MESA

CONTENTS

Sr no Description Pg no

1 Abstract 3

2 Introduction to Common Rail 4

3 Structure of Common Rail Direct Injection System 5

4 Common Rail Injection System 13

5 Operating Principle 14

6 Advantages 17

7 An insight to Cdi Engine 18

8 Principle in VTEC Engines 20

9 Principle in VVTi Engines 21

10 Conclusion 22

2

ABSTRACT

Looking at the 3.6 million years since man has evolved the invention of

passenger cars seems only yesterday, but since the first cars produced by Sir Henry

Ford there have been tremendous achievements in the field of engine performance

and design. We now have engines running on countless kinds of fuels producing un-

imaginable power outputs.

Among the many factors responsible for improvement in the engine has been the fuel

injection system with the addition of cylinders and various other components. The

injector has been a step forward from the age-old carburetor, thereby improving the

performance of the engine.

One now has the choice of various fuel injection systems such as

1. Inline type

2. Distributor type

3. Common rail type

With the state-of-the-art common-rail direct fuel injection we have achieved an

ideal compromise between economy, torque, ride comfort and long life. Whereas

conventional direct-injection diesel engines must repeatedly generate fuel pressure for

each injection, in the Common rail injection engines the pressure is built up

independently of the injection sequence and remains permanently available in the fuel

line.Calls for lower fuel consumption, reduced exhaust gas emissions, and quiet

engines are making greater demands on the engine and fuel injection system. These

demands can only be met by a fuel injection system that atomizes fuel at the nozzle

finely enough and at high injection pressure. At the same time the injected fuel

quantity must be very precisely metered, the rate of discharge curve must have an

exact shape, and pre-injection and secondary injection must be performable. A system

that meets these demands is the common rail fuel injection system. The common rail

upstream of the cylinders acts as an accumulator, distributing the fuel to the injectors

at a constant pressure of up to 1600 bar. Here high-speed solenoid valves, regulated

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by the electronic engine management, separately control the injection timing and the

amount of fuel injected for each cylinder as a function of the cylinder's actual need.

COMMON RAIL DIESEL INJECTION

INTRODUCTION

Diesels known for their power handling capabilities acquired the title workhorse

engines. Diesels may reside in heavy-duty trucks, buses, tractors, and trains, not to

mention large ships, bulldozers, cranes, and other construction equipment. Gasoline

engines might dwell in the typical passenger vehicle, lawn equipment and recreational

vehicles.

There are basically 2 types of popular engines used in the world today:

1. Petrol engines

2. Diesel engines

Petrol fuel is injected as an air/fuel mixture into the combustion chamber and

ignited by the spark from spark plugs.

Diesel fuel is pressurized and injected into the combustion chamber through a

fuel injector nozzle, just when the air in the chamber has been subjected to high

pressure that it is hot enough to ignite the fuel spontaneously.

Traditional fuel injection systems for diesel engines are designed with the

objective to secure acceptable fuel spray characteristics during the combustion

process at all load conditions. Incorrect injection causes reduced efficiency and

increased emission of harmful species.. Among the advantages claimed with respect

to the common rail concept are injection rate shaping, variable timing and duration of

the injection, in addition to variable injection pressure, enabling high injection pressure

even at low engine loads. Medium speed diesel engines are different from the

automotive diesel engines, especially in that the majority of them operate at

constant load and speed most of the time, and the advantages of the more

complicated common rail system may not be justified. The common rail injection

system is not capable of supplying all possible rate shapes, and rate shaping is mostly

restricted to delivering a pre injection prior to the main injection. When the rate of

injection is the key to an effective combustion process, it is vital to determine how the

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rate of injection from the common rail system compares to the rate of injection from a

traditional injection system.

STRUCTURE OF COMMON RAIL DIRECT INJECTION SYSTEM

The Common Rail Direct Diesel Injection system consists of the following parts:

Injection nozzle:

Injects fuel into the combustion chamber (for direct injection) or pre-combustion (for

indirect injection).

Fuel Supply Pump:

The fuel supply pump in low pressure stage is responsible for maintaining an

adequate supply of fuel to the high pressure components. This applies:

1. Irrespective of operating state.

2. With a minimum of noise.

3. at necessary pressure.

4. Throughout the vehicle’s service life.

The fuel supply pump draws fuel out of the fuel tank and conveys it

continuously in the required quantity to the high pressure fuel injection installation.

Many pumps bleed themselves automatically so that starting is possible even when

fuel tank has run dry.

