of "20 km/h in 5th gear". Early AT gearboxes generally did not have manual shift mode, which was one of the reasons for the high fuel consumption of automatic transmission cars in the past.
New car standard
6 mt & 6 in contrast. On the premise that all engines use 1.5L-NA self-priming engine, the fuel consumption of 6AT is often higher. The reason is that the technical level of most machines ≤6AT is quite low, and even after the patent protection period of Lai planetary gear set ends, the manufacturing cost is not as high as that of some wet dual-clutch gearboxes.
The torque converter used in these machines will be "unresponsive". Theoretically, at the speed of < 10 km/h, the engine drives the torque converter, and the guide wheel stirs the gearbox oil to drive the turbine to run. The loss of oil as a "forced oil" transmission will be greater, but it can accelerate smoothly enough. This is why it is generally believed that the fuel consumption of at models will be higher, but it cannot be generalized.
One-way locking clutch is one of the core structures of hydraulic torque converter. In many excellent AT models, when the speed exceeds the standard of 10km, the clutch will promote the rigid combination transmission of turbine pump wheel; In this state, the transmission efficiency of hydraulic torque converter is not lost to MT, and even a few high-end models will have a high efficiency of more than 95%, which is a high standard that MT can hardly achieve.
Therefore, the fuel consumption of a small number of automatic transmission vehicles is higher than that of manual transmission options. The reason is nothing more than that the equipped at gearbox technology is backward; But these cars are basically entry-level cars, and the level is ≤ 65438+100000, which is determined by the product positioning.
Key point: wet dual clutch gearbox does not have this problem! The reason is that its transmission structure is also a "clutch", and it is wet, with lubrication and heat dissipation system, which is much more stable and durable than MT.
The transmission efficiency of this machine is generally above 90%, and the option of ≥ 65438+100000 is as high as 95%. The key is that the shift speed can reach millisecond level. Compared with manual gear with "seconds" as the timing unit, shortening the shift time (speed decrease) can greatly reduce fuel consumption.
The automatic transmission equipped with this machine has almost no manual option in the main range of 8.0/ 1.5 million, so there is no intuitive reference for the fuel consumption level. Therefore, many users still insist that manual transmission cars are more fuel efficient.
The reason is that the fuel consumption of the remaining manual gears is still relatively low. But if the comprehensive thrust-to-weight ratio is calculated, the result is not only embarrassing, but may even be unacceptable.
Cross comparison
1.5L-NA compact car with self-priming power.
1.5T turbocharged compact car
The two cars seem to have the same engine displacement and the same size and grade; But the former is a 4.5-meter joint venture vehicle with curb weight of 1.2 tons; The latter is a 4.7-meter domestic car with kerb mass 1.5 tons, so it should be very reasonable to evaluate it with "different products at the same level".
Because these cars are limited by manufacturing costs, they cannot use lightweight and high-strength aluminum alloy materials; Domestic cars must ensure the strength (safety) of the body structure, so they can only use a lot of steel to strengthen the structure. So these cars will be a little heavy. If the engine power reserve is120 kw/270 n m (1500 ~ 4000 rpm), the maximum thrust-to-weight ratio is only about 105 HP/t, which is some "pony &; The combination of "cart", but the performance level is still 9 seconds 100.
The power reserve of "1.5L- joint venture option" is 85kW/145n m. Although the power difference is large, the thrust-to-weight ratio is still close to 100Hp/T/t, but the output power of naturally aspirated engine is very low at middle and low speeds, which will cause poor acceleration experience. If you want to feel a good sense of acceleration, you can only accelerate by pulling up the speed frequently, but this state will consume a lot of oil.
So over time, the users of these vehicles get used to the weak performance. When the shift speed exceeds 2000 rpm, it will feel like losing a coin. Then such a driving style will definitely make fuel consumption lower, and the level of accelerating 100 kilometers for more than ten seconds is not fun to drive, so pursue the ultimate low fuel consumption. In order to prove that the fuel consumption of MT cars is low, this sentence will pop up when looking at the dusty taillights in front: automatic cars have high fuel consumption, but they don't know that people are experiencing driving pleasure.
Summary: MT cars in the range of 50/80,000 are often more fuel-efficient than cars of the same class; The joint venture MT option in the range of 8.0/150,000 is not worth discussing, so the fuel consumption performance of integrated automatic transmission vehicles ≥ 80,000 is actually quite good, except CVT with great transmission loss, so let's talk about it.