It has been known for nearly a century that by recycling the exhaust gas and adding renewal oxygen for combustion, it is possible to operate a standard diesel engine in air restricted conditions. However in order to operate under these conditions, such as found in underwater vessels, exhaust gas management systems are required to process the combustion products. The characteristics of recycled working fluids and the effective disposal of the exhaust gases leads to conflicting system operational requirements. In order to operate the whole system as a compact and efficient power unit, a compromise needs to be found between the performance of the engine with the recycled exhaust and the physical size and efficiency of the exhaust processing system.Previous research using non-conventional or contaminated atmospheres for underwater vehicles power systems, pollution control and mine engineering has mainly used three methods of supplying the intake atmosphere. The first uses a normal air intake with the contaminate gas being added at or near the manifold. The second method incorporates the complete recycling process with an oxygen and moderating fluid topping up system. The last system uses a gasometer, filled with the artificial atmosphere, to supply the engine. In an attempt to ameliorate the problems of these techniques and provide realistic and accurate data, the University of Calgary has developed an experimental test facility specifically for non-conventional diesel engine operation. The facility enables engine performance data to be acquired whatever the composition and state of the intake working fluid. In the future this data can then be used to design a practical exhaust gas management system.This paper describes the experimental test facility, built around an IDI diesel engine, which allows precise control, monitoring and mixing of the non-air working fluids entering the engine.