[tasdrouille]

This is a TDI nozzle used in a bosch rotary pump system. It have 5 holes and there's a spring loaded needle in the middle. Once a certain pressure is reached (220 bar) the needle pops and fuel is injected. So regardless of hole size, the injection pressure is the same.

In a diesel it is desirable to have the shortest injection duration possible for efficiency.

In a TDI proper atomization is critical and largely dependent on the nozzle design and condition. The nozzle sits tight between the valves in our flat head (yup, the head is completely flat). There is a small bowl in the piston and fuel is injected in a cone spray towards the bowl lips.