Difference between On-Car and Off-Car Injection Cleaning

Difference between On-Car and Off-Car Injection Cleaning


Carburetors were used in the past to deliver fuel to the engine, but modern day automobiles use fuel injection systems. The sophisticated systems deliver just the right amount of fuel to ensure that the engine runs optimally. Increased fuel efficiency, decreased emissions and improved performance are the benefits of using modern day fuel injection systems, such as the Bosch fuel injectors. Continuous usage of your vehicle will result in buildup in the fuel injectors. Regular cleaning and maintenance of fuel injectors to maintain performance and mileage.

Benefits of fuel injector cleaning

The advantages of cleaning the fuel injector directly depend on the condition of the injector. When you experience lags in your car and it doesn’t offer a good mileage anymore, it is time for fuel injection cleaning. The fuel injectors are clogged mainly due to the use of cheap gasoline. When you purchase advanced fuel injectors, such as the Ford fuel injectors, you may not read a fine print suggesting to use high-quality gasoline.

High-quality gasoline has about 1000 parts per million of detergent in the fuel. This is not expensive for the gasoline suppliers. However, more than 85% of the gas sold, has only one-tenth of the recommended level. This means that the cheaper gas you use for your engine doesn’t have an effective self-cleaning mechanism and as a result, there will be a buildup of chemicals in the fuel injection system.

Engines designed to provide high-mileage and cars designed for several short trips will benefit greatly from a thorough fuel injection cleaning service. Experts recommend that you take your car for fuel injection cleaning at least every 25,000 to 30,000 miles. If you experience any limitation in the performance of your vehicle, you should clean fuel injectors right away.

On-car and off-car fuel injection cleaning

You can clean the fuel injectors without removing those from the car. This involves supplying the cleaner through the fuel injection system, to remove the dirt and debris. This could be a DIY project because the fuel injection cleaning systems are readily available. You need to purchase a cleaning kit that is compatible with the make and model of your fuel injection system. While it is not very expensive, you need to have extensive knowledge on assembling and disassembling fuel injectors, to make this on-car cleaning effective. Also, when there is too much dirt accumulated in the system, on-car cleaning won't be useful.

Off-car fuel injection cleaning provides a thorough cleaning of the fuel injectors and the end result will be a fuel injection system that will be good as new. It should be done by a professional, as it requires special equipment for cleaning the fuel injectors. It can cost you more, but once fuel injectors are cleaned professionally, you don’t have to worry about the performance for another 30,000 miles. The cost of maintenance will be offset by the money you save on fuel and regular car maintenance. The biggest benefit of using off-car cleaning service is that the fuel injectors will undergo flow-testing to ensure optimal performance after cleaning.


German Quality Fuel Injectors:
Pte fuel injectors
Siemens Deka fuel injectors
Marantz fuel injectors
Tre fuel injectors
Rc fuel injectors
Ford racing injectors
Fic fuel injectors
Accel fuel injectors

Understanding the Lifetime of Fuel Injectors

Understanding the Lifetime of Fuel Injectors


Fuel injectors are one of the major components of the vehicle, as they spray an appropriate amount of pressurized fuel to fire up the engine. Leading models such as Bosch fuel injectors can last for 1 billion cycles. Theoretically, it means that the fuel injectors should last the lifetime of your car. Practically, it is not the case. The driving conditions, fuel composition and other real world issues cause the fuel injectors to fail, even before their lifetime.

Fuel injectors are thoroughly tested in the laboratory working conditions and the lifetime is usually determined after applying the real-road factors. However, actual conditions on the road can be entirely different from the laboratory conditions. Everything including your driving style, road conditions, weather, fuel quality, maintenance cycle and others influence the lifetime of the fuel injectors. Typically, the fuel injectors will work properly up to 50,000 – 100,000 miles, after which a replacement becomes necessary.

When you have installed state-of-the-art ford racing injectors, you can prolong their life by following some simple maintenance practices. The first thing you should do to extend the lifetime of fuel injectors is using high-quality fuel. While it is expensive, it will help you to maintain engine performance and prevent degradation, extending the life of your car itself. Cheap gasoline lacks the amount of additives required to prevent a buildup of carbon and debris.

You should choose your vehicle depending on your driving habits. Frequent stops and short trips result in accumulation of more debris in the fuel injectors. By choosing the right model, you can postpone the necessity of replacing the injectors. The fuel filter is responsible for keeping most of the debris from entering the fuel injectors. It requires regular replacement, so that the dirt doesn’t circulate inside the high-performance injectors. You should always replace fuel filters according to the manufacturer requirements.

Running a fuel injector cleaner from time to time will help you to reduce accumulation of debris. The DIY cleaning kits can be used, without removing the fuel injectors from the car. You can use these kits to clean the fuel injectors at home for every 10,000 miles. You should be extremely careful while using the cleaner kit and follow the steps properly to prevent damage to the car engine. It is better to take your car for a thorough and professional fuel injector cleaning, every 30,000 miles to ensure that you don’t have to replace it sooner.

If you have problems in engine performance, power or mileage, your mechanic may suggest replacing fuel injectors. It is an expensive task and you may not be ready for it. If you don’t listen to the advice of the experts, you will end up damaging your car’s engine beyond repair. Bad fuel injectors must be replaced quickly, to ensure that your car’s engine is maintained properly. When you replace the worn out fuel injector in your vehicle, you will immediately notice an improvement in performance. The money you spend for top class Accel fuel injectors will be worth it.

