What is the DLC Common Rail Injector?


Lately, there has been quite a bit of chatter amongst the forums and message boards concerning the new DLC common rail injectors, and just what, exactly, makes them so much better. Let’s clear away some of the mystery and see what the DLC injector means to your vehicle, because at $3000+ per injector change, we all need the info, not the hype.

What is DLC, or Diamond Tip?

While the DLC, or Diamond Like Coating, is certainly a massive advance on the longevity of the Common Rail injector, the term “Diamond Tip” is really nothing more than a selling tool by the manufacturer. DLC is actually a metallic coating, which can be applied only to specific metals, with specific properties, under specific conditions. The method of actually creating this metal, and bonding it to the base metal, is actually quite complicated, and reads more like an episode of Star Trek. Whilst the technology for this process is fairly new, one of the first practical applications of DLC was with large, medium speed Diesel Injection engines utilising heavy oil as a fuel source. This is a market where Baileys Diesel Group has its roots. Here is what you need to know..

A surface with a DLC coating is up to five times harder than hardened tool steel, with a friction coefficient of around half (and with a dry friction coefficient of five to six times better). What does this mean for the injector? Essentially, it means that the DLC Common Rail injector operates far more efficiently, and experiences much less wear and tear. As an added benefit, the DLC injector is much more tolerant of fuel contamination (and to a lesser extent, the poorer quality fuel available in Aus).

When we talk about a DLC Common Rail injector, the DLC coating has actually only been applied to certain parts of the injector. The Denso DLC injector, for example, has only had this coating applied to the actuating armature at the top of the injector, and the nozzle needle at the tip of the injector. The problem with this approach, as we have seen, is that about 95% of the time, the Common Rail injector failure occurs with the main spindle down the centre of the injector.

As you can see, while the new DLC injectors are certainly a step up from the previous generation of Common Rail injector, they are not yet the cure-all that they have been billed to be. While they are providing a higher level of reliability and performance that vehicle owners and service facilities have been demanding, the main cause of failure has not been addressed. Until this happens, the OEM DLC injector will still have room for improvement.