Fuel injector device for injecting fuel into a combustion chamber of an internal combustion engine

A fuel injector device for injecting fuel into a combustion chamber of an internal combustion engine, the fuel injector device comprising:

• a nozzle injector body having a longitudinal axis, the nozzle injector body includes an inner annular surface that defines an injector cavity adjacent and fluidly connected to a sac, the sac includes at least one injector orifice, the inner annular surface includes a nozzle seat positioned upstream of the sac;
• and
• a valve needle configured to reciprocate in the injector cavity along the longitudinal axis to control fuel delivery through the at least one injector orifice, the valve needle includes a needle tip portion, wherein the needle tip portion includes a needle seat portion adjacent a relief portion that extends from a needle tip, wherein the needle seat portion extends at a needle seat angle about the longitudinal axis, wherein the relief portion extends at a relief seat angle about the longitudinal axis, the relief seat angle being greater than the needle seat angle such that the relief portion is configured to increase a sac volume, the sac volume being defined by the inner annular surface of the sac, the relief portion, and the needle tip, when the nozzle seat portion abuts against the nozzle seat.