About

• Maruti was the first one to get a BS-VI petrol engine and that too on its smallest car - Alto 800. Subsequently, other engines followed suit. On the sidelines of the XL6 launch, CV Raman, senior executive director (Engineering) said that BSVI compliant engine will have lower fuel efficiency than BSIV compliant.For example, if the WagonR used to claim a fuel efficiency of 23kmpl, seldom will someone achieve it in the actual driving conditions. Their real-time figure may be somewhere close to 18kmpl. However, post BS-VI, if the WagonR engine claims an efficiency of 21kmpl, the real world will still be 18kmpl. In terms of diesel engines, the claimed as well as real-world numbers will be lower. This is another reason why Maruti is hesitant about getting BS-VI diesels. 

why a BS-VI compliant engine (we know only petrols for the moment) is claimed to give lower fuel efficiency?

• One is the testing method of the vehicle. This contributes to a 5-8 per cent reduction in fuel efficiency.

• second the Powertrain, as well as changes in a few components to conform to BS-VI, will accounts for a lower claimed fuel efficiency.

• If it is a diesel powertrain, the claimed fuel efficiency goes down even more. This is because from the engine perspective, not only will the components be upgraded but also the soot from the Diesel Particulate Filter has to be burnt. This will require more fuel to be expended and hence the efficiency goes down.

Background

What are Bharat Stage norms? 

• The Bharat Stage are standards instituted by the government to regulate emission of air pollutants from motor vehicles. The norms were introduced in 2000. With appropriate fuel and technology, they limit the release of air pollutants such as nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter (PM) and sulphur oxides from vehicles using internal combustion engines. As the stage goes up, the control on emissions become stricter. Thus Bharat Stage VI norms are two stages ahead of the present Bharat Stage IV norms in regulating emissions. These norms are based on similar norms in Europe called Euro 4 and Euro 6. 

Differences between two stages 

• The extent of sulphar is the major difference between Bharat Stage IV and Bharat Stage VI norms. BS-IV fuels contain 50 parts per million (ppm) sulphur, the BS-VI grade fuel only has 10 ppm sulphur. BS VI can bring PM in diesel cars down by 80 per cent . The new norms will bring down nitrogen oxides from diesel cars by 70 per cent and in petrol cars by 25 per cent. BS VI also make on-board diagnostics (OBD) mandatory for all vehicles. OBD device informs the vehicle owner or the repair technician how efficient the systems in the vehicle are.