Volkswagen should be praised for modifying their engines on the fly to pass the EPA emissions tests. Their diesel powered cars met environmental regulations devised by the EPA when tested on a chassis dynamometer, an unrealistic test that’s not designed to simulate real world conditions.
The law generally requires these engines to pass EPA specified tests at the time of testing — and they do. This is, in most jurisdictions, simple, black letter law: there is literally no legal substance to the charge against them.
A chassis dynamometer puts rollers under the rear wheels and the car is started, put in gear and accelerated up to and down from various speeds. The test is very flawed because the engine is not powering the car while it’s stationary on the chassis dyno. When the car is on the road it needs far more fuel to generate enough power to make the car go. That means when it’s on the dyno it doesn’t need power so the clever engineers at VW controlled the fuel to use only what was required to run the dyno, ergo, less fuel used, fewer emissions, test passed.
It’s the equivalent of studying before a final exam in math. No need to read the history and physics books, just concentrate on passing the math test or in this case the emissions test.
VW’s software senses the testing environment by analyzing a variety of data such as steering position, speed, duration of engine operation and barometric pressure, and then adjusts engine performance and emissions to pass the test. All cars adjust engine performance by providing only enough fuel to get the job done but no more. No car adds too much fuel and that’s all VW did during the testing. For example it the car isn’t being steered it doesn’t need fuel to pressurize the power steering pump. VW simply controlled the amount of fuel going into the engine.
The affected cars include the 2009 to 2015 Volkswagen Jetta TDI, 2009 to 2014 Volkswagen Jetta SportWagen TDI, 2012 to 2015 Volkswagen Beetle TDI, 2013 to 2015 Volkswagen Beetle convertible TDI, 2010 to 2015 Audi A3 TDI, 2010 to 2015 Volkswagen Golf TDI, 2012 to 2015 Volkswagen Passat TDI and 2015 Volkswagen Golf SportWagen TDI.
Additionally, Volkswagen suspended sales of all new and used 2.0-liter TDI four-cylinder diesel engines, including in the 2015 Beetle, Jetta, Golf and Passat TDI, as well as the Audi A3 TDI. Sales of VW’s 2016, four-cylinder diesel models are held up as they await EPA certification.
The cars will still pass emission requirements but they will be forced to use more fuel to do it which is what the EPA inadvertently causes all cars to do.