Emission Standards in Light and Heavy Vehicles Final Report1

Emission Standards for Light and Heavy Vehicles

ABSTRACT

The need to control the emissions from automobiles gave rise to the computerization of

the automobile. Hydrocarbons, carbon monoxide and oxides of nitrogen are created

during the combustion process and are emitted into the atmosphere from the tail pipe.

There are also hydrocarbons emitted as a result of vaporization of gasoline and from the

crankcase of the automobile. The clean air act of 1977 set limits to the amount of each of

these pollutants that could be emitted from an automobile. The manufacturers’ answer

was the addition of certain pollution control devices and the creation of a self adjusting

engine. 1981 saw the first of these self adjusting engines. They were called feedback fuel

control systems.

In my seminar, I am giving a brief idea of emission standards in light and heavy vehicles.

Some of the more popular emission control devices installed on the automobile are: EGR

VALVE, CATALYTIC CONVERTER, AIR PUMP, PCV VALVE, EVAPORATIVE

CONTROL SYSTEM.

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INTRODUCTION

Emission requirements for light road vehicles have existed in the EU since the early

1970s, while the first requirements for heavy vehicles came in at the end of the 1980s.

Compared with the US and some European countries (Sweden, Norway and Austria), the

EU was late in introducing requirements that were strict enough to force the use of

catalytic converters in petrol vehicles.

The current exhaust emission requirements regulate four groups of compounds: nitrogen

oxides (NOx), hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM).

Of these, carbon monoxide is less significant from the point of view of health and the

environment. For light vehicles (under 3.5 tonnes) the emission standards differ

depending on the engine type (petrol or diesel). Emissions of the greenhouse gas carbon

dioxide are not currently regulated for any type of vehicle.

The way in which the emission standards for light and heavy road vehicles in the EU

have been stiffened over the years is shown in tables 1 and 2. The standards for both light

and heavy vehicles are designated "Euro" and followed by a number (usually Arabic

numerals for light vehicles: Euro 1, 2, 3.., and Roman numerals for heavy vehicles: Euro

I, II, III..).

Emission standards also exist for two and three-wheeled vehicles (motorcycles and

mopeds) and for engines for non-road machinery, but these are not covered here

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TEST CYCLES

Emissions are measured using a standardized test cycle that is designed to simulate real

driving. For light vehicles the entire vehicle is tested and emissions are measured in

g/km. For heavy vehicles the engine is bench-tested and the results are expressed in

relation to the engine power (g/kWh). A vehicle or engine that is tested and approved in

one EU country may then be sold throughout the union without any requirement for

further testing.

Light vehicles are subjected to a transient cycle in which the vehicle follows a prescribed

driving pattern that includes accelerations, decelerations, changes of speed and load, etc.

In the case of heavy vehicles two different test cycles have been used in the EU since

2000: one transient (ETC, European Transient Cycle) and one stationary (ESC, European

Stationary Cycle). The stationary cycle consists of a sequence of constant engine speed

and load modes. Smoke opacity is measured on the ELR (European Load Response) test.

For the type approval of new heavy vehicles with diesel engines according to the Euro III

standard (year 2000), manufacturers have the choice of using either of these tests. For

type approval according to the Euro IV (year 2005) limit values the emissions have to be

determined using both the ETC and the ESC/ELR tests. The latter also applies to the

category Enhanced Environmentally friendly Vehicles (EEVs).

Outside the EU several other test cycles are used, so emission standards from different

countries are not always directly comparable. In December 2003 however, the EU, US,

Japan and China agreed to draw up a common scientific platform to measure and

benchmark air pollution from traffic.

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EUROPEAN STATIONARY CYCLE (ESC)

The ESC test cycle (also known as OICA/ACEA cycle) has been introduced, together

with the ETC (European Transient Cycle) and the ELR (European Load Response) tests,

for emission certification of heavy-duty diesel engines in Europe starting in the year 2000

(Directive 1999/96/EC of December 13, 1999). The ESC is a 13-mode, steady-state

procedure that replaces the R-49 test.

The engine is tested on an engine dynamometer over a sequence of steady-state modes

(Table 1, Figure 1). The engine must be operated for the prescribed time in each mode,

completing engine speed and load changes in the first 20 seconds. The specified speed

shall be held to within ±50 rpm and the specified torque shall be held to within ±2% of

the maximum torque at the test speed. Emissions are measured during each mode and

averaged over the cycle using a set of weighting factors. Particulate matter emissions are

sampled on one filter over the 13 modes. The final emission results are expressed in

g/kWh.

