Imagine your diesel engine becoming more efficient, more powerful, and cleaner with an upgrade in the fuel injection system. That’s what happened when common rail diesel engines came into play.
When a high-pressure fuel rail delivers fuel to individual injectors, you get control of the fuel delivery that provides increased performance plus lower emissions.
It is a significant step forward compared to the older diesel technologies, where precision and fuel control were more of a challenge.
Basics of Common Rail Diesel Engines
Understanding modern diesel engines and their development, common rail technology is very important. It makes vehicle performance better through precise fuel injection, and it also means lower emissions and better fuel consumption.
History and development
Common rail injection can be traced back almost 100 years ago with significant use in submarine diesel engines in the 1910s.
Improvements in technology and components have made it commonplace for diesel engines to meet restrictions on emissions, as well as achieve better performance and fuel efficiency for diesel engines.
Key Components
There are three components to a common rail diesel engine:
- High-Pressure Pump – To create the fuel pressure for injection.
- Common Rail – The high-pressure fuel bank.
- Injectors – Precision-valve nozzles that inject fuel into the engine’s combustion chamber.
Each of these components performs a function and collectively provides fuel delivery into the diesel engine in a very precise manner.
Operating Principles
A common rail diesel engine operates by keeping fuel at high pressure in the common rail.
The fuel is then delivered to the injectors on command. The ability to time the amount of fuel being injected into the cylinders offers benefits such as:
- More efficient combustion
- Less fuel consumption
- Less harmful emissions
Because the fuel is kept at a constant high pressure, injections can happen at all points in the engine cycle, providing you flexibility in the timing, duration, and rate of any injections.
Advantages of Common Rail Diesel
Common Rail technology significantly improves several performance measures of diesel engines, changing the way operators work with diesel fuel.
#1. Increased Performance.
Common Rail systems can greatly improve an engine’s performance compared with standard pumps.
All of the fuel delivered is delivered under high pressure, with exact timing, resulting in a quicker and more complete combustion, which in turn, helps with increased power and acceleration from your vehicle.
#2. Fuel Efficiency.
Fuel savings can be a characteristic of Common Rail systems.
Common Rail systems are designed to optimize fuel consumption with a precise use of fuel delivery allowing less fuel to generate the same power, and resulting in improved fuel economy!
#3. Emissions Improvements.
By reducing emissions, you are contributing to the emissions improvements and a cleaner environment.
The ability of Common Rail technology to better control emissions has made an improvement, by greatly reducing exhaust emissions, and negative pollutants, through improved combustion of fuels resulting in less soot and particulates from your exhaust system.
#4. Improvements In Noise Levels.
Expect a more quite diesel engine.
Common Rail systems generate a reduced level of noise from the engine and smooth operation compared to their predecessors due to the better timing and fuel delivery of an exact diesel injection system.
#5. Better Precision and Control.
Common Rail technology creates better precision and control.
The ability to specify the timing and amount of injection provides the operator with opportunities for verification and accuracy, continued reliability in performance, and contributes to the quality of the engine and advancement of diesel technology.
Common Rail Diesel Disadvantages
While common rail systems offer a range of benefits, they can also have some disadvantages:
- Cost: Common rail systems are more expensive to manufacture and install than traditional fuel injection systems which can lead to increased vehicle costs.
- Maintenance: The components that run under high pressure and high engineering tolerances required for common rail diesel engines can lead to maintenance costs and increases in the level of repair complexity if a problem does develop.
- Durability: Because common rail systems run under high pressure, the additional wear and tear on engine components over time could negatively affect the service life of an engine.
Common Rail vs Direct Injection
Common rail systems have a fuel rail that is under a high-pressure that sends fuel to solenoids that control the delivery of fuel to solenoid valves into each piston within the engine.
In general, this system allows for better control of the timing and amount of fuel injected into the engine, which leads to better fuel economy, better (lower) emissions, and better performance characteristics.
In addition, common rail systems tend to produce less noise than traditional journeymen’s and direct injection systems, which can improve the user experience even further.
Whereas, direct injection systems inject the fuel directly into the combustion chamber of each piston. Direct injection can maintain more fuel efficiency than older indirect injection systems as the fuel is not required to “swirl” in the combustor or pre-combustor, which robs energy from the combustion process.
In general, common rail systems provide better overall fuel efficiency and performance for most diesel applications.
That said, the best option of common rail versus direct injection engine designs really depends on the engine and engine design/manufacturer goals.
Parts of Common Rail Systems
A common rail diesel engine has multiple high-technology parts that function together and deliver the exact. fuel amount under high-pressure.
Fuel Injectors/Nozzles
Fuel injectors play a significant role in performance for an engine. They inject precise amounts of fuel into the combustion chamber.
Fuel injectors contain either a solenoid valve or piezoelectric valves that open and close very rapidly, ensuring they deliver a very accurate injection method.
Spray pattern nozzles function by atomizing the fuel sent into the engine’s individual combustion chambers. The nozzles are a significant function of an injector as they specify the spray pattern to maximize mixing of the air-fuel mixture for combustion and lower emissions.
High-Pressure Pump
The high-pressure pump is the heart of the common rail system, which compresses fuel at between 20,000 – 40,000 psi.
This is significant as it creates a very fine fuel atomization for the fuel injected, fuelling efficiency, and performance.
Fuel Rail/Pressure Accumulator
The fuel rail is like a manifold that distributes high-pressure fuel via pipes to the injectors. The fuel rail must be robust enough to handle extreme pressure, but still able to perform under different engine conditions.
