Why did Volkswagen need to cheat U.S. government emission rules with its four-cylinder diesels?
At the heart of the diesel push was VW's desire to boost its lackluster sales in the U.S. with a unique selling proposition and at the same time expand the market for what is still a very European-centric technology. The trouble was the engines proved expensive to keep clean.
In 2009 VW was touting the cleanliness of a new family of 2.0-liter engines. It bragged that the first model to be sold, the Jetta BlueTDI was "one of the cleanest and most economicalcars of its class in the world."
VW proudly claimed it had modified the European engine with a different combustion system and a so-called lean NOx trap, or LNT, exhaust after-treatment to meet far tougher emissions targets than in Europe.
"Implemented together, these measures reduce nitrogen oxide emissions by 90 percent," VW said in a 2008 statement.
In the same statement, Jens Hadler, then director of VW's powertrain development, said: "I think this motor will help the diesel get its big break in America."
The trouble is, the cleanliness of VW's four-cylinder diesels was an illusion. It took the International Council on Clean Transportation working with West Virginia University on a study carried out last year to discover that a diesel Jetta with the LNT was emitting up to 35 times the EPA's required limit on NOx, and a Passat fitted with a urea-based selective catalytic reduction, or SCR, system was emitting up to 20 times the limit. Threatened with a stop on its car sales, VW admitted that it had been using an illegal "defeat device" that understood when the car was being tested in laboratory conditions and activated an ultraclean mode.