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I thought it was more a case of "some car manufacturers cheated" and not "almost all diesel cars emit several times more than they should". How is this possible

I thought it was more a case of "some car manufacturers cheated" and not "almost all diesel cars emit several times more than they should". How is this possible?

Spare_account 11y ago
The test is accurate and measures emissions very well. The cars emit NOX at levels lower than the legal limits during the test. There is no mistake during the test and no cheating (apart from VW). However, when the cars are used by normal drivers, the usage patterns are so significantly different than the test sequences that the emissions profile changes. In the majority of cases the NOX emissions from cars used by normal people exceed the EU limits. This does not, as I understand it, mean that the cars are illegal. The cars all passed the tests in the test environment. That is the requirement and they met the requirement. No law is being broken but that is only because the law is not fit for purpose.
makomk 11y ago
The tests simply don't match modern real-world driving patterns. For example, apparently real-world drivers tend to accelerate much more rapidly than