Emission Norms and their importance – BS II, III, and IV
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In our previous articles we had dealt with topics such as the working of petrol and diesel engines, suspension systems etc. Another interesting technical element is the emission norm, known in India as the BS norm. These norms control the emission of the car and are of large importance for car manufacturers. Today we take a close look at these norms.
In the earlier days of development of automobiles, the main issue was to get the car moving in the fastest and safest manner. With globalization and improved economic conditions, there has been a huge increase in number of cars and other vehicles coming out of manufacturing plants. With increase in number of vehicles, the amount of exhaust gasses emitted is also increasing exponentially, thus having significant influence on the environment. If this is not controlled, companies may sacrifice the environment for profits, thus harming the environment structurally. It is for this reason that Governments across the world have implemented emission standards to ensure that companies ensure that emissions are not too much. In India, these standards have been captured under the name Bharat Stage, BS for short.
First, it is important to know the contents of exhaust gases and necessity of controlling it before knowing how the Government has decided on implementing different Emission norms
Emission control on cars and trucks have one purpose i.e. to reduce amount of pollutants and environmentally damaging substances released by vehicles. The consequences of pollutants are dangerous. The air we breathe and water we drink may become contaminated with chemicals that adversely affect our health.
Initially, during the development of automobiles not much attention was given to emissions. However, this changed when winter day in England, smog was spotted. In simple words, SMOG is the name given to the combination of FOG and Smoke, thus standing for dirty air.
However, smog not only appears as dirty air, it is also an irritant to a person’s eyes, nose, and throat. The key elements in smog are Hydro-carbons, NOx (oxides of nitrogen) and Sulphur-oxides. These particles react with each other and cause polluting smog.
Pollutants in Automotive exhaust fumes
The main automotive pollutants – Hydro-carbon, Carbon monoxide, and Oxides of nitrogen - emissions are also present in engine exhaust fumes. These emissions are caused by different reasons.
Hydro carbon emissions are caused largely by unburned fuel from combustion chambers, and can also originate from evaporative sources such as a petrol tank. CO emissions are a by-product of combustion process and they result from incorrect air/fuel mixtures. NOX emissions are caused when cylinder temperatures exceed 1371 degree centigrade; in this case, nitrogen and oxygen combine to form NOx.
All these components are harmful in their own way and thus are subject to government scrutiny.
Emission Norms in India
It was in 1991 that first time emission norms were introduced in India for petrol cars; diesel cars followed in 1992. From then onwards, new cars manufactured in India had to adhere to these standards; their exhaust fumes could not contain more than specified quantity of pollutants.
These standards were compounded with the implementation of mandatory catalytic converters in 1995 for the 4 Metro cities, thus reducing pollution further.
From 2000, India introduced stricter Emission standards modeled on the European ones. This meant the birth of Bharat Norms, with the first set of norms known as Bharat Stage II, followed by BS III, and BS IV (BS I was the earlier, Indian standard).
The tables given below give details of Emission norms at different stages and area of implementation. Here we are focusing on petrol engines, but diesel engines have similar norms also. Interestingly, you will see that initially HC and NOx were considered in one category.
Similar rules as for petrol cars apply to CNG and LPG versions, however the maximum norm for HC is altered. We won’t go into the calculation here.
Given the norms, obviously the government needs to have methods to test the exhaust fumes also. For this purpose a gas analyzer is used. A typical exhaust gas analyzer has a long sample hose with a probe at the end of hose. The probe is inserted to the vehicle’s tailpipe. When the analyzer is turned on, an internal pump moves an exhaust sample from tail pipe through the sample hose and the analyzer. A water trap and filter in the hose removes moisture and carbon particles.
The pump forces an exhaust sample through a sample cell in the analyzer. In the sample cell, a beam of infra red light passes through the exhaust sample. Using light spectography, the analyzer then determines the quantities of HC and CO (if the analyzer is a two gas analyzer) or HC, CO, CO2 and O2 if it’s a four gas analyzer. Some analyzers called five gas analyzers can also measure NOX. Nearly all analyzers currently used are four or five gas machines. Most of gas analyzers measure the gases in percentages or parts per million.