There are three designs:

1. electric fuel pump

2. Mechanically driven gear pump

3. Tandem fuel pumps.

In axial-piston and radial-piston distributor pumps, a vane type supply pump is used as

pre-supply pump and is integrated directly in the fuel injection pump.

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Fuel Filter:

The service life design of the fuel injection system depends on a specific

minimum purity of the fuel. Functions of fuel filter are:

1. Particulate filtration:.

2. Water Separation:

Two filters can also be fitted in parallel, resulting in greater particulate storage

capacity. Connecting the filter in series produces a higher filtration efficiency. Pre-filter

is fitted on the suction or pressure side if requirements are particularly high with a filter

fineness matched to the main filter.

The Rail of Common Rail Injection System:

The common rail is a modular system,

and can therefore be easily adapted for

different engines.

Besides acting aas fuel accumulator,

the fuel rail also distributes fuel to the

injectors. The function of the high

pressure accumulator is to maintain the

fuel at high pressure. In so doing

accumulator volume has to dampen pressure fluctuations caused by fuel pulses

delivered by the fuel pump and the fuel injection cycles. This ensures that, when the

injector opens the injection pressure remains constant.

High-pressure Line:

In common rail systems, they serve as the connection between the high pressure

pump and the rail and from rail to the injector. The pipe is made of steel as it has to

withstand high pressures. The following types of fittings are used:

1. Sealing cone and union nut

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2. Heavy duty insert fittings

3. Perpendicular connection fittings.

The high pressure fuel lines must withstand the systems maximum pressure as well

as pressure variations that can attain very high fluctuations. The lines are seamless

precision made steel tubing in killed cast steel which has particularly consistent

microstructure.

Fuel injection pumps:

.

Diesel fuel injection pumps are

generally divided into two

categories:

1. Mechanically controlled fuel

injection pumps are available as:

1. In-line type

2. Distributor type

2. Electronically controlled fuel

injection pumps are available as:

1. In-line type

2. Distributor type

3. Common Rail type

Mechanically controlled fuel injection pumps:

In-line Fuel Injection pumps have the same number of plungers as cylinders in

the engine. They have been around the longest and include Camshaft-Less (PFR)

types.

Electronically controlled fuel injection pump:

An electronically controlled fuel injection pump utilizes a microcomputer to

control fuel injection quantity and injection timing according to running conditions of the

engine. Unlike conventional mechanical control, fuel injection quantity and injection

timing are controlled electronically, thereby resulting in fine and accurate control. It can

be referred to as Electronic Control Diesel or ECD.

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High-pressure stage of the radial-piston distributor injection pump:

Radial-piston high-pressure pumps produce higher injection pressures than

Axial-piston high-pressure pumps. Consequently, they also require more power to

drive them.

The radial-piston high-pressure pump is driven directly by the distributor-pump drive

shaft.

The main pump components are

• the cam ring

• the roller supports

• rollers

• the delivery plungers

• the drive plate

• the front section (head) of the distributor shaft

The drive shaft drives the drive plate by means of

radially positioned guide slots. The guide slots simultaneously

act as the locating slots for the roller supports. The roller

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supports and the rollers held by They run around the inner cam profile of the cam ring

that surrounds the drive shaft. The number of cams corresponds to the number of

cylinders in the engine. The drive plate drives the distributor shaft. The head of the

distributor shaft holds the delivery plungers which are aligned radially to the drive-shaft

axis (hence the name “radial-piston high-pressure pump”). The delivery plungers rest

against the roller supports. As the roller supports are forced outwards by centrifugal

force, the delivery plungers follow the profile of the cam ring and describe a cyclical-

reciprocating motion.

Injector:

A 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. Different

types of injectors are

Solenoid Valve Injector:

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.

Piezo-Inline Injector:

The nozzle needle on piezo-inline injector is controlled indirectly by servo valve. The

required injected fuel quantity is then controlled by the valve triggering period. The

nozzle is kept closed by the rail

pressure exerted in the control

chamber. When the piezo actuator is

triggered, the serve valve opens and

closes the bypass passage.

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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.

Electronic Control Unit:

An Engine Control Unit (ECU), also known as

Engine Management System (EMS) is an electronic

device, fundamentally a computer, that is part of an

internal combustion engine, which reads several

sensors in the engine and uses the information to

control the ignition systems of the engine. This

approach allows an engine's operation to be controlled in great detail, allowing greater

fuel efficiency, better power and responsiveness, and much lower pollution levels than

earlier generations of engines. Because the ECU is dealing with actual measured

engine performance from millisecond to millisecond, it can compensate for many

variables that traditional systems cannot, such as ambient temperature, humidity,

altitude (air density), fuel octane rating, as well as the demands made on it by the

driver. In addition, it is able to a large degree to compensate for the gradual wearing of

the engine as it ages, which in practice allows it to extend engine life to two or three

times that of engines of twenty years ago.

