There are many fuel saving "cheats" on the Internet, but most of them are experience talk from a practical point of view, and even many are outdated, even wrong experiences. Even if it is true, but for novices, they also know why they do not know why, so if you want to take another step towards the "old driver", you must not only know "how to do" to save fuel, but also know "why" to save fuel.
I participated in the riders' club activities, everyone has the same car, the same road conditions, it is because of different driving habits, fuel consumption is up to 4 differences! I show fuel consumption of 6.5L, and the rider in front of me is 10.2L.
First, let the engine save fuel
Have you ever heard of the concept of the so-called most economical speed? Generally, the car is the most fuel-efficient at about 60-90 kilometers per hour, and this most economical speed is actually determined by the economic number of engine revolutions and the gearbox transmission gear ratio. It is also affected by wind resistance, rolling resistance and other factors. Cold knowledge: If on the plateau, because the air is thin, the air resistance is reduced, then the economic speed will be higher than in the zero altitude area. For example, a car driving 70Km on the plain is the most fuel-efficient, but in the highlands, the most economical speed may be 75 or 80Km/h.
As you probably know, the engine has a concept of maximum thermal efficiency. At present, the highest mass production car is BYD's Xiaoyun 1.5L self-priming engine, with a maximum thermal efficiency of 43.04%, in general, more than 38%, even if it is a good level, it can exceed 40%. However, this maximum thermal efficiency can only be achieved in a certain number of revolutions and under certain output power conditions. Therefore, if we want to save fuel, we must know our car and try to keep the engine working "in the most economical working range".
The "most economical working range" of each engine is not the same, most of the four-cylinder engine is above 2000 rpm, taking my car, BYD Tang generation as an example, its most economical working conditions appear in the engine 2000-2200 rpm, output power 28-42Kw. That is to say, when I drive, I try to let the engine work at this number of revolutions and this output power, and the engine burns the most fully and the efficiency is the highest. If you do not know what the economic conditions of your car are, you can consult the manufacturer or 4S shop, or query the engine thermal efficiency distribution map of the model. If you know your own model, please share it and study it with you.
Second, driving fuel saving
You carefully control the throttle, keep the engine output at 28-42Kw, and flexibly shift gears, so that the engine is always around 2000 rpm. Now your engine is the most thermally efficient, that is, the same unit of fuel can exercise a longer mileage, but at this time, a foot of sharp braking, you may use half a liter of oil in exchange for the initial speed is converted into the thermal energy of the brake pads.
Therefore, the high efficiency of the engine does not mean that driving can save fuel, from the driving point of view, less on the brakes, try to use the accelerator to control the speed is the best choice. It doesn't cost oil to step on the brakes, but after your speed is reduced, don't you need to use oil to raise it?
How can I put on the brakes less? There is a car in front of you, and you can't crash into it. This requires driving experience, which can be summed up in nothing more than four words - prejudgment in advance!
For example, 100 meters ahead is a signal light, if you judge that the green light can not go, then this foot oil does not have to be given. Loose throttle belt sliding, before reaching the intersection and then braking. If conditions permit, you can even control the speed without stepping on the brakes, keep it just to the intersection to turn green, and go straight through. On the contrary, constantly accelerating at the deep throttle and then braking is the most fuel-intensive.
We know that when the parking is not turned off, there is also an idle fuel consumption, which is about 1-2L an hour. Why does traffic jam cost oil in urban road conditions? A total of 2 kilometers of road, blocked you for half an hour, idle fuel consumption is fast to 1L, you run 2 kilometers with 1L oil, equivalent to 100 kilometers of fuel consumption of 50L, can you not cost oil?
There is no way to block the manual gear when it encounters traffic jams, if it is blocked very dead, then turn off the fire. We all think that the automatic start and stop of the engine is very chicken, but this function with 48V light mixing can indeed reduce idle fuel consumption.
In addition, since it is a manual gear, there is one more thing to pay attention to, that is, to shift gears. The principle is to minimize the energy loss caused by the gear shift. When you step on the clutch, the power of the engine is interrupted, and the fuel consumed is wasted. Therefore, when changing gears and lifting the clutch, do not drag mud with water, many novices also carry a lot of bad habits of driving school, and the high-end position also slowly lifts the clutch, which is completely unnecessary. When the clutch plate is semi-linked, it will generate a lot of heat, which not only costs oil, but also shortens the service life of the clutch plate. Start by paying attention to oil separation and avoid idling.
As for the timing of the gear change, I know what the most economical working conditions of the engine are, and how many conversion gears should be clear, right? Also take my car as an example, if it is a manual gear, 2400 rpm or so upshift, then the engine is always in the economic rpm range.
Third, the use of cars to save fuel:
Vehicles at a uniform speed, the engine work is mainly used to resist the vehicle's wind resistance and rolling resistance, there is a part of the battery power supply, supply air conditioning, electricity in the car, here is not discussed, in 70-80Km below, open the window than open the air conditioner fuel saving, higher than 80Km, generally speaking, the air conditioner is more fuel-efficient than the window, after all, the wind resistance of the open window is too large.
Wind resistance is related to the windward area, wind resistance coefficient, air density and other factors of the vehicle, and is proportional to the square of the speed. We basically couldn't change the shape of the vehicle, so we could only work on speed. At high speed, a uniform speed of 110Km can save about 1 liter of oil than 120Km.
