w3s3 legislation

8/17/2019 W3S3 Legislation

1/6

© IFPEN / IFP School 2014

Sustainable MobilityTechnical and environmental challenges for the automotive sector

Week 3 – Session 3 – Legislation

Maria Thirouard


2/6

W3 – S3 – Legislation p. 1


In previous lessons we’ve looked at the different components of an engine and so now we have a

better understanding of how an engine works. We’ve also seen the global efficiency of an engine,

energy distribution, and how efficiency equals CO2 emissions.

LegislationIn this lesson we will discuss regulations regarding pollutant emissions.

As you know, legislation concerning a car’s pollutant emissions is implemented all over the world in

order to limit pollution. This means that car manufacturers need to comply with these regulations

to be allowed to sell their cars. But, how does it all work?

Well, legislation is a procedure that explains how to measure pollutant emissions during a particular

test. These measurements need to be done under very specific conditions.


3/6



Driving CyclesOne important parameter specified in the legislation is what we call the driving cycle. A driving

cycle is a graph of vehicle speed versus time that needs to be followed by the car during the test.

The driving cycle is supposed to represent the typical driving conditions of a car in a given place.

Driving cycles are produced by different countries to assess the performance of vehicles in terms offuel consumption and pollutant emissions.

Here you can see the New European Driving Cycle or NEDC. The NEDC cycle consists of 4 repeated

urban driving cycles, or UDCs, and one Extra-Urban driving cycle or EUDC. You can notice that the

cycle uses very steady acceleration and deceleration phases, which represent a soft driving style.

In this graph you can see the driving cycle used in the US. It is called the Federal Test Procedure or

FTP. This cycle represents a more “aggressive” driving behavior than the NEDC cycle. But not all the

driving conditions are represented in this driving cycle.

In addition to this, other driving cycles were added to better represent driving conditions on the

highway, high speed and high acceleration driving style, and the impact of the use of air

conditioning on emissions.


4/6



The driving cycle is tested in a test cell specifically designed and approved to do car testing. Theexhaust gases are collected and regulated pollutants are measured. The measurements given by

this test are: fuel consumption, CO2 emissions, HC, CO, NOx and particulate emissions. At the end,

we divide the mass of the measured pollutants by the distance traveled by the car during the test

to get the emissions in g/km. In order for the car to be validated, the emissions need to be lower

than the limitation set in the legislation.

So, when you see the value of fuel consumption or of CO2 emissions in the technical information

given for a car, this value represents the fuel consumption during the driving cycle test of the

country. In our example, this is the NEDC cycle.

You will not however see in this technical information the pollutant emission values. This is

because, if the car has been validated, the pollutant emissions are necessarily within the limitations

of the current legislation.


5/6



This is the general procedure. As I’ve said before, the advantage of having a standardized driving

cycle is that the measurements are robust and can be easily compared from one vehicle to another.

This is very important since there is always an error when doing measurements. Besides, since

limits are continuously being reduced, measurements need to be continuously improved. In that

way we can limit error and guarantee repeatability.

However, the cost of having a repeatable and comparable procedure is that it does not accurately

reflect the reality. Since car manufacturers are obliged to comply with emission legislation, all

engine parameters are optimized in the operating conditions of the driving cycle. This means thatwhen we get outside of these operating conditions, engines are not developed to limit pollutant

emissions. And the truth is that, depending on the driving situation, we might be outside of the

driving cycle operating conditions a great deal of time.

Another problem is that different driving cycles and different legislation can provide different fuel

consumption and emission values for the same car. Seeing as driving cycles don’t represent real-life

driving, it is quite difficult to obtain those fuel consumption values once you drive the car in normal

conditions.

However, you can always count on the fuel consumption value of a standardized driving cycle to

identify a model that will generally consume less fuel.


6/6



For all these reasons, a Worldwide harmonized Light vehicles Test Procedure is currently being

developed. This procedure defines a globally harmonized standard for determining the level of

pollutants and CO2 emissions from light-duty vehicles. Development is being led by experts from

the European Union, Japan and India. The US was originally in the group but they withdrew in June

2010. As you can imagine, it’s a very difficult task, but we hope that their hard work will result in a

more representative driving cycle in future years.

Summary

From what we’ve seen so far, we can deduce that engine conception is a complex task for engineers

nowadays. Indeed, such a process requires continuous research and innovation, taking into account

the client’s needs in terms of performance, power and torque, and the client’s comfort - so noise

level, for example, must be acceptable. And herein lies the real difficulty: all this needs to be done

without forgetting about CO2 and pollutant emissions, and of course, keeping everything at a

convenient price depending on the car market segment.

As you can imagine, complying with emission legislation is a key issue in an engine’s development.

w3s3 legislation

Documents