Diesel Injection Components - Engine Builder Magazine

Diesel Injection Components

For some time now, most of the development in diesel technology has been aimed towards making the engines environmentally-friendly. But as diesel engines have become cleaner, the power levels have also increased. This is somewhat backward to what the country went through in the ’70s with gasoline engines.

The problem back in the ’70s was we were trying to clean the engine’s emissions by adding more devices, but there were no design improvements to make any efficiency improvements. Back then, the OEs were just coming to terms with new devices to control emissions; however, technological advances and different ways of thinking have now enabled manufacturers to have the best of both worlds – more power AND a greener environment.

To find out how this is possible, we must go back to the subject of common rail injection, which we have been discussing in detail for the last few columns. Common rail injection has been in existence for a long time but has become more popular in diesel engines over the past decade. In order to have a cleaner running engine, you have to make it more efficient.  

One thing that has been discovered with diesel fuel injection is the higher the pressure at which it is injected creates more efficiency. The purpose of common rail injection is to deliver high-pressure fuel to the injector. Fuel in a common rail system will be injected into the combustion chamber through the injector nozzle at pressures as high as 28,000 psi. This is far from the mechanical systems of the past  that would inject fuel into the combustion chamber at 2,000 to 3,000 psi.

When diesel fuel is injected at high pressure, you can only imagine the difference in the fuel atomization. Fuel atomization, along with port swirl is the biggest contributing factor to the efficiency of today’s diesel engines. The increased atomization of fuel from the common rail injection also created design changes to the piston and combustion chambers along with the design of the intake ports and valve train.

In order to inject diesel fuel at high pressures, you need a very unique pump known as a high-pressure fuel pump. The pump is usually engine-mounted and driven by the engine gear train. A regulator controls the amount of pressure that the pump makes. The regulator, also known as the fuel-metering valve, regulates the amount of fuel that the high-pressure fuel pump will intake.

Even though the engine drives the high-pressure pump, the pump will produce the necessary high pressures regardless of the engine speed. After the pump has been pressurized, the fuel is stored in the fuel rails. The fuel rails are accumulators for the high-pressure fuel to be delivered to the injectors through lines that branch off of them. The fuel rails also dampen vibrations from the high-pressure fuel pump and injection cycles from the injectors.

Inside the fuel rails is a fuel rail pressure sensor that reads the pressure in the fuel rail for the PCM (Powertrain Control Module). The PCM uses the input from the fuel rail pressure sensor to determine how much to open the fuel regulator. If more pressure is needed, the PCM will command the regulator to open for more fuel to be taken in by the high-pressure pump.

A fuel rail pressure control valve also controls high-pressure fuel in the fuel rails. The pressure control valve is usually placed in the end of the fuel rail where it will be opened or closed by the PCM for precise pressure control inside the fuel rails. This helps to keep the optimum fuel pressure in the fuel rails to be delivered to the injectors for various demands placed on the engine.

Just in case the fuel pressure was to spike abnormally, the fuel rails have a fuel rail pressure limiter inside of them also. If fuel pressure were to get out of hand for some strange reason, the limiter would open allowing the excess pressure to return to the fuel tank.

As high-pressure fuel travels through the rails and lines, it arrives at the injector, which is controlled by the PCM. When the PCM commands the injector to open, fuel enters the injector and is sent through some intricate passages in the injector that leads to the injectors tip.

The tip of the injector has microscopic holes through which the fuel will be delivered that create a very fine mist. The droplet size of the fuel as it is sent through the tip is about 7 times smaller than a human hair. Injectors can be actuated by a solenoid type of driver or a Piezo electric device.

Solenoid actuated injectors have been around for some time, but have been replaced with Piezo actuation. Piezo is a type of crystal that is wafer-thin and generally stacked on top of each other. These stacks of Piezo crystals, when energized by the PCM, will expand and open the injector’s valve, and its actuation is 4 times faster than a solenoid.

The PCM uses inputs from sensors on the engine to control actuators, which control fuel delivery. Fuel delivery is based upon demands on the engine, such as the amount of boost, the throttle position, engine temperature, etc. With the use of common rail, there can be multiple injections per combustion cycle. This can also be beneficial during cold weather start-ups.

The use of common rail has brought about many advantages to the diesel engine. These advantages are higher injection pressures for increased atomization of fuel, multiple injections per combustion cycle, and more reliable pressure regardless of engine speed. The benefits include the reduction of emissions, reduction in diesel particulate matter, reduction in noise, increased fuel efficiency and increased performance.

Even though diesel engines are becoming cleaner, more emission-friendly, the use of electronics along with better engineering keeps propelling power levels and durability. I think that as diesel engines continue to evolve and get even more efficient, they will become more of a competitor for the car buying public’s transportation needs in the near future.in order to inject diesel fuel at high pressures, you need a very unique pump known as a high-pressure fuel pump. the pump is usually engine-mounted and driven by the engine gear train.After the pump has been pressurized, the fuel is stored in the fuel rails, which are accumulators for the high-pressure fuel to be delivered to the injectors through lines that branch off of them.

You May Also Like

Shop Solutions – January 2024

Before installing cam bearings, make sure to chamfer any oil holes and clean up back grooves of any sharp edges.

Engine Builder and Engine Pro present Shop Solutions in each issue of Engine Builder Magazine and at enginebuildermag.com to provide machine shop owners and engine technicians the opportunity to share their knowledge to benefit the entire industry and their own shops. Those who submit Shop Solutions that are published are awarded a prepaid $100 Visa gift card. Submit your Shop Solution at [email protected]. You must include your name, shop name, shop address and shop telephone number. Submitted Shop Solutions not published will be kept on file and reevaluated for each month’s new entries.

Shop Solutions December 2023

Check out the latest shop solutions from builders around the country.

The Impact of Fuel Type on Engine Performance

When it comes to choosing the right fuel for your vehicle, several factors should be taken into consideration. These factors include the vehicle’s engine design, manufacturer recommendations, intended usage, and personal preferences.

Component Cleanliness

It can’t be overstated how important the cleaning machines are in the modern engine shop. Shop owners who prioritize effective and efficient cleaning techniques will find success in a more streamlined process.

Billet Blocks and Heads vs. Cast Iron

Billet aluminum has a lower yield strength or higher modulus of elasticity, meaning it will flex, or absorb energy easier under tension or stress than cast aluminum, without incurring permanent damage.

Other Posts

Shop Solutions November 2023

Many times, the flange diameter of the rod nuts will contact the radius around the nut seat on some rods. Some jobs may not warrant the expense of spot facing the nut seat on the connecting rods. In that case, it can be quicker and more effective to just machine a chamfer on the ARP rod nuts.

The CNC Landscape Continues to Grow Inside Engine Shops

Several manufacturers named automation as one of the biggest continuing trends surrounding CNC equipment these days, and it’s clearly a key contributor to a CNC machine’s ability to do more without human interference.

Crankshaft Counterweights

Most engines are internally balanced, meaning all weight adjustment is done on the crankshaft counterweights. However, some stock and modified engines require external balancing due to an increased stroke or larger pistons, and the crankshaft counterweights that would be required to offset the increased inertia simply don’t fit inside the crankcase.

Shop Solutions – October 2023

A written warranty provides benefits for you and your customer. It sets expectations, protects both parties and is a great marketing tool that encourages repeat business.