New WLTP testing standard

On the Road

More detailed, more realistic, more transparent: the WLTP testing standard for emissions and fuel consumption for automobiles is now compulsory in many countries as of September 2017. But what exactly takes place during these improved tests? Pascal Mast, head of TÜV SÜD’s Emissions and Fuel Economy Testing,
gave us the lowdown.

Illustration Axel Pfaender

1 Fasten Your Seatbelt
When an automaker wants approval for a new type of passenger car, they come to us for emissions and fuel economy testing. First, the roll resistance of the vehicle is determined—which usually takes place on a runway of a decommissioned airport. The driver accelerates the vehicle for three kilometers, then releases the gas pedal, letting the car roll until it comes to a stop, at which point the distance is measured. The roll resistance is an important value for our laboratory calculations.

2 On your marks, Get Set, Go!

In the lab, the vehicle is tested twice: first at 23 degrees Celsius, which has always been the case. What’s new is that we’re now doing testing at ambient temperatures of 14 degrees Celsius. That’s because fuel consumption varies with temperature. The colder it is outside, the higher the fuel consumption, since it takes longer for the motor to warm up. We test both a fully-equipped vehicle and a bare-bones model on the test rollers at both temperatures. Urban driving, cross-country trips and highway journeys are simulated over the course of 30 minutes. The values determined in the laboratory testing will appear later on the vehicle registration document.

3Sweating it Out 

The evaporative emissions measurements take place in an enclosed test chamber, which resembles a one-car garage in layout and size. Here we measure how much oil and fuel evaporate when the vehicle is at rest. What’s important is that the car’s engine be warmed up before the vehicle disappears into the chamber for 48 hours.

4 Out in the Wild

What’s new—and more—the WLTP standard is the testing outside the laboratory. The vehicle is driven for two hours under real-life conditions in what is known as the Real Driving Emissions Test: through the city, across the countryside and on the highways. For data collection, mobile measuring technology is mounted onto the vehicle’s trailer hitch. The RDE Test gets emissions and fuel consumption figures that are very close to the car’s real-world performance, and these values may not exceed the laboratory values by more than 2.1 times.

5 Start Your Engine!

If—and only if—all of these values are okay can a vehicle be approved. As part of the TÜV SÜD process, we send a technical report to the responsible authorities. However, if the values from the RDE Tests too greatly exceed those of the lab testing, the vehicle model cannot be approved and the manufacturer must do follow-up work on the car.