Re: Difference between BS3 and BS4

GBD Approved

You have been observing the change in weather for the last 30 years. How old are you

1. Different manufacturers have used different methods to reduce emitted particles. From FI, to reducing power, to inclusion of Cat-Cons, SAI (Secondary Air Injection), better flow of spent gases and a host of other changes.

2. Same as above, various methods have been used to ensure less polluting particles are emitted.

3. Yes, new norms for fuel as well. The metro cities in India have been using BS IV fuel for a year at least, maybe more.

4. If you replicate the changes done by the manufacturers, then theoretically you should be able to upgrade your bike. But you don't need to. Your BS III motorcycle is legal to be used for the next 15 years from the date of registration.

Re: Difference between BS3 and BS4

See the logic is simple, as "The Monk" never age he just cross the numbers . Similarly, from the time I have been in my senses I have observed climate change, and after 30yrs regarding my age, I stopped keeping a tab on the young years I have passed , after all its just the numbers and the grey hair


Now coming back to the topic I was looking for some more technical knowledge about it, as I just know Bharat Stage is for emission norms, what goes inside is something which I want to know.


I am looking for my Mentor OldFox Sir to comment on this, if he may please.

Re: Difference between BS3 and BS4

While I am no expert, I will give this a shot :-)

Bharat Stage emission norms have 3 parts to the specifications:

1. Classification of vehicles and their emission limits.
2. Methods & test cycle norms for testing the vehicles.
3. Mandatory hardware for vehicles (although for 2 wheelers this part has been relegated to the proposed BS-6 norms).

Broadly speaking BS-4 norms for 2 wheelers specify an HC+NOx emission reduction of approximately 23% to 60% depending on the class of 2 wheeler.

In addition the combined HC+NOx emission norms, the BS-4 standard for the first time in BS norms history defines the emission norms for monitoring NOx independently for 2 wheelers.

The above mentioned requirement has compelled bike makers to adapt Electronic Fuel Injection, better & more efficient 3 way catalytic converters & O2 sensors.

Further, for the first time, BS-4 establishes the first evaporation emission standards for 2 wheelers. This new requirement compels bike makers to design & use sealed fuel systems.

BS-4 norm also establishes crankcase emission norms that prohibit direct release of crankcase emission into atmosphere. In other words, just installing a simple rubber breather pipe will no longer cut the ice. The standard also specifies deterioration & aging cycle norms for the whole system.

In addition all of above, the BS-4 standards has harmonized the required testing cycle to the Worldwide Harmonised Motorcycle Test Cycle (WMTC). This is a significant shift from the more sedate Indian Driving Cycle (IDC) as required by BS-3. The WMTC reflects more realistic driving conditions.

Therefore to answer your queries:

Depending on the hardware on the BS-3 bikes, one would need to install any or all of these; a completely new fuel system including a sealed fuel tank, O2 sensors, EFI, crankcase breather recirculating system & exhaust system with bigger & better catcons.

The work for converting a carb bike to EFI will naturally be more extensive, whereas a bike like Ninja 300 which already meets Euro 4 norms may only require a ECU swap with revised fuel & ignition maps.

While people in general compare BS-4 standard to Euro 4, the BS-4 norms for HC+NOx emissions fall somewhere between Euro 3 & Euro 4. However, for independent NOx limits, BS-4 is 10 years behind Euro 3!!! The primary reason for this is non availability of Euro 4 spec fuel.

Therefore, the bottom line is that even after meeting BS-4, our 2 wheelers are still 'dirty' compared to their Euro-4 counterparts.