A significant part of the fuel rail is the pressure accumulator. The pressure accumulator mitigates fuel pressure fluctuations, ensuring a continuous level delivery of pressurized fuel as required by the engine for consistent and accurate control of fuel injection.
Engine Control Unit/Sensors
The Engine Control Unit (ECU) or Engine Control Module (ECM) is the engine intelligence. It uses a very complicated series of sensors to continuously obtain data for engine speed, engine load, engine temperature, etc.
It then uses this data to make real-time changes to the amount of fuel injected (timing, duration, or pressure) using an electronic engine control.
Injection Process and Timing
When it comes to overall performance, injection pressure management and the control of the fuel injection timing and rate are two key components.
Both of these functions are critical to the operation of your engine, as they need to be controlled for the proper combustion to take place so that your engine is able to produce the correct power.
Injection Pressure Management
In order to improve the spray pattern and fuel atomization and mixing as it enters the combustion chamber, fuel injection in a common rail diesel engine operates at high pressure.
The injectors are controlled electronically, allowing the ECU to manage fuel delivery pressure, which can be up to 25,000 psi, dependent on the engine load and operating conditions.
Controlling injection pressure management allows us to improve engine efficiency, reduce emissions, and make sure cylinders are not running lean.
Injection Timing and Rate
The timing of injecting fuel into the combustion chamber is especially important. The ECU on your engine calculates the optimum timing of the fuel injection event, based on additional factors such as engine speed and load.
Direct injection allows precise control of the amount of fuel injected, as well as how long injection occurs (rate), and since you know you are getting the right amount of fuel at the right time for combustion.
Multiple Injection Events
The common rail system can also provide a multiple injection event during one combustion event.
This may happen during pre-injection to pre-condition the combustion chamber, main injection, which generates power, and post-injection to reduce emissions or clean the particulate filter.
Environmental Impact and Emissions Regulations
If you are going to be able to understand common rail diesel engines, you need to understand their environmental impact from the initiation of diesel exhaust emission regulations.
First, you need to ask how these engines meet emissions standards, how particulates, such as soot, are reduced, how aftertreatment systems can mitigate environmental impacts, and determine their efficiency.
Emissions Standards
Diesel vehicle owners should be aware of diesel particulate matter and nitrogen oxides as the two main emissions, both of which can negatively affect human health.
As a result of these emissions, there are emissions regulations in place worldwide, which demanded advancements to the technology in diesel engines.
Then there are newer common rail diesel engines which comply with emissions regulations by using precision control of fuel injection to reduce nitrous oxide emissions.
Particulates and Soot Reduction
Soot and particulates from diesel combustion are a key environmental impact of diesel consumption. With common rail, you can better combust more fuel with less soot and particulates emitting from the engine.
Engines that do generate emissions use PM filters, which actually capture the soot and particulates, and periodically burn them off during the engine’s regeneration phase.
Aftertreatment Systems
The aftertreatment of exhaust gases is another important step in reducing emissions.
With diesel engines having systems like Selective Catalytic Reduction (SCR) and Diesel Particulate Filters (DPF), these systems are used for removing harmful emissions.
SCR converts nitrogen oxides into nitrogen and water vapor, and DPF traps particulate matter, which is occasionally oxidized to prevent clogging.
Common Rail Systems in Various Vehicle Makes
Common rail systems are a process that has changed how fuel is injected into diesel engines; however, the concept of common rail is never used in the same way or designed in the same way by major automobile manufacturers for their specific vehicle makes and models.
Cummins
On your Cummins engine, the common rail system generates a more advanced fuel delivery system while maximizing performance.
Cummins utilized the concept and began incorporating common rail into their engines early in the new millennium, providing lower noise and emissions.
Bosch Systems
Bosch is an innovator in automotive engines and in common rail systems.
You will find Bosch in a multitude of manufacturers based on their supply volume as a contributor of common rail systems. Bosch manufactures high-pressure fuel pumps and controlled fuel injectors to ensure efficient delivery of fuel.
GM’s Duramax
If you own one of GM’s known power plants, the Duramax engine, then you own a common rail system that adds increased performance of common rail diesel, and why Duramax-powered trucks are known for fuel efficiency.
The Duramax engine is a collaboration of GM and Isuzu, deriving out of a powertrain group strengthens engineering systems and common rail fuel injection technology.
Dodge’s Powertrain
If you have a Dodge heavy-duty truck it, most likely has a powertrain built with a common rail system in Ram vehicles.
Dodge has an ability to maximize the output of power and fuel consumption of their own automotive engines, even in the cases of Cummins powertrain vehicles.
Future Trends and Innovations
The world of common rail diesel engines is evolving quickly. The emergence of hybrid technologies, improved electronic controls, and new injector designs are modifications to improve efficiency, lower emissions, and better overall performance.
Integration with Hybrid Technologies
Very soon, you could find common rail diesel engines with hybrid powertrains that transmit the high torque and ability of diesel fuel, along with combining electric motor responsiveness in an emission-free operation.
Combining diesel with hybrid technology is an innovative development that will improve fuel economy and reduce emissions without losing power.
Improvement in Electronic Controls
New sophisticated electronic advancements make certain the precision use of effective fuel pressure control of the direct fuel injection systems and injection timing.
As these controls become sophisticated and advance, modern diesel engines will embrace the advancements.
Improvements in Injector Design
Injectors are vital components in all common rail systems. The designs have new enhancements.
Designs now express higher fuel pressures with variable fuel delivery to offer finer fuel atomization.
Higher precision with fuel and combustion is cleaner and more efficient, resulting in performance across a wide variety of different conditions.