CRDi stands for Common Rail Direct Injection meaning, direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors. Whereas ordinary diesel direct fuel-injection systems have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence. This pressure then remains permanently available throughout the fuel line. The engine's electronic timing regulates injection pressure according to engine speed and load. The electronic control unit (ECU) modifies injection pressure precisely and as needed, based on data obtained from sensors on the cam and crankshafts. In other words, compression and injection occur independently of each other. This technique allows fuel to be injected as needed, saving fuel and lowering emissions Gasoline or petrol engines were using carburetors for supply of air-fuel mixture before the introduction of MPFI system .but even now carburetors are in use for its simplicity and low cost. Now a days the new technology named Gasoline Direct Injection (GDI) is in use for petrol engines. The GDI is using the principle of CRDi system. Now let usexamine the various factors that lead to introduction of GDI technology.