Bharat Stage-6: All You Need To Know About BS-6 norms

Bharat stage 6 bs 6 emission revolution

Bharat Stage-6 or more popularly BS-6 is the latest version of the  Emission Standards for the Indian automobiles. Currently, India is following Bharat Stage-4 norms and has planned to switch over to BS-6 norms from 1st of April 2020. As per the supreme Court's verdict, the production and sales of BS-4 vehicles is to be  stopped completely after march 2020. Bharat Stage or BS norms are based upon the Euro Norms followed in European Countries. The European Countries are currently following Euro-6 norms. To meet the global standards, Indian government planned to skip BS-5 and jump directly to Bharat stage-6 norms.

What is BS-6 ?
Bharat stage 6 bs6 what is bs 6
Bharat stage-6 or BS-6 are Indian emission norms based on Euro-6 norms. These norms focus particularly on reduction of particulate material and Oxides of Nitrogen (NOx) from the automobile emissions. They also focus no the levels of carbon monoxide (CO) and Hydrocarbons (HC)  for petrol engines. For all this, they suggest a two fold approach. First, they will focus on improving the quality of fuel by reducing its Sulphur content. Second, they will upgrade the existing technologies in vehicles to effectively utilize this fuel and reduce the emissions to the desired level. They have provisions to reduces particulate matter by 80 percent. Further, they will reduce the NOx emissions from petrol engines by 80% and from Diesel engines by 70%.

BS-6 Grade Fuel

BS-6 grade fuel will be one of the cleanest fuel available in the world. This fuel will have  5 fold lesser Sulphur content than the BS-4 grade fuel. The BS-4 grade fuel consists of 50 parts per million of Sulphur which would be further reduced to the level of 10 ppm in BS-6 grade fuel. The combustion of sulphur in engine produces sulfur oxides and sulfides. The oxides combine with water vapour present in air and form sulfuric acid. This causes acid rains. The sulfides are released in atmosphere as particulate materials. Hence the reduction of sulfur content of fuel will reduce the level of particulate materials as well as sulfur oxides in the exhaust gases. But to reduce the sulfur content from fuel the oil companies have to make huge investments. These investments may increase the cost of fuel marginally.

Can We Use BS-6 Fuel In A BS-4 Vehicle?

The Petrol pumps have started providing BS-6 grade fuel in most of the cities. Now, the biggest question in mind of people is "can they run their existing BS-4 or BS-3 vehicles on BS-6 grade fuel? ". The answer is "Yes". We can run our Bharat Stage-3 and stage-4 vehicles on BS-6 grade fuel. Running these vehicles on Bharat Stage-6 grade fuel would help in reduction of their emission levels. However,  there which may cause problems to fuel injected engines in long run. The sulfur in fuel has lubricating properties. Hence, the reduction in the level of sulfur from fuel may cause wear & tear of fuel injectors in long run.

Can We Use BS-4 Fuel In A BS-6 Vehicle?

The Bharat Stage-4 fuel contains greater amount of Sulfur. Using this fuel in BS-6 cars may cause some problems. Combustion of this fuel would produce a greater amount of particulates. These particulates may cause the choking of Diesel Particulate Filters fitted in Diesel Engines. The choking of DPF would increase the back pressure on engine, reducing its peak power. It may also damage the DPF, which is very expensive to replace. However, the use of BS-4 fuel in a BS-6 petrol engine would not at all cause any problem.

Technology Changes In Petrol Engines.

As per Bharat Stage-6 norms, the emission of carbon monoxide is to be reduced by 30% and NOx by 80%. The BS-6 norms also sets limits for Hydrocarbon and particulate emissions, which were not specified in earlier normsTo meet the emission requirements of Bharat Stage-6, the carburetors in petrol engines need to be replaced by the programmed fuel injectors. To further reduce tail pipe emissions, the exhaust system would be fitted with three way catalytic converters. The norms also mandates On-Board Diagnostic System (OBD) for all BS-6 compliant vehicles. Let's look at all these technologies in some detail. 

Programmed Fuel Injection System 

Programmed fuel injection pfi Bharat stage 6 bs6
Pic Credit: HeroMotocorp

The carburetors would no longer be available in Bharat Stage-6 vehicles. The BS-6 petrol engines need to be equiped with programmed fuel injector and an advanced engine management system in order to meet the strict emission norms. The engine management system consists of a network of sensors to monitor the different engine parameters. The data collected by the sensors is analysed by an on board computer called ECU. The ECU or engine control unit is a mini computer which analyses the sensors data and process it based on the programs already stored in it. The ECU then controls ignition, fuel injection and engine cooling accordingly. The quantity of fuel supply is decided by the Engine control unit based on the precise measurements of amount of air intake. This  helps in proper combustion of fuel inside the engine, reducing the level of pollutants in exhaust.