The rolling resistance is mainly related to the weight of the car and the tire pressure. What is rolling resistance? Imagine that when the tire rolls forward, the ground will deform and produce resistance, and the deformation from the ground will recover to produce elasticity. The difference between this resistance and elasticity is rolling resistance. Therefore, if you want to reduce rolling resistance, the first is to reduce weight, and the second is to boost.
The mess in the car is best clear, some people commute to work, and the trunk has to put two boxes of mineral water, which is completely unnecessary. The other is the tire pressure. The higher the tire pressure, the smaller the rolling resistance and the lower the fuel consumption, but everyone knows that the tire pressure cannot be increased indefinitely, and the high tire pressure will also bring a problem, the grip will decrease, the braking distance will become longer, and the ditch and ditch will be more bumpy. You can make your own choice here. For example, if the manufacturer recommends a tire pressure of 240, you have no problem hitting 280. The braking distance does become longer – see earlier, predict in advance that we can even barely step on the brakes.
Fourth, the limit of fuel saving
Understand the optimal operating conditions of the engine and vehicle, then what we have to do is to keep the engine in efficient working conditions under various road conditions. I roughly divide the common road conditions into the following four types:
1. High speed:
Generally, when the automatic car is running at a uniform speed of 110-120Km, it is the best working condition of the engine, which is also intentionally set by most car companies. The wind resistance is similar to the output power of the optimal operating conditions, and the maximum grade matching rpm is exactly the economic rpm. And some models are not enough gear ratio, high-speed 120 are dry to 3000 rpm, this kind of car is obviously slower will be more fuel-efficient.
The highway conditions are relatively simple, we just need to find the most economical working area of the engine. Gears are certainly the highest, with the number of revolutions and output power also controlled by throttle. Most car owners feel that high-speed fuel saving, in fact, this is not the case, high-speed driving wind resistance is greater, 120Km is not the most economical speed of the vehicle, but at this speed, the engine is in the highest thermal efficiency range.
2. National highways (including intercity expressways and provincial highways):
The general speed limit is 60-80, there may be traffic lights, but the road is very smooth. Speed limit 60-80, wind resistance is smaller than on high speed, but at this time the engine is difficult to maintain economic conditions, mainly the power of uniform driving is not enough - the wind resistance is small, the load of the vehicle is small, the output power may only be 20Kw, at this time the engine gasoline combustion is not the most sufficient.
At this time, the most fuel-efficient driving mode (theoretically), like the hybrid, is called "pulse taxiing", because the load of the engine at a uniform speed is too low to enter the optimal working conditions, so we enter the acceleration condition and increase the load of the engine. Or keep the engine 2200 rpm, output power 28-42Kw, speed increased to about 80, immediately loosen the throttle for sliding with gear. The engine slowly fell from 2200 rpm to about 1500 rpm, and the speed was also reduced to 60Km, at which time the throttle was clicked and the 2200 rpm was accelerated. And so it goes.
In this way, the uniform speed is driven and decomposed into acceleration - two parts of coasting, and when accelerating, the engine is in the best working condition and the thermal efficiency is the highest. When coasting, the engine with gear taxi is not fuel injection, which is equivalent to zero fuel consumption, that is to say, in this working mode, driving 100 meters, about only 50 meters of the engine is fuel injection. Note that it is a sliding with gear, and a neutral taxi is idle fuel consumption, although it can be slid farther.
3, the urban area is smooth road conditions (similar to the late night city, only traffic lights, basically no cars)
The general speed limit in the urban area is between 40-60, and the pulse sliding method can still be used, but it is necessary to hang a lower gear, third or fourth gear. The taxiing speed is also lower and requires more frequent operations. When to accelerate and when to coast, can be dynamically adjusted according to the traffic signals in front. This is indeed the most fuel-efficient method of opening, but the theory is easy, in fact it is not easy to operate. I once used this pulse sliding method to drive my 2.2-ton old Tang out of the 100-kilometer limit fuel consumption of 5.8L.
4. Congestion in urban areas
There is no way! Not only is it not fuel-efficient, but it is easy to accumulate carbon, and the manual gear needs to be frequently stepped on to control the clutch speed, which is very tiring. This is the limitation of fuel vehicles. Because of this frequent start-stop condition, the engine can only idle, or run in the inefficient range. The plug-in mixed car is different, it can be driven by electricity when it is congested, there is no idle speed, and there is a step. Wait until the road is clear, and then charge the battery with the redundant power of the engine. This is also the main reason for the fuel economy of hybrid vehicles.
Saying that manual transmission is more fuel-efficient than automatic transmission is also outdated. The manual transmission is efficient and does save fuel in the hands of the old driver. However, the gear is limited, and it is difficult to compare with the double clutch. If the dual clutch is properly adjusted, the transmission efficiency is not inferior to that of the manual transmission, and the gear change speed is faster. Although the CVT transmission is inefficient, its ECO mode can make the engine always in a more economical rpm range, the footwork is softer, and it can also be more fuel-efficient than the manual transmission.
Written in the end: From the perspective of principle, we can see that the limitations of pure fuel vehicles, the low torque of the engine is insufficient, and in the initial stage, in order to have enough torque, it can only pull up the number of revolutions, wasting fuel in vain. In addition, the efficiency range of the economy is too narrow, and it is difficult to maintain fuel economy. Relying on the "extreme operation" of the manual transmission, the actual operation is very difficult. The fundamental of fuel saving is to save money, if it is only the urban transportation, I recommend considering trams or plug-in hybrids when buying a car.