Abstract: A method and system for controlling both the pressure and temperature at the engine air intake, engine crankcase, and at the engine exhaust so that pressure and temperature conditions are equilibrated. Engines are tested both at simulated high altitudes (operating air at barometric pressures lower than the local barometric pressure at the test site) and low altitudes (operating air at barometric pressure higher than the local barometer at the test site) and at a variety of operating air temperatures. The method and system provide for the balancing of air pressure at the engine air intake and crankcase and engine exhaust. The effect of unbalanced air pressure is on engine emission test results is demonstrated.