lab technician holding injector part up to eye for close examination
F3 closed loop and DFI 21 injectors: Paired for precision.

Common rail and injector innovations boost flexibility, while cutting costs and complexity.

If you’re a medium- or heavy-duty diesel engine manufacturer, you’re likely struggling with how to overcome the considerable regulatory challenges you face. It’s a game of trade-offs between fuel delivery, pressure and performance in your attempts to cut carbon dioxide emissions, maintain the lowest possible levels of particulate matter and nitrogen oxide emissions, plus boost fuel economy.

One of the best ways to meet your targets is to increase the pressure at which fuel is injected into the engine. This creates a finer fuel spray, which combusts more efficiently. But, with higher pressures, the likelihood of fuel injector valve leakages increases, which can completely offset any performance gains.

So, what’s the solution? How about an injector that virtually eliminates leaks – even at 3,000 bar pressure? Better – an injector that when paired with a new common rail system creates a flexible, modular package that can cut costs, reduce complexity and improve durability? Sound good?

Then meet DFI 21.


Smaller really is better.

The DFI 21 is the latest medium- and heavy-duty diesel engine fuel injector advance from Delphi Technologies. It uses a smaller nozzle control valve to deliver:

  • Multiple injections for optimal combustion performance. Capable of nine injections per cycle, the DFI 21 reduces response times, providing improved valve dynamics and control.
  • Very low leakage supplying very high efficiency. The DFI 21 allows for 3,000 bar operation with virtually no fuel consumption penalty. And at lower bar pressures, it can result in better fuel efficiency. It also cuts the temperature of back leaks for improved robustness. The very low leakage also results in significantly lower operating temperature in turn reducing the risk of harmful fuel deposits.
  • Overall reduction in injector envelope size. Going smaller on the nozzle control valve translates into reduced injector material content, and reduced packaging space requirements.


Diesel fuel injectors lined up in a row to show differences in capabilities.



 Side by side comparison of closed loop control systems.


Proven performance.

Let’s step back in time for a moment.

At Delphi Technologies, we’ve always pushed the boundaries in diesel technology. It’s now more than 10 years since we put the world’s first 2,500 bar electronic unit injector, the E3.3, into production for heavy-duty applications. The E3.3 delivered class-leading emissions performance in exactly the same injector envelope as existing unit injectors.

We then developed the F2 family of common rail systems. The F2 family was unique in that it was designed to provide the benefits of common rail systems in flexible packages that could be engineered to fit existing engines – whether the engines were designed for unit injectors, unit pumps, or conventional remote pump fuel systems. The F2 injectors featured 2 millimeter diameter, three-way nozzle control valve technology to deliver low static injector leakage and class-leading dynamic leakage.  

But we knew we could do better. Enter the new F3 common rail system with DFI 21 injectors.

Fast Take: Unique benefits of the F3 closed-loop system.




A perfect combination.

With the F3, we’ve preserved what was best about the F2 while adding features such as enhanced closed-loop controls to better manage more and smaller injector events over the life of the engine.

At the heart of the F3 system is the DFI 21. With this ground-breaking injector, we halved the diameter of the nozzle control valve from 2 millimeters to an industry-leading 1 millimeter. Not only does this reduce leakage and allow for higher injection pressures, but it creates a smaller package that can be used in high-performance medium- and heavy-duty diesel applications.

We also developed and deployed new miniaturized production techniques to ensure consistent, precision manufacturing at the sub-micron level.

Brand-new closed-loop technology with embedded electronics in the injector monitors the operation of the injector and adjusts performance in real time to provide consistent performance over the life of the injector, as well as tamper proofing.  

And, the overall package has been designed to be more modular, and more flexible, with no additional wiring required, making it easy to integrate into existing engine designs. This speeds up development times, while also reducing cost and complexity.


1mm nozzle control valve with a 10 euro cent coin
The 1-millimeter nozzle control valve on our DFI 21 injectors, shown here in comparison to a Euro coin, delivers up to nine injector events per cycle verses the standard two or three on a typical Euro VI system.


Looking ahead.

At Delphi Technologies, we are continuing to develop a range of products for diesel applications. This includes fuel injection systems, after treatment, sensors, engine electronics and software, as well as our class-leading gasoline and alternative fuel technologies.