Everything You Need to Know About BS3 and BS4 engines

With the Supreme Court ban on selling BS3 automobiles, there is a lot of uncertainty going on about the future of these cars and bikes. There are many lingering doubts among existing owners and those who purchased BS3 vehicles when dealerships were offering them at extraordinary discounts, on a future ban or whether long term car or two wheeler insurance will be available for the said vehicles.


Through this article, we bring to rest many of the doubts that you have. And if you have anymore questions, please post them in the comments section and we will get back to you. So let’s start with the first question:

  1. What is the difference between a BS3 & BS4 engine?

BS3 and BS4 engines are almost the same in terms of mileage and performance figures, but the difference is in the exhaust emissions from both engines. Those familiar with vehicles will think exhaust gases have everything to do with the exhaust system and catalytic converter. Fitting a more restrictive exhaust system won’t make a BS3 engine BS4 compliant. We have to go deep and address the problem at the heart, which is the combustion chamber where fuel is burnt or rather exploded to produce the said exhaust gases. The changes to a BS4 car and a BS4 bike engine are also different.

How are BS4 two wheelers different from BS3?

  • BS4 two wheelers have an Evaporative Emission Control (EEC) system to absorb fuel vapours formed when the vehicle is parked outside. These vapours consist mainly of unburned hydrocarbons, which escape during refuelling, and are extremely harmful to the environment.
  • They also get a three-way catalyst system and oxygen sensors. The new catalytic system has a larger volume and surface area of the catalyst and the oxygen sensors help in a more efficient burning of fuel, lowering harmful NOx emissions.

How are BS4 four wheelers different from BS3?

  • Petrol vehicles will have Multi-Point Fuel Injection (MPFi) and three-way catalytic converters.
  • Diesel vehicles should have as mandatory Common Rail Direct Injection (CRDi) with Turbocharger & Exhaust Gas Recirculation (EGR) systems. Exhaust system should have a Diesel Oxidation Catalyst (DOC) system converting unburnt hydrocarbon and carbon monoxide emissions to carbon dioxide and water.
  1. What is the main reason behind the discontinuation of BS3 vehicles?

To decrease pollution in the air is the simple answer. India is one of the polluted countries in the world with the air in many of the metropolitan cities unhealthy for breathing. With the introduction of BS4 vehicles, the exhaust emissions from these engines have lower amounts of the main polluting substances like Carbon monoxide, Nitrous oxides, Hydrocarbons and other particulate matter like antimony, cobalt, benzene etc.

BS4 engines also have BS4 fuel which has a different constitution where the sulphur content is lower, thereby decreasing harmful SOX emissions. BS4 fuel has been introduced in the country from 2010 on wards, so you needn’t be concerned about its availability.

  1. Can BS3 vehicles be continued to use?

You can continue to use your BS3 vehicle as long as you like and sell it as well. There are no government objections imposed yet, preventing you from using a BS3 vehicle or selling an already owned one. Using BS4 fuel in a BS3 engine vehicle will also have no issues for the engine, but using BS3 fuel in a BS4 engine can damage it in the long run.

  1. Will a BS3 vehicle owner face problems to re-insure the vehicle?

Insurance companies will continue to extend car insurance and 2 wheeler insurance services for BS3 vehicles. You can get instant quotes through various car insurance calculators available online. Insurance companies are also offering two wheeler insurance for up to 3 years of coverage, so you can put your worries to rest by opting for such plans which will help you in the long run.

BS4 technical details source : teambhp


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