Test The Limits

Will Car Makers Fail The WLTP Emissions Test?

By Steve Remondi

March 04 2015

Emission regulations are changing in a way that is going to have huge impact on car manufacturers. The Worldwide harmonized Light vehicle Test Procedures (WLTP) are scheduled to replace the current New European Drive Cycle in 2017. The procedures will be implemented in most of the world including Europe, Japan, India, South Korea, Russia, and China.

The implementation of the WLTP was due to the consumer pressures to ensure the reporting fuel economy and CO2 emissions values reflecting the real car performance. Recent report by Transport & Environment in Europe found that in average the gap between real-world consumption and car makers’ claims has widened from 8% in 2001 to staggering 31% in 2011 for private motorists. The additional fuel burned compared to official test results costs typical driver a €500 a year.

The goal of WLTP is to represent more realistically how the cars are being driven today. For example, the average vehicle driving speed in NEDS is 43 km/h while in WLTP is a much more realistic 54 km/h. This difference causes doubling the impact of aerodynamics on vehicle fuel economy. The implementation of WLTP will generate major challenges to the car industry that will require significant investments into engineering solutions and a lot of hard work.

Significant aerodynamics improvements will be needed to fulfill the new regulations.

Wind tunnels will continue to play a significant role in car development. After all, 30 years of investment and relative data on different car designs gives engineers confidence. But, in the field of aerodynamics, wind tunnels have their limitations. They lack flexibility and don’t tell you why problems are occurring, and offer no solutions for remedy. Until now, wind tunnel tests have generated results good enough for regulatory demands and marketing purposes – but that’s changing quickly. In addition, wind tunnels are only an approximation to the real world conditions.

It’s Exa’s belief that achieving a sub-0.30 drag coefficient is almost impossible using wind tunnels alone. Both Jaguar and Tesla recently achieved breakthrough drag numbers exclusively through simulation, 0.26 and 0.24 respectively. The current “holy grail” of aerodynamics is a drag coefficient of 0.20. This value is achievable, however it will require the use of sophisticated optimization methodologies used jointly with simulations.

More manufacturers are starting to discover the important role simulation can play in generating breakthroughs in aerodynamic design and engineering. It’ll be a tough learning curve but with careful attention to aero, WLTP has a real potential to warm up currently frosty relations between customers and car makers when it comes to fuel economy. Attractively designed new cars that don’t come with an unexpected financial penalty at the fuel pumps are good news for everyone.