The Maximum limits for the measures gases are ser by government for particular vehicle as mentioned in tables above.
Norms Applied to Fuels
Besides norms applied to exhaust fumes (and hence the car’s engineering), fuels are also subject to certain rules. In India, the Ministry of Environment and Forest notified fuel specifications. Herein maximum limits for critical ingredients (like benzene) have been specified for engine fuel.
Automotive Engineering and Emission Norms
Given engine norms, auto manufactures need to do adaptations in their engineering to achieve these norms.
While a discussion on this will be very technical, here are some points that manufacturers will focus on:
- Temperature in the cylinder as this affects completeness of combustion
- Recirculating exhaust fumes
- Better catalytic technology
- Changes in proportions of fuel and air
At some points, introducing more expensive technology in order to comply with stricter norms will not make sense to manufacturers. It is for this reason that we have seen localized phase out of certain models, such as the Maruti 800.
Non Structural Emission Influences
Besides changes in auto engineering structure, emissions can also vary across cars for situational reasons. The below is an analysis of this variation, listing certain reasons for changes in emissions.
Excessive HC emissions may be caused by
- Ignition system misfiring
- Improper ignition timing
- Excessively lean or rich air/Fuel ratio
- Low cylinder compression
- Defective valves, guides, or filters
- Defective rings, pistons or cylinders
- Vacuum leaks
All these issues lead to incomplete combustion, thus releasing HC into the air.
Excessive CO emissions are caused by
- Rich air/fuel mixtures
- Dirty air filter
- Faulty injectors
- Higher than normal fuel pressures
- Defective system input sensor
Excessive HC and CO emissions caused by
- Plugged Positive Crank case Ventilation system (PCV system)
- Excessively rich air/Fuel ratio
- Stuck open heat riser valve
- AIR pump inoperative or disconnected
- Engine oil diluted with gasoline
Higher than normal NOX emissions may be caused by
- An overheated engine
- Lean air/fuel mixtures
- Vacuum leaks
- Over advanced ignition timing
- Defective EGR system
Emission norms are controlled by government and the same implemented at manufacturer plant itself. The same applied to fuels also. Hence customers need not worry much about whether their vehicle is BS III version or BS IV version, since any new car they purchase will conform to existing norms. An already registered BS III version car can be used in city where BS IV norms are introduced, until or unless government declares specific restrictions about the same.
That being said, the aim of this article is to give brief information about the pollutants from an automobile perspective and explain the necessity of introducing norms from time to time and causes for difference in emissions.
Do please submit your questions for further information on BS norms and pollutants
Comments on this article
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because of greed for money,,it doesn't cost that much to produce it,,but there going to get all they can from us one way or aotehnr,,its the American way,,so i am told anyway,,in my opinion,,it could be cheaper than it is,,but then that would mean we,d actually have a few dollars left from our pay day after filling up,,wouldn't this be something,,anyway,,good luck,,i hope this help,s.May 28, 2012 by Ladie
THE ARTICLE IS TOO MUCH USEFUL... I WANT TO ASK ONE QUESTION AND THAT IS TATA NANO 2012 IS COMPATIBLE WITH BS4 (ACCORDING TO ADVT) BUT MARUTI 800 IS NOT COMPATIBLE WITH BS4... HOW IS IT? AND IF MARUTI 800 IS NOT SOLD IN METROS AS IT IS NOT COMPATIBLE WITH BS4 THEN IF ONE BUY USED 800 IN MUMBAI IS THERE ANY REQUIREMENT TO PAY ADDITIONAL AMOUNT AS NON ADHERING TO NORMS? HOW MUCH LIFE OF 800 IS FIXED FOR USAGE IN MUMBAI? THANXApril 20, 2012 by Milind Tendle
In Birbhum District of West Bengal whether registration of BS-II compliant Tata four wheeler be done as on July 2011?July 03, 2011 by Sourav Mukherjee