During emission certification testing, the certification personnel may request additional

random testing modes within the cycle control area (Figure 1). Maximum emission at

these extra modes are determined by interpolation between results from the neighboring

regular test modes.

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EUROPEAN TRANSIENT CYCLE (ETC)

The ETC test cycle (also known as FIGE transient cycle) has been introduced, together

with the ESC (European Stationary Cycle), for emission certification of heavy-duty diesel

engines in Europe starting in the year 2000 (Directive 1999/96/EC of December 13,

1999). The ESC and ETC cycles replace the earlier R-49 test.

The ETC cycle has been developed by the FIGE Institute, Aachen, Germany, based on

real road cycle measurements of heavy duty vehicles (FIGE Report 104 05 316, January

1994). The final ETC cycle is a shortened and slightly modified version of the original

FIGE proposal.

Different driving conditions are represented by three parts of the ETC cycle, including

urban, rural and motorway driving. The duration of the entire cycle is 1800s. The

duration of each part is 600s.

Part one represents city driving with a maximum speed of 50 km/h, frequent

starts, stops, and idling.

Part two is rural driving starting with a steep acceleration segment. The average

speed is about 72 km/h

Part three is motorway driving with average speed of about 88 km/h.

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LIGHT VEHICLES

The light category of vehicles covers road vehicles under 3.5 tonnes, i.e. both passenger

cars and light commercial vehicles. The first exhaust emission requirements for these

were specified in Directive 70/220/EEC, which has been stiffened several times.

The Euro 1 requirements (91/441/EEC), which came into force in 1992-93, forced the

manufacturers to install three-way catalytic converters in petrol vehicles. Euro 2 was

subsequently introduced in 1996-97 (94/12/EC), and in 1998 the standards for Euro 3 and

4 (98/69/EC) were agreed, to take effect in 2000 and 2005 respectively, see table 1.

Standards also exist for light commercial vehicles. The limit values for these are

generally slightly higher than for passenger cars and are dependent on the weight class -

the heavier the vehicle, the higher the permissible emissions.

The requirement levels for 2000 and 2005 were agreed after several years of joint work

between the Commission, the automotive industry and the oil industry - the so-called

Auto-Oil Programme - on the basis of achieving good air quality in Europe by 2010 at the

lowest cost.

Fuel quality standards were also stiffened as a consequence of the project, both to reduce

emissions and to permit the introduction of new emission control technology, which in

many cases requires a low sulphur content in order to work (see fact file). The highest

permitted sulphur content for petrol was set at 150 ppm (parts per million) in 2000 and 50

ppm in 2005, and for diesel at 350 ppm in 2000 and 50 ppm in 2005. As the result of a

new decision in 2003 (2003/17/EC) the limit for both fuels will be reduced to 10 ppm in

2009. 10 ppm fuel must be made generally available in the member countries by 2005.

As can be seen from table 1 (below) the Euro 2-4 standards are different for diesel and

petrol vehicles. Under the current Euro 3 and forthcoming Euro 4 standards diesel

vehicles are allowed to emit around three times more NOx than petrol vehicles.

Emissions of particulates from petrol vehicles are not regulated since these are very low

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compared to emissions from diesel engines. Some direct-injection petrol engines can

however emit almost the same level of particulates as a diesel engine.

When the Euro 4 requirements were decided it was generally believed that they would

compel the use of particulate filters on diesel vehicles. A number of manufacturers have

however developed models that meet the requirements without further exhaust gas

treatment, although particulate filters appear to be necessary on most larger engines.

New legislation on durability was introduced along with the Euro 3 and 4 standards,

making manufacturers responsible for the emissions from light vehicles for a period of

five years or 80,000 km (Euro 3) and five years or 100,000 km (Euro 4). The same

directive included a decision to introduce on-board emission diagnostic systems (OBD)

between 2000 and 2005 and a requirement for a low-temperature emission test (7°C) for

petrol vehicles with effect from 2002. The member countries were also given the right to

introduce tax incentives for early introduction of 2005-compliant vehicles.

From figure 1 it is apparent that the Euro 4 requirements (2005) permit much higher

emissions of NOx and particulates than the requirements in the US and Japan at the

corresponding time.

