AUTOMOBILE ENGINEERING LAB PROJECT

FUEL INJECTION SYSTEM

&

STEERING SYSTEM

Abhimanyu Goyat 09107001

Aziz Luna 09107014

Fuel injection

Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having replaced carburetors during the 1980s and 1990s. A variety of injection systems have existed since the earliest usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream.

Modern fuel injection systems are designed specifically for the type of fuel being used. Some systems are designed for multiple grades of fuel (using sensors to adapt the tuning for the fuel currently used). Most fuel injection systems are for gasoline or diesel applications.

Objectives

The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system is optimized. There are several competing objectives such as:

Power output Fuel efficiency Emissions performance Ability to accommodate alternative fuels Reliability Driveability and smooth operation Initial cost Maintenance cost Diagnostic capability Range of environmental operation Engine tuning

The modern digital electronic fuel injection system is more capable at optimizing these competing objectives consistently than earlier fuel delivery systems (such as carburetors). Carburetors have the potential to atomize fuel better.

Determining how much fuel to supply

The primary factor used in determining the amount of fuel required by the engine is the amount (by weight) of air that is being taken in by the engine for use in combustion. Modern systems use a mass airflow sensor to send this information to the engine control unit.

Data representing the amount of power output desired by the driver (sometimes known as "engine load") is also used by the engine control unit in calculating the amount of fuel required. A throttle position sensor (TPS) provides this information. Other engine sensors

used in EFI systems include a coolant temperature sensor, a camshaft position sensor, and an oxygen sensor which is installed in the exhaust system so that it can be used to determine how well the fuel has been combusted, therefore allowing closed loop operation.

Supplying the fuel to the engine

Fuel is transported from the fuel tank (via fuel lines) and pressurised using fuel pump(s). Maintaining the correct fuel pressure is done by a fuel pressure regulator. Often a fuel rail is used to divide the fuel supply into the required number of cylinders. The fuel injector injects liquid fuel into the intake air (the location of the fuel injector varies between systems).

Carburetor

The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine "runs rich" and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The carb is in charge of getting the mixture just right.

On new cars, fuel injection is becoming nearly universal because it provides better fuel efficiency and lower emissions. But nearly all older cars, and all small equipment like lawn mowers and chain saws, use carbs because they are simple

Parts of a carburetor:

A carburetor is essentially a tube.

There is an adjustable plate across the tube called the throttle plate that controls how much air can flow through the tube.

At some point in the tube there is a narrowing, called the venturi, and in this narrowing a vacuum is created.

In this narrowing there is a hole, called a jet, that lets the vacuum draw in fuel.

Carburetor Tuning

The carb is operating "normally" at full throttle. In this case the throttle plate is parallel to the length of the tube, allowing maximum air to flow through the carb. The air flow creates a nice vacuum in the venturi and this vacuum draws in a metered amount of fuel through the jet.

When the engine is idling, the throttle plate is nearly closed (the position of the throttle plate in the photos is the idle position). There is not really enough air flowing through the venturi to create a vacuum. However, on the back side of the throttle plate there is a lot of vacuum (because the throttle plate is restricting the airflow). If a tiny hole is drilled into the side of the carb's tube just behind the throttle plate, fuel can be drawn into the tube by the throttle vacuum. This tiny hole is called the idle jet. The other screw of the pair controls the amount of fuel that flows through the idle jet.

Both the Hi and Lo screws are simply needle valves. By turning them you allow more or less fuel to flow past the needle. When you adjust them you are directly controlling how much fuel flows through the idle jet and the main jet.

When the engine is cold and you try to start it with the pull cord, the engine is running at an extremely low RPM. It is also cold, so it needs a very rich mixture to start. This is where the choke plate comes in. When activated, the choke plate completely covers the venturi see this video of the choke plate to see it in action). If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet (since the end of the carb's tube is completely covered, all of the engine's vacuum goes into pulling fuel through the jets). Usually this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If you then open the choke plate the engine will start running normally.