Aeromotive 340 Stealth Fuel Pump Installation

Aeromotive 340 Stealth Fuel Pump Installation

The fuel pump is responsible for providing your car’s engine, with a pressurized fuel. Modern day electrical fuel pumps are submerged in fuel tanks for optimal performance. The fuel pump design has changed a great deal, compared to the olden days.

As the high-pressure equipment is kept immersed in liquid, the chances of overheating are very less. Even if the fuel pump creates a spark, it will be controlled without any setback within the tank. Also, when the fuel tank is placed away from the engine, it adds to the safety factor. In the case of collision, the chances of the fuel tank exploding are quite low, which enhances overall safety. The fuel pump performs the most important task, to ensure vehicle performance.

When you need to replace the fuel pump in your car, the Aeromotive 340 stealth in-tank fuel pump is the best choice. This fuel pump provides 30% more fuel flow, which means that your car can always operate at its peak performance levels. This fuel pump bolsters onto the existing assemblies, allowing you to easily replace the pump, as and when it is needed. For almost all vehicles that are compatible with aftermarket pumps, the Aeromotive 340 pump can be used.

The fuel pump must be replaced, when you have issues with the flow of the fuel. Problems such as a slow flow of the fuel, low or absent fuel pressure could all indicate a problem with the fuel pump. When the fuel and air are not mixed in the right amount to generate enough pressure, your car’s mileage could suffer. Replacing fuel pump is a DIY job, if you are an experienced car owner, with a complete understanding of the owner’s manual.

Before working with fuel pump installation, drain the fuel tank, as much as possible. The fuel injected vehicles require depressurizing the fuel system first, before replacement. Otherwise, fuel may be sprayed at very high pressure and it could result in fire accidents. The in-tank fuel pumps are usually fitted from the top. Removing the back seat of your car will expose an access panel underneath, which you can find the fuel tank. After locating the empty fuel tank, remove the fuel pump. Disconnect the fuel line and remove the fuel pump from the tank. Disconnect the wires from the pump, before removing it. Before removing the tank entirely, you should note down the placement of these wires, so that you know how to do it right, while installing the new Aeromotive 340 fuel pump.

The installation process is easier, compared to the removal process. You need to insert the fuel pump inside the tank. Then, connect the fuel lines. The retaining strap under the fuel tank must be properly fitted. This may vary depending on the model of the car. Then, you should connect the filler tube hose and the electrical connector. Finally, you can connect the negative battery cable. When you complete these steps without a glitch, you can fill the fuel tank with gasoline and test the vehicle on the road.

Fuel Injector Problems and Their Effect on Engine Performance

Fuel Injector Problems and Their Effect on Engine Performance

Clogged injector filters • electrical defect in injectors • Engine Performance • Fuel Injector Problems • Injector winding problems


Fuel injectors are meant to work in extreme heat and pressure conditions. They are manufactured to perform optimally for several billion cycles. Ideally, the fuel injectors should last the lifetime of cars, but it is rarely the case. Fuel injectors fail because the vehicle is never driven in ideal conditions on the road. The fuel injectors atomize the fuel and send it as a steady and straight jet of fuel, to the engine to fire up. Any malfunctioning of the fuel injector will result in angled spray pattern, which is not useful to enhance engine performance.

#1 Unused fuel becomes baked

Improper fuel system maintenance will result in the creation of heatsink, which will heat up unburned fuel, causing it to bake. These participles will form a layer over the injector orifice and pintle, altering the spray pattern. The faulty cooling system will result in continuous overheating of the engine, reducing its performance. In the long run, the O2 sensor will get damaged and the engine will be over fueled to compensate for the loss of performance.

#2 Clogged injector filters

Any foreign particles in the fuel rail, fuel lines or fuel tanks will clog the injector filters or fuel filters. This will inhibit the fuel flow and affect the spray pattern. Routine maintenance will keep your vehicle in proper condition. In most of the circumstances, the foreign particles are rust, which affects the engine performance. The under fueling will make the engine sluggish and it could also result in overheating. In closed loop O2 systems, the engine is usually over fueled, to counter the effects of clogged filter.

#3 Injector winding problems

Regular use of fuel injectors could result in wear and tear. The coil windings of the injector may become overheated, due to cooling problems. When the windings lose their magnetic performance, it could result in broken or open windings. The internal parts of the injector may rust, when the engine is not operated regularly. Contaminated petrol with water particles or other adulterants can cause the cooling system to fail. When the pintle is not properly placed, it could result in fuel leaks.

#4 Mechanical and electrical defect in injectors

Sometimes, defective manufacturing will result in mechanical leaks in the injector. It could also result due to the improper handling of the injector, during the installation or removal process. Ignition system failure will be a direct result of a non-functioning injector. Mechanical problems could also result in overheating of injectors. In such cases, engine fuel fire is a common and dangerous consequence. There is also a huge potential for engine damage. The ECU is the electrical unit that controls the injectors. Improper electrical connectivity will result in misfiring or weak firing. This could happen during improper storage or careless vehicle maintenance.

Fuel injector problems will result in poor engine performance and poor fuel economy. Fuel leaks are far more dangerous and they should be addressed immediately. The best method to deal with fuel injector problems is a replacement and proper maintenance thereafter.

Corvette Headlight Replacement Lens

Corvette Headlight Replacement Lens

General Motors launched the Chevrolet Corvette model in 2005, which was scheduled to be commissioned in 2013. The car is affectionately referred to as C6 and the exposed headlights are one of the most attractive features of the vehicle. The headlight comes with acrylic or plexiglass cover. GM continued to provide support for the C6 headlight and lenses for a while, until 2015. These were available with the OEM supplier a few years ago. However, now the production of the lenses and headlight assemblies have been discontinued. This means that you need to find a reliable third party supplier that won't drain your bank account.

