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

by guscost 11y ago

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.

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

by guscost 11y ago

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

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.