To borrow an idea from the late legendary cartoonist Walt Kelly and his beloved possum Pogo, Friday the 13th came on a Wednesday for Volkswagen this month. Jan. 13, 2016, was the day when Volkswagen CEO Matthias Müller was planning to reveal the car maker's plans to fix its diesel emissions problem to U.S. Environmental Protection Agency Administrator Gina McCarthy. Apparently, the plan didn't pass muster because Müller left after an hour without saying anything.
Volkswagen's problems actually began nearly 10 years ago when engineers figured out that they could install a routine into the engine control computer that was able to discern when the car was undergoing an emissions test. When it detected such a test, the computer modified the control program so that the car would pass the test, but as researchers discovered, that routine only worked when the test was under way.
This meant that during routine driving, Volkswagen diesels put out more emissions than were allowed. Exactly how bad those emissions were depended on how the car was being driven, and on the type of emissions control system installed. Some older diesels emitted nearly 40 times the level of nitrogen oxide than was allowed.
The "cheat device" software (as the EPA calls it) figured out when the car was being tested by watching the relative speeds of the front and rear wheels. When the front wheels were turning but the rear wheels weren't (which is what happens during a dynamometer test used for emissions testing), then the control computer knew that a test was going on.
The obvious question then becomes, if the control computer can make the car clean enough sometimes, why can't it do it all the time? Depending on the type of emissions control system that's installed in the car, that might work, but for older Volkswagen cars, it won't. Apparently to make those cars clean enough, the engines won't perform adequately for real-world use. Some newer cars, however, may be able to be fixed with a software change.
Newer Volkswagens use a catalytic converter along with urea injection to reduce NOx (oxides of nitrogen) emissions to acceptable levels. Apparently, the biggest problem with this solution is that it uses more urea than the engines do now, which would cost Volkswagen a lot of money, but the company's V6 engines and more recent four-cylinder, 2.0-liter engines can apparently use this approach. Then the only problem becomes the um … aroma. My experience is that at idle a VW diesel using urea smells like being downwind from a porta-potty that's a week overdue for cleaning.
Increasing the amount and frequency of urea injection for newer diesel engines can apparently be accomplished with a software fix, but older Volkswagens don't use urea injection. Worse, they don't have the required catalytic converter, nor do they have the plumbing necessary for urea injection. While it may be theoretically possible to adjust the older diesel engines with revised software, apparently fuel mileage would plummet and the diesel's previously strong performance would vanish.