Headlight lens issues

The headlight is certainly very important, especially if you don’t always drive in daylight conditions. As you drive your car on the road, the headlights are subjected to regular wear and tear. The amount of abuse the headlights undergo determine their longevity. The headlight lenses will lose their potential due to severe exposure to UV rays. The seals between the inner and outer cover may experience micro fissures, which will affect the efficiency of your car headlights. The headlight lens may just fail because of impact from the debris on the road. Dimming headlights and lights casting a yellow shade should be addressed at the earliest to ensure proper road visibility.

Best C6 headlight replacement lens is just a click away

Finding the right C6 headlight replacement lens is now easy as HighPerformanceInjectors has updated its inventory of C6 headlight lens. The high demand for our world-class headlight replacement lens encouraged us to air express 500 lenses and 500 more lenses will be added to our inventory in the next few days.

Our specialty C6 headlight replacement lenses are reinforced with UV protection, through our professional grade UV protection polyurethane hardened clear coat. This adds necessary UV protection to the existing polycarbonate plastic of the headlight lenses. The advanced protection ensures that the lenses don’t fade, get yellow or fog for the next 10 years. No other manufacturer is capable of providing such a quality assurance for headlight lens.

Our website is the best place to purchase C6 Corvette replacement headlights because we offer a pair of lens for just $289, including shipping. Unlike other manufacturers, we don’t intend on increasing the price soon, due to the demand for the lenses. The high-quality lenses match the manufacturer requirements and you will find it easier to replace the headlight lenses on your own. You have to take action immediately, when you notice your headlights going dim before they burn out completely.

Replacing headlight lens can be done, if you understand the owner’s manual. The exposed headlight design of the C6 Corvette makes it easy to replace the lens on your own. However, you should never attempt a DIY replacement project, if you are not sure of the car’s mechanism. You can refer to videos on YouTube for replacement instructions. If you are unsure of your skills, it is best to leave the task to the professionals.

Automobile Technology: CRDI (Common Rail Direct Injection)

Automobile Technology: CRDI (Common Rail Direct Injection):    

CRDI (Common Rail Direct Injection)

     CRDi stands for Common Rail
Direct Injection meaning, direct injection of the fuel into the
cylinders of a diesel engine via a single, common line, called the
common rail which is connected to all the fuel injectors.

   
 Whereas ordinary diesel direct fuel-injection systems have to build up
pressure anew for each and every injection cycle, the new common rail
(line) engines maintain constant pressure regardless of the injection
sequence. This pressure then remains permanently available throughout
the fuel line. The engine's electronic timing regulates injection
pressure according to engine speed and load. The electronic control unit
(ECU) modifies injection pressure precisely and as needed, based on
data obtained from sensors on the cam and crankshafts. In other words,
compression and injection occur independently of each other. This
technique allows fuel to be injected as needed, saving fuel and lowering
emissions.

     More accurately measured and timed mixture spray
in the combustion chamber significantly reducing unburned fuel gives
CRDi the potential to meet future emission guidelines such as Euro V.
CRDi engines are now being used in almost all Mercedes-Benz, Toyota,
Hyundai, Ford and many other diesel automobiles.

History

     The common rail system
prototype was developed in the late 1960s by Robert Huber of Switzerland
and the technology further developed by Dr. Marco Ganser at the Swiss
Federal Institute of Technology in Zurich, later of Ganser-Hydromag AG
(est.1995) in Oberägeri. The first successful usage in a production
vehicle began in Japan by the mid-1990s. Modern common rail systems,
whilst working on the same principle, are governed by an engine control
unit (ECU) which opens each injector electronically rather than
mechanically. This was extensively prototyped in the 1990s with
collaboration between Magneti Marelli, Centro Ricerche Fiat and Elasis.
The first passenger car that used the common rail system was the 1997
model Alfa Romeo 156 2.4 JTD, and later on that same year Mercedes-Benz C
220 CDI.

     Common rail engines have been used in marine and
locomotive applications for some time. The Cooper-Bessemer GN-8 (circa
1942) is an example of a hydraulically operated common rail diesel
engine, also known as a modified common rail. Vickers used common rail
systems in submarine engines circa 1916. Early engines had a pair of
timing cams, one for ahead running and one for astern. Later engines had
two injectors per cylinder, and the final series of constant-pressure
turbocharged engines were fitted with four injectors per cylinder. This
system was used for the injection of both diesel oil and heavy fuel oil
(600cSt heated to a temperature of approximately 130 °C). The common
rail system is suitable for all types of road cars with diesel engines,
ranging from city cars such as the Fiat Nuova Panda to executive cars
such as the Audi A6.

Operating Principle

     Solenoid or piezoelectric
valves make possible fine electronic control over the fuel injection
time and quantity, and the higher pressure that the common rail
technology makes available provides better fuel atomisation. In order to
lower engine noise, the engine's electronic control unit can inject a
small amount of diesel just before the main injection event ("pilot"
injection), thus reducing its explosiveness and vibration, as well as
optimizing injection timing and quantity for variations in fuel quality,
cold starting and so on. Some advanced common rail fuel systems perform
as many as five injections per stroke.

     Common rail engines
require very short (< 10 second) or no heating-up time at all ,
dependent on ambient temperature, and produce lower engine noise and
emissions than older systems. Diesel engines have historically used
various forms of fuel injection. Two common types include the unit
injection system and the distributor/inline pump systems (See diesel
engine and unit injector for more information). While these older
systems provided accurate fuel quantity and injection timing control,
they were limited by several factors:

• They were cam driven, and
injection pressure was proportional to engine speed. This typically
meant that the highest injection pressure could only be achieved at the
highest engine speed and the maximum achievable injection pressure
decreased as engine speed decreased. This relationship is true with all
pumps, even those used on common rail systems; with the unit or
distributor systems, however, the injection pressure is tied to the
instantaneous pressure of a single pumping event with no accumulator,
and thus the relationship is more prominent and troublesome.


