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I too am curious on how it really happen. If one burn 1 gallon of diesel get x amount of NOx, wouldn't 40x NOx need to burn 40x amount of diesel? What does t

by tkinom 11y ago

I too am curious on how it really happen. If one burn 1 gallon of diesel get x amount of NOx, wouldn't 40x NOx need to burn 40x amount of diesel? What does the SW do that? Dial down the power of the engine to 1/40th of "normal operations" during the testing?

tkinom 11y ago
Nevermind, got the answer here: http://spectrum.ieee.org/cars-that-think/transportation/advanced-cars/how-professors-caught-vw-cheating http://spectrum.ieee.org/cars-that-think/transportation/adva...
- x0x0 11y ago
  from the article [Dan] Carder [director of West Virginia University’s Center for Alternative Fuels, Engines and Emissions (CAFEE)] did, however, shed light on diesel exhaust. The problem, he says, is one of thermal management. Catalytic converters break down NOX only when they’re hot, and keeping them hot may sometimes require that you burn more fuel than you need for the performance you want. You might want to run the engine on a lean fuel-air mixture, but you have to run it rich. “There’s also a trap for NOX that acts like a sponge,” Carder points out. “But if you saturate it with NOX, then you have to go to a rich-burning condition to use the catalyst to reduce the NOX” and thus wring out the sponge.
mzs 11y ago
No, but good question. NOx production varies wildly on factors such as atomization of fuel, ratio vs stochiaometric in mix, temperature of combustion...
ubercore 11y ago
I don't know if it directly answers your question, but NOx emissions are dependent on combustion temperature I believe, so the ECU could potentially adjust fuel and timings to create conditions that don't spew NOx, but don't perform as well either. Then when on the road, it opens back up to increase performance but liberate more of the NOx that otherwise might be bound up in less harmful substances or caught by the particulate filter/catalytic converter.

by tkinom 11y ago

tkinom 11y ago

Nevermind, got the answer here: http://spectrum.ieee.org/cars-that-think/transportation/advanced-cars/how-professors-caught-vw-cheating http://spectrum.ieee.org/cars-that-think/transportation/adva...

x0x0 11y ago
from the article [Dan] Carder [director of West Virginia University’s Center for Alternative Fuels, Engines and Emissions (CAFEE)] did, however, shed light on diesel exhaust. The problem, he says, is one of thermal management. Catalytic converters break down NOX only when they’re hot, and keeping them hot may sometimes require that you burn more fuel than you need for the performance you want. You might want to run the engine on a lean fuel-air mixture, but you have to run it rich. “There’s also a trap for NOX that acts like a sponge,” Carder points out. “But if you saturate it with NOX, then you have to go to a rich-burning condition to use the catalyst to reduce the NOX” and thus wring out the sponge.

mzs 11y ago

No, but good question. NOx production varies wildly on factors such as atomization of fuel, ratio vs stochiaometric in mix, temperature of combustion...

ubercore 11y ago

I don't know if it directly answers your question, but NOx emissions are dependent on combustion temperature I believe, so the ECU could potentially adjust fuel and timings to create conditions that don't spew NOx, but don't perform as well either. Then when on the road, it opens back up to increase performance but liberate more of the NOx that otherwise might be bound up in less harmful substances or caught by the particulate filter/catalytic converter.