The Tech Behind the VW Scandal

The Tech Behind the VW Scandal

Revelations that Volkswagen, the world’s biggest carmaker, rigged its emissions testing to trick regulators and boost its sales have sent shock waves through the car industry. In September, the company admitted that it had used special software to detect and lower emissions during laboratory tests of some of its diesel vehicles in an attempt to promote great fuel economy, abundant torque, but reduced greenhouse gases and pollutants.


All modern vehicles have dozens of computers in them and some of those computers help coordinate the function of the engine for optimum performance while making sure there aren’t too many bad chemicals coming out of the exhaust pipe.

With that in mind, these cheating Volkswagen and Audi cars are diesels and diesels have one more really important computer controlled parameter that other regular gas burning vehicles don’t have to worry about and that is the amount of unburned fuel going into exhaust.

And so, that sounds bad since you don’t really want unburned fuel going into your exhaust but in the case of a diesel you have something called a NOx trap. This is a device the traps and absorbs unburned diesel fuel along with Nitrogen Oxide that is part of the harmful pollutants coming out of the exhaust and without this N0x trap working properly these chemicals would otherwise go into the atmosphere.

So you have to keep in mind that the effectiveness of this trap is enhanced with unburned diesel fuel getting trapped into it. However, allowing unburned fuel to fill up the N0x trap means your not getting effective fuel mileage either.

And so Volkswagen had a problem on its hands as it’s diesel vehicles where know for getting great fuel economy, but the NOx trap only works well when more fuel is being used. Therefore, VW had to implement what is called a ‘defeat device‘, which is a software hack used to run when it knew it was getting tested for exhaust emissions.


With that in mind,  a defeat device is a special program found inside these on-board computers that can make it look like the vehicle is meeting the proper emissions standards even when it isn’t.

So the car would detect using this defeat device when it was getting an emissions test, the software would make the car use more fuel enabling the N0x trap to work well thus reducing pollutants out the exhaust.

Once the vehicle was back on the road the computer software would detect it was not getting tested again and it would then run the other software designed to use less fuel but ignore the pollutants being emitted out of the exhaust. And it looks like it was letting up to 40 times the amount of pollutants in the air it was suppose to.


The EPA (the environmental protection agency) said it was an on-board software computer system that was able to check the steering wheel position, speed, how long the engine was on, and even the atmospheric pressure. All of that would help determine if it was going through a test.

In other words, there is no way this was accidental since it looks like the software was designed very carefully to cheat an official emissions test. And so this is some pretty serious deception and that is why Volkswagen is in such serious trouble. In fact, their CEO, Martin Winterkorn just stepped down as a result.


So, how about a possible fix? Well, if you own one of the 11 million diesel Jetta’s, Beetles, Golf’s, Psatts, and Audi’s effected the good news is that your car is still safe to drive and I’m sure at some point VW will issue some type of recall where they will have to update the software in the vehicle. When that happens you might then get fewer miles per tank of gas.

Also too,it looks like lawyers are already gearing up for class action lawsuits so it is possible at some point owners might be compensated for this blunder – though I wouldn’t hold my breath on that one.



CNET On Cars – What you need to know about the VW emissions scandal

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