Bharat Stage 6 or more popularly BS6 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 BSa6 norms from 1st of April 2020. As per the Supreme Court’s verdict, the production and sales of BS4 vehicles are 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, the Indian government planned to skip BS-5 and jump directly to Bharat stage-6 norms.
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What Is Bharat Stage 6 Or BS6
Bharat stage 6 or BS6 are Indian emission norms based on Euro 6 norms. These norms focus particularly on the reduction of particulate material and Oxides of Nitrogen (NOx) from the automobile emissions. They also focus on 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 25% and from Diesel engines by 70%.
BS6 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 the engine produces sulfur oxides and sulfides. The oxides combine with water vapour present in the air and form sulfuric acid. This causes acid rains. The sulfides are released in the 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 BS6 Fuel In A BS4 Vehicle?
The Petrol pumps have started providing BS6 grade fuel in most of the cities. Now, the biggest question in the mind of people is “can they run their existing BS4 or BS3 vehicles on BS6 grade fuel? “. The answer is “Yes”. We can run our Bharat Stage 3 and stage 4 vehicles on BS6 grade fuel. Running these vehicles on Bharat Stage 6 grade fuel would help in the reduction of their emission levels. However, there which may cause problems to fuel-injected engines in the 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 the long run.
Can We Use BS4 Fuel In A BS6 Vehicle?
The Bharat Stag 4 fuel contains a greater amount of Sulfur. Using this fuel in BS6 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 the engine, reducing its peak power. It may also damage the DPF, which is very expensive to replace. However, the use of BS4 fuel in a BS6 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 25%. The BS6 norms also set limits for Hydrocarbon and particulate emissions, which were not specified in earlier norms. To meet the emission requirements of Bharat Stage 6, the carburettor in petrol engines need to be replaced by the programmed fuel injectors. To further reduce tailpipe emissions, the exhaust system would be fitted with three-way catalytic converters. The norms also mandate the On-Board Diagnostic System (OBD) for all BS6 compliant vehicles. Let’s look at all these technologies in some detail.
The carburetors would no longer be available in Bharat Stage 6 vehicles. The BS6 petrol engines need to be equipped 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 onboard computer called ECU. The ECU or engine control unit is a mini-computer which analyses the sensors data and process is 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 the amount of air intake.This helps in proper combustion of fuel inside the engine, reducing the level of pollutants in the exhaust.
Electronic Carburetors Or E-CARBS
While most of the two-wheeler manufactures are going with Fuel Injection Technology, Bajaj Motors have introduced E-CARBS for their entry level BS6 motorcycles. They are using Electronic Carburetors in their 100-125 cc motorcycles. Although, the fuel injectors are precise and fuel-efficient but they also have some problems with them. The fuel injection system along with the fuel pump is costly and adds substantially to the overall price of the vehicle. The fuel pump always needs a certain amount of fuel in the tank to maintain its operational head and required cooling. In case the level of fuel goes below the prescribed limits, the pump would start pumping air which may damage it. Keeping these points in mind Bajaj motors planned to go with Electronic Carburetors in their 100 and 125 cc motorcycle. E-CARBS are modified version of carburettors They are consist of a network of sensors and an Electronic Control Unit (ECU). The sensors like MAP sensor, Engine RPM sensor, Intake Air temperature sensor collects the data of incoming air to the carburetor. This data is then analysed by the ECU and accordingly, it controls the fuel supply in carburetor. The ECU controls the fuel supply by controlling the low and high jets of the carburetor. This is done by using electronic valves fitted in the jets. The Electronic Carburetor system also consists of Oxygen sensor in the exhaust pipe. This sensor acts as a feedback sensor and helps the ECU in keeping the air-fuel ratio precise. The greatest advantage of E-CARBS is their retro-fitment i.e. they can be fitted easily in the vehicles with normal carburetors. This ability of electronic carburetors may help in up-gradation of the huge lot of BS4 motorcycles available in the market to BS6.
Three-Way Catalytic Converters
To further reduce the level of NOx in tailpipe 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 into non-toxic gases like N2, CO2, H2O etc. They consist of two ceramic plates, the ‘reducing plate’ and the ‘oxidising plate’. These plates have a porous honeycomb structure. The reducing plate converts the NOx into N2 while the oxidising plate converts CO and HC into CO2 and H2O.
Technology Changes In Diesel Engines
As per the Bharat Stage 6 norms, the NOx emissions from a diesel engine 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 associated with this are:
1. Fitting Diesel Pre Filters in the exhaust system.
2. Using Selective Catalytic Reduction (SCR) or Exhaust Gas Recirculation techniques to reduce NOx in emissions.
Diesel Particulate Filter
Diesel particulate filter is a device used to filter out the particulate materials from the vehicle’s exhaust gases. They can be fitted in the exhaust system, either before or after the catalytic converters. DPFs contain honeycomb-shaped filters made of silicon carbide or cordierite. The shoot particles 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 the engine causing it to underperform. 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 the 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 into N2 through the process of reduction. N2, being a non-toxic gas, do not cause any harm to the environment. The only problem with SCR is that the DEF needs 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 from 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 the reduction in NOx emissions. The NOx is produced inside the engine when the combustion temperature becomes extremely high. The EGR uses this fact to reduce the emission of NOx. When the temperature becomes very high, the EGR recirculates some amount of exhaust gases back into the combustion chamber. The exhaust gases areintercoolerd before they enter the combustion chamber. The supply of exhaust gases limits the amount of air intake to the engine. Due to less air intake, less fuel is burnt in the engine cylinder. Theintercoolerd exhaust gases also absorb some of the heat of the combustion chamber. This brings 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.
Check Engine Light
On-board diagnostics or OBD is a necessary feature of Bharat Stage 6. All the BS6 vehicles whether Diesel Or Petrol need to have On-Board Diagnostic system. The OBD is required to monitor the performance of a different element of the emission control system. The various electronic components related to the 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 then 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 the information 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 then analyses the fault code stored in ECU and gives us the exact information of the problem. This information can then be used to diagnose the problem.
Bharat Stage 6 is a major challenge for the Indian automobile industry. The technical advancements required to meet BS6 norms has led to huge investments in R&D by 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. 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.