What is a BS4 Engine and How it differ from BS3?

Bharath Stage (BS) is an emission norm which is regulation in India for automobile manufacturers.

Basically BS-4 is regulation for everything that is emitted from vehicle. The regulations not only covers exhaust emission but for evaporation emission, light emission, noise emission, tyre gas emission and perhaps a few more.

It is not just the engine that is altered but few other parameters are also taken into consideration.


What are BS3 and BS4 Engine? 

BS is basically the emission standards given by Government of India to regulate the air pollutants coming from internal combustion engine. BS stands for Bharat Stage and are set by the central pollution control board. BS standard is generally applicable to all the vehicles that are running in the country.

You may have heard of other standards like Euro… in Europe and Tier 1, Tier 2, used in USA.

More the number assigned, less air polluting the engine or less pollutants, the engine is releasing. In India, the BS 4 Engines are applied for the NCR and some other cities while, BS 3 Engines are applied nation wide. Although, in coming years the BS4 engines will be applied nationwide i.e. the manufacturing of BS3 engines will stop.

Evaporation emission:

A canister is connected to the fuel tank from hose which draws out of cloud of water vapour in fuel tank after the ignition is off. Instead of letting this vapour into atmosphere through fuel tank lid, it is directed to canister. The canister absorbs this vapour and stores in semi condensed form. When you start the engine again, some of the vapour from the canister is sent into the engine and thus the canister is again free to absorb the fresh vapour.

Light emission:

This defines maximum and minimum intensity of light used in vehicle, including headlamp low and high beam, turn indicators, fog lamps, tail lighr, brake light and reverse light.

Heat emission:

These are the regulations for various heat sources in vehicles like light, engines and exhaust.

Electromagnetic emission:

Few electrical and electronics in the vehicle emit electromagnetic radiations. These include devices like alternator/magneto coil, sensore used, infotainment devices such as wireless modem.

Noise emission:

This relates to noise emitted form various sources of vehicle like engine, gear box, horn, chain and even tyres.

Tyre gas emission:

When tyres get worn out, harmful gases are emitted form them.

All the above are regulated differently to different categories of vehicle.

Bs4 demands for lower limits of air pollutants like oxides of nitrogen, carbon monoxide, hydrocarbons and particulate matter, lower decibel of idle and pass, lower release of fuel vapour in atmosphere.