• Jul 13, 2005

When VW ran into emission certification problems with their Touareg diesel earlier in the year, it cast doubts on the viability of an emissions-reduction technique called "urea injection". One of the main drawbacks of diesels is an increase in the emissions of nitrogen oxides (NOx), one of the nastier pollutants and a result of the high temperatures and localized areas of lean combustion inherent to diesel operation. Urea injected into the exhaust stream of a diesel decomposes into ammonia, which then lends towards the breakdown of NOx into oxygen, nitrogen, and carbon dioxide. The issue isn't the effectiveness of the technique; it's the maintenance aspect of the whole arrangement. Current Mercedes diesels that use the technique require a urea refill every 10,000 miles or so; the EPA worries that consumers won't follow this schedule and emissions non-compliance will result (they require that emissions systems will remain functional for 10 years or 150,000 miles). So what's the problem? Install a low-urea warning light (I don't think I want to know what the symbol for that is going to look like), offer the stuff up for sale in parts stores, and get on with the task of saving some oil. Ah, but companies like Mercedes want to make the system "invisible" to owners. With oil changes going out to God-knows-how-long and many other fluids considered to be "lifetime fills", it's about time we put the owner back in charge of a simple maintenance task or two.



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    • 1 Second Ago
  • 12 Comments
      • 9 Years Ago
      A picture of Calvin peeing on a Mercedes logo just poped into my head... Maybe that's why Mercedes wants to make this system 'invisible'? On the other hand, I think it would be great to see expensive Mercedes cars driving around with a urinal stuck to the back of the car. :-)
      • 9 Years Ago
      Maybe the solution to the problem is as simple as strapping a neighbor's cat to the firewall and there would be a constant supply of urea. Knowing how the neighbor's cat loves to spray, this would be a far superior solution than scraping said kitty of the road once meets a BMW the wrong way.
      • 9 Years Ago
      it has to be injected into the exhaust, after combustion but before it hits the catalitic converters, it's a catalistic chemicle that reacts once burned with the exhaust in the cats.
      • 9 Years Ago
      It's called that cause it's related to urine, it's ammonia based
      • 9 Years Ago
      #8, I think its because the urea is added to the exhaust.
      • 9 Years Ago
      I just read that Ford is prototyping a "duel fueling" system for their next generation diesel passenger cars in California (well, maybe 1st gen because they havn't had diesel cars since the early '80s, but the point is that they supposedlu use all that new "clean diesel" tech). The concept of "duel fuel" is that pumps will have a single "gun" (dont know what they call them) with 2 nozzles, one for diesel and one for urea. The article didnt mention that incredibly small amounts of urea are needed... but whatever. Its fine with me. Diesel is awesome, and if this gets people to stop complaining then its good with me. Just between that and the higher cost of ULSD, I'm wondering whether diesel will still be attractive as it is.
      • 9 Years Ago
      Wait, so now it's a good idea to pee in fuel tanks? I'm so confused.
      • 9 Years Ago
      What a freaking name. It sounds like somehing you would here during a prostate exam
      • 9 Years Ago
      The Japanese would have a simple solution to remind owners to fill up their urea tanks. Since the Japanese were pioneers of the horrid "your door is ajar" audible warnings using synthesized human speech, we could look forward to a wonderful phrase, "Your BMW needs to use the Potty".
      • 9 Years Ago
      #7: Ford's dual injector system begs the question: why not just add the urea to the diesel at the pump as a fuel additive? This seems like a no-brainer unless there's a good reason that no one is doing it...
      • 9 Years Ago
      I agree with the EPA on this one... the less maintenance that falls on the owners the better. You seem to have forgotten (again) that most people that drive cars are not enthusiests, people seems to have a hard enough time getting their oil changed - which is crucial for the car to run. How much you want to bet that lazy owners would just say screw it and never refill their urea (haha). As for the first post, I think having the engine shut off if their was no more urea left is a PR and logistical disaster waiting to happen, especially considering the sensor will inevitably fail - we ARE talking about VW and Mercedes cars here - which have a tendency for minor but crucial things to go wrong with their cars... like sensors... for emissions... and lie and then get fined 1.1 million dollars... *cough*VW*cough*
      • 9 Years Ago
      The EPA is worried about non-compliance? But an interlock switch on the urea tank: no urea, no engine crank. Next problem? Urea is cheap! Drivers figure out how to put gas in the tank, and wiper fluid in the resevoir. I think they can handle a 10K urea fill... Give us some credit, VW!