Suprsession of Carburetors

In the 1970s and 1980s in the US, the federal government imposed increasingly strict exhaust emission regulations. During that time period, the vast majority of gasoline-fueled automobile and light truck engines did not use fuel injection. To comply with the new regulations, automobile manufacturers often made extensive and complex modifications to the engine carburetor(s). While a simple carburetor system is cheaper to manufacture than a fuel injection systems, the more complex carburetor systems installed on many engines in the 1970s were much more costly than the earlier simple carburetors. To more easily comply with emissions regulations, automobile manufacturers began installing fuel injection systems in more gasoline engines during the late 1970s.

The open loop fuel injection systems had already improved cylinder-to-cylinder fuel distribution and engine operation over a wide temperature range, but did not offer further scope to sufficient control fuel/air mixtures, in order to further reduce exhaust emissions. Later Closed loop fuel injection systems improved the air/fuel mixture control with an exhaust gas oxygen sensor and began incorporating a catalytic converter to further reduce exhaust emissions.

Fuel injection was phased in through the latter '70s and '80s at an accelerating rate, with the US, French and German markets leading and the UK and Commonwealth markets lagging somewhat. Since the early 1990s, almost all gasoline passenger cars sold in first world markets are equipped with electronic fuel injection (EFI). The carburetor remains in use in developing countries where vehicle emissions are unregulated and diagnostic and repair infrastructure is sparse. Fuel injection is gradually replacing carburetors in these nations too as they adopt emission regulations conceptually similar to those in force in Europe, Japan, Australia and North America.

Many motorcycles still utilize carburetored engines, though all current high-performance designs have switched to EFI.

The InjectorA fuel injector is nothing but an electronically controlled valve. It is supplied with -pressurized fuel by the fuel pump in your car, and it is capable of opening and closing many times per second.

When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel -- to make as fine a mist as possible so that it can burn easily.

A fuel injector firing

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.

Fuel injectors mounted in the intake manifold of the engine

The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.

In this picture, you can see three of the injectors. The fuel rail is the pipe on the left.

In order to provide the right amount of fuel, the engine control unit is equipped with a whole lot of sensors.

Engine Sensors

In order to provide the correct amount of fuel for every operating condition, the engine control unit (ECU) has to monitor a huge number of input sensors. Here are just a few:

Mass airflow sensor - Tells the ECU the mass of air entering the engine Oxygen sensor(s) - Monitors the amount of oxygen in the exhaust so the ECU can determine

how rich or lean the fuel mixture is and make adjustments accordingly Throttle position sensor - Monitors the throttle valve position (which determines how much

air goes into the engine) so the ECU can respond quickly to changes, increasing or decreasing the fuel rate as necessary

Coolant temperature sensor - Allows the ECU to determine when the engine has reached its proper operating temperature

Voltage sensor - Monitors the system voltage in the car so the ECU can raise the idle speed if voltage is dropping (which would indicate a high electrical load)

Manifold absolute pressure sensor - Monitors the pressure of the air in the intake manifold The amount of air being drawn into the engine is a good indication of how much power it is

producing; and the more air that goes into the engine, the lower the manifold pressure, so this reading is used to gauge how much power is being produced.

Engine speed sensor - Monitors engine speed, which is one of the factors used to calculate the pulse width

There are two main types of control for multi-port systems: The fuel injectors can all open at the same time, or each one can open just before the intake valve for its cylinder opens (this is called sequential multi-port fuel injection).

The advantage of sequential fuel injection is that if the driver makes a sudden change, the system can respond more quickly because from the time the change is made, it only has to wait only until the next intake valve opens, instead of for the next complete revolution of the engine.

Common rail direct fuel injection CRDI

On diesel engines, it features a high-pressure (over 1,000 bar or 15,000 psi) fuel rail feeding individual solenoid valves, as opposed to low-pressure fuel pump feeding unit injectors (Pumpe/Düse or pump nozzles). Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 1,800 bar or 26,000 psi.

In gasoline engines, it is used in gasoline direct injection engine technology.