•
They were limited in the number and timing of injection events that
could be commanded during a single combustion event. While multiple
injection events are possible with these older systems, it is much more
difficult and costly to achieve.


• For the typical
distributor/inline system, the start of injection occurred at a
pre-determined pressure (often referred to as: pop pressure) and ended
at a pre-determined pressure. This characteristic resulted from "dummy"
injectors in the cylinder head which opened and closed at pressures
determined by the spring preload applied to the plunger in the injector.
Once the pressure in the injector reached a pre-determined level, the
plunger would lift and injection would start.

     In common rail systems, a high-pressure pump stores a
reservoir of fuel at high pressure — up to and above 2,000 bars (psi).
The term "common rail" refers to the fact that all of the fuel injectors
are supplied by a common fuel rail which is nothing more than a
pressure accumulator where the fuel is stored at high pressure. This
accumulator supplies multiple fuel injectors with high-pressure fuel.
This simplifies the purpose of the high-pressure pump in that it only
has to maintain a commanded pressure at a target (either mechanically or
electronically controlled). The fuel injectors are typically
ECU-controlled. When the fuel injectors are electrically activated, a
hydraulic valve (consisting of a nozzle and plunger) is mechanically or
hydraulically opened and fuel is sprayed into the cylinders at the
desired pressure. Since the fuel pressure energy is stored remotely and
the injectors are electrically actuated, the injection pressure at the
start and end of injection is very near the pressure in the accumulator
(rail), thus producing a square injection rate. If the accumulator, pump
and plumbing are sized properly, the injection pressure and rate will
be the same for each of the multiple injection events.

Advantages & Disadvantages

Advantages


   CRDi engines are advantageous in many ways. Cars fitted with this
new engine technology are believed to deliver 25% more power and torque
than the normal direct injection engine. It also offers superior pick
up, lower levels of noise and vibration, higher mileage, lower
emissions, lower fuel consumption, and improved performance.

     In India, diesel is cheaper than petrol and this fact adds to the credibility of the common rail direct injection system.

Disadvantages

     Like all good things have a
negative side, this engine also have few disadvantages. The key
disadvantage of the CRDi engine is that it is costly than the
conventional engine. The list also includes high degree of engine
maintenance and costly spare parts. Also this technology can’t be
employed to ordinary engines.

Applications

     The most common
applications of common rail engines are marine and locomotive
applications. Also, in the present day they are widely used in a variety
of car models ranging from city cars to premium executive cars.


   Some of the Indian car manufacturers who have widely accepted the
use of common rail diesel engine in their respective car models are the
Hyundai Motors, Maruti Suzuki, Fiat, General Motors, Honda Motors, and
the Skoda. In the list of luxury car manufacturers, the Mercedes-Benz
and BMW have also adopted this advanced engine technology. All the car
manufacturers have given their own unique names to the common CRDi
engine system.

     However, most of the car manufacturers have
started using the new engine concept and are appreciating the long term
benefits of the same. The technology that has revolutionized the diesel
engine market is now gaining prominence in the global car industry.

     CRDi technology revolutionized diesel engines and also petrol engines (by introduction of GDI technology).

   By introduction of CRDi a lot of advantages are obtained, some of
them are, more power is developed, increased fuel efficiency, reduced
noise, more stability, pollutants are reduced, particulates of exhaust
are reduced, exhaust gas recirculation is enhanced, precise injection
timing is obtained, pilot and post injection increase the combustion
quality, more pulverization of fuel is obtained, very high injection
pressure can be achieved, the powerful microcomputer make the whole
system more perfect, it doubles the torque at lower engine speeds. The
main disadvantage is that this technology increase the cost of the
engine. Also this technology can’t be employed to ordinary engines.

Autoelex Blog: Engine Combustion - Compression Ignition (Diesel)

Autoelex Blog: Engine Combustion - Compression Ignition (Diesel):

Engine Combustion - Compression Ignition (Diesel)

In
a diesel or compression ignition engine, the first and major difference
compared to a spark ignition engine is the way that fuel and air is
prepared for combustion, also, the way combustion is initiated. 

Diesel engines
induce air only during the intake stroke - the air charge is compressed
in the cylinder, heating it accordingly, the final temperature at the
end of the compression stroke is above the self ignition temperature of
the fuel and this factor is essential, as this initiates the combustion
event when the fuel meets with the hot air. The advantage of compressing
air only is that we don't have to consider self ignition of any
fuel/air during compression (as per gasoline engine) as at this point in
the engine cycle, there is no fuel to burn! The combustion process is
quite different to the gasoline engine, the timing and rate of
combustion is controlled via the introduction of fuel into the cylinder
(via the fuel injection system). The combustion process itself takes
place at the interface between the fuel and air. Therefore, sufficient
air motion in the cylinder (generally swirl in a diesel engine) is
essential to sweep away the products of combustion, ensuring that the
fuel charge always has sufficient oxygen at the flame interface to
prevent to formation of soot due to localised oxygen starvation. 

