Video: Consumer Reports Shows Efficiency Drop For VW Dieselgate Cars When in ‘Cheat Mode’

It’s now been nearly a month since the initial news broke that Volkswagen AG had purposely programmed certain diesel-engined cars with ‘cheat devices’ designed to ensure that they met tough EPA emissions targets when tested on a dynamometer but then ignored all emissions targets when on the road.

The now ironic advert for the Volkswagen Jetta, some of which have the emissions-cheating engine in them.

The Dark Side? The now ironic advert for the Volkswagen Jetta, some of which have emissions-cheating diesel engines in them.

In the intervening time, we’ve seen a great deal of focus on Volkswagen’s board, many of whom have now lost their jobs as a consequence of the scandal, as well as a full-scale congressional inquiry into the admitted malpractice in the U.S. As we detailed last week, a total of 11 million cars are now believed to be affected worldwide, some 430,000 of which are in the U.S.

As we detailed last week, Volkswagen plans to refit the engines of non-complaint cars with the necessary software (and hardware for older models) to bring those cars in compliance with EPA regulations. During a tense interrogation at the hands of a U.S. House ENergy and Commerce investigations subcommittee on Capitol Hill last week, U.S. Boss Michael Horn even admitted the illegal engine software appeared to have been coded by someone at Volkswagen in order to preserve performance and economy.

We, like many other news outlets, have wondered just how much performance and economy would have suffered if cars had been built by Volkswagen to comply with emissions tests at all times. Now, thanks to the clever folks at Consumer Reports, we don’t have to wonder any more.

Consumer Reports was able to force two Diesel cars into Cheat Mode.

Consumer Reports was able to force two Diesel cars into Cheat Mode.

At the heart of the scandal is software which detects if a car is being driven on a dynamometer in a testing laboratory or being driven on the road. Illegal in every way, it turns on all necessary emissions controls systems and ensures fuel ratio mixes are set so that tailpipe emissions meet the required standards. When the car detects that it is not on a dynamometer (namely when all four wheels are moving instead of just two) it defaults to a non-compliant ‘road’ mode in which emissions are more than 40 times the legal limit but where power and fuel economy are improved as a result.

All Consumer Reports needed to do, was to figure out how to do the reverse: convince the car’s on-board control system that it was being driven in a laboratory when in fact it was being driven on a road — and then record the results.

One of the few outlets with the technical skills and equipment to pull this particular stunt off, Consumer Reports‘ in-house engineers did just that, figuring out that by turning off traction control and disconnecting the rear-wheel rotation sensors of both cars was enough to convince them that they were being tested in a lab, thus turning the ‘cheat mode’, emissions-compliant engine management profile on.

The first car, a 2011 Volkswagen Jetta Sportwagen with the affected EA189 engine in it and no urea injection system — one of the models affected by the recall — demonstrated a 0.6 second increase in its 0-60 mph time with the ‘cheat mode’ software ensuring an EPA-compliant exhaust emission. Similarly, fuel economy on a highway test fell from the 50 mpg that Consumer Reports had previously tested with non-compliant, over-limit emissions to 46 mpg.

Consumer Reports shows that fuel economy and performance drop when emissions are within compliance.

Consumer Reports shows that fuel economy and performance drop when emissions are within compliance.

The second car, a 2014 Volkswagen Jetta Sedan with a built-in AdBlue urea injection system, demonstrated a smaller, 0.1-second drop in acceleration time, and a 3mpg drop in fuel economy from 53 mpg to 50 mpg.

That might not seem like much of a difference on paper, but as Consumer Reports explains in the video above, those few miles per gallon were what Volkswagen used to give itself an apparent advantage over the competition. In a market where diesel cars are considered a niche-market product, Volkswagen presumably felt it needed the edge those extra few miles per gallon gave it — consequences be damned.

Like Consumer Reports, we’d suggest nobody carries out the modifications the consumer magazine did to their cars in order to conduct these tests — but with Volkswagen promising a costly fix to bring affected cars into compliance, Consumer Reports says it will test Volkswagen’s official fix and campaign for restitution for owners if power or efficiency are impacted.


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