Multi-point fuel injection

Multi-point fuel injection injects fuel into the intake ports just upstream of each cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) systems can be sequential, in which injection is timed to coincide with each cylinder's intake stroke; batched, in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; or simultaneous, in which fuel is injected at the same time to all the cylinders. The intake is only slightly wet, and typical fuel pressure runs between 40-60 psi.

Many modern EFI systems utilize sequential MPFI; however, in newer gasoline engines, direct injection systems are beginning to replace sequential ones.

Gasoline Direct Injection(GDI), also known as Petrol Direct Injection or Direct Petrol Injection or Spark Ignited Direct Injection(SIDI) or Fuel Stratified Injection(FSI), is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines. The gasoline is highly pressurized, and injected via a common rail fuel line directly into the combustion chamber of each cylinder, as opposed to conventional multi-point fuel injection that happens in the intake tract, or cylinder port.

In some applications, gasoline direct injection enables a stratified fuel charge (ultra lean burn) combustion for improved fuel efficiency, and reduced emission levels at low load.

The major advantages of a GDI engine are increased fuel efficiency and high power output. Emissions levels can also be more accurately controlled with the GDI system. The cited gains are achieved by the precise control over the amount of fuel and injection timings that are varied according to engine load. In addition, there are no throttling losses in some GDI engines, when compared to a conventional fuel-injected or carbureted engine, which greatly improves efficiency, and reduces 'pumping losses' in engines without a throttle plate. Engine speed is controlled by the engine control unit/engine management system (EMS), which regulates fuel injection function and ignition timing, instead of having a throttle plate that restricts the incoming air supply. Adding this function to the EMS requires considerable enhancement of its processing and memory, as direct injection plus the engine speed management must have very precise algorithms for good performance and drivability.

STEERING SYSTEM

The steering system is the key interface between the driver and the vehicle. The main requirement is that the steering should be precise, with no play. In addition, the steering system should be smooth, compact and light. It must also provide the driver with a perfect feel for the road surface and help the wheels return to the straight-ahead position. The standard steering arrangement is to turn the front wheels using a hand-operated steering wheel via the steering column. The steering column may contain several joints to

allow it to deviate somewhat from a straight line. These joints may also be part of the collapsible steering column design to protect the driver in frontal crash situations.

Operating mechanisms

There are two basic steering mechanisms:

Rack and pinion steering

Recirculating ball steering.

Most modern cars use the rack and pinion steering mechanism. The recirculating ball mechanism has the advantage of a much greater torque multiplication, thus it was originally used on larger, heavier vehicles while the rack and pinion was limited to smaller and lighter cars. But with the almost universal adoption of power steering, this is no longer an important advantage, leading to the increasing use of the rack and pinion mechanism on new cars. However, power-assisted recirculating ball steering systems are still applied today in dynamic sports cars, upper class cars, off-road vehicles and vans. Despite the ability to safely transmit high torques, the recirculating ball system is characterized by low system friction, high efficiency and good noise performance. In the rack and pinion system, a pinion gear is attached to the steering shaft, i.e. turning the steering wheel turns the pinion gear which then moves the rack. The rack and pinion gear is enclosed in a metal tube, with each end of the rack protruding from the tube. It does two things:

It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.

It provides a gear reduction, making it easier to turn the wheels.

Rack-and-pinion Systems• Tie rod assemblies• Tie rod ends• Steering knuckles• Steering shaft• Steering column• Flexible coupling• Universal joint (if needed)• Lower ball joints• Backup fasteners (cotter pins or lock nuts)

Tie Rod Ends• Ball-and-socket joint• Tapered ball stud fits into a tapered hole• Inner tie rod ends on rack-and-pinion units thread onto the end of the rack• May be sealed at factory, or may have a grease fitting• Rubber dust cover or boot protects the socket• Threads on tie rods and sleeve or adjuster are used to adjust the length of the tie rod assembly to set wheel alignment(toe)

Steering Column Assembly Components• Steering wheel• Steering column• Steering shaft• Ignition key mechanism and switch• Flexible coupling and universal joint• Turn signal mechanisms, horn controls, tilt mechanism, anti-theft steering lock mechanism, headlight and dimmer switchcontrols, windshield wiper and washer controls, cruise control, transmission gear selector, and other components

