Gaseous and particulate exhaust emissions are characterized for a 1,200-bhp, two-stroke cycle diesel; a 1,000-bhp, four-stroke cycle precombustion chamber diesel; and a 900-bhp, four-stroke cycle, direct injection diesel using steady-state modal testing and a versatile exhaust dilution-collection system. In addition, a 150- bhp, four-stroke cycle, precombustion chamber, turbocharged diesel was characterized for use in experimental water injection evaluations. Water injection downstream of the turbocharger compressor and upstream of the turbocharger exhaust turbine are evaluated for their particulate removal effectiveness on a small turbocharged diesel engine. The water droplets are inertially separated using cyclone separators designed for minimum pressure drop and cutsize. Up to 50 percent of the total particulate mass generated was removed using a combination of both inlet and exhaust water injection techniques.