An electronic control unit contains the hardware and software (firmware). The

hardware consists of electronic components on a printed circuit board (PCB). The

main component on this circuit board is a microcontroller chip (CPU). The software is

stored in the microcontroller or other chips on the PCB, typically in EPROMs or flash

memory so the CPU can be re-programmed by uploading updated code. This is also

referred to as an (electronic) Engine Management System (EMS). Sophisticated

engine management systems also may communicate with transmission control units

or directly interface electronically-controlled automatic transmissions, traction control

systems, and the like.

There are two main types of control for multi-port systems

• The fuel injectors can all open at the same time,

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• 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.

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.

The range of tasks performed by the engine control unit includes the following

functions:

• Common-rail injection

• Delivery control of the high-pressure pump

• Engine speed limitation

• Deceleration fuel cut-off

• Fuel pump

• Air supply

• Drive control

• Diagnosis

A separate data network links the engine management system with the

generator and the glow control unit, which lies at the heart of an innovative quick-start

glow system. This shortens the preheating time for the engine to just a moment, so

that the diesel is now also the equal of a petrol engine in this respect.

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Engine Sensors:

In order to provide the right amount of fuel, the engine control unit is equipped

with a whole lot of sensors. Let's take a look at some of them.

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 - 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.

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COMMON RAIL INJECTION SYSTEM

Nothing ‘COMMON’ About It.

More Torque, Less Emission and Less Noise.

While the Japanese are leading in petrol direct injection technology, Germany's

Bosch, working in conjunction with several European car makers, pioneered Common-

Rail Direct Injection for diesel engines.

Compare with petrol, diesel is the lower quality ingredient of petroleum family.

Diesel particles are

larger and heavier

than petrol, thus more

difficult to pulverise.

Imperfect pulverisation

leads to more unburnt

particles, hence more

pollutant, lower fuel

efficiency and less

power. Common-rail

technology is intended

to improve the pulverisation process.

The rail assembly used in CRDi is as shown in figure.

The main components on the rail assembly are:

1. Common pressure accumulator (the “rail”)

2. High pressure regulator (option)

3. Inlet metered high-pressure supply pump with

integrated lift pump

4. Injectors

5. Electronic control unit (ECU)

6. Filter unit

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To improve pulverisation, the fuel must be injected at a very high pressure, so

high that normal fuel injectors cannot achieve. In common-rail system, the fuel

pressure is implemented by a strong pump instead of fuel injectors. The high-pressure

fuel is fed to individual fuel injectors via a common rigid pipe (hence the name of

"common-rail"). In the current first generation design, the pipe withstand the pressure

as high as 1,350 bar or 20,000 psi. Fuel always remains under such pressure even in

stand-by state. Therefore whenever the injector (which acts as a valve rather than a

pressure generator) opens, the high-pressure fuel can be injected into combustion

chamber quickly. As a result, not only pulverisation is improved by the higher fuel

pressure, but the duration of fuel injection can be shortened and the timing can be

precisely controlled.

Benefited by the precise timing, common-rail injection system can introduce a

"post-combustion", which injects small amount of fuel during the expansion phase thus

create a small scale combustion before the normal combustion takes place.

What’s the purpose ?

This further eliminate the unburnt particles, also increase the exhaust flow

temperature thus reduce the pre-heat time of the catalytic converter. In short, "post-

combustion" cuts pollutants.

How effective is it?

According to PSA's press release, its new common-rail engine (in addition to

other improvement) cuts fuel consumption by 20%, doubles torque at low engine

speeds and increases power by 25%. It also brings a significant reduction in the noise

and vibrations of conventional diesel engines. In emission, greenhouse gases (CO2) is

reduced by 20%. At a constant level of NOx, carbon monoxide (CO) emissions are

reduced by 40%, unburnt hydrocarbons (HC) by 50%, and particle emissions by 60%.

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OPERATING PRINCIPLE

A feed pump delivers the fuel through a filter unit to the high pressure pump

through feed pipe.

The high-pressure pump delivers fuel to the high-pressure accumulator (the

rail). The electronically controlled injectors inject fuel into the combustion chamber

when the solenoid valve is actuated. Because the injection pressure is independent of

engine speed and load, the actual start of injection, the injection pressure, and the

duration of injection can be freely chosen from a wide range.

