The Definitive Car Owners Guide to Emission Testing and What It All Means

All vehicles that are sold in the United States and many other countries have to have a certification of emission testing to confirm that the car or truck meets federal emission standards.

There is also the issue of fuel economy standards that you need to consider and part of the testing process involves ensuring that the manufacturer’s claims regarding fuel economy figures are accurate.

If you want more online information about emission testing you might want to go to, meanwhile, here is a look at the key points of emission testing and how it impacts you as a motorist.

Satisfying air quality standards

The primary purpose of vehicle emission testing is to ensure that the exhaust emissions coming from the rear of your car are in compliance with defined air quality standards.

The test involves checking for the potential presence of a variety of pollutants, with the main culprits being CO2, NOx, and various particulates, otherwise described as the microscopic particles that are produced by diesel engines.

As you might imagine, standards have evolved since the first testing began and, predictably, in view of the growing awareness of the impact of poor air quality caused by emissions, these tests have become stricter with each new set of standards introduced.

Who tests the vehicles?

You might be surprised, or alarmed to discover that the testing to ensure that vehicles are compliant with current emissions standards is left in the hands of the car manufacturers themselves.

The scandal that shocked the motoring industry when VW was discovered to have been “adjusting” the test results definitely created a sense of alarm but that watershed moment also managed to ensure that government bodies became more rigorous in their checking procedures.

Government agencies are given access to the production line and as a way of trying to be sure that no subsequent vehicles make it onto the road when they are not compliant with emissions standards, a random selection process is in operation.

The government agency will select test cars randomly and then subject them to their own testing to see if the results are the same.

There is also the issue of consistency across different models and to address this problem a record system is in place where each vehicle’s tire pressures fluid levels are recorded. The air temperature in the designated test area is also recorded for consistency and accuracy.

Carrying out the test

When a new vehicle has been selected for emission testing and has been taken to the designated testing area it is placed on a rolling road.

This rolling road is designed to simulate the experience of driving the vehicle on a road but allows the tester to check all of the vehicle’s responses in a controlled laboratory environment.

The test involves a series of predetermined tests that allow the testing equipment to measure emissions readings collected by gas analyzers that have been put into the vehicle’s exhaust system beforehand.

The same test is applied to all makes and models of car there is no distinction or exceptions made for vehicles that have larger engines, different gearbox configurations, or larger than normal wheel sizes.

A new testing environment

The impact of that VW testing scandal has been fully felt across the worldwide automotive industry and there were already calls to toughen up the testing process before the so-called dieselgate scandal created what can be described as a “line in the sand” moment that changed attitudes and heralded the introduction of much tougher testing procedures.

What we now have in place is the Worldwide harmonized Light vehicle Test Procedure, otherwise known by its acronym as WLTP.

Is WLTP more accurate?

The key question is whether WLTP has managed to fix the problems of the past and created a testing system that provides an accurate reflection of the carmakers’ emission figures.

If you were to compare the old with the new it would be fair to say that the testing environment doesn’t look fundamentally different as the test is still carried out on a rolling road.

However, what happens on that rolling road is definitely different.

The new test cycle includes running the vehicle at higher speeds and subjecting the car to much more dynamic levels of acceleration and deceleration. Combined with a stricter vehicle setup procedure and more stringent measurement conditions the conclusion can be reached that WLTP is more accurate than its predecessors.

Still room for improvement

Although great strides have been made in improving emission testing standards there are still gaps that need to be filled in order to be totally satisfied that the way emissions are measured is completely accurate.

This is one good reason why the Real Driving Emissions test has also been introduced in some regions.

This testing takes place outside of the laboratory and measures the vehicle’s output on a public highway instead.

The same rules apply, in that the vehicle is taken off the production line at random, before being subjected to a series of tests that the car would have to perform when it is being driven by you if it was your own vehicle.

This means driving the car at different speeds and while being subjected to varied payloads, for instance.

Measure exhaust fumes

A key aspect of the testing process is to measure exhaust emissions and the test involves using a Portable Emissions Measuring System (PEMS)to analyze the exhaust gases.

What about MPG?

Finally, one of the key figures you probably look for when buying a car is how good the fuel economy is.

Vehicles are also tested to verify if the manufacturer’s MPG claims can be substantiated.

A dynamometer is used to simulate driving conditions and the test subjects the vehicle to different wind speeds and payloads in order to see how it performs.

Knowing more about the emissions testing process and how it works should give you a bit more confidence that the interests and safety of the public are at heart when it comes to testing air quality and identifying potential sources of pollution.

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