9 ms·

I'm pretty sure that owners can refill the tank by themselves, but manufacturers are required to have a big enough tank that it can be done by the dealer as par

by makomk 11y ago

I'm pretty sure that owners can refill the tank by themselves, but manufacturers are required to have a big enough tank that it can be done by the dealer as part of the regular servicing schedule. The tank itself not so much a US thing as it is a modern diesel car thing; it's part of the emissions control system on I think most new diesels.

guscost 11y ago
Wow, I hadn't heard this. What a counterproductive, idiotic piece of regulation.
- ZeroGravitas 11y ago
  It's not an idiotic regulation. If you fit a tiny reservoir that needs to be topped up every week then most customers wouldn't bother, and the car would be spewing extra toxins. So you have to make it large enough that normal servicing will ensure it is filled.
  - guscost 11y ago
    Using "limp mode" with warnings to ensure the tank stays filled (and the car does not run at full throttle unless it is filled) is a much better solution. When the sales guy told me the tank only had to be filled at service intervals, it sounded strange. People on the TDI forums thought it was just because VW didn't want to scare away customers with an extra thing to do, but you can buy the stuff at any gas station and pouring it into the tank is not difficult. When the scandal broke the assumption was that they mistuned the DEF cars out of arrogance, and again to avoid spooking customers with extra maintenance. Now it sounds much more like they tuned it that way because this regulation would have crippled the car with an enormous DEF tank otherwise. It is possible that such a regulation combined with a 10,000 mile service interval only makes engineering sense on mid-size trucks or larger. This doesn't have anything to do with them failing to build a working LNT solution and cheating with those previously, of course.
  - Grishnakh 11y ago
    It's very simple: make the car so that if the tank hits empty, the car doesn't run any more. If you think that's a problem, then please explain why this isn't also a problem for the gas tank. I don't know of any cars which will continue to drive (but spewing extra toxins) when the gas or diesel tank is empty. Customers don't seem to have much of a problem topping up their diesel tank every week or two....
- criddell 11y ago
  The legislation is in place because consumers are lazy.
  - guscost 11y ago
    "Limp mode" is a much better solution, switching that on will basically guarantee the fluid gets refilled in short order. And actually I'm not so quick to assume this is only a stupid decision either. Hanlon's razor still applies but there is also a distinct possibility that this regulation was "encouraged" as a play to make small diesel cars less competitive.
    - criddell 11y ago
      It's a different solution, but I don't know if it would be better. How do you think it's better? VW doesn't want their cars going into limp mode. They don't want customers calling up asking why their car is acting funny. They don't want to increase the maintenance load on their customers. They don't want customers coming in for unnecessary service appointments (especially for stuff they wouldn't be able to charge for). Making a tank big enough to last as long as the motor oil seems like an easy, low tech solution. Sometimes simple is better.
      - guscost 11y ago
        See my reply above, I'm inclined to believe that storing enough DEF for correct dosing through a 10,000 mile service interval may not be feasible for a small car. After hearing about this regulation it seems an obvious reason why they would keep the cheat enabled even after adding a DEF system.
        criddell 11y ago
        > I'm inclined to believe that storing enough DEF for correct dosing through a 10,000 mile service interval may not be feasible for a small car. It is feasible and they already do it.
gherkin0 11y ago
My dad has a US Volkswagen diesel. He's told me he can refill the urea tank, but he can't reset the computer to tell it the tank was filled, so there's very little point for him to actually refill it. His car will stop working unless he brings it into the dealer, one way or the other.
- Grishnakh 11y ago
  See, this is a great example of how our regulators have failed miserably. This kind of practice should be outright banned. There should not be anything on a car that requires you to take it to a dealer to reset; any competent mechanic should be able to do any service on the car, and not need a special dealer-only computer system to make the car recognize the service.
- vonmoltke 11y ago
  My car recognizes when I refill the tank. Not sure what is going on with your dad's car.
- teh_klev 11y ago
  Has he tried getting an OBDII reader (they're really cheap) and resetting the fill status himself?
guscost 11y ago
After looking into this the only thing I can find is a reference to 4,000 mile capacity[0], way less than a TDI service interval. Maybe they mistuned it just so customers wouldn't have to pour a bottle of stuff into the tank, which would have been an awful idea. Or maybe the catalyst they used isn't sufficient to meet US NOx standards with the optimum fuel-air ratio, I guess we will have to wait and see. [0]https://www3.epa.gov/otaq/documents/nonroad/420f14017.pdf https://www3.epa.gov/otaq/documents/nonroad/420f14017.pdf

by makomk 11y ago

guscost 11y ago

Wow, I hadn't heard this. What a counterproductive, idiotic piece of regulation.

