The “PCO” nozzle is a new design for direct injection diesels. It uses an outward opening poppet valve with orifices similar to those in hole-type nozzles. Hydrocarbons, NOx, light duty particulates and noise can be reduced.The orifices are completely covered when the valve is closed. No “sac” or orifice fuel can escape into the cylinder to increase hydrocarbons. The initial injection rate is reduced, lowering emissions and noise.With a near-vertical installation, the PCO can be substituted for hole-type nozzles and use the same combustion system. No fuel leakoff is required. Tests have been conducted in dynamometer engines and vehicles.Performance can be a trade-off, depending on the combustion system match. Remaining development work includes re-optimizing the combustion system for the PCO, enhancing the rate control capability, and demonstrating durability. Nozzle coking has been minimized with design and installation improvements but remains a concern.