AEI’s Super Cell and Altitude Cells are uniquely configured to simulate altitude conditions, with controlled intake air supply sources that are maintained isobarically with the exhaust out pressure. The majority of other facilities’ engine test cells that offer “altitude” capability are only able to maintain exhaust out pressure, and then create a simulated intake supply pressure by increasing intake restriction. Then for transient operation, that intake restriction valve must be modulated to attempt to achieve a certain pressure level. AEI’s isobarically controlled intake and exhaust systems eliminates the need for feed forward control of the intake restriction, therefore, providing a better altitude environment for transient development requirements.