Fig 1 - Air motion in a diesel engine is generally 'swirl'

The overall
volume of the combustion chamber itself has a variable air/fuel ratio
during operation, that is only chemically correct at the fuel to air
interface. In most operating conditions, the average air/fuel ratio in
the cylinder is considerably weak (compared to stoichiometric). The
engine power output is controlled by the amount of fuel injected, so
no throttling is needed and this improves efficiency at part load due to
the lack of pumping losses associated with restricting the airflow into
the engine. The technical term associated with diesel type combustion
is ‘diffusion’ combustion, as the fuel burning takes place at the
interface where fuel diffuses into the air, and vice-versa. 

Due to the fact
that fuel and air have to be mixed during the compression/expansion
cycle (as opposed to pre-mixed, outside the cylinder) this reduces the
amount of time available to complete the whole mixing and combustion
process. Hence, generally speaking, diesel engines cannot rev as highly
as gasoline engine. Therefore, to get more power from a diesel engine
you increase the torque by turbocharging it! - common practice these
days. It’s notable though that the diesel engine combustion cycle, and
engine itself, is more efficient than gasoline for several reasons - the
higher compression ratio increases the cycle efficiency, the lack of a
throttle reduces pumping losses and the high precision, metered
injection system reduces cylinder-to-cylinder variation.

Fig 2 - A common rail diesel fuel injection (FIE) system

Diesel engines
have undergone considerable development over the last few years, mainly
in the area of fuel injection system technology. These developments have
enabled sophisticated, electronically controlled injection systems,
that can help reduce particulate emissions as well a engine noise
emissions. I think that anybody would agree that travelling in a modern
diesel engine car is no longer a noisy or unpleasant experience. Modern
diesels are very refined and smooth in operation!

Fig 3 - Direct and Indirect fuel injection - direct injection is predominant now!

All modern
diesel engines for passenger cars use direct injection technology (as
opposed to indirect). In the past, indirect injection - injecting fuel
into a pre-chamber - was technology used to create the required air
charge motion to speed up the combustion event, thus increasing the
maximum possible engine speed and power density. However, the increased
surface area of the combustion and pre-chamber increases heat losses and
reduces efficiency and has now been completely superseded by direct
injection systems for most applications. In a modern diesel engine, the
fuel injector nozzle sprays a complex, engineered spray pattern into the
hot , highly turbulent combustion chamber gases, to initiate the
combustion event at around TDC.  The fuel is injected radially into the
combustion chamber, the liquid fuel vaporises and mixes with the air as
it travels away from the injector tip nozzles. The fuel self-ignites at
multiple ignition sites along each of the injection sprays. 

Fig 4 - Diesel spray pattern and combustion from a thermal image system

The design of
the combustion chamber, in the piston bowl, is critical to the
efficiency of the combustion event. This design creates the necessary
motion and energy in the cylinder charge to make sure that each tiny
droplet of fuel has sufficient oxygen for complete combustion, right
throughout the injection period. 

Fig 5 - The 3 phases of diesel combustion

The initial
combustion takes a certain time period to establish, known as the delay
time, then the fuel will auto-ignite creating a very rapid energy
release and the flame spreads rapidly through the fuel that is exposed
to sufficient air for combustion. This creates a rapid rise in cylinder
pressure, forcing the piston down the cylinder. As the power (or
expansion) stroke continues, further mixing of fuel and air occurs,
accompanied by further, more controlled combustion period where energy
release is controlled by injection rate. Note that it is the rapid
release of energy, after the delay period, which causes the
characteristic combustion ‘knock’ associated with diesel engine.

Fig 6 - Common rail, electronic diesel systems allow multiple injection events with better control of the combustion process

Modern,
electronic fuel injection systems, with multiple injection events,
effectively reduce this noise via a more gradual introduction of the
fuel into the cylinder (via pre-injection events) as opposed to a
single-shot event, where all fuel is injected at once (causing rapid
pressure rise and noise). Note that single-shot injection strategies
were all that was possible with a simple rotary or in-line injector pump
in the past. In summary, the key points to consider with respect to the
compression ignition engine are:

• The fuel/air mixture is prepared internally in the cylinder, during the engine cycle and relies on self ignition
• The engine power is controlled via the quantity of fuel injected in each engine cycle. 
• The
  compression ratio is not limited by the fuel as the compressed charge is
  just air, It is only limited by the strength of the engine design as
  peak cylinder pressures are very high
• In operation, engine maximum torque is limited by peak pressures/mechanical loading
• Rapid pressure rise, generated by the self-ignition of the fuel, creates the diesel engine noise

Aircraft systems: Fuel-Injection Systems

Fuel-Injection Systems:

Fuel-Injection Systems

The
fuel-injection system has many advantages over a conventional carburetor
system. There is less danger of induction system icing, since the drop
in temperature due to fuel vaporization takes place in or near the
cylinder. Acceleration is also improved because of the positive action
of the injection system. In addition, fuel injection improves fuel
distribution. This reduces the overheating of individual cylinders often
caused by variation in mixture due to uneven distribution. The
fuel-injection system also gives better fuel economy than a system in
which the mixture to most cylinders must be richer than necessary so
that the cylinder with the leanest mixture operates properly.

Fuel-injection
systems vary in their details of construction, arrangement, and
operation. The Bendix and Continental fuel-injection systems are
discussed in this section. They are described to provide an
understanding of the operating principles involved. 

Bendix/Precision Fuel-Injection System

The Bendix
inline stem-type regulator injection system (RSA) series consists of an
injector, flow divider, and fuel discharge nozzle. It is a
continuous-flow system which measures engine air consumption and uses
airflow forces to control fuel flow to the engine. The fuel distribution
system to the individual cylinders is obtained by the use of a fuel
flow divider and air bleed nozzles.

Fuel Injector

The fuel injector assembly consists of:

1. An airflow section,
2. A regulator section, and
3. A fuel metering section. Some fuel injectors are equipped with an automatic mixture control unit.