IS THERE ANY BS II CATEGORY ENGINE IMPORT RESTRICTIONS EXIST,PLEASE GIVE ME THE DETAILS AND THE LAST EFFECTIVE DATE FOR REGISTRATIONS OF SUCH ENGINES IN MOTOR VEHICLES DEPARTMENT,KOLKATA.March 12, 2011 by Sujit Das
When do the BS4 norms become effectiveAre they in force w.e.f. 1st Apr-2010 as originally intented? or the implementation is deferred?January 10, 2011 by Raja
Hi, Emission testing is done with help of analyser and the norms are set in the anallyser itself. If the exhaust gas contains excessive proportion of CO,NOX,HC then it would give reading for necessity of controling exhaust from vehicle. The permisible limits are as mentioned in tables.January 04, 2011 by Shiva, CarTrade Expert
Please throw some light on the workflow for performing the emission test for petrol (with regulated, unregulated catalyst in car/truck and bike), diesel vehicles (with and without OBD) in India. How many types of procedures are to be tested for vehicle exhaust emissions in India? How many gases are being tested currently by emission tester in India?December 31, 2010 by Emission Analyser Aspirant
Really this article is very useful to understand what is BSII, III, IV. Your article clearly explains about the pollution differences of the above. Thank youDecember 30, 2010 by Guru
Excellent article, and very productive and knowledgable info.Thanks.December 30, 2010 by Manoj Joshi
emission normsDecember 29, 2010 by Manish
Wanted to know of one has to do a pollution check on his/her cars in regular intervals? If so what is its frequency and does this rule vary from state to state?December 27, 2010 by Pranab
Excellent Shiva. Simply gr8. Need not be a techie to understand. The way you have explained, anyone can understand the basics of BS norms.December 27, 2010 by Amit
brief & excellent material. interested in working & operation of Petrol and Deiesel Engines.December 27, 2010 by R MUTHUKUMAR
The move to remove subsidy from diesel is not going to solve any problem & control pollution moreover it will result in price hike of basic commodities as most of the transportation is done by these pick-ups, further there will be black marketing of diesel. I was very surprised by the comment of the union minister for environment that the diesel SUVs should be taxed heavily to control pollution, I think the government of our country already takes more than the actual cost of every CBU/DIRECT IMPORT vehicle as custom duty from customers , it does not stop here the state governments are charging as high as 6% of the cost of a vehicle as road tax & registration chasges what else does the hon'ble minister wants?? "jahan panah tusi great ho".December 27, 2010 by RAJAT PANJETA
Well done Shiv. It has come out well and very easy for even the common man who sits behind the wheel.I wish it is translated to all regional languages and published in Newspapers , so that even the Drivers and Cleaners or Conductors will understand what is the Pollution Control in India.You can also write another aricle on Diesel and give the Hartridge Number,Bosch Number,and the European equivalent,which I forget,as I have done an exhaustive study of Black smoke emissions versus fuel consumption which I got my Doctorate.Kindly give the equivalents for all the three and whether any other new Diesel Numbers have come for other countries like Japan, China etc.??Good SHOW, and Keep it up.Dr P C Rao, Pune 26 dec 10December 26, 2010 by Dr P C Rao
would like to know in details the BHARAT STAGE NORMS for Diesel Engines. Also please inform weather these B s NORMS apply only to Vehicle or all diesel Engines other than Vehicles & how they are controlledDecember 26, 2010 by Rajen Agarwalla
Am considering buying the Yeti. Would like to know how a diesel in general and the Yeti, in particular, compare with petrol sedans.Thanks.December 26, 2010 by Irshad Tyabji
please give me an ads on my websites that is that www.nanosoon.comDecember 26, 2010 by Arun
What about Diesel Vehicles?December 26, 2010 by Gopal
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