3 ms·

> The KBA believes that a coolant thermostat that is activated during normal driving to protect engine parts in [sic] an illegal defeat device This badly writt

> The KBA believes that a coolant thermostat that is activated during normal driving to protect engine parts in [sic] an illegal defeat device This badly written line is the only technical information in the article. Since a thermostat is only a temperature sensor, I don't get how it constitutes a defeat device of any type. I also don't get how activating a sensor to read coolant temperature protects anything. And why would an installed sensor be turned off anyway?

deleted 7y ago
[deleted]
ewhanley 7y ago
A thermostat in the context of an internal combustion engine is a coolant flow control device. It typically diverts coolant to the radiator when the engine initially reaches operating temperature and then directs flow to manage ideal operating temps.
- JorgeGT 7y ago
  I know this, it's a pretty standard function that almost all cars have, and does not constitute a defeat device per se. It's also active all the time, that's how your car displays the coolant temp. in your dashboard. They should really explain how Daimler used this to cheat.
  - rootsudo 7y ago
    Depending on how cooled the engine is, it affects emissions levels. A open thermostat makes a car run richer, generating less horsepower. There is a direct correlation between engine operating temp, condition of the thermostat and emissions/fuel economy.
    - korethr 7y ago
      > Depending on how cooled the engine is, it affects emissions levels. A open thermostat makes a car run richer, generating less horsepower. This is true on gasoline engines, which are homogeneous-charge, air-throttled designs, and target an operating point as close to stoichimetric as possible. Diesel engines are fuel-throttled, and by design run well lean of peak-EGT, stoichimetric, and even peak power due to their stratified-charge nature (overall stoich is rich-as-fuck at the combustion site). A diesel will blowing black smoke and melting holes in its pistons before it ever comes close to stoich, much less rich. A (relatively) richer running diesel engine will be making more power, not less. A diesel running cold with an open thermostat won't necessarily have it's fuel ratios affected so much as its injection timing. Injection timing absolutely does have an effect on emissions and fuel economy at any one given fueling/power-output level.
Rychard 7y ago
In an automotive context, a thermostat controls the flow of coolant through the engine block to maintain a specific temperature. This allows the engine to run more efficiently. https://en.wikipedia.org/wiki/Thermostat#Automotive https://en.wikipedia.org/wiki/Thermostat#Automotive
- calvinmorrison 7y ago
  It keeps the engine temperature in target ranges. It opens when the engine is at the temperature and the water pump moves coolant through the thermostat housing and to the radiator. when it is below the temperature it closes, and it doesn't flow in the same path (usually it just flows back through the head. Old cars had fans that always ran, often times off the crankshaft. If cold coolant ran through the radiator it wouldn't maintain proper temperature with the fan running! Same situation with highway driving. There's so much airflow to cool the engine - being able to block off coolant is very important. Newer cars with electric fans use this in combination with the thermostat to provide more efficient cooling (by not running fans all the time). Cars with electric fans use a coolant temp sensor (sometimes on the radiator, or the block, or elsewhere) that kicks over a switch to turn fans on and off. Then you have a temperature gauge which sends a signal to your dashboard/ecu. The computer uses this in combination with a bunch of other data pieces to make the engine run smoothly. Anyway, that was all just random info
Glawen 7y ago
The wsj has too few infos, however if you can read german, there are very detailed articles: https://www.sueddeutsche.de/auto/daimler-mercedes-glk-rueckruf-kraftfahrtbundesamt-1.4495109 https://www.sueddeutsche.de/auto/daimler-mercedes-glk-rueckr... As i understand it, the motor seemed to artificially open the thermostat to keep the engine colder than usual. Now my guess, as an automotive engineer, is that they did this to reduce the time where the engine is in the normal operating range. It makes no sense to me, unless the emissions test only applies when the engine is in normal temperature. Or, second guess, as the engine is colder, it emits less NOx, because NOx appear when the combustion temperature is too high. Or simpler: the thing activates when the coolant is 20 deg celsius, the starting temperature of the test
- toast0 7y ago
  > Or, second guess, as the engine is colder, it emits less NOx, because NOx appear when the combustion temperature is too high. That's a major issue. NOx emissions are caused by engine heat interacting with nitrogen and oxygen from outside air, which gets you to a nasty trade-off. Run the engine hotter and get more efficient combustion, therefore less CO2 emissions; or run the engine cooler and get less NOx emissions. By design, Diesel engines combustion happens at much higher pressure and temperature than gasoline engines, which is why diesels produce much more NOx. Diesel emission fluid can reduce NOx, but also reduces efficiency, meaning more CO2 will be released.
  - Glawen 7y ago
    True, it is a constant compromise that the engine is doing at each injection. For the article, i think the journalists just didn't understand the explanation, and it is probably the simpler solution : they enabled the emission cleaning algorithm when the coolant at startup is 23 degrees, so clearly a defeating device.
jacquesm 7y ago
A thermostat in a car is more than just a sensor, it is usually also directly opening or closing a conduit through which coolant can flow into the engine.

deleted 7y ago

[deleted]

ewhanley 7y ago

A thermostat in the context of an internal combustion engine is a coolant flow control device. It typically diverts coolant to the radiator when the engine initially reaches operating temperature and then directs flow to manage ideal operating temps.

