Consumer Reports Activates "Defeat Device" while Driving VW Jetta TDI, Fuel Efficiency Drops

Consumer Reports Activates "Defeat Device" on 2015 and 2011 Jetta TDI, Tests Fuel Economy 1 photo
Photo: screenshot from Youtube
Dieselgate sounds like a major case of industrial espionage or political scandal, but it's a very real problem that could impact the way we drive in coming years. Volkswagen has fitted millions of TDI turbocharged diesel engines with so-called "defeat devices" that artificially lower NOx emissions when the cars are being tested.
CEOs and other bosses have been endlessly apologizing for deceiving buyers. Meanwhile, governments and buyer groups have been thinking of ways to sue VW. Still, some say they love their TDI engines but are concerned about the upcoming recalls affecting performance in any way.

Consumer Reports could answer some of these questions in the video below. They think they've activated the cheat mode on a 2015 Jetta sedan and a 2011 Jetta wagon. How? First, the accelerator pedal needs to be pressed five times in a row. Next, the rear wheel sensor needs to be deactivated to fool the car into thinking it's on a test bench.

Unfortunately, the consumer goods reviewers didn't have a rolling NOx testing device, but they were able to measure fuel consumption by attaching a device to the injection system.

According to these tests, performance will be affected. On the 2011 Jetta, the 0 to 60mph sprint time goes from 9.9 seconds in normal mode to 10.5 seconds with the NOx-reducing cheat. On the newer model, the numbers relatively unchanged, so 2015 Jetta and Golf owners have nothing to worry about.

Contrary to what you might think, the defeat device increases fuel consumption while active, even though NOx emissions go down – from 53 mpg highway to 50 mpg on the 2015 model and from 50 down to just 46 mpg highway in the case of the 2011 car.

That's news for the people who bought a TDI Clean Diesel engine because it offers economy numbers similar to a hybrid, if not better. It might also affect the re-sale value of current models. Future Volkswagen TDI models (if they will even exist in America) may not stand out in a market filled with adequate Toyotas and Hondas.

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About the author: Mihnea Radu
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Mihnea's favorite cars have already been built, the so-called modern classics from the '80s and '90s. He also loves local car culture from all over the world, so don't be surprised to see him getting excited about weird Japanese imports, low-rider VWs out of Germany, replicas from Russia or LS swaps down in Florida.
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