When fuelling a diesel engine with PPO fuel injector condition and settings are important for reliable operation. Injectors should be checked for spray quality, dripping when held below opening pressure and, with injectors with adjustable opening pressure, the opening pressure of all injectors should be carefully balanced. Injector maintenance should be performed at reduced frequencies.
Injectors in indirect injection engines[edit | edit source]
Indirect injection engines generally use pintle type injector nozzles. These injectors provide a spray of fuel that impinges upon hot surfaces within the combustion chamber allowing combustion to begin.
Experiment by German DIYers have found that use of injectors from later engines from the same series often gives good results. Injectors from more modern indirect injection engines are often of a flat cut type
Flat cut type pintle nozzles[edit | edit source]
Flat cut pintle nozzles were developed to provide a small amount of pre-injection which begins to combust providing an environment where the main fuel charge burns more readily. This reduces harsh combustion noise by reducing the ignition delay. Less fuel is present in the combustion chamber as the main combustion event begins and so the peak combustion chamber pressure and associated noise is reduced. A flat is cut into the throttling pintle to allow a small spray as the needle lifts. When fuelling with PPO the pre-injection provides an improved environment for the combustion of the main fuel charge. These nozzles provide a degree of self cleaning as the high pressure jet from the flat cut blasts carbon deposits from the nozzle.