Sunday, October 1, 2023

RDE norms and its impact on automobiles

Real Driving Emission

Real Driving Emissions (RDE) is form of phase II of BS6 standards.

The RDE regulations bound automobile companies to measure pollutants emitted from a vehicle in a real-world driving scenario. A Portable Emissions Measurement System (PEMS) is used for this purpose.

As part of RDE norms, all diesel vehicles are required to have Selective Catalytic Reduction (SCR) systems, which incur additional costs for carmakers and may even be too costly for some smaller vehicles.

By using Diesel Exhaust Fluid (AdBlue), SCR reduces tailpipe emissions of nitrogen oxides (NOx) by converting pollutants into nitrogen, water, and tiny amounts of carbon dioxide.

What is SCR- Selective Catalytic Reduction?

SCR is a technology that uses a urea-based diesel exhaust fluid (DEF) and a catalytic converter to significantly reduce oxides of nitrogen (NOx) emissions. SCR convert Nitrogen oxide into Diatomic nitrogen and water tiny amounts of carbon dioxide.

What is AdBlue for Diesel engine?

AdBlue is liquid that helps to reduce emissions of nitrogen oxides, or NOx, from your car’s exhaust

As pollution is increasing day by day, government is taking various steps to curb it. Various steps like- moving to ZEV, Hybrid vehicles, Flex Fuel bases vehicles and recently moving to Hydrogen based cars. Well this step could be only option in last, but i hope in 2030, these will be completed. 

You must have listen Indian government has declared to Ban BS4 cars from April 2020. BS6 will be adopted by replacing BS4. And BS6 will be mandatory from April 2020. Now this- RDE norms will be added along with BS6
compliance from April 2023. So what are meaning of BS4 and BS6. Why it is important for car maker. What will be impact on automakers?

What are these BS4 and BS6 compliance?

These are emission norms regulated by Government of India. Mission of Bharat stage is to improve environment by reducing CO2, CO, Nitrogen oxides and Hydrocarbons.

Bharat Stage is based on EURO emission standard, which started in 2000. In 2023 Bharat Stage 6 is latest standard based upon EURO 6 standard.

Compared to the BS4 norms, BS6 norms have increased restrictions on the permissible pollutants emitted by petrol and diesel engines.

Before going direct to understand changes due to BS6 norms, let’s understand engine and its configuration.

What is Engine and its size?

Engine is mechanical device which produce power by burning fuels. Amount to power an engine can produce does depend on its size also on uses of turbochargers. Engine size means how much space the engine piston operates in. Bigger engine size number, more air and fuel each piston can push when they move, leading to more engine power.

Engine displacement refers engine capacity. IF an engine is described as 2.0 liter 4 cylinder engines it mean engine has an estimate capacity of 500cc in each of its cylinder.

What changes will be done in BS6 car?

  1. When we move BS4 to BS6 we have do major changes in engine configuration. Changes like- Change in engine displacement, changes in fuel injection and its amount, Changes in valve timing, Changes in Engine size, Addition of advance sensor and devices for emission monitoring and control.
  2. Installation of Selective Catalytic Reduction and Diesel Particulate Filter to monitor emission levels in BS6 vehicles. However, it was not present in the BS4 norms.
  3. Integration of a mandatory Onboard Diagnostic (OBD) that can inform vehicle owners/technicians how efficient different vehicle systems are.
  4. Electronic fuel injectors will be used in cars. This will replace old carburetors.
  5. Introduction of Real Driving Emission (RDE) Norms to measure real-world and real-time emissions of a vehicle in addition to only tested emissions.

Why need of RDE norms in India?

RDE norms will be implemented and effective from 1st April 2023. To understand RDE norms and its need, we have to first understand how emission testing is done of any vehicle. Currently emission testing is done in laboratory to comply BS6 standard. As a result, carmakers’ emission values generally differ greatly from real-world conditions. Government decided to develop a testing method that can measure emissions in actual driving conditions rather than labs. This
decision of RDE norms is to further reduce air pollutant from vehicle.

With effect from April 1st, 2023, RDE Norms will bind carmakers to test and measure pollutants emitted from their vehicles in a real-world driving scenario.

For this purpose, carmakers will be required to equip their vehicles with a Portable Emissions Measurement System (PEMS). So as per RDE norms all vehicles running on a diesel engine will be required to have Selective Catalytic Reduction (SCR) systems onboard.

When BS6 was started in India, larger diesel engine (more than 2.0 Ltr) has already upgraded SCR system. But small capacity diesel engine follows LNT system which allow vehicle to achieve lower pollution level.

What changes need to done in car under RDE norms?

  1. PEMS- Portable emission measurement system will be installed in car. All vehicles running on diesel engine required to have SCR- Selective catalytic reduction system. By using AdBlue, the Selective Catalytic Reduction systems will greatly reduce emissions of compounds such as nitrogen oxides (NOx) by converting pollutants into water, nitrogen and minute amounts of carbon dioxide
  2. Now as per new RDE norms vehicles will have onboard self diagnosis device to monitor emission level in real world driving scenario. This OBD device will check emission level in car and will display an alert to driver if emission level increased beyond the parameter of BS6 norms.
  3. Programmed fuel injectors will be equipped which will manage amount of fuel injection and its timing.
  4. Entire power train to be changed for 2.0 or more than 2.0 liter capacity engine which will be fully BS6 compliant. 
  5. Under new RDE norms, car makers have to use more sophisticated and expensive SCR system for all types of diesel engine cars. Due to which cost of vehicle will increased.

How PEMS works in car?

A Portable Emissions Measurement System (PEMS) is used to measure vehicle emissions on the road rather than in the laboratory. This methodology, soon to be included as part of the official test for new cars, is used by Emissions Analytics to build a detailed database of real-world emissions. Data from over 1000 real-world vehicle tests is available via subscription. See below picture for understanding:-

What is impact of RDE norms on Carmakers?

Now car makers have to change in their engine configuration to meet these norms. Car manufacturers have to change power train fully BS6 compliant. Due to which production costs will increased as well vehicle cost will be increased.

As explained above, what changes come in BS6 car, you see automobile car maker has to change a lot of thing n engine, which add additional cost in manufacturing.  To meet these changes car maker has to spend a lot of money.

For example if Maruti Suzuki, India’s largest car manufacturer needs to adopt BS6 compliant, then they need to change all diesel engines which could be most costly for them since they making a large volume cars. So they decided to discontinue all diesel cars in 2020.

But some car manufacturer like Honda, Hyundai, Tata and Mahindra continue to make diesel cars in India.  Soon after RDE norms they have decided to halt production of diesel car in their plants also.

So from April 2023, you may not be able to buy Honda City 5th generation, Hyundai i20 diesel, Verna, Toyota Innova Crysta, Skoda and Octavia cars, etc.


  • RDE norms are additional measures with BS6 norms to reduce more emission. 
  • It is second phase of BS6 compliance. 
  • RDE norms will be implemented in India from April-2023.
  • RDE norms will cover all diesel engine either it is small or large capacity engine.
  • Due to RDE norms cost of car manufacturing will be increased.
  • In RDE norms, electronic fuel injection (EFI) to be equipped in cars.
  • PEMS to be used with new model car for testing emission level in real world scenario. 
  • SCR will be used as per RDE norms.
  • In real world scenario, driver will get displayed alert if emission level increased beyond BS6 limit then user needs to service his car.