Airflow Section

Figure 1

The airflow consumption of the engine is measured by sensing impact pressure and venturi throat pressure in the throttle
body. These pressures are vented to the two sides of an air diaphragm. A
cutaway view of the airflow measuring section is shown in Figure 1.
Movement of the throttle valve causes a change in engine air
consumption. This results in a change in the air velocity in the
venturi. When airflow through the engine increases, the pressure on the
left of the diaphragm is lowered due to the drop in pressure at the
venturi throat. [Figure
2] As a result, the diaphragm moves to the left, opening the ball
valve. Contributing to this force is the impact pressure that is picked
up by the impact tubes. 

Figure 2

Figure 3

[Figure 3] This
pressure differential is referred to as the “air metering force.” This
force is accomplished by channeling the impact and venturi suction
pressures to opposite sides of a diaphragm. The difference between these
two pressures becomes a usable force that is equal to the area of the
diaphragm times the pressure difference.

Regulator Section

The regulator
section consists of a fuel diaphragm that opposes the air metering
force. Fuel inlet pressure is applied to one side of the fuel diaphragm
and metered fuel pressure is applied to the other side. The differential
pressure across the fuel diaphragm is called the fuel metering force.
The fuel pressure shown on the ball side of the fuel diaphragm is the
pressure after the fuel has passed through the fuel strainer and the
manual mixture control rotary plate and is referred to as metered fuel
pressure. Fuel inlet pressure is applied to the opposite side of the
fuel diaphragm. The ball valve attached to the fuel diaphragm controls
the orifice opening and fuel flow through the forces placed on it.
[Figure 4]

Figure 4

The distance
the ball valve opens is determined by the difference between the
pressures acting on the diaphragms. This difference in pressure is
proportional to the airflow through the injector. Thus, the volume of
airflow determines the rate of fuel flow.

Under low power
settings, the difference in pressure created by the venturi is
insufficient to accomplish consistent regulation of the fuel. A
constant-head idle spring is incorporated to provide a constant fuel
differential pressure. This allows an adequate final flow in the idle
range.

Fuel Metering Section

Figure 5

The fuel
metering section is attached to the air metering section and contains an
inlet fuel strainer, a manual mixture control valve, an idle valve, and
the main metering jet. [Figure 5] The idle valve is connected to the
throttle valve by means of an external adjustable link. In some injector
models, a power enrichment jet is also located in this section.

Figure 6

The purpose of
the fuel metering section is to meter and control the fuel flow to the
flow divider. [Figure 6] The manual mixture control valve produces full
rich condition when the lever is against the rich stop, and a
progressively leaner mixture as the lever is moved toward idle cutoff.
Both idle speed and idle mixture may be adjusted externally to meet
individual engine requirements.

Flow Divider

The metered
fuel is delivered from the fuel control unit to a pressurized flow
divider. This unit keeps metered fuel under pressure, divides fuel to
the various cylinders at all engine speeds, and shuts off the individual nozzle lines when the control is placed in idle cutoff.

Figure 7

Referring to
the diagram in Figure 7, metered fuel pressure enters the flow divider
through a channel that permits fuel to pass through the inside diameter
of the flow divider needle. At idle speed, the fuel pressure from the
regulator must build up to overcome the spring force applied to the
diaphragm and valve assembly. This moves the valve upward until fuel can
pass out through the annulus of the valve to the fuel nozzle. [Figure
8] Since the regulator meters and delivers a fixed amount of fuel to the
flow divider, the valve opens only as far as necessary to pass this
amount to the nozzles. At idle, the opening required is very small; the fuel for the individual cylinders is divided at idle by the flow divider.

Figure 8

As fuel flow
through the regulator is increased above idle requirements, fuel
pressure builds up in the nozzle lines. This pressure fully opens the
flow divider valve, and fuel distribution to the engine becomes a
function of the discharge nozzles.

A fuel pressure
gauge, calibrated in pounds per hour fuel flow, can be used as a fuel
flow meter with the Bendix RSA injection system. This gauge is connected
to the flow divider and senses the pressure being applied to the
discharge nozzle. This pressure is in direct proportion to the fuel flow
and indicates the engine power output and fuel consumption.

Fuel Discharge Nozzles

Figure 9

The fuel
discharge nozzles are of the air bleed configuration. There is one
nozzle for each cylinder located in the cylinder head. [Figure 9] The
nozzle outlet is directed into the intake port. Each nozzle incorporates
a calibrated jet. The jet size is determined by the available fuel
inlet pressure and the maximum fuel flow required by the engine. The
fuel is discharged through this jet into an ambient air pressure chamber
within the nozzle assembly. Before entering the individual intake valve
chambers, the fuel is mixed with air to aid in atomizing the fuel. Fuel
pressure, before the individual nozzles, is in direct proportion to
fuel flow; therefore, a simple pressure gauge can be calibrated in fuel
flow in gallons per

hour and be
employed as a flowmeter. Engines modified with turbosuperchargers must
use shrouded nozzles. By the use of an air manifold, these nozzles are
vented to the injector air inlet pressure.

Continental/TCM Fuel-Injection System

The Continental
fuel-injection system injects fuel into the intake valve port in each
cylinder head. [Figure 10] The system consists of a fuel injector pump, a
control unit, a fuel manifold, and a fuel discharge nozzle. It is a
continuous-flow type, which controls fuel flow to match engine airflow.
The continuous-flow system permits the use of a rotary vane pump which
does not require timing to the engine.

