The fuel economy of an automobile, refers to the ability of a certain quantity of fuel to complete the transport workload. Automotive Fuel costs account for about 30% of the cost of the automobile transport, fuel economy flying car transportation costs have a great impact, Automobile fuel. At the same time, the current world's energy problems and environmental protection issues have become increasingly prominent, also require automakers to reduce fuel consumption, to conserve oil resources, reduce air pollution. Therefore, to improve the car's fuel economy, has become a major issue of common concern of car users and society as a whole.
Comment automotive fuel economy in the world generally with fuel consumption or oil itinerary. The fuel consumption is the unit mileage vehicle loaded with the required fuel volume. China and Europe are traveling one hundred km fuel consumption (L) to indicate that L/100km; The oil trip is fully loaded car, per unit volume of fuel mileage, the United States is to use a gallon of fuel mileage expressed as the number that mile / gal (miles / gallon). The former said Act, the smaller the value, the better the fuel economy; latter method, the greater the value, the better the fuel economy (translation relationship: 1 gallon = 4.546 L, 1 mile = 1.609km).
In addition, the motor transport sector commonly hundred tonne-kilometers fuel consumption per car to travel one hundred kilometers of the amount of fuel consumed to transport one ton of cargo L/100mkvt.
The size of the resistance of the gasoline fuel economy indicator with the engine characteristics and vehicle weight, the vehicle speed and various sports, such as air resistance, rolling resistance, and the climbing resistance, drivetrain efficiency and the reduction ratio have a relationship, and thus in the numerical often there is a difference with the actual situation.
Determination of rules
The fuel economy of an automobile, there are two determination: driving test method; another constant fuel consumption test is performed on a flat road and under certain conditions.
Isokinetic hundred kilometers
Isokinetic fuel consumption when driving the car in no slope flat good road for a constant speed 100 km fuel consumption. The so-called the isokinetic also included in the isokinetic traveling to different speed, different speeds of isokinetic traveling 100 km fuel consumption is different.
Select period slope flat cement pavement or asphalt pavement, cars were different speed in top gear (every 10 km / h the speed to take a point) constant speed to complete this journey, the average round trip (to eliminate wind and slope effects), write down the amount of fuel consumption, can be obtained with different speed Car hundred kilometers, the so-called constant speed 100 km fuel consumption. Its shape is generally two high intermediate concave. Course of various types of vehicles, even if the same type of vehicle, the location and depth of the dent is very different.
The circulating fuel consumption
Constant fuel consumption and actual driving conditions are very different, in fact, can not fully assess the car's fuel economy. Now generally cycle to evaluate the fuel economy of an automobile fuel consumption. Cycle fuel consumption is driving the fuel consumption of the car in the typical sections within a specified period to set different conditions, at least, we should require constant velocity, the acceleration and deceleration of the three kinds of conditions, the complex also included in the starting and idling suspended a variety of conditions, and then converted into a hundred kilometers. For example, China has 6 conditions cycle fuel consumption (truck) and urban cycle fuel consumption of the 4 conditions (passenger cars), European cycle fuel consumption of the ECE-R15 condition, road cycling and urban cycle fuel consumption in the United States.
In general, the cycle fuel consumption obtained even with constant speed 100 km (specified speed) fuel consumption weighted average achieved combined fuel consumption for the scientific evaluation of the car's fuel economy. But sometimes not strictly call this combined fuel consumption cycle fuel consumption, so the fuel consumption of city and highway fuel consumption of modern cars are given a more comprehensive manner, it should be a comprehensive urban fuel consumption and highway fuel consumption, also referred to as the urban cycle fuel consumption and road cycling fuel consumption in our country, more simply known as the city fuel consumption and highway fuel consumption.
How to improve the car's fuel economy
Current car engines are high-speed petrol engine, the higher the thermal efficiency of the engine fuel utilization the higher, more fuel-efficient. The thermal efficiency of the engine with the increase in the compression ratio to increase car gasoline engine compression ratio is generally in between 9.3-10.5. Also, the gas distribution system variable device (variable valve lift variable camshaft angular variable intake pipe length, etc.) and the lean-burn technology, to achieve the purposes of fuel economy.
Same time, many of the large automobile manufacturing companies in the world to actively develop and promote diesel engines, automotive gasoline engines to diesel engine easier to achieve the purpose of further fuel savings. Due to advances in technology, the diesel engine vibration, noise, per unit mass (weight) aspects gasoline shorten the gap, but the power is still relatively small. Flat due to the diesel engine load changes, significant fuel economy than gasoline.
Engine power and load rate have a great impact on fuel economy. The general engine cylinder displacement decide on the output power, reasonable choice of automobile emissions, according to the actual needs of the user to keep the car driving high power utilization, to improve vehicle fuel economy makes sense.
The automotive driveline affect
The driveline of the car have a major impact on the fuel economy of an automobile. Transmission gear is more, not only the car smooth-shifting, but the engine increases the opportunity to run in economic conditions, and help to improve fuel economy. Therefore, modern cars tend to the 5-speed or more transmission or Variator guarantee under any condition with the engine in the possibility of working in the most economical operating conditions. In the case of the same speed, the engaging speed gear, the transmission ratio is small, the engine speed is low; engagement downshift transmission ratio corresponding to the engine speed is high. Seen by the engine load characteristic, when the engine load is the same, is generally lower speed fuel consumption rate is smaller. In certain driving conditions, the smaller the speed ratio of the transmission lines, the higher the fuel economy of an automobile, and the economy driving of the car in the high position. To good road conditions traveling at a higher speed, the the device speed ratio of cars in the transmission is less than 1 overdrive hang overdrive in the case of the same speed, engine speed can be relatively low, and relatively reduce fuel consumption .
The transmission ratio of the transmission lines, including the transmission gear ratio and the ratio of main reducer, good on the road driving a small speed ratio of main reducer can improve a car's fuel economy. However, many objects in the car has a "critical point" too far it will go in the opposite. The main reducer same, too small will make the most high-end power is too low, but will make the car's fuel economy deterioration, the general design reducer drive ratio has a range, so hang directly file still The larger back-up power for acceleration or on a small slope.
Car Styling important impact
Due to the increased speed of modern automobile, car styling, fuel economy also have a major impact, the faster the speed, the greater the impact, which is commonly known as "drag". Reduce the air resistance by reducing the frontal area of the car and the air resistance coefficient achieved in general the windward area depends on the volume of the car, air resistance depends on body shape. To this end, the compact auto body and streamlined ways to improve fuel economy. Many cars air resistance coefficient in the 0.28-0.3 about, played a significant role in reducing fuel consumption.
Vehicle driving system, the resistance of the entire process of moving is to drag and rolling resistance. Rolling resistance is mainly derived from the vehicle weight, and the drag is different, under normal circumstances, the power consumption brought by the drag W = CV3 (V power of 3) (C representative of the air resistance coefficient, V representative of vehicle speed), if the same conditions , the drag coefficient is smaller, the higher utilization rate of 1 liter of oil. Based on actual test data, more than 10 kilometers per corresponding increase in 1 liter / 100 km fuel consumption, when a car traveling at 80 km / h, 60% of the fuel is used to overcome the longitudinal drag. The drag coefficient drop of 10%, fuel consumption is down 7%.
Generally speaking, body height exceeding 1.5 meters automotive air resistance coefficient is relatively large, compared with the same type of power system low body car not only reduce the travel speed and fuel consumption increases. Therefore, the combination of space, speed, fuel consumption is contradictory, can only obtain a reasonable balance point, can not have everything automotive.