In Korea, the number of LPG vehicles is increasing continuously because LPG is cheaper than Gasoline. Also in Europe, the CNG fuel is a good solution to meet $CO_2$ regulation. In order to use LPG/CNG fuel, new EMS ECU must be developed for every type of vehicles and it requires huge development cost. In order to reduce development cost and time, SIEMENS VDO has developed an Interface Box. It supports EMS ECU in the car and manages LPG/CNG fuel injection system. Basically the Interface box can be used with any kind of EMS ECU. The Interface Box controls LPG/CNG injector through the injection command of gasoline EMS ECU. It calculates required amount of based on the fuel temperature and pressure and sends feedback signal to ECU for fuel correction. Also, it controls LPG/CNG specific actuator such a Shut off valves and LPG switch inputs.