The supersonic combustion ramjet based air breathing propulsion system is most suitable for cruising a hypersonic vehicle [1]. Intake or inlet is a crucial part of the scramjet and has significant effect on its performance. Scramjet intake design process at preliminary stage involves evaluation of shock angles, shock hitting points for a given geometry and design Mach number. There after performance testing is carried out using inviscid flow consideration. During the flight, the vehicle experiences off-design conditions such as varying freestream Mach number which affects the intake performance. At the same time, some geometrical features of the intake such as ramp angle, leading edge radius, isolator length and width also affect the intake performance. Hence the present investigation is carried out to study the effect of variation of freestream Mach number, isolator length and width on the flow structure and performance parameters for a literature based scramjet intake considering inviscid nature of flow. The performance parameters chosen in the present investigation are total pressure recovery, static pressure ratio, static temperature ratio, kinetic energy efficiency, adiabatic compression efficiency, non-dimensional entropy increase.