Figure 10

Fuel-Injection Pump

Figure 11

The fuel pump
is a positive-displacement, rotary-vane type with a splined shaft for
connection to the accessory drive system of the engine. [Figure 11] A
spring-loaded, diaphragm-type relief valve is provided. The relief valve
diaphragm chamber is vented to atmospheric pressure. A sectional view
of a fuel-injection pump is shown in Figure 12.

Fuel enters at
the swirl well of the vapor separator. Here, vapor is separated by a
swirling motion so that only liquid fuel is delivered to the pump. The
vapor is drawn from the top center of the swirl well by a small pressure
jet of fuel and is directed into the vapor return line. This line
carries the vapor back to the fuel tank.

Figure 12

Ignoring the
effect of altitude or ambient air conditions, the use of a
positive-displacement, engine-driven pump means that changes in engine
speed affect total pump flow proportionally. Since the pump provides
greater capacity than is required by the engine, a recirculation path is
required. By arranging a calibrated orifice and relief valve in this
path, the pump delivery pressure is also maintained in proportion to
engine speed. These provisions assure proper pump pressure and fuel
delivery for all engine operating speeds.

A check valve
is provided so that boost pump pressure to the system can bypass the
engine-driven pump for starting. This feature also suppresses vapor
formation under high ambient temperatures of the fuel, and permits use
of the auxiliary pump as a source of fuel pressure in the event of
engine-driven pump failure.

Fuel/Air Control Unit

Figure 13

The function of
the fuel/air control assembly is to control engine air intake and to
set the metered fuel pressure for proper fuel/air ratio. The air
throttle is mounted at the manifold inlet and its butterfly valve,
positioned by the throttle control in the aircraft, controls the flow of
air to the engine. [Figure 13]

The air
throttle assembly is an aluminum casting which contains the shaft and
butterfly-valve assembly. The casting bore size is tailored to the
engine size, and no venturi or other restriction is used.

Fuel Control Assembly

The fuel
control body is made of bronze for best bearing action with the
stainless steel valves. Its central bore contains a metering valve at
one end and a mixture control valve at the other end. Each stainless
steel rotary valve includes a groove which forms a fuel chamber.

Fuel enters the
control unit through a strainer and passes to the metering valve.
[Figure 14] This rotary valve has a cam-shaped edge on the outer part of
the end face. The position of the cam at the fuel delivery port
controls the fuel passed to the manifold valve and the nozzles. The fuel
return port connects to the return passage of the center metering plug.
The alignment of the mixture control valve with this passage determines
the amount of fuel returned to the fuel pump.

Figure 14

By connecting
the metering valve to the air throttle, the fuel flow is properly
proportioned to airflow for the correct fuel/ air ratio. A control level
is mounted on the mixture control valve shaft and connected to the
cockpit mixture control.

Fuel Manifold Valve

The fuel
manifold valve contains a fuel inlet, a diaphragm chamber, and outlet
ports for the lines to the individual nozzles. [Figure 15] The
spring-loaded diaphragm operates a valve in the central bore of the
body. Fuel pressure provides the force for moving the diaphragm. The
diaphragm is enclosed by a cover that retains the diaphragm loading
spring. When the valve is down against the lapped seat in the body, the
fuel lines to the cylinders are closed off. The valve is drilled for
passage of fuel from the diaphragm chamber to its base, and a ball valve
is installed within the valve. All incoming fuel must pass through a
fine screen installed in the diaphragm chamber.

Figure 15

From the fuel-injection control valve, fuel is delivered to the fuel manifold valve, which provides a central point for

dividing fuel
flow to the individual cylinders. In the fuel manifold valve, a
diaphragm raises or lowers a plunger valve to open or close the
individual cylinder fuel supply ports simultaneously.

Fuel Discharge Nozzle

The fuel
discharge nozzle is located in the cylinder head with its outlet
directed into the intake port. The nozzle body contains a drilled
central passage with a counterbore at each end. [Figure 16] The lower
end is used as a chamber for fuel/air mixing before the spray leaves the
nozzle. The upper bore contains a removable orifice for calibrating the
nozzles. Nozzles are calibrated in several ranges, and all nozzles
furnished for one engine are of the same range and are identified by a
letter stamped on the hex of the nozzle body.

Figure 16

Drilled radial
holes connect the upper counterbore with the outside of the nozzle body.
These holes enter the counterbore above the orifice and draw air
through a cylindrical screen fitted over the nozzle body. A shield is
press-fitted on the nozzle body and extends over the greater part of the
filter screen, leaving an opening near the bottom. This provides both
mechanical protection and an abrupt change in the direction of airflow
which keeps dirt and foreign material out of the nozzle interior.

When To Replace A Fuel Injector

When To Replace A Fuel Injector

During its evolution, the fuel injector has moved from the intake manifold to the combustion chamber. This has made them more precise in dispensing fuel. If this precision is thrown off by restrictions, electrical problems or fuel problems, it can cause driveability issues.



Here are 10 signs to look for when you need to replace a fuel injector or it needs service.





1. Restrictions

A restriction of only 8% to 10% in a single fuel injector can lean out the fuel mixture and cause a misfire. When this occurs, unburned oxygen enters the exhaust and makes the O2 sensor read lean. On older multiport systems that fire the injectors simultaneously, the computer compensates by increasing the “on” time of all the injectors, which can create an overly rich fuel condition in the other cylinders.

Direct fuel injectors are more sensitive to restrictions because of the precise amount of fuel they inject into the combustion chamber.



