What VW did.

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Dave Saxton
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What VW did.

Post by Dave Saxton » Wed Sep 23, 2015 11:37 pm

Volks Wagon AG recently admitted that engine management computers on its Audi and VW diesel motors were programmed to run a different calibration when the car was hooked up to an emissions testing dynometer and when the cars were regularly driven on the road. This allowed the car to "pass emissions" by reducing the amount of nitrious oxide (NOx) emissions during testing compared to normal operation. This is being described as terrible thing to do. But is it really?

NOx is one component in urban smog. It is a result of excessive combustion temperatures. Excessive combustion temps are the result of more efficient combustion. Which also results in a massive reduction in other pollutants such as co1, unburned hydro carbons and diesel particulates (black smoke), and excessive fuel consumption. So the trade off was an increase in NOx against much better fuel economy, and much cleaner overall emissions. It results in a net co2 emissions reduction.

Nox has always been a difficult problem. Improving efficiency increases combustion temps. With gasoline, and some diesel, engines since the 1970s; have used EGR. EGR is Exhaust Gas Recirculation. By introducing some of the spent exhaust gasses at the cylinder intake the combustion temperatures are decreased. But the efficiency is also reduced. Therefore the resultant incomplete combustion must be completed by other means, such as catalytic converters and air injected into the exhaust system.

Another well known way to improve combustion efficiency, but it increases combustion temps, is to start the fuel burn earlier in the crankshaft cycle. With gasoline engines this is done by "advancing the spark." With diesels this is done by "advancing the injector timing." This is done all the time. The results are a significant improvement in fuel economy and also power production. I suspect this all the VW engineers did. They simply maximized power production and maximized fuel efficiency (which also yields much cleaner overall emissions) when the car was cruising down the highway as mandated since 2011 by US Gov agencies.

This is probably a case of conflicting rules and regulations.
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Byron Angel
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Re: What VW did.

Post by Byron Angel » Sun Oct 18, 2015 1:29 pm

The VW scandal is legitimate from the point of view of institutional integrity (although I find it absolutely laughable that our massively corrupt and scandal-ridden government seats itself in judgment of such matters).

However, from a practical perspective, I am forced to ask the following questions: have government pollution control standards perhaps passed the point of diminishing returns? Have we perhaps already achieved a suitably clean standard for internal combustion engines? Is 10x or 40x a needlessly miniscule emission limit really the cataclysmic transgression it is claimed to be? Is the "zero pollution" goal really designed to protect the environment (as we are ceaselessly told) or is the true goal to ultimately legislate the internal combustion engine out of commercial existence?

I do not know for certain, but I do wonder.


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Re: What VW did.

Post by RF » Sun Oct 25, 2015 5:05 pm

The main problem that will emerge from this is that it will damage the reputation of diesel cars as being 'environment friendly'

So far the other major manufacturer of diesel cars, Peugeot-Citroen, appears to have had no focus placed on them by the mass media, so it looks that there are no issues with their emissions testing.
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