The findings of the study that has become so popular today would have not turned many heads, if the baseline certification emissions were not measured by California Air Resources Board (CARB).
01 Oct 2015 | 4386 Views | By Arvind Thiruvengadam
The study started as a routine academic project aimed at studying the effect of real-world driving conditions on the emissions performance of modern diesel passenger cars in the US. The study was specifically aimed at testing the vehicles in the state of California, which is characterised by unique driving conditions ...
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The study started as a routine academic project aimed at studying the effect of real-world driving conditions on the emissions performance of modern diesel passenger cars in the US. The study was specifically aimed at testing the vehicles in the state of California, which is characterised by unique driving conditions and traffic pattern. What resulted from the project was completely a chance.
The findings of the study that has become so popular today would have not turned many heads, if the baseline certification emissions were not measured by California Air Resources Board (CARB). This is a classic case of a regulatory body participating in an academic research to unearth interesting trends in real-world emissions. Often, projects such as this are performed under a small budget, and contribution of resources from government organisations such as CARB improves the value of the findings.
The 'defeat device' in this case was an engine control unit (ECU) algorithm that detects the vehicle is being tested for emissions certification. This algorithm sets the vehicle to perform the best in emissions control to achieve the stringent United States Environmental Protection Agency (USEPA) and CARB standards.
The motive behind the 'defeat device' itself is not known, as it is something only the manufacturer can answer. West Virginia University Centre for Alternative Fuels Engines and Emissions' (WVU CAFEE) research directly did not discover the 'defeat device' algorithm. This is not possible with a limited dataset available. However, the data collected by CAFEE created the curiosity amongst regulators that something that they were not aware of could be at play.
The three vehicles tested in the study were a VW Jetta, VW Passat and BMW X5, all of model year 2012. The vehicles were recruited based on technology and not any manufacturer. The study was aimed at evaluating a lean NOx trap and a selective catalytic reduction (SCR). From the findings, the VW Passat threw the biggest red flag. Being experienced in modern diesel engine technology as researchers, we were expecting extremely low emissions from the SCR technology. Although, the SCR technology faces certain limitations under low engine load operation, conditions such as extended freeway driving should produce near-zero emissions. However, this was not the case. Moreover, we collected the most comprehensive set of data on the Passat over a 2,500-mile journey between Los Angeles and Seattle. This extensive data set covered every possible driving condition. The third vehicle tested in the study (BMW X5) produced low emissions both in real-world and in certification tests.
Modern engine controls are so sophisticated that it is incredibly difficult to discern differences in vehicle performance between alternate strategies (in this case an emissions certification strategy). Manufacturers often work with multiple constraints to meet both emissions standards and delivering the much sought after performance and fuel economy of the customers. For a mechanical engineer, these are interesting challenges in engine design. Sophisticated controls and algorithms also provide pathways to conceal certain processes to gain the system. Such controls could not be detected without extensive real-world testing and evaluation. However, such testing would increase the cost and time for certification. Therefore, providing a regulatory challenge.
A popular question that has come up recently is that “what will happen to the cars post recall and the fix?”. That question is very difficult to be answered because the motive behind the 'defeat device' is not known. Popular theories are fuel economy; however, there could be far greater underlying reasons. SCR technology requires urea injection (an added consumable to customer) to control NOx emissions. The conservation of urea to prevent frequent fill-ups by customers could also be a possible reasoning. Durability of engine components could be another. But, in my opinion, manufacturers have the ability to meet both emissions standards and fuel economy. The path to achieving those goals could mean more expense, but it is not an engineering impossibility.
On a separate note, regulators in India need to address their vehicular pollution with aggressive standards and robust testing methods. Diesel car technologies sold in India are significantly old and only regulations can drive the inception of advanced technology in Indian cars. The cost of vehicles will surely increase but that is the cost, as a car owner, one has to pay to contribute to a cleaner environment.
(Arvind Thiruvengadam , the author of this article, is Research Assistant Professor, Center for Alternative Fuels, Engines and Emissions Mechanical and Aerospace Department, West Virginia University. He carried out the real-world emissions testing at WVU).
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