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Table 1. EU emission standards for passenger cars and UBA proposal (2008). There

are also standards for carbon monoxide, but these are not included in the table.

Passenger

cars

PM (mg/km) NOx (g/km) HC (g/km) HC+NOx

(g/km)

diesel petrol diesel petrol diesel petrol diesel petrol

Euro 1

(1992-93)

140 -- -- -- -- -- 0.97 0.97

Euro 2

(1996)

80/1001 --

-- -- 0.7/0.91 0.5

Euro 3

(2000)

50 -- 0.50 0.15 -- 0.20 0.56 --

Euro 4

(2005)

25 -- 0.25 0.08 -- 0.10 0.30 --

Euro 5-

UBA

proposal

(2008)

2.5 2.5 0.08 0.08 0.05 0.05 -- --

(1 Indirect Injection (IDI) and Direct Injection (DI) engines respectively.)

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HEAVY VEHICLES

The first EU directive to regulate emissions from heavy vehicles, i.e. road vehicles

heavier than 3.5 tonnes, came in 1988 (88/77/EEC). Before that there had been a

common standard within the UN Economic Commission for Europe (ECE R49).

The Euro I standards for medium and heavy engines were introduced in 1992-93

(91/542/EC). The same directive also laid down standards for Euro II, which took effect

in 1995-96.

On the basis of the Auto-Oil Programme (see Light vehicles above) a directive

(1999/96/EC) was adopted in 1999 giving standards for Euro III (2000), IV (2005) and V

(2008). See table 2 below.

Euro V differs from Euro IV in its stricter emission requirement for NOx. The Euro V

requirements are still indicative, since many countries were unsure of the potential of

emission control technology when the directive was adopted. According to the

Commission's review in December 2003 it is however perfectly possible to achieve these

requirements.

Some engine manufacturers are now able to meet Euro IV requirements without further

exhaust gas treatment, but for many this is likely to require the use of both particulate

filters and NOx reduction (see fact file below). Euro V is very likely to require special

NOx reduction.

The 1999 directive also contains special voluntary standards for enhanced

environmentally friendly vehicles (EEVs), as well as requirements for on-board

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diagnostic systems (OBD) and provisions regarding the durability of emission control

devices from 2005.

The directive has since been revised on a couple of occasions, partly to prevent

manufacturers from adapting engines to give low emissions solely at the speeds used in

the test cycle for certification.

Figure 2 permits comparison between the requirements that apply to emissions of NOx

and particulates from heavy diesel vehicles in the EU, US and Japan.

Table 2. EU emission standards for heavy vehicles, and UBA proposals for 2008 and

2010. There are also standards for carbon monoxide and special standards for

methane for gas-driven vehicles, but these are not included in the table.

NOx

(g/kWh)

HC

(g/kWh)

PM

(mg/kWh)

Euro I (1992-93) 9.0 1.23 400

Euro II 1995-96) 7.0 1.1 150

Euro III (2000) 5.01 0.662 100/1603

Euro IV (2005) 3.51 0.462 20/303

Euro V (2008) 2.01 0.462 20/303

Euro V - UBA

proposal (2008)

1.01 0.462 2/33

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Euro VI - UBA

proposal (2010)

0.051 0.462 2/33

1 Both ESC and ETC test cycle.

2 ESC test cycle only.

3 ESC and ETC test cycle respectively.

FUTURE EMISSION STANDARDS

A review of emission standards for road vehicles in the EU began in autumn 2003. This

work is being carried out by a sub-group of the Commission's Motor Vehicle Emissions

Group (MVEG), with the participation of the member countries and various stakeholders.

On the basis of this work the Commission will present a consultation document followed

by proposed directives containing new standards. The proposed directives for light and

heavy vehicles are expected to be issued in spring and autumn 2005 respectively, and the

requirement levels will probably begin to apply in 2010. Among the questions the sub-

group will consider are the access to emission control technologies, their performance

and costs, and whether changes need to be made to the fuel standards.

The development of new technology in recent years, combined with new findings

regarding harmful health effects, especially of particulates, makes it likely that the

Commission will propose significant reductions in emission limits, primarily for diesel

vehicles. In 2003, the German Environment Agency (UBA) published a proposal for new

emission standards for motor vehicles, see tables 1 and 2.

For passenger cars the UBA proposals include the following:

- Emission requirements should be fuel-neutral, i.e. the same for all fuels.

