The combustion heat release rate curve of ideal state should be at this point once burned, is actually not to do, it will burn a little earlier, also could not make it an ideal state, but it is just an ideal state between the two directions can be optimized, the first is the rate of short combustion duration, faster the better, you can burn, but can burn as soon as possible. The second is that you can't burn up at the top, then the center of your heat release rate is as close as possible to the upper and lower points. These two directions are fuel efficient. It also means that we should do this two of the most fuel-efficient, the key is the burning rate as soon as possible, fast TDC is short, and soon after also can try to put it near the TDC, in fact is to increase efficiency.

There are several ways to improve efficiency. First, reducing the speed can effectively increase the rate of combustion. The rate of combustion is calculated from the angle of combustion, and the burning quality is the same. When the speed is low, the same time angle is saved. So, this is one of the reasons for a low speed, that is, after low speed, you can burn faster. Second is to reduce the speed, can obviously improve mechanical efficiency, all kinds of friction loss and so on, with the decline in speed will decrease, and its combustion efficiency will continue to increase, mechanical efficiency is also improving.

But there are some problems, not the lower the better, the speed is too low, the combustion of the intake system will decline, will lead to a decrease in combustion efficiency. Not to say that the lower the faster, low to a certain extent, soon. There is also a lower speed, power will decline, the need for a larger displacement of the engine to meet the requirements. So in fact, when the displacement is large, the mechanical efficiency will be affected. But now some technologies, such as common rail, variable cross section, and dual boost technology, can improve low speed performance, and now new technologies that make engines slow down should be easier to implement. In general, speed reduction can reduce fuel consumption in a certain range.

So how much speed appropriate? We pay more attention to what is commonly used in vehicle speed, when we are concerned about the optimization matching of transmission ratio in determining the optimal speed and common speed, transmission ratio of the number of suitable. In accordance with the total weight of 55T, the common speed of 85km/h, the engine economic speed 1350rmp, transmission ratio of 3.083, the most suitable for the use of requirements, the best economic type. With the implementation of the new GB1589, the total weight dropped to 49T, and the transmission ratio of 2.846 was better.

In addition to the engine speed and torque, one is transmission, one is power, the two forces and reaction force to form the main moment. The car on the road is mainly two resistance, one is upwind resistance, and one is rolling resistance. With a total weight of 55 tons, with the speed of the abscissa speed from 0 to 100, you can see that the rolling resistance and windward resistance are increasing, but rolling resistance is accounted for a large proportion of the proportion of wind drag is much smaller.

From the demand of gross weight and power, the demand for power increases with the increase of total weight and speed. According to the total weight of 55 tons, the speed of 85 kilometers, the power demand is 120 kilowatts, much smaller than the actual. Because it is considered on the road running, without considering the acceleration and uphill, this is the speed of a few years ago overload conditions common in general 60km/h, so the impact of speed on power to weight ratio. Now strict governance overload, the speed of the high speed boost after the demand for substantial power increase, while the weight drop, but the weight reduction of the effects is not so high speed, high torque, high power engine is more suitable for the current logistics transportation environment.

Vehicle power is guaranteed by displacement, in addition, there are other factors affecting displacement. The most important is the emission regulations, in three to five in the main Baotou beiben heavy truck parts is to control the speed of the engine, 1200rmp under control, so Baotou beiben heavy truck parts of low engine speed is not entirely to the mechanical efficiency and fuel efficiency, but also to avoid the consideration of emission regulations. If the vehicle 85km/h, the engine speed is controlled at 1200rmp, not only not subject to emission regulation control, and fuel consumption can be greatly reduced. The speed ratio is less than 2.9, the engine output torque is greater than 12L, the displacement is more than 2400N.m.