Modern diesel engines are equipped with four valves per cylinder to increase air flow by reducing interference. This configuration also allows engineers to position the fuel injector in the center of the combustion chamber for uniform fuel dispersion within the cylinder. Computers can manage the fuel injectors with such precision that multiple injections of different fuel volumes are made during each power stroke. By introducing a small dose of fuel, called a pilot injection, just a few ten-thousandths of a second before the main shot of fuel, the combustion is "softer" and noise is reduced considerably.
