Screenshot 2015-09-22 at 16.26.27

Emissions reporting problem larger than just Volkswagen, affects gasoline cars too

According to a study published last week by Transport & Environment, the scandal over Volkswagen’s cheating on emissions testing is a tiny part in a huge problem.  T&E is a Europe-focused research group working on environmental issues related to transportation.  Their study, Don’t Breathe Here, performed independent testing of a large number of cars and found the overwhelming majority (9 out of 10 cars tested) failed to meet emissions standards while driving on the road.  The standard in question, Euro 6, went into effect on September 1, 2015.

The study doesn’t list the tested vehicles and their actual real world driving conditions emissions.   Instead it focuses on the methodological problems with the NEDC testing system.   The result is the same result as we see with Volkswagen’s TDI Diesels.  That the cars pass emissions tests in the laboratory, but when tested on the road the emissions are way above the legal limit.

It’s not just diesel vehicles that have this problem, in Europe, but the gasoline powered ones as well.

UPDATE Sept 28, 2015 – BMW responded to the report outlined below saying their cars do not have this problem.

In the Volkswagen case, the EPA and CARB have found that VW/Audi 2.0 liter TDI Diesel cars were designed to detect an emissions test.  When undergoing an emissions test the engine configures its emissions control equipment to give great results, and in normal driving the engine turns off that equipment.  That means for normal use these cars from VW and Audi pollute way beyond the legal limit, when they’re touted as ultra clean vehicles.  Since that revelation VW’s stock price has nose-dived, as the company is facing litigation and investigations around the world.

The study says U.S. vehicles are cleaner, because reported emissions results of cars sold in America are cleaner than those sold in Europe.  Therefore, according to the study, the technology is right there on the shelf ready to use on cars sold in Europe.  Given the revelation that Volkswagen has cheated in its reported emissions results, we might take that with a grain of salt, eh?

According to T&E

The reason for the continuing high emissions from new cars is an ineffective system for testing vehicles that deliver impressive reductions of emissions in laboratory tests but fail to replicate this performance when driven on the road. This problem is extensive for diesel cars and vans that typically emit on average around five times more pollution than permissible limits when driven on the road. But gasoline cars are not exempt – one in five modern petrol cars reportedly fail to achieve emissions limits on the road. Laboratory tests are unrepresentative because the current EU test cycle (New European Drive Cycle, NEDC) is too slow and has insufficient acceleration. The test procedure contains loopholes the manufacturers exploit to get low results. Emissions are only optimised for the tested conditions and there is substantial anecdotal evidence that cars detect when they are tested and deploy “cycle beating” techniques to reduce emissions.

The Euro 6 regulation requiring “real world testing” was adopted in 2007, but the actual test procedure has not been finalized.

The T&E report points at technology that’s available and known to work, but isn’t being used in cars sold in Europe:

  • The diesel particulate filter and gasoline particulate filter both reduce particulates in the emissions.  These are simple, cheap and effective.
  • Selective catalytic reduction reduces diesel NOx emissions in combination with other after-treatment systems.  The downside of SCR systems is a urea tank that must be refilled from time to time.  To limit that impact car makers often configure the SCR to under-utilize urea and therefore emit more pollution than necessary.
  • Engine management:  Diesel NOx emissions can be significantly reduced by by timing the fuel injection, with late injection reducing NOx at the cost of fuel efficiency.
  • A Lean NOx Trap is a catalytic converter that’s triggered when the engine is idling, capturing NOx.  These require occasional flushing with unburnt fuel when the adsorber is filled with NO2.
Source: Transport & Energy

Source: Transport & Energy

But it’s not just the technology which is the problem, it’s that the NEDC test cycle does not properly stress engines.  The two blue dotted lines show the minimum and maximum possible torque values, and the grey dots show all the actual torque output values for a specific engine.  The red dots show the subset of engine performance hit by the NEDC test cycle.

Vehicle manufacturers are, according to the NEDC study, optimizing their engines for the spots hit by the NEDC test at the detriment to emissions performance in other non-tested performance levels.

Specifically, the T&E report gives these reasons why a car can pass the test but still poison the air:

  • The NEDC test cycle itself is not representative of real-life driving profiles;
  • Test conditions are optimised by the manufacturer to achieve the lowest possible test results that are not replicated on the road. This includes exploiting flexibilities and loopholes in the protocols that govern the testing process in the laboratory and the preceding;
  • Off-cycle parts of the engine map are not optimised for air pollution emissions reduction, leading to emissions.
  • On-cycle parts of the engine map are optimised for emissions reduction in a way unrepresentative of that achieved in normal driving. This includes “cycle beating” techniques that detect when the vehicle is being tested;
  • Some aftertreatment devices only work when they have properly warmed up, so during cold starts emissions are not properly regulated and may be several times greater than in normal operation; • When the engine undergoes a sudden transition, such as a rapid acceleration or increase in engine load, the vehicle’s control technology can take a moment to adjust to the new conditions, and during this time a large ‘spike’ in emissions can occur.

The report goes on to describe specific ways automakers can game the testing procedures to inflate their results.

  • Fully charge the 12v battery, then disconnect the alternator.  That avoids engine power loss from running the alternator.
  • Pulling back the brake calipers to reduce drag.
  • Removing weight off the vehicle.
  • For tests occurring on a test track, use a track with an extremely smooth surface to reduce rolling resistence

Another report, published by TheICCT (the group which exposed the Volkswagen scandal), goes into more details on the NOx problem with diesel engines, and various abatement technologies that can be used.

Both reports say what will make the biggest impact in real emissions improvements is the real driving emissions (RDE) testing which goes into effect in Europe in 2016.  Under this new testing framework, diesel passenger cars will have to prove that they can keep NOX emissions at reasonably low levels during an on-road test that more closely represents real-world driving situations.

The discussion in both these reports are focused on Europe’s emissions testing procedures, because both groups are based in Europe.  While both say that the EPA’s testing methodology is far more advanced than Europe’s, and that emissions results on cars sold in America are much better than European cars, can we trust that assertion now?

The key issue in this scandal is that Volkswagen cheated on the EPA test results for six years before getting caught.  How many of the other automakers have also been cheating?

Yesterday, Greg Archer the Clean Vehicles Manager at T&E posted a press release saying that the Volkswagen scandal is just the tip of the iceberg.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.
Bookmark and Share
  Clean Diesel, Dieselgate, Vehicle Emissions. Bookmark.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.


  1. Pingback: BMW has no Dieselgate, while VW skimped on emissions control | The Long Tail Pipe

  2. Pingback: VW insists Dieselgate decisions made by low-level engineers, not by upper management | The Long Tail Pipe

  3. Pingback: More evidence Dieselgate affects other automakers besides Volkswagen | The Long Tail Pipe

Leave a Reply