Slashdot Mirror
EPA To Overhaul Emissions Testing In the Wake of VW Cheating
New submitter kheldan writes with this snippet from The Consumerist: A week after ordering Volkswagen to recall 500,000 vehicles that contain "defeat devices" designed to cheat emissions tests, the Environmental Protection Agency announced it would overhaul its compliance processes to ensure vehicles meet standards not only in controlled environments but in real-world driving conditions, and adds What may be the story-behind-the-story here, are the two Elephants in the Room: One, how many other automakers in the world have been 'gaming' the system like German automakers apparently have been all along, and Two, are these changes to the certification process at the USEPA going to 'trickle down' to the state and local levels, affecting routine emissions testing of individual vehicles? Questions peripheral to these may include: How much is this going to affect new vehicle prices in the future, and how much is this going to affect the fair market value of used vehicles?
You're right that the technology is installed and works, but the performance and maintenance downsides are severe. I didn't want to make my original post too long to read, but here's more detail to explain.
Most small VWs (Jetta, etc) use a "lean NOx trap" to capture NOx in a zeolite sponge. The zeolite fills up with NOx and needs to be cleaned out periodically (every minute or two, takes a few seconds). During the cleaning cycle, engine power is limited to *20%* of maximum. VW's patent says they wait until the driver eases off on the throttle to do it, but still, that's a huge performance hit and a big incentive to cheat (by not doing the cleaning.)
See patent link in my original post for details (warning: machine-translated from German.)
In VW's larger vehicles (Passat, mostly), the car carries an extra tank full of gallons of urea, which is sprayed into the exhaust to react with the NOx. This reaction needs precise temperature controls (which probably limits engine performance), and the tank is big and heavy. By using less urea than needed, VW can use a smaller lighter tank, which needs to be refilled less often. (VW pays for urea replacement for the first 30,000 miles.)
No, even when breaking the law, German engineering does not screw around.
VW's patented setup sounds far less ideal than the well understood SCR/DEF setup everyone else uses. 20% of max power to burn out the NOx trap? No way in hell would I want that!
The precise temperature controls you allude to for SCR/DEF is hogwash. You've got quite a bit of leeway to get up to temp before the system starts dosing before throwing codes and going into limp mode (think like over an hour of operation). If you didn't, then all of us in places with 4 real seasons would have diesels that wouldn't go anywhere because DEF freezes at about 18 degrees F. Where I live, we can go months with temps lower than that, and it takes time to thaw the DEF so it'll flow.
DEF consumption is 1-3% of fuel consumption. So figure 1-3 gallons of DEF used for every 100 gallons of diesel; that's for the puny little 2 liters in a VW all the way up to the 13L monsters in a Peterbilt... 1-3% of fuel, like clockwork. How many gallons of DEF would be needed to go the oil change interval on a VW TDi? Not many.
Lastly, on DEF, any fool paying stealership prices deserves to get ripped off. Drive to a truck stop and enjoy ISO rated DEF/AdBlue at $2.70 or so a gallon. My last DEF fill cost me a whopping $16 for my truck at just over 6 gallons in ~8k miles.. A 3.0L diesel truck that gets 24-27 MPG in mixed driving. A 2.0L TDi should be able to go 12k+ miles on 5 gallons considering how much less fuel they burn than my truck does.
OSX pwns.