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- Particulate requirements should be strengthened by a factor of ten. The requirements of

Euro 4 can be met without emission control equipment, at least for small cars, and a

particulate filter removes 90 per cent or more of particulates in the entire size range.

- The NOx requirement for diesel cars should be strengthened by a factor of three, down

to the same level as for petrol vehicles.

- The summation value for NOx + HC for diesel cars should be replaced with an HC limit

value regardless of engine type.

If petrol vehicles are also covered by the proposed new particulate requirement it may

mean that direct injection engines will have to be fitted with particulate filters.

The proposal for heavy vehicles means:

- Fuel-neutral requirements.

- The agreed but as yet indicative particulate standards for 2008 are lowered by a factor

of ten, for the same reason as above.

- The agreed but as yet indicative NOx requirements for 2008 are halved, and then halved

again in 2010.

In its report, the UBA discusses whether emissions of particulates should also be counted

by number, or whether it would suffice merely to regulate the weight. It concludes that

confining the limit to weight could lead to the engine makers concentrating primarily on

eliminating the largest and heaviest particles, which have relatively little effect on health.

It would therefore like to supplement the current weight-based standards with limits on

the maximum number of particles within the size range that is inimical to health.

The extra cost of the UBA Euro 5 proposals for a diesel car, compared with Euro 4, is

estimated to run to 200-400 euros.

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It would cost practically nothing, on the other hand, for a heavy vehicle to switch from

Euro V to Euro VI, since it would suffice in that case to improve the emission control

equipment that is already needed to meet Euro V requirements.

The need to reach a relatively quick agreement on the exhaust emission requirements that

will apply from 2010 is not just important so that the industry has time to prepare for the

production of cleaner vehicles. It also gives the member countries the right to bring in tax

incentives to favour those vehicles that comply with the requirements early, such as

diesel cars fitted with particulate filters.

FACTFILE: EMISSION CONTROL TECHNOLOGY

FOR VEHICLES

Petrol-driven passenger cars

A petrol engine without emission control produces large emissions of nitrogen oxides and

unburnt hydrocarbons. The technology that manufacturers have used to meet stiffer

emission requirements is the three-way catalytic converter. This consists of a ceramic

material with microscopically small channels, coated with a very thin film of precious

metals. As the exhaust gases pass through the converter the hydrocarbons and carbon

monoxide are oxidized by the oxygen that is released when the nitrogen oxides are

reduced to nitrogen (N2).

The three-way catalytic converter has been fitted to all petrol passenger cars sold in the

EU since the start of the 1990s and has become increasingly efficient as emission

requirements have become stricter. The biggest problem is during cold starts, since a

certain temperature (300-400ºC) has to be reached before the catalytic process starts to

work.

In the case of petrol engines that use an excess of air (known as lean burn technology) the

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three-way catalytic converter has no effect on emissions of NOx. Some manufacturers

use an NOx storage catalytic converter (see Diesel vehicles below) to meet the standards.

Petrol vehicles with direct injection (GDI, FSI, SCi, etc.) produce relatively high

emissions of particulates, which means that these may require special particulate

reduction if emission requirements are stiffened (see Diesel vehicles below).

Diesel-driven passenger cars

The biggest environmental and health problems associated with diesel vehicles are

emissions of nitrogen oxides and particulates, both of which are higher than for petrol

vehicles.

Nitrogen oxides. Because a diesel engine works with an excess of air the three-way

catalytic converter cannot be used to reduce emissions of NOx. Exhaust Gas

Recirculation (EGR) technology, in which some of the exhaust gases are recirculated

through the combustion chamber, can reduce NOx formation by lowering the

temperature. The reduction potential is limited however, which means that further

treatment of exhaust gases is likely to be necessary in order to meet future requirements.

One further treatment method is to use an NOx catalytic converter. This works by

trapping and storing nitrogen oxides chemically in an NOx trap, and then reducing them

periodically to nitrogen by injecting additional fuel and by using a catalytic converter.

This method requires low-sulphur fuel (10 ppm), since sulphur is captured more easily

than nitrogen in the NOx trap, as well as being more difficult to remove.

Another method - although mainly applied to heavy vehicles - is selective catalytic

reduction (SCR). This involves reducing the nitrogen oxides to nitrogen gas in a catalytic

converter with the aid of ammonia (injected as urea). The reduction efficiency

approaches 80-90 per cent. Disadvantages include the added operating cost of using urea,

the possibility of increased ammonia emissions and the loss of effect when the urea tank

is empty. Some questions also exist regarding the durability of the technology. One

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advantage is that higher levels of NOx can be permitted during the combustion process,

which can consequently be better optimized for low fuel consumption.

