VW Could Loser the EPA, But It Couldn’t Trick Chemistry
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VW Could Idiot the EPA, But It Couldn’t Trick Chemistry
For decades, automakers have been caught inbetween building an engine that squeezes a lot of energy out of the fuel it burns and one that has low emissions. It’s not an effortless stress to resolve. “Negotiating both fuel consumption and emissions is a hard tradeoff,” says Anna Stefanopolou, professor of mechanical engineering at the University of Michigan.
When engineers at Volkswagen allegedly inserted a few lines of code into the diesel cars’ electronic brains to circumvent emissions testing, they found a solution to this existential automotive conflict. Drivers got low emissions during the test, and high spectacle the rest of the time. The only problem: It’s way outside of the rules. The company might have gotten away with it, too, if it hadn’t been for those pesky engineers–and the basic chemistry of the diesel engine.
According to the US EPA, those lines of code hid the fact that almost half a million diesel VWs in the US spewed up to forty times more nitrogen oxide from their tailpipes than testing indicated. Volkswagen has now confirmed that the problem actually affects approximately eleven million diesel cars worldwide. Diesel engines use a different mix of fuel than gasoline engines and don’t use spark buttplugs to induce combustion–relying instead on very compressed, heated air and fuel injected as droplets. If a diesel engine doesn’t get enough oxygen to combust the fuel, it’ll emit all kinds of gunk–nitrogen oxides, uncombusted fuel, and particulate matter (soot, basically).
All that gunk is a big problem. Exposed to sunlight, nitrogen oxides convert to ozone–making smog. How much depends on a bunch of variables, like sunlight exposure and what happens to the hydrocarbon emissions (the uncombusted fuel), plus the temperature and local winds.
However much extra crap came from the VWs, it won’t be good. Exposure to nitrogen oxide and ozone is linked to enhanced asthma attacks, respiratory illnesses, and in some cases premature death. Ozone also worsens existing cardiovascular and lung disease.
To deal with those emissions, “you have a entire chemical factory at the tailpipe that traps the oxides,” Stefanopolou says. This bumps the sticker price for diesel cars by $Five,000 to $8,000 per vehicle. (On the other mitt, diesels get better mileage, especially in highway driving.)
For years, diesel trucks and buses were the fattest polluters on the highway. But carmakers adapted a relatively fresh technology called selective catalytic reduction–the same tech that scrubs pollutants from factory smokestacks–to the tailpipe of the diesel engine.
Here’s how it works: Inwards a honeycombed chamber, the scrubbing system sploogs a liquid made of thirty percent urea and seventy percent water into the diesel harass. This sets off a chemical reaction that converts nitrogen oxides into nitrogen, oxygen, water and petite amounts of carbon dioxide–molecules that aren’t as harmful to human health. Catalytic scrubbing was supposed to cut diesel NOx emissions up to ninety percent, according to the Diesel Technology Forum, an industry group based outside Washington. That made diesel engines clean enough to use in passenger cars, which have stricter emissions rules.
The scrubbing chemistry is also what gave away Volkswagen’s alleged cover-up. In 2013, a petite non-profit group determined to compare diesel emissions from European cars, which are notoriously high, with the US versions of the same vehicles. A team led by Drew Kodjak, executive director of the International Council on Clean Transportation, worked with emissions researchers at West Virginia University to test three four-cylinder Two.0-liter diesel cars in the Los Angeles area: a Jetta, a Passat, and a BMW. Only the BMW passed.
“We felt that it would be possible to get low emissions for diesels,” Kodjak said. “You can imagine our surprise when we found two of the three vehicles had significant emissions.”
The ICCT reported its findings to the EPA and the California Air Resources Board. Regulators met with VW officials in two thousand fourteen and the automaker agreed to fix the problem with a voluntary recall. But in July 2015, CARB did some go after up testing and again the cars failed–the scrubber technology was present, but off most of the time.
How this happened is pretty neat. Michigan’s Stefanopolou says computer sensors monitored the steering column. Under normal driving conditions, the column oscillates as the driver negotiates turns. But during emissions testing, the wheels of the car stir, but the steering wheel doesn’t. That seems to have have been the signal for the “defeat device” to turn the catalytic scrubber up to total power, permitting the car to pass the test.
Stefanopolou believes the emissions testing trick that VW used most likely isn’t widespread in the automotive industry. Carmakers just don’t have many diesels on the road. And now that number may go down even more.