A throttleable exhaust venturi (700) is described herein that generates strong suction pressures at an exhaust outlet (718) by accelerating an incoming ambient fluid stream with the aid of a venturi to high gas velocities and injecting a combustion exhaust stream into the ambient fluid stream at an effective venturi throat (728). A mixing element (544) downstream of the venturi throat ensures that the mixed fluid stream recovers from a negative static pressure up to local atmospheric pressure. A physical (724) and the effective (728) throat of the venturi (700) are designed to promote mixing and stabilize the ambient fluid flow to ensure that high velocity is achieved and the effective venturi is operable over a variety of combustion exhaust stream mass flow rates.