The introduction of pilot injection, which is adjusted depending on engine

needs, results in significant engine noise reduction, together with a reduction in NOx

emissions.

The pressure in the system is controlled by the actuator.

The figure shows all the components in a common rail system for a fully equipped, 4

cylinder, passenger car diesel engine. Depending on the type of vehicle and its

application, some of the components may not be fitted.

The sensors and setpoint generators are not depicted in their real installation

position to simplify presentation. Exceptions are the exhaust-gas treatment sensors

and the rail pressure sensor as their installation positions are required to understand

the system. Data exchange between the various sections takes place via the CAN bus

in the interfaces suction:

• Starter Motor

• Alternator

• Electronic Immobilizer

• Transmission control

• Traction Control System

• Electronic Stability Program

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System Diagram For Passenger Cars

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ADVANTAGES

Compact Design:

The compact design of the injector outline enables the common rail system to

be used on two or four valve per cylinder engines.

Modular System:

With one electronically driven injector per engine cylinder, the system is

modular and can be used on three-, four-, five-, and six-cylinder engines.

Responsiveness at low revs:

The Common Rail system maintains the fuel injection under high pressure even

at low turnover. This allows the engine to develop high torque at low revs and across a

wide power range. The result is an engine which is smooth, responsive and which

offers excellent pick-up for safe and easy overtaking. In addition, fuel economy is

maintained even at low revs.

Independent Injection Pressure:

The injection pressure is independent of

the engine speed and load, enabling high

injection pressures at low speed if required.

Lower NOx Emissions:

Injection sequences, which include periods

both pre and post the main injection, can be

utilized to reduce emissions, particularly NOx,

enabling the system to meet the stringent emissions levels required by EURO-3 and

US-98 legislation and beyond.

Full Electronic Control:

Common rail offers all the benefits of full electronic control fuel metering and

timing, as well as the option to interface with other vehicle functions

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AN INSIGHT INTO THE CDI ENGINE

Pilot Injection Feature:

The high combustion pressure of up to 145 bar (2130 psi) in the CDI engine,

and the rate at which this pressure rises during the combustion process normally

produce higher noise levels in direct injection engines than in their pre-chamber

(indirect injection) counterparts.

However, the trail-blazing CDI system employs a piece of technical wizardry

known as pilot injection' to overcome this problem a few seconds before the main fuel

injection, a small amount of diesel is injected into the cylinder and ignites, thereby

establishing the combustion process and setting the ideal conditions for the main

combustion process. Consequently, the fuel ignites faster with the result that the rise in

pressure and temperature is less sudden.

If the pilot is injected very close

to the main injection, (Figure 4c) the

effect is similar to initial rate control,

which some call a “boot-shaped”

injection diagram. When injected very

close to the main, the pilot has little

time to mix before the main injection,

so the noise reduction is less that that

at optimum timing for noise but less

soot is formed in the diffusion burn.

The end effect, however, is not only a reduction in combustion noise but also a

reduction in nitrogen oxide (NOx) emissions thanks to pilot injection and the lower

cylinder temperature.

The total effect of these measures is a CDI engine with noise levels below those of

comparable pre-chamber engines.

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VVT-i

. In 1998, "Dual" VVT-i (adjusts both intake and exhaust camshafts) was first

introduced in the RS200 Altezza's 3S-GE engine. Dual VVT-i is also found in

Toyota's new generation V6 engine, the 3.5L 2GR-FE V6,found in the Avalon, RAV4,

and Camry in the US, the Aurion in Australia, and various models in Japan, including

the Estima. Other Dual VVT-i engines include the upcoming 1.8L 2ZR-FE I4, which

will see implementation in Toyota's next generation of compact vehicles. By

adjusting the valve timing, engine start and stop occur virtually unnoticeable at

minimum compression, and fast heating of the catalytic converter to its light-off tem.

VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve

timing technology developed by Toyota. The Toyota VVT-i system replaces the

Toyota VVT offered starting in 1991 on the 4A-GE 20-Valve engine. The VVT system

is a 2-stage hydraulically controlled cam phasing system.VVT-i, introduced in 1996,

varies the timing of the intake valves by adjusting the relationship between the

camshaft drive (belt, scissor-gear or chain) and intake camshaft. Engine oil pressure

is applied to an actuator to adjust the camshaft perature is possible, thereby

reducing HC emissions considerably..

