Dales Super Store - Injector Sets | 1994-1998 Dodge Cummins 5.9L 12v

With your 1994-1998 Cummins 5.9L, you have a choice in injector style; VCO (Valve Covering Orifice) or SAC.

SAC nozzles are louder and better suited for mid-level power applications and tend to have more longevity. The nozzle has a teardrop shape with a cavity in the bottom to feed the injector and a needle at the end which closes the valve cavity. This process leaves a small amount of fuel inside the cavity cooling the nozzle, prolonging its life and giving you a crisp, clean injection. SAC style injectors tend to have more idle noise, and you may hear a knocking. The takeaway? If your truck is middle of the road power-wise and you don’t mind a little idle haze, a SAC style injector may be right for you.

VCO injectors have a moving needle at the tip of the injector, which covers the hole at the end and causes a clean end to the injection process. Because of this, the fuel pattern can be weak at the beginning of injection, but because of their design VCO injector nozzles can be much larger than their SAC counterpart, allowing you for more available power. If you are concerned with a noisy idle or are pushing higher power limits, a VCO injector may be your best bet.

Simply put, an injector with a smaller hole count and larger orifice size will penetrate deeper into the piston bowl. This can be either an advantage or a drawback, depending on the RPMs on your application. An injector of the same flow with a larger hole count but smaller orifice size will produce a finer fuel spray, but penetrate shallower into the bowl, causing it to burn sooner at lower boost levels. This all comes down to efficiency at a given RPM.

At a lower RPM, 7-hole injectors better disperse fuel which results in increased burn efficiency, which in turn equals more power. There is a cross-over point around 2000RPM where the deeper penetration of the 5-Hole injector will result in a more complete burn. While each injector style has it’s own benefits, the differences are minimal unless your running high RPM. The 5-Hole injector is by far the most common and is typically the best choice for most applications.