Rack-and-pinion Steering

• Steering gear: pinion transmits rotary motion to the rack, which converts this movement into linear, side-to-side motion• Rack is mounted to the sub-frame (or frame) with rubber bushings. Inner and outer tie rod assemblies connect the rack tothe steering knuckles.• Can be either manual or power assisted

A tie rod at each end of the rack connects via the swivel ball joint to the steering arm which finally moves the wheel. The specific advantage of the rack and pinion design is a good feedback and a direct steering "feel". In a recirculating ball steering box, a box is clamped over a worm drive that contains dozens of ball bearings. The ball bearings loop around the worm drive and then out into a recirculating channel where they are fed back into the worm drive again. As the steering wheel is turned, the worm drive turns and forces the ball bearings to press against the channel inside the nut. This forces the nut to move along the worm drive. The nut itself has a couple of gear teeth cast into the outside of it and these mesh with the teeth on a sector gear which is attached to the cross shaft.

Recirculating Ball Steering Gear

• Input shaft is called a worm shaft because at its end is a worm gear• Worm gear provides gear reduction to reduce steering effort• Worm gear meshes with and acts upon a ball nut• Ball nut meshes with and acts upon teeth on the sector gear (output)• Sector gear transmits movement through the sector shaft (or pitman shaft) to the pitman arm

Conventional Linkage ComponentsPitman arm – Usually splined to the sector (output) shaft with a press fit. Most sector shafts and pitman arms have a master or “blind” spline that permits installation in the correct position only. The pitman arm is connected to the center link with a ball socket or pivoting bushing. The ball socket or bushing may be either a part of the pitman arm or part of the

center link. When the ball socket or bushing is part of the center link, the pitman arm is a non-wearing item and would only need to be replaced if bent or damaged. This is the more common arrangement.

Idler arm – The idler arm bolts to the frame or subframe and attaches to the center link to support the linkage. It corresponds to the pitman arm to complete a strong and symmetrical linkage set. There are many different designs of idler arms, and again, if the center link does not have a pivot socket or bushing at the connection, the idler arm will

Power steering systems

As vehicles have become heavier and switched to front wheel drive, along with an increase in tire width and diameter, the effort needed to manually turn the steering wheel has increased. Therefore power steering (or rather power-assisted steering) was introduced to assist the driver. A specific advantage of power steering is speed adjustable steering, where the steering is heavily assisted at low speed and lightly assisted at high speed. This feature is gradually becoming commonplace across all new vehicles. There are two types of power steering systems - hydraulic and electric/electronic. Also hydraulic-electric hybrid systems are possible.

1. Electronic speedometer in the vehicle 2. Electronic control unit (ECU) 3. Electro-hydraulic transducer 4. Rack and pinion power steering gear 5. Engine-driven steering pump 6. Oil reservoir with fine filter 7. Anti-vibration expansible hose

The dominating steering solution for today’s vehicles is rack and pinion hydraulic steering. In a hydraulic power steering system, a part of the rack contains a cylinder with a piston in the middle. The piston is connected to the rack. Supplying a higher pressure fluid to one side of the piston forces the piston to move, which in turn moves the rack. The hydraulic power steering system uses hydraulic pressure supplied by an engine-driven pump to assist the turning motion of the steering wheel. This system offers good value and functionality, a high level of reliability, and has a proven safety record. Major components, aside from the rack and pinion, include the pump providing the hydraulic pressure, the valve assembly, the rack tube housing as well as flexible bellows and pressure lines.

Power Steering Pump• Four main types of power steering pumps have been used. They are the roller, vane, slipper, and gear types. The pump must provide sufficient pressure for steering assist at all engine speeds to meet the various steering demands.• A fluid reservoir is often mounted on the pump housing, or it may be a separate component.• The need for assist is greatest during periods of low-speed maneuvering, which may occur at idle or low engine speeds, and less when cruising at high speed.• When the pump is turning fast and steering demands are low, most of the fluid is diverted back to the inlet side of the pump through a pressure relief valve. The two-stage pressure relief and control valve provides the correct amount of steering assist at different rpms, and opens a bypass port to the pump intake when pressure gets too high.• Some power steering pumps are capable of producing up to 1,500 psi.• A power steering pump can require a significant amount of horsepower. Some vehicles’ control module will sense the increased engine load caused by power steering demands at idle and increase the idle to prevent stalling or stumbling.

