A pressure relief valve having a housing with an inlet port, an outlet port and a curvilinearly extending housing interior sidewall that defines a flow passageway through the housing from the inlet port to the outlet port. A piston assembly that is moveable between a closed position to establish a fluid-tight seal between the inlet port and the outlet port, and an open position to permit fluidic flow of pressurized fluid from the inlet port to the outlet port. The piston assembly has a piston head having a parabolically shaped piston face and elliptical perimeter that, when the inlet piston assembly is moved to the open position, aligns with the housing interior sidewall to provide a continuous transition from a position immediately upstream of the piston to a position immediately downstream of the piston.