Particulates. The formation of particulates can be reduced to some extent by modifying

the combustion process. Smaller engines can meet Euro 4 requirements in this way.

Particulate filters are however required for larger engines and when emission

requirements are stiffened. They consist of a ceramic matrix of silicon carbide, perforated

with microscopic channels. As the exhaust gases pass through, a large proportion of

particulates (90-99 per cent) stick to the walls of these channels.

The trapping of particulates means that the channels become blocked, and the filter

therefore has to be raised to a high temperature at regular intervals to burn off the

particulates. Various methods have been developed to achieve this combustion, including

a brief additional injection of fuel and a catalytic substance that reduces the temperature

required. One requirement for low particulate emissions is a fuel with a low sulphur

content.

Combined methods. Toyota is the only manufacturer so far to succeed in developing a

catalytic converter that reduces emissions of both particulates and nitrogen oxides -

particulates by 90 per cent and nitrogen oxides to the level that applies for petrol vehicles

in 2005. The system is based on EGR (see above), NOx storage and an integrated

catalytic converter and particulate trap.

Heavy vehicles

Practically all heavy road vehicles have diesel engines. In common with diesel cars, the

emissions that are most important to reduce are NOx and particulates.

In the case of NOx the Euro V requirement for 2008 (max. 2 g/kWh) is expected to

compel the use of SCR (see above) on all new heavy vehicles, while Euro IV (3.5 g/kWh)

can be met by some manufacturers using EGR technology without the need for further

treatment of exhaust gases.

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Particulate reduction by means of filters is easier to solve for heavy diesel vehicles than

for light ones, since heavier vehicles have a higher exhaust temperature. This makes the

critical phase - burning off particulates from the filter - easier to achieve.

A particulate filter is often combined with an oxidation catalytic converter that reduces

the content of carbon monoxide and hydrocarbons in the exhaust gases.

EMISSION CONTROL SYSTEMS

The need to control the emissions from automobiles gave rise to the computerization of

the automobile. Hydrocarbons, carbon monoxide and oxides of nitrogen are created

during the combustion process and are emitted into the atmosphere from the tail pipe.

There are also hydrocarbons emitted as a result of vaporization of gasoline and from the

crankcase of the automobile. The clean air act of 1977 set limits as to the amount of each

of these pollutants that could be emitted from an automobile. The manufacturers answer

was the addition of certain pollution control devices and the creation of a self adjusting

engine. 1981 saw the first of these self adjusting engines. They were called feedback fuel

control systems. An oxygen sensor was installed in the exhaust system and would

measure the fuel content of the exhaust stream. It then would send a signal to a

microprocessor, which would analyze the reading and operate a fuel mixture or air

mixture device to create the proper air/fuel ratio. As computer systems progressed, they

were able to adjust ignition spark timing as well as operate the other emission controls

that were installed on the vehicle. The computer is also capable of monitoring and

diagnosing itself. If a fault is seen, the computer will alert the vehicle operator by

illuminating a malfunction indicator lamp. The computer will at the same time record the

fault in it's memory, so that a technician can at a later date retrieve that fault in the form

of a code which will help them determine the proper repair. Some of the more popular

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emission control devices installed on the automobile are: EGR VALVE, CATALYTIC

CONVERTER, AIR PUMP, PCV VALVE, CHARCOAL CANISTER.

CATALYTIC CONVERTER

Automotive emissions are controlled in three ways, one is to promote more complete

combustion so that there are less by products. The second is to reintroduce excessive

hydrocarbons back into the engine for combustion and the third is to provide an

additional area for oxidation or combustion to occur. This additional area is called a

catalytic converter. The catalytic converter looks like a muffler. It is located in the

exhaust system ahead of the muffler. Inside the converter are pellets or a honeycomb

made of platinum or palladium. The platinum or palladium are used as a catalyst ( a

catalyst is a substance used to speed up a chemical process). As hydrocarbons or carbon

monoxide in the exhaust are passed over the catalyst, it is chemically oxidized or

converted to carbon dioxide and water. As the converter works to clean the exhaust, it

develops heat. The dirtier the exhaust, the harder the converter works and the more heat

that is developed. In some cases the converter can be seen to glow from excessive heat. If

the converter works this hard to clean a dirty exhaust it will destroy itself. Also leaded

fuel will put a coating on the platinum or palladium and render the converter ineffective.

