| With the development of automobile industry and the consciousness of environmental protection becoming strengthened, higher demands are brought forward for automobile drive ability, economy and emission performance. In China, manufacturing is divided so detailed that engines and chassis are often made from different factories. So how to fulfill the best compatible between engine and chassis to make the automobile own better drive ability, economical and emission performance become very important in the process of studying the match of the vehicle. Driving performance and fuel economy not only depend on the engine performance, but also on the transmission parameters selection and the power train matching. Engine and power train are two important elements, which are fetal to the normal running. The matching between them will directly affect the performance and fuel economy. The Truck transmission parameters should be optimized to make the engine work almost in the low-fuel consumption region when it operates in the real driving modes. There are two kinds of design on matching between engine and power train. One is that optimizing the power train if the certain engine is chose definitely. The other is that optimizing the engine if the power train is given in advance. According to the given task, the method of optimizing the power train was chosen. From the automobile theory, the extent of the power-transmission matched with the vehicle driving cycle has a major influence on the performance of the vehicle. So in order to simulate the performance of the vehicle, two problems must be resolved: the first question is the establishment of the driving cycle, that is to say the driving cycles of the vehicle must like the vehicle's real word driving condition, the second question is the simulation model of the vehicle should be approached to the real vehicle. In order to evaluate the fuel economy of the business automobiles, and then look for some measures to decrease the fuel consumption of the vehicle. In our country, the 6-cycle is used as the standard driving cycle to evaluate the fuel economy of the business car. Moreover, there are a lot of scientific researches in and abroad showed that there could be a big gap between the results of tests that are normally used and of real world measuring. So a common method was used to derive representative driving cycle based on the collection and analysis of driving behavior data and statistical information about heavy-duty vehicle used on the highway. From above analysis, in the process of vehicle power match the test of the driving cycle palys an important role. In order to optimize the vehile, the driving cycle of the vehicle running on a certain road or region must be tested. The reason is that in anytime, the vehicle working condition is concentrated on several regions. So based on the on-road test, many driving parameters of the vehicle is tested, such as velocity, speed, fuel consumption, gear shifting ect. . Then probability statistic method is uset to decide the driving cycle of the vehicle. And based on this driving cycle, an effective method can be applied to optimize the performance of the vehicle. In this paper, after on-road testing the driving performance of a heavy-duty truck under freeway condition, a representative driving cycle was developed from velocity versus time driving information. Then, CRUISE was used to simulate the dynamic behavior of the truck. It involves simulating the complete drive train and the driver behavior in the model. The validity of the model is proved by comparing the results of the simulation to the results of the on-road tests. After establishment the driving cycle of the vehicle, which can represent the real-word drving conditon of the truck, in order to establish the vehicle model as accuately as possible, the advance simulation software-AVL-CRUISE is used to establish the vehicle model. AVL-CRUISE is designed specially for matching engines and chassis and then it can calculate the performance of vehicles. All of the calculation model have passed experiments test, so the results of the calculation is precise and reliable. This paper introduces the main function, application scope, and operation course of AVL-CRUISE, also including the introduction of elements. And then, according to the chosen vehicle (SX1384BP366), the paper calculates and analyzes its driving and economy performance. Based on the model developed by CRUISE, the driving performance and fuel consumption are calculated. The driving performance includes maximum velocity, acceleration from standstill and elastic acceleration. The results of the test present that the model of the truck is very accurate. At last, three optimization projects were calculated by CRUISE. From the results we can see that the driving performance and fuel consumption become better at the same time if the first project was adopted. The fuel consumption decrease by 11.2%。The simulation result also was validated by experiment. So the truck should be assembled the rear axel which ratio is 4.8 and the 9JS150 gearbox.
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