2. Turbo Troubles

In turbocharged engines, dirty injectors can have a dangerous leaning effect that may lead to engine-damaging detonation. When the engine is under boost and at a higher rpm, it needs all the fuel the injectors can deliver. If the injectors are dirty and can’t keep up with the engine’s demands, the fuel mixture will lean out, causing detonation to occur. The leaning out may cause higher than normal exhaust temperatures and turbo failure.



3. Heat Soak

When the engine is shut off, the injectors undergo heat soak. Fuel residue evaporates in the injector nozzles, leaving the waxy olefins behind. Because the engine is off, there is no cooling airflow moving through the ports and no fuel flowing through the injectors to wash it away, so heat bakes the olefins into hard varnish deposits. Over time, these deposits can build up and clog the injectors. Even if a vehicle has low mileage, short drive cycles and increased heat soaks can clog the injector.

Since the formation of these deposits is a normal consequence of engine operation, detergents are added to gasoline to help keep the injectors clean. But if a vehicle is used primarily for short-trip driving, the deposits may build up faster than the detergents can wash them away. On four-cylinder engines, the No. 2 and No. 3 injectors are in the hottest location and tend to clog up faster than the end injectors on cylinders No. 1 and No. 4. The same applies to the injectors in the middle cylinders in six- and eight-cylinder engines. The hotter the location, the more vulnerable the injector is to clogging from heat soaks. Throttle body injectors are less vulnerable to heat soak because of their location high above the intake manifold plenum.

Heat soak can affect direct-injection injectors due to their placement in the head. Even with the higher pressures, the orifices can become clogged over time.





4. Increase or Decrease in Long- and Short-Term Fuel Trims

The fuel calibration curves in the Powertrain Control Module (PCM) are based on OEM dyno testing using a new engine. Fuel pressure is within a specified range for that engine, and the injectors are all clean and new. The PCM’s built-in adaptive fuel control strategies allow it to adjust both short-term and long-term fuel trim to compensate for variances in fuel pressure and fuel delivery to maintain the correct air/fuel ratio — but only within certain limits.

The PCM may not be able to increase injector duration enough to offset the difference if:

• An injector becomes clogged with fuel varnish deposits and fails to deliver its normal dose of fuel when it’s energized, or

• Fuel pressure to the injector drops below specifications because of a weak fuel pump, plugged fuel filter or leaky fuel pressure regulator.

This can leave the air/fuel mixture too lean, causing the cylinder to misfire.





5. Not Enough Resistance

The solenoid at the top of the injector creates a magnetic field that pulls up the injector pintle when the injector is energized. The magnetic field must be strong enough to overcome the spring pressure and fuel pressure above the pintle, otherwise the injector may not open all the way. Shorts, opens or excessive resistance in the injector solenoid can also cause problems.

Typically, the solenoids often short internally when injectors fail, which causes a drop in resistance. If the specification calls for 3 ohms, for example, and an injector measures only 1 ohm, it will pull more current than the other injectors. Too much current flow to an injector may cause the PCM injector driver circuit to shut down, killing any other injectors that also share that same driver circuit. One way to check the injectors is with an ohmmeter.




6. Longer Crank Times

An injector leak will cause the rail to lose pressure while the vehicle is sitting resulting in a longer than normal crank because the rail will need extra time to pressurize.



A normal crank time in a diesel common-rail injection system is usually around three to five seconds. This is how long it will take the common-rail pump to build fuel pressure to the “threshold.” The fuel rail pressure threshold for cranking occurs around 5,000 psi. Normal common-rail systems will operate at 5,000 psi at idle and can reach up to 30,000 psi at wide open throttle.



7. Failed Balance Tests

If you suspect that an injector is clogged or malfunctioning, an injector balance test can isolate the bad injector. Scan tools that can disable injectors can isolate an injector for diagnostics. Engine rpm drop may not be an effective diagnostic method when performing a cylinder balance test where an injector is disabled.



A more effective method is looking at the voltage changes from the O2 sensor. Leaking injectors and some dead injectors can be missed even when an injector is disabled. Other problems with the ignition system and mechanical components also may not show an rpm loss when an injector is turned off. If an injector is good, the voltage from the O2 sensor will drop to or below 100mV. If the problem is a closed or dead injector, the long-term fuel trim may have compensated enough so that the voltage doesn’t change.

Another effective test is to measure the pressure loss in the fuel rail when each injector is fired and pulses for a set period of time. Use an electronic injector pulse tester for this. As each injector is energized, a fuel pressure gauge is observed to monitor the drop in fuel pressure. The electrical connectors to the other injectors are removed, isolating the injector being tested. The difference between the maximum and minimum reading is the pressure drop.

Ideally, each injector should drop the same amount when opened. A variation of 1.5 to 2 psi or more is cause for concern. No pressure drop, or a very low pressure drop, is a sign the orifice or tip is restricted. A higher than normal pressure drop indicates a rich condition that could be caused by a stuck plunger or worn pintle.



8. Misfire Codes

A lean misfire may trigger a misfire code and turn on the check engine light. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected.





9. Vehicle Won’t Start With Full Tank

Major symptoms of contaminated fuel can include cranking no-start, hard starting, stalling, loss of power and poor fuel economy. Because symptoms of fuel contamination generally appear immediately after refueling, the fuel gauge needle pegged on full should always be a diagnostic red flag. Remember to ask if the vehicle has recently been refueled because some drivers just add fuel rather than topping off their tanks.



10. Lack of Maintenance

If an owner has neglected maintenance services like oil changes and filter replacements, chances are the fuel injectors will suffer. For port fuel applications, not changing the oil can result in blowby and a compromised PCV system, which builds up contaminates on the tip of the injector. Not changing the oil in an engine with direct fuel injection can result in a worn fuel pump camshaft lobe.





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