Catalytic oxidizers became widespread after regulations on automobile emissions

were made mandatory nationwide in the U.S. in 1968. Now they are used in most

cars around the world. Because catalytic oxidizers cannot operate in the presence of

lead, their introduction caused leaded gasoline to be phased out. Catalytic oxidizers

are also used in industrial processes to reduce harmful emissions, but their most

common appearance is in automobiles.

Ideally the byproducts of an automobile engine are only carbon dioxide, water, and

some nitrogen. This is similar to the chemical output of animals. But in practice, the

combustion process in an engine is never 100% efficient, leaving behind hot, yet

unburned hydrocarbons. Prior to the 1960s, these emissions were allowed to escape

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into the atmosphere, until it was realized that they were a public and environmental

health hazard. Now, catalytic oxidizers fitted to a car's tailpipe rapidly oxidizes a

large percentage of the remaining unburnt hydrocarbons, resulting in cleaner

emissions. However, the speed at which catalytic oxidizers must operate to catch

unburnt hydrocarbons before they fly out the tailpipe puts limits on how efficient

the oxidation process can be.

The quality of catalytic oxidizers has increased steadily over the years, resulting in

cars which are cleaner and cleaner. Still difficult is the lowering of CO2 (carbon

dioxide) emissions. CO2 cannot be oxidized into anything more harmless, and it is a

known greenhouse gas, contributing to global warming.

PCV VALVE

The purpose of the positive crankcase ventilation (PCV) system, is to take the vapors

produced in the crankcase during the normal combustion process, and redirecting them

into the air/fuel intake system to be burned during combustion. These vapors dilute the

air/fuel mixture, they have to be carefully controlled and metered so as not to affect the

performance of the engine. This is the job of the positive crankcase ventilation (PCV)

valve. At idle, when the air/fuel mixture is very critical, just a little of the vapors are

allowed in to the intake system. At high speed when the mixture is less critical and the

pressures in the engine are greater, more of the vapors are allowed in to the intake

system. When the valve or the system is clogged, vapors will back up into the air filter

housing or at worst, the excess pressure will push past seals and create engine oil leaks. If

the wrong valve is used or the system has air leaks, the engine will idle rough, or at worst

engine oil will be sucked out of the engine.

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EGR VALVE

The purpose of the exhaust gas recirculation valve (EGR) valve is to meter a small

amount of exhaust gas into the intake system, this dilutes the air/fuel mixture so as to

lower the combustion chamber temperature. Excessive combustion chamber temperature

creates oxides of nitrogen, which is a major pollutant. While the EGR valve is the most

effective method of controlling oxides of nitrogen, in it's very design it adversely affects

engine performance. The engine was not designed to run on exhaust gas. For this reason

the amount of exhaust entering the intake system has to be carefully monitored and

controlled. This is accomplished through a series of electrical and vacuum switches and

the vehicle computer. Since EGR action reduces performance by diluting the air /fuel

mixture, the system does not allow EGR action when the engine is cold or when the

engine needs full power.

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EGR works by recirculating a 5-10% of an engine's exhaust gas back to the engine

cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with

inert gas which slows the combustion, and lowers the peak temperatures. Because NOx

formation progresses much faster at high temperatures, EGR serves to limit the

generation of NOx. EGR valves remain closed at engine idle since the inert gas received

from the EGR would not provide necessary power to keep an engine running at low

RPM.

Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet

manifold, which is called external EGR. A control valve (EGR Valve) within the circuit

regulates and times the gas flow. Some engine designs perform EGR by trapping exhaust

gas within the cylinder by not fully expelling it during the exhaust stroke, which is called

internal EGR.

In modern diesel engines, the EGR gas is cooled through a heat exchanger to allow the

introduction of a greater mass of recirculated gas.

EGR Valves have been around for a long time. Way back in 1972 GM used them in an

attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air

pollution, mainly photochemical smog, that kind of smog which is formed when strong

sunlight shines down on the exhaust gasses we puke out of our tailpipes by the billions of

cubic feet a day.

The automotive engineers figured that they needed to do something to lower the peak

combustion temperatures which only occurred under certain high load driving conditions.

