Why is there a power difference between Bharat Stage 4 (BS-IV) & Bharat Stage 6(BS-VI) Engines?

To regulate the pollution emitted by cars and two-wheelers, the government of India has put forth regulations known as Bharat Stage Emission Standards (BSES). The Central government has mandated that all vehicle manufacturers, both two-wheelers and four-wheelers, should manufacture, sell and register only BS6 (BSVI) vehicles from 1 April 2020.

So now the question arises will we get the same power from the bs6 engine which we used to get from bs4.

No, we will not get the same power from the bs6 engine because of various reasons.

1. Fuel Injection Method 

          This method is being used in most of the two-wheelers and four-wheelers that are bs6 compliant.  

Pros to it are:

1. Greater Mileage
2. Low Vibration
3. Less Pollution 
4. Low noise 

Cons to it are:

1. Less Performance
2. High maintenance Cost
3. There has to be atleast 1 litre petrol in reserve for two wheelers.

generally only motor enthusiasts will feel a power difference between these two engines or those who are driving these engines for a long time .

the main difference between these engines is that in bs 4 engines the petrol is going to engines through a small pipe while in bs6 engines it is getting directly injected which leads to more fuel efficiency but less power