JorgeGT 7y ago
I know this, it's a pretty standard function that almost all cars have, and does not constitute a defeat device per se. It's also active all the time, that's how your car displays the coolant temp. in your dashboard. They should really explain how Daimler used this to cheat.
- rootsudo 7y ago
  Depending on how cooled the engine is, it affects emissions levels. A open thermostat makes a car run richer, generating less horsepower. There is a direct correlation between engine operating temp, condition of the thermostat and emissions/fuel economy.
  - korethr 7y ago
    > Depending on how cooled the engine is, it affects emissions levels. A open thermostat makes a car run richer, generating less horsepower. This is true on gasoline engines, which are homogeneous-charge, air-throttled designs, and target an operating point as close to stoichimetric as possible. Diesel engines are fuel-throttled, and by design run well lean of peak-EGT, stoichimetric, and even peak power due to their stratified-charge nature (overall stoich is rich-as-fuck at the combustion site). A diesel will blowing black smoke and melting holes in its pistons before it ever comes close to stoich, much less rich. A (relatively) richer running diesel engine will be making more power, not less. A diesel running cold with an open thermostat won't necessarily have it's fuel ratios affected so much as its injection timing. Injection timing absolutely does have an effect on emissions and fuel economy at any one given fueling/power-output level.

Rychard 7y ago

In an automotive context, a thermostat controls the flow of coolant through the engine block to maintain a specific temperature. This allows the engine to run more efficiently. https://en.wikipedia.org/wiki/Thermostat#Automotive https://en.wikipedia.org/wiki/Thermostat#Automotive

calvinmorrison 7y ago
It keeps the engine temperature in target ranges. It opens when the engine is at the temperature and the water pump moves coolant through the thermostat housing and to the radiator. when it is below the temperature it closes, and it doesn't flow in the same path (usually it just flows back through the head. Old cars had fans that always ran, often times off the crankshaft. If cold coolant ran through the radiator it wouldn't maintain proper temperature with the fan running! Same situation with highway driving. There's so much airflow to cool the engine - being able to block off coolant is very important. Newer cars with electric fans use this in combination with the thermostat to provide more efficient cooling (by not running fans all the time). Cars with electric fans use a coolant temp sensor (sometimes on the radiator, or the block, or elsewhere) that kicks over a switch to turn fans on and off. Then you have a temperature gauge which sends a signal to your dashboard/ecu. The computer uses this in combination with a bunch of other data pieces to make the engine run smoothly. Anyway, that was all just random info

Glawen 7y ago

The wsj has too few infos, however if you can read german, there are very detailed articles: https://www.sueddeutsche.de/auto/daimler-mercedes-glk-rueckruf-kraftfahrtbundesamt-1.4495109 https://www.sueddeutsche.de/auto/daimler-mercedes-glk-rueckr... As i understand it, the motor seemed to artificially open the thermostat to keep the engine colder than usual. Now my guess, as an automotive engineer, is that they did this to reduce the time where the engine is in the normal operating range. It makes no sense to me, unless the emissions test only applies when the engine is in normal temperature. Or, second guess, as the engine is colder, it emits less NOx, because NOx appear when the combustion temperature is too high. Or simpler: the thing activates when the coolant is 20 deg celsius, the starting temperature of the test

toast0 7y ago
> Or, second guess, as the engine is colder, it emits less NOx, because NOx appear when the combustion temperature is too high. That's a major issue. NOx emissions are caused by engine heat interacting with nitrogen and oxygen from outside air, which gets you to a nasty trade-off. Run the engine hotter and get more efficient combustion, therefore less CO2 emissions; or run the engine cooler and get less NOx emissions. By design, Diesel engines combustion happens at much higher pressure and temperature than gasoline engines, which is why diesels produce much more NOx. Diesel emission fluid can reduce NOx, but also reduces efficiency, meaning more CO2 will be released.
- Glawen 7y ago
  True, it is a constant compromise that the engine is doing at each injection. For the article, i think the journalists just didn't understand the explanation, and it is probably the simpler solution : they enabled the emission cleaning algorithm when the coolant at startup is 23 degrees, so clearly a defeating device.

jacquesm 7y ago

A thermostat in a car is more than just a sensor, it is usually also directly opening or closing a conduit through which coolant can flow into the engine.