Three Way Catalytic Converters

Three way catalytic converters Bharat stage 6 bs 6

Catalytic Converter

To further reduce the level of NOx in tail pipe emissions, the Bharat Stage-6 vehicles would be fitted with "Three Way Catalytic Converters". The catalytic converters  convert the poisonous gases like NOx, CO and HCs in to non toxic gases like N2, CO2, H2O etc. They consists of two ceramic plates, the 'reducing plate' and the 'oxidising plate'. These plates have porous honeycomb structure. The reducing plate converts the NOx in to N2 while the oxidising plate converts CO and HC in to CO2 and H2O. 

Technology Changes In Diesel Engines

As per the Bharat Stage-6 norms, the NOx emissions from a diesel engines are to be reduced by 70% and particulates by 80%.
To achieve this, the engines need to be equipped with Euro-6 compliant technologies. Two major technical changes to associated with this are:

  • 1. Fitting Diesel Pre Filters in exhaust system.
2. Using Selective Catalytic Reduction (SCR) or Exhaust Gas Recirculation techniques to reduce  NOx in emissions.

Diesel Particulate Filter
Diesel Particulate Filter DPF bharat stage 6 bs6 diesel engine

Diesel particulate filter is a device used to filter out the particulate materials from vehicle's exhaust gases. They can be fitted in exhaust system, either before or after the catalytic converters. DPFs contain honey comb shaped filters made of silicon carbide or cordierite. The shoot particle in the exhaust gases get trapped when they pass through the filters. Thus, the gases coming out of the DPF are free from particulate material. The trapping of particulates inside the DPF may lead to the clogging of the filters. This will increase the back pressure on engine  causing it to under perform. The clogged filters can be cleaned by a process called regeneration. This can be done by driving your vehicle at high speed on a long ride. This will cause the temperature of DPF to rise beyond 600-700 degree celsius. This high temperature burns out the shoot particles accumulated in the DPF. Regeneration can also be done at service stations.

Selective Catalytic Reduction

NOx reduction is one of the key provisions of the Bharat Stage-6 norms. Selective Catalytic Reduction or SCR is a technology used to reduce the amount of NOx in the exhaust gases. The SCR unit is mounted after DPF in exhaust system. The selective catalytic reduction unit selectively reduces NOx from the exhaust gases without affecting the other gases. The SCR unit consists of a DEF tank and DEF dosing unit. DEF is also called 'Diesel Exhaust Fluid'. It is an aqueous solution of urea and deionised water. The DEF acts on exhaust gases and convert NOx in to N2 through the process of reduction. N2, being a non toxic gas, do not cause any harm to environment. The only problem with SCR is that, the DEF need to be refilled after some period of time.

Exhaust Gas Recirculation

The problem with SCR is its high cost of maintenance. The aqueous  Urea solution called Adblue also needs to be refilled time to time. A good substitute for SCR is Exhaust Gas Recirculation or EGR. Many Bharat Stage-6 vehicles would also be using EGR instead of SCR for reduction in NOx emissions. The NOx is produced inside engine when the combustion temperature becomes extremely high. The EGR uses this fact to reduce emission of NOx. When the temperature becomes very high, the EGR recirculates some amount of exhaust gases back in to the combustion chamber. The exhaust gases are intercooled before they enter the combustion chamber. The supply of exhaust gases limit the amount of air intake to the engine. Due to less air intake, less fuel is burnt in the engine cylinder. The intercooled exhaust gases also absorb some of the temperature of combustion chamber. This bring down the engine temperature to a lower level, reducing the level of NOx emissions. The recirculation of exhaust gases also leads to some power loss. Due to this reason they are less popular than SCR and are generally used for small cars. 

On-board Diagnostics

Check Engine light malfunction indication lamps Bharat stage 6 bs6 on board diagnostics
Check Engine Light

On-board diagnostics or OBD is a necessary feature of Bharat Stage 6. All the BS-6 vehicles whether Diesel Or Petrol need to have On-Board Diagnostic system. The OBD is required to monitor the performance of different element of emission control system. The various electronic components related to emission control system can be monitored and diagnosed through OBD. The key components of an OBD system are:
1. Engine Control Unit Or ECU
2. Check Engine Light Or Malfunction Indication Lamp (MIL) 
3. OBD Scan Tool

The ECU collects the data through various sensors located all across the vehicle. It than gives commands to the actuators like fuel injector or CDI. In case of a fault in any of these sensors or actuators , a fault code is generated in ECU. The ECU than gives us theinformation of this malfunction  by glowing check engine light. Now, this fault can be analysed using an OBD Scan tool. These tools can be connected to the ECU through OBD port given specifically for this purpose. The tool than analyses the fault code stored in ECU and gives us  the exact information of the problem. This information can than be used to diagnose the problem. 

Bharat Stage 6 is a major challenge for Indian automobile industry. The technical advancements required to meet BS-6 norms has led to huge investments in R&D by the auto manufacturers. The problems for oil companies are no less. They are also investing huge sums to upgrade their refineries, in order to produce BS-6 grade fuel. But at last, this all cost would have to be borne by the customers. The prices of cars and bikes would rise due to technical advancements qq. We may also see some hike in fuel prices in the coming future. It would be interesting to see, if the Government provides any subsidy to the BS-6 vehicles or the fuel.  


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