In order to open and close the injector nozzle, bosch cummins injectors usually use piezoelectric or solenoid technology. Fuel can spray into the combustion chamber in solenoid types (found in older 5.9L and 6.7L Cummins) https://www.bbiinjectorsdirect.com/the-power-of-bosch-injectors-unlocking-optimal-diesel-performance/