A secondary air injector for use with an exhaust flow simulation system. A typical exhaust flow simulator is a burner-based system, in which exhaust from a combustive burner is exhausted through an exhaust line. The secondary air injector is placed downstream the burner to create a desired thermal condition or composition of the exhaust gas. The injector comprises a hollow ring fitted around the exhaust line, with multiple holes for evenly injecting the air into the exhaust line.