EMISSION STANDARDS IN LIGHT AND HEAVY VEHICLES full report
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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 manufacturersâ„¢ 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 and presentation, 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.
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
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.
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 Ã‚Â±50 rpm and the specified torque shall be held to within Ã‚Â±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.
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.
Â¢ Part one represents city driving with a maximum speed of 50 km/h, frequent starts, stops, and idling.
Â¢ Part two is rural driving starting with a steep acceleration segment. The average speed is about 72 km/h
Â¢ Part three is motorway driving with average speed of about 88 km/h.
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 and implimentation, 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 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 (7Ã‚Â°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.
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.)
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 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
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.
- 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.
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 (300-400Ã‚ÂºC) 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 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 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.
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.
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 emission control devices installed on the automobile are: EGR VALVE, CATALYTIC CONVERTER, AIR PUMP, PCV VALVE, CHARCOAL CANISTER.
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 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.
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.
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.
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 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!!
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. 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.
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 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."
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 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 â€ Mumbai, Kolkata, Chennai, New Delhi â€ and the mini metros â€ 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.
The diesel and gasoline car segment would also be in the same category from April 2005
ROAD TRAFFICâ„¢S SHARE OF EMISSION
EURO STANDARDS FOR PETROL CARS
EURO STANDARDS FOR DIESEL CARS
The European Commission's Motor Vehicle Emissions Group: europa.eu.int/comm/enterprise/automotive/mveg_meetings/
The report of the German Environment Agency (Umweltbundesamt): Future Diesel. July 2003. Can be downloaded from umweltdaten.de/
Emission standards, test methods, emission data for all models of car, etc., can be found at vcacarfueldata.org.uk (Vehicle Certification Agency, UK).
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27-09-2010, 12:59 PM
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This article is presented by:Tarun S Kumar
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.
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.
. 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.
Methods to reduce emission in SI engine.
Automotive emissions are controlled in three ways; one is to promote more complete combustion so that there is 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 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.