VVTL-i

In 1998, Toyota started offering a new technology, VVTL-i, which can alter valve lift

(and duration) as well as valve timing. In the case of the 16 valve 2ZZ-GE, the

engine has 2 camshafts, one operating intake valves and one operating exhaust

valves. Each camshaft has two lobes per cylinder, one low rpm lobe and one high

rpm, high lift, long duration lobe. Each cylinder has two intake valves and two

exhaust valves. Each set of two valves are controlled by one rocker arm, which is

operated by the camshaft. Each rocker arm has a slipper follower mounted to the

rocker arm with a spring, allowing the slipper follower to move up and down with the

high lobe with out affecting the rocker arm. When the engine is operating below 6000

rpm, the low lobe is operating the rocker arm and thus the valves. When the engine

is operating above 6000 rpm, the ECU activates an oil pressure switch which pushes

a sliding pin under the slipper follower on each rocker arm. This in effect, switches to

the high lobe causing high lift and longer duration.

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VTEC

Honda’s 2008 Accord

Engine and Transmission:

Honda has upgraded both the engines for the new accord - the new 2.4-liter engine

now makes 177 horsepower at 6300rpm (7% in horsepower compared to its

predecessor) and 218Nm of torque at 4300rpm. Accord’s new engine also features

superior technolgies like iVTEC(Variable Valve Timing and Lift Electronic Control)

and VTC (Variable Timing Control). Because of the the use of new fuel injector, new

dual probe spark plugs, near-zero evaporative emissions equipment and the special

i-VTEC system that leaves one exhaust valve closed in each cylinder at low rpm the

retuned engine is expected to offer superior mileage/fuel efficiency.

Accord’s new v6 engine displaces 16% more than the current 3.0-liter Accord V-6.

The increase in displacement leads to a 10% increase in horsepower and a

substantial 18% boost in torque as compared to the previous V-6. 2008 Honda

Accord’s 3.5L engine develops 268bhp at 6200 rpm and 336Nm of torque at 5000

rpm. Accord’s new engine is not just VTEC, It features a new generation of Honda’s

advanced Variable Cylinder Management (VCM) - the variable displacement

technology with a special SOHC i-VTEC valvetrain that allows the engine to operate

in three different modes. (During startup, acceleration or when climbing hills - any

time high power output is required - the engine operates on all six cylinders. During

moderate speed cruising and at low engine loads, the system operates just one bank

of three cylinders. For moderate acceleration, higher-speed cruising and mild hills,

the engine operates on four cylinders) Depending on driving conditions, the engine

operates on three, four or all six cylinders to help boost fuel economy or power as

needed. Honda claims improved mileage for both the engines. To absorb the

inevitable vibrations while the engine was running on three or four cylinders, Honda

uses active engine mounts and active noise control system. The same 5 speed

automatic/manual may be offered.

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CONCLUSION

In India the scenario is quite dismal. While on one hand the high petrol prices

have prompted car manufacturers to get in technologies that are efficient, the

subsidies on diesel have let the diesel engine technology languish at abysmal depths.

Because diesel engine technology in India is from a prehistoric era, people's

perception of diesel engines is also very bad.

It is only now because of the emission control norms that diesel engine

makers are being forced to upgrade technologies. The simplest and cheapest way of

doing that is to turbo-charge the engine. Turbocharging is welcome because it

makes the engine more efficient. Telco, the largest manufacturer of diesels now has

turbocharged engines for its commercial vehicle range. Next is the step forward to

direct injection. For DI engines to be acceptable on passenger cars, the

manufacturers will have to adopt some of the latest technologies like common rail or

unit injector systems because the current crop of DI engines in the country do not

suit applications where emission considerations are paramount.

But do not be disappointed. There are already some great hi-tech engines

have made there way into the country, albeit in some of the higher end cars. The first

to arrive on the scene was the common rail diesel on the Mercedes-Benz E220 CDI.

The inline four cylinder 16-valve engine is a delight as is the C200 CDI one. Then

there is the 2.0-litre Duratorq DI 16-valve turbodiesel on the Ford Mondeo. Lower

down the affordability stakes is another excellent 1.9-litre common rail electronic

direct injection engine that will do duty on the Skoda Octavia 1.9 TDI. The CRDi

diesel engine, which is supposed to combine the performance and handling of a

petrol engine with the fuel efficiency of a diesel engine, has been developed by

Hyundai Motor Company, South Korea, in association with Detroit Diesel, U.S. for its

Accent CRDi.

REFERENCES:

“ Internal Combustion Engines” by V Ganeshan, McGraw Hill .

“ Internal Combustion Engines” by Mathur, Sharma, Dhanpat Rai and Sons

“ A Course in CI Engines” by V M Domkundwar, Dhanpat Rai and Sons