They figured they could do so at the expense of power and fuel economy but what the

heck, ya can't have everything! If they could only add something to the combustion

chamber that would act like sort of a fire extinguisher to cool the combustion

temperatures that would do it.

So they invented a way to allow some very inert gas to get back into the combustion

chamber only when needed. They needed a source of this gas - it wasn't air, cuz that

contains oxygen and nitrogen which caused the problem in the first place. So they chose

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carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the

exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious

chemicals) Suppose we allow some of the exhaust gas to get back into the intake

manifold under strict control and only when we need it? That would cool the combustion

chamber and prevent the formation of the NoX. Maybe we should call it recirculated

exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name

associated with a car part, so they called it exhaust gas recirculation (EGR) since there

was nobody around with that name.

It's really pretty simple - it can be open when it isn't supposed to be, or it can be closed

when it is supposed to be open. Not rocket science, but it is science. If it is open when it

is not supposed to be open, at idle for instance, It will act like one monster vacuum leak

and the engine will not idle or will idle really roughly. If it doesn't open when it is

supposed to open you will probably experience a symptom of "pinging" or "knocking"

since the combustion chamber temperature will be higher than normal (one of the main

causes of pinging in an engine).

There are a zillion different types of EGR valves some of which work strictly on vacuum,

and some which work on a combination of vacuum and pressure. Some have electronic

controls, some have mechanical controls. I won't go into detail here about all the different

types but suffice it to say that most can be checked by looking inside to see if the plunger

shaft is stuck open or doesn't move when the engine is revved up (after it is warmed up).

Replacement is probably the easiest part since most are held in by two small bolts and

have a vacuum line connected to it. The hard part is whipping out your Visa card to pay

for it since most of them will drain your reserves in a hurry!!

EVAPORATIVE CONTROLS

Gasoline evaporates quite easily. In the past these evaporative emissions were vented into

the atmosphere. 20% of all HC emissions from the automobile are from the gas tank. In

1970 legislation was passed, prohibiting venting of gas tank fumes into the atmosphere.

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An evaporative control system was developed to eliminate this source of pollution. The

function of the fuel evaporative control system is to trap and store evaporative emissions

from the gas tank and carburetor. A charcoal canister is used to trap the fuel vapors. The

fuel vapors adhere to the charcoal, until the engine is started, and engine vacuum can be

used to draw the vapors into the engine, so that they can be burned along with the fuel/air

mixture. This system requires the use of a sealed gas tank filler cap. This cap is so

important to the operation of the system, that a test of the cap is now being integrated into

many state emission inspection programs. Pre-1970 cars released fuel vapors into the

atmosphere through the use of a vented gas cap. Today with the use of sealed caps,

redesigned gas tanks are used. The tank has to have the space for the vapors to collect so

that they can then be vented to the charcoal canister. A purge valve is used to control the

vapor flow into the engine. The purge valve is operated by engine vacuum. One common

problem with this system is that the purge valve goes bad and engine vacuum draws fuel

directly into the intake system. This enriches the fuel mixture and will foul the spark

plugs. Most charcoal canisters have a filter that should be replaced periodically. This

system should be checked when fuel mileage drops.

AIR INJECTION

Since no internal combustion engine is 100% efficient, there will always be some

unburned fuel in the exhaust. This increases hydrocarbon emissions. To eliminate this

source of emissions an air injection system was created. Combustion requires fuel,

oxygen and heat. Without any one of the three combustion cannot occur. Inside the

exhaust manifold there is sufficient heat to support combustion, if we introduce some

oxygen than any unburned fuel will ignite. This combustion will not produce any power,

but it will reduce excessive hydrocarbon emissions. Unlike in the combustion chamber,

this combustion is uncontrolled, so if the fuel content of the exhaust is excessive,

explosions, that sound like popping, will occur. There are times when under normal

conditions, such as deceleration, when the fuel content is excessive. Under these

conditions we would want to shut off the air injection system. This is accomplished

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through the use of a diverter valve, which instead of shutting the air pump off, diverts the

air away from the exhaust manifold. Since all of this is done after the combustion process

is complete, this is one emission control that has no effect on engine performance. The

only maintenance that is required is a careful inspection of the air pump drive belt.

Air injection technology first appeared during the late 1960s and was used

extensively throughout the 1970s. It was still widely used by some manufacturers through

the 1980s, but applications began to fade as automakers developed cleaner-running

engines. The typical mechanical air injection system consists of a network of hoses and

tubes, a belt-driven air pump and air-management valves. Since that time, air injection

systems have become more diverse in nature, sometimes using the onboard computer to

control system operation. Some engines use pulse-air systems that do not use a pump.