The control module may also turn off the A/C compressor or the alternator at such times.

Two Main Types of Power Steering

• Power rack-and-pinion steering• Integral power steering gearbox – Conventionalrecirculating ball steering gear with a hydraulic controlsystem built in

Power rack-and-pinion steering systems include thefollowing:• Power cylinder – a hydraulic cylinder inside the rack or gear housing• Power piston – a double-acting, hydraulic piston in the power cylinder that acts upon the rack• Control valve mechanism – located in the steering gear; senses and controls power assist• Hydraulic lines – steel tubing from the control valve to the power cylinder that carries the power steering fluid• Most power rack-and-pinion units have a small tube that runs along the housing and connects to each bellows boot. This tube allows the air pressure in the bellows boots to equalize from one side to the other during turns.

Integral power steering systems

• Commonly used with linkage-type steering• Steering gearbox contains a conventional wormand- sector gear. The hydraulic power piston and directional control valve are mounted inside the gearbox housing.• As with power rack-and-pinion units, the valve may be a spool valve or a rotary valve with a torsion bar.• When the steering wheel is in the straight-ahead position, the valve maintains equal pressure on both sides of the power piston. Oil flows back to the pump reservoir. During a turn, the control valve routes oil to one side of the power piston,which pushes it in the desired direction to provide assist. The oil on the non-pressurized side of the piston is forced back through the control valve and to the pump reservoir.

Variable Assist (Speed Sensitive) Power Steering

• Efforts to improve fuel economy by conserving horsepower have led to the development of computer controlled hydraulic and/or electric steering systems. Varying the amount of assist according to vehicle speed helps conserve power while improving road feel at high speed, where less assist is desirable.

• With some hydraulic systems, fluid output from the pump is controlled; others control the fluid pressure at the steering gear. Variable assist systems use signals pertaining to vehicle speed, engine RPM, and other parameters from the Vehicle Control Module and/or other modules to determine and control the correct fluid pressure, and thus the amount of power assist provided.

Electric Power Steering

• Computer-controlled electric power rack steering systems are used on some vehicles. These systems use a small electric motor within the housing to assist in moving the rack. Some include a recirculating ball steering gear.• Computer-controlled electric systems typically use inputs from the antilock brake wheel speed sensors, steering angle and steering effort sensors, and other inputs to provide the proper amount of steering assist.

Four-Wheel Steering

• Systems have been in production for several years on a variety of models• Several different types of four-wheel steering systems are used. Generally, at low speeds, the rear wheels turn in the opposite direction from the front wheels, reducing the turning radius for tighter turning and easier parking.• At high speeds, the rear wheels turn in the same direction as the front wheels, providing for improved handling and stability.• Simple hydraulic systems permit four-wheel steer only at high speeds (over 30 mph) and in the same direction, while electronic four-wheel steering systems can provide sophisticated rear steering using a computer to determine rear steering angles. These systems permit same-direction steering during a gentle turn, and then as the steering wheel

is turned more sharply, the rear wheels straighten and then begin to turn in the opposite direction from the front. A steering control module uses inputs from several sensors to determine the correct steering angles.• Early, mechanical four-wheel steering systems function similarly, but use a shaft connected from the front gearbox to a rear gearbox through a planetary gearset to achieve the proper rear steering mode.• Rear steering is subtle: same-direction steering is limited to about 1.5° and opposite direction steering has a maximum of about 6° to 12° depending on the system and vehicle speed. Same-direction rear steering begins to diminish after the steering wheel is turned through 120° and at 240°, the rear wheels are straight. Turning the steering wheel farther causes the rear wheels to begin turning in the opposite direction.