Haiyan brand mini-car is designed and manufactured to replace tricycle. It is necessary to maintain the advantages of light and flexible tricycles, and to solve the shortcomings of unstable driving and high labor intensity of tricycles. Although this requirement has been met, the technical performance of the car is poor. Take Haiyan SW7 10 bus as an example: the speed is about 50 ~ 60 kilometers per hour, the fuel consumption is 5 liters per 100 kilometers, the fuel tank capacity is 15 liters, and there are many faults. All of them are eliminated after 1978.