And now a Mercedes "diesel gate" ?

Carl Leermakers · Feb 2, 2016

And now comes Mercedes : Forbes article here. Forty times the allowable NOx emissions in cold weather? Well I suppose technically that's not cheating at the test labs (as VW presumably did) if no test labs are freezing cold inside... But perhaps the question is not really whether you're cheating at the test labs, but rather cheating on the world.

"We need to protect our engines in cold weather". Great. Protecting schoolchildren from 40 times too much NOx when we drop our kids off at school in cold weather, anyone?

McRat · Feb 2, 2016

Best I can tell, they are referring to Bluetec urea systems.

What I can't tell if they are referring to the startup cycle, or when the engine is at full operating temp.

Something to note about ICE vehicles, they do have ECM tables that defeat some of the emissions during startup. This allows the engine to warm up quicker and reduces certain emissions at the expense of other emissions.

To make a fuel efficient diesel, which have very high combustion pressures, NOx emissions are the biggest stumbling block. You either waste fuel and make more CO2, or you make more NOx and less CO2.

Diesels emit less CO2 than gasoline engines per kWh of output. EV's aren't CO2 "free", they just produce less than ICE vehicles, since a lot of electricity is generated by burning hydrocarbon fuel.

So if your goal is to reduce global CO2 emissions, diesels are part of the answer. But like all engineering, there are trade-offs.

Carl Leermakers · Feb 2, 2016

Understood and agreed. But there's no limit to CO2 emissions (as opposed to for example CO or NOx); in Europe (or at least Belgium) there's just a (big) tax consequence for the buyer based on the CO2 emissions of his or her car. The NOx emissions have no tax consequences for the buyer, but the NOx emissions limit is mandatory for the manufacturer. So CO2 is a selling argument, whereas NOx is not. Exceeding the mandatory NOx limits by 4000% (in certain circumstances) in order to limit CO2 emissions is therefore, well, hmmm, "interesting".

And of course EV's aren't CO2-free. They probably are NOx-free or at least below any mandatory NOx-limit however, and not cheating on the subject.

Doug_G · Feb 2, 2016

I'm sure all ICE engines emit excessive pollutants during their warm-up in cold weather. This is just something you have to tolerate, due to limitations on the technology.

Nothing to see here... move along...

(Also this is not Tesla related news, so the thread will be moved.)

Carl Leermakers · Feb 3, 2016

Fair enough (should have been in thread about how dieselgate could affect EV sales).

However the question was not whether ICE cars pollute more when they are cold (yes of course), but why the official diesel tests are 'tuned' to simply ignore a (sometimes) 4000% violation of limits. As today's decision of the European Parliament proves, it will remain a long fight. A fight which I think is very important in respect of promoting EV's - something to take a minute to examine and create awareness about, not to simply ignore and move along, imho.

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And now a Mercedes "diesel gate" ?

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