School of Hard NOx

Oh dear, VAG seem to have cocked up, huh?

The fact that the EPA in the US caught them gaming the system with emission testing is interesting, and given that they face a huge fine, and the CEO Martin Winterkorn, having recently ousted Ferdinand Piech from his role, has now resigned.

I’m more interested in the tech. Simplified, it all hinges on EGR. It’s a common trick to disable EGR in a tuned diesel- in many ways it’s a huge pain in the arse, reducing efficiency, and therefore power and economy, and being prone to clogging up intakes, so with an EGR delete, your diesel will do better MPG, perform better, and not get so claggy. Also, as a diesel runs with excess air, if you don’t run EGR, you produce less particulates (soot), which is good.

The disadvantage comes with NOx production. No EGR means more NOx, which is one form of pollution generated by internal combustion engines, with health and environmental impact. This, and other pollutants, are regulated by EU Directives in Europe, and the EPA in the states, and cars that do not meet the standards cannot be sold new.

So, there’s a balancing act: try to keep particulates down, power and MPG up, but don’t create too much NOx.

Some diesels do this with AdBlue, but VAG have claimed to be able to meet the latest standards without the extra complication, cost, and space of the kit needed to inject it, managing with just a DPF. Nice trick.

Trick would seem to be the operative word, and you have to admire it. We’ve seen how networked cars are now, and that meant a clever algorithm was able to detect when the car was on a rolling-road being emmission-tested, and crank up the EGR, lovering the NOx output. On the road, EGR is reduced, so up goes the power and MPG. WIN!

How the conversation at Wolfsburg may have gone. From CommitStrip, click for original.

How the conversation at Wolfsburg may have gone. From CommitStrip, click for original.

Trouble is, that’s specifically not allowed by the EPA (PDF, 2.35MB), leaving VAG with a big headache stateside.

This does set me thinking if the diesel car boom could be ending: in particular, the UK’s CO-based taxation favours diesels, but as the amount of emissions gear required to meet the regulatory standards increases, the performance of the engines comes down and the complexity increases, and so therefore does cost. In one way, VAG’s (rather elegant) trick was actually good for the consumer, reducing costs and increasing performance, while seeming to meet all required standards. In another, it’s a cynical attempt to evade emissions law, risk public health, and increase profit. For sure, the fix is going to be painful for both VAG and its customers in the US: it remains to be seen if they have a problem in Europe too.

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