This paper demonstrates the advantages and main design features of the Pacer Comet 4 system intended to test gas turbine engines for the United States Air Force. Building upon the existing test cell system and applying both technological advancements and lessons learned, Pacer Comet 4 will replace the aging Pacer Comet III (PC3) system which has served the engine test cell mission for over 20 years. Pacer Comet 4 applies modern Commercial off the Shelf (COTS) technology to an open architecture to improve capability, expandability, and sustainability. The modular nature of hardware and software design allows replacement of individual components with minimal impact to the remaining system. Mounting the data acquisition system near the source of the measured signal increases the maintainability, facilitates future expansion, allows out of test cell calibration, and limits the exposure of wiring to noise sources. By converting the analog signals to digital before leaving the frame, line losses are reduced. Converted signals are brought off of the frame and control signals are brought onto the frame via Ethernet network cabling. The Pacer Comet 4 system incorporates networked video capability for observation of critical engine test observation items, facility control, remote data access, intercom system, and Engine Health Management plus Data Repository Center (EHM+DRC) compatible data storage. The software design has a robust executive with comparatively simple test program sets (TPS). This will allow new test procedures to be added with relative ease.