A method of minimizing deposits in a fuel injector

A fuel injector comprises a fuel flow passage about a central axis (2) of the fuel injector, the passage including a valve seat (3) inclined at a first angle to the central axis; and a needle orifice (6); wherein the passage further comprises a first volume between the valve seat and the needle orifice; and a first edge (9) between the valve seat and the first volume; wherein the first volume is chosen such that fuel flow remains substantially laminar as it passes over the first edge; the passage further comprising an annulus (10) at the base of the first volume, radially outwardly of the needle orifice, and a second edge (11) between the annulus and the needle orifice; wherein fluid passing over the second edge is caused to cavitate, such that deposits in the needle orifice are substantially removed.