ZeroGravitas 11y ago
It's not an idiotic regulation. If you fit a tiny reservoir that needs to be topped up every week then most customers wouldn't bother, and the car would be spewing extra toxins. So you have to make it large enough that normal servicing will ensure it is filled.
- guscost 11y ago
  Using "limp mode" with warnings to ensure the tank stays filled (and the car does not run at full throttle unless it is filled) is a much better solution. When the sales guy told me the tank only had to be filled at service intervals, it sounded strange. People on the TDI forums thought it was just because VW didn't want to scare away customers with an extra thing to do, but you can buy the stuff at any gas station and pouring it into the tank is not difficult. When the scandal broke the assumption was that they mistuned the DEF cars out of arrogance, and again to avoid spooking customers with extra maintenance. Now it sounds much more like they tuned it that way because this regulation would have crippled the car with an enormous DEF tank otherwise. It is possible that such a regulation combined with a 10,000 mile service interval only makes engineering sense on mid-size trucks or larger. This doesn't have anything to do with them failing to build a working LNT solution and cheating with those previously, of course.
- Grishnakh 11y ago
  It's very simple: make the car so that if the tank hits empty, the car doesn't run any more. If you think that's a problem, then please explain why this isn't also a problem for the gas tank. I don't know of any cars which will continue to drive (but spewing extra toxins) when the gas or diesel tank is empty. Customers don't seem to have much of a problem topping up their diesel tank every week or two....
criddell 11y ago
The legislation is in place because consumers are lazy.
- guscost 11y ago
  "Limp mode" is a much better solution, switching that on will basically guarantee the fluid gets refilled in short order. And actually I'm not so quick to assume this is only a stupid decision either. Hanlon's razor still applies but there is also a distinct possibility that this regulation was "encouraged" as a play to make small diesel cars less competitive.
  - criddell 11y ago
    It's a different solution, but I don't know if it would be better. How do you think it's better? VW doesn't want their cars going into limp mode. They don't want customers calling up asking why their car is acting funny. They don't want to increase the maintenance load on their customers. They don't want customers coming in for unnecessary service appointments (especially for stuff they wouldn't be able to charge for). Making a tank big enough to last as long as the motor oil seems like an easy, low tech solution. Sometimes simple is better.
    - guscost 11y ago
      See my reply above, I'm inclined to believe that storing enough DEF for correct dosing through a 10,000 mile service interval may not be feasible for a small car. After hearing about this regulation it seems an obvious reason why they would keep the cheat enabled even after adding a DEF system.
      - criddell 11y ago
        > I'm inclined to believe that storing enough DEF for correct dosing through a 10,000 mile service interval may not be feasible for a small car. It is feasible and they already do it.

gherkin0 11y ago

My dad has a US Volkswagen diesel. He's told me he can refill the urea tank, but he can't reset the computer to tell it the tank was filled, so there's very little point for him to actually refill it. His car will stop working unless he brings it into the dealer, one way or the other.

Grishnakh 11y ago
See, this is a great example of how our regulators have failed miserably. This kind of practice should be outright banned. There should not be anything on a car that requires you to take it to a dealer to reset; any competent mechanic should be able to do any service on the car, and not need a special dealer-only computer system to make the car recognize the service.
vonmoltke 11y ago
My car recognizes when I refill the tank. Not sure what is going on with your dad's car.
teh_klev 11y ago
Has he tried getting an OBDII reader (they're really cheap) and resetting the fill status himself?

guscost 11y ago

After looking into this the only thing I can find is a reference to 4,000 mile capacity[0], way less than a TDI service interval. Maybe they mistuned it just so customers wouldn't have to pour a bottle of stuff into the tank, which would have been an awful idea. Or maybe the catalyst they used isn't sufficient to meet US NOx standards with the optimum fuel-air ratio, I guess we will have to wait and see. [0]https://www3.epa.gov/otaq/documents/nonroad/420f14017.pdf https://www3.epa.gov/otaq/documents/nonroad/420f14017.pdf