As a step in our continuing efforts to develop ceramic components for the internal combustion engine, we recently built and tested a 4-cylinder direct injection diesel engine of 1236 cc displacement. Pistons, cylinders, cylinder head-plates, a turbocharger wheel and piston rings were designed with FEI stress analysis and fabricated from solid silicon nitride or tinanium nitride-based cermet. The durability of ceramic components was confirmed by the test operation of a single-cylinder engine. After NDE test of every component to ensure the absence of defects (which may create premature component fracturing). a horizontally opposed 4-cylsnder engine was assembled and tested on a dynamometer.The effect of piston-cavity design and fuel-injection pressure on the engine's performance was investigated. Although remarkable improvements in performance were observed after specific changes, further design improvement is still needed. The engine has been tested at full 45 PS at 4500 RPM. and subsequently installed on a small passenger-car for demonstration runs.