Instead, alternating pressures in the exhaust stream are used to pull air into the exhaust

system. As obsolete as this technology seems, some late-model vehicles use a high-tech

air injection system using an electric air pump controlled by the vehicle's Powertrain

Control Module (PCM).

Essentially an emissions "add-on" installed by the automakers to help further clean up

emissions, the air injection system supplies air to the exhaust stream to promote

additional burning of exhaust gases such as hydrocarbons (abbreviated as HC) and carbon

monoxide (abbreviated as CO). Some systems also supply air to the catalytic converter to

further reduce HC, CO and oxides of nitrogen (NOx), a major contributor to

photochemical "smog."

TU RBOCHARGER

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Turbochargers are an integral part of the advanced clean diesel system. They increase the

efficiency and performance of a diesel engine and extract more power out of a given

engine compared to a non-turbocharged engine.

The turbocharger consists of a set of two connected fans (or turbines) that recycle the

energy from wasted exhaust gases. In gasoline engines, it takes 9,000 gallons of air to

burn 1 gallon of fuel. For diesels, it takes 20,000 gallons.

Satisfying this appetite for air is the turbocharger's job. The turbo, along with common

rail fuel injection and direct injection, gives the diesel its phenomenal efficiency by

extracting more power from the same size engine.

The power output of any engine is determined in large part by how much air and fuel can

be packed into its cylinders: the more air and fuel, the greater the power.

All internal combustion engines are basically air pumps. Fuel is combined with air, then

it is ignited, and, in turn, this powers the engine. Air is pulled into the engine when the

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piston moves down in the cylinder and creates a vacuum. In other words, the weight of

the atmosphere "pushes" air into the cylinder.

As air and fuel must combine in very precise ratios, and fuel is pumped into cylinders at

high pressures, the limiting factor for power output is how much air the engine can get.

Enter the turbocharger. In addition to the air provided by the weight of the earth's

atmosphere (at sea level, this pressure is 14.7 pounds per square-inch), turbochargers

blow additional air (between 5-20 lbs. per square inch in additional atmospheric pressure)

into the cylinder, thereby increasing power and improving efficiency. Drivers experience

this firsthand when they drive through the mountains or high elevations. Less

atmosphere equals less power. Turbochargers, in effect, create their own atmosphere.

Turbochargers contribute to the advanced clean diesel system of lower emissions by

increasing the efficiency of the combustion process and burning fuel more efficiently

BHARAT III EMISSION NORMS

To reduce pollution in the atmosphere, the Automotive Research Association of India

(ARAI), Pune, has decided to implement the Bharat Stage III emission norms for

gasoline and diesel vehicles in 11 cities across the country.

The Bharat Stage III norms are equivalent to the Euro III norms,

Talking to presspersons, he said the 11cities that had been identified are the four metros

— Mumbai, Kolkata, Chennai, New Delhi — and the mini metros — Bangalore,

Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra.

These norms, to take effect from April 2005, would be applicable for the four-wheelers to

begin with, he said. Simultaneously, he noted that for the two and three-wheeler

population of the country, the Bharat Stage II would be made applicable across the

country.

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The diesel and gasoline car segment would also be in the same category from April 2005

ROAD TRAFFIC’S SHARE OF EMISSION

EMISSION STANDARDS

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EURO STANDARDS FOR PETROL CARS

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EURO STANDARDS FOR DIESEL CARS

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REFERENCES

The European Commission's Motor Vehicle Emissions Group:

http://europa.eu.int/comm/enterprise/automotive/mveg_meetings/

The report of the German Environment Agency (Umweltbundesamt): Future Diesel. July

2003. Can be downloaded from www.umweltdaten.de/

uba-info-presse/hintergrund/FutureDiesel_e.pdf

Emission standards, test methods, emission data for all models of car, etc., can be found

at www.vcacarfueldata.org.uk (Vehicle Certification Agency, UK).

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http://www.vcacarfueldata.org.uk/

http://www.umweltdaten.de/uba-info-presse/hintergrund/FutureDiesel_e.pdf

http://www.umweltdaten.de/uba-info-presse/hintergrund/FutureDiesel_e.pdf

http://europa.eu.int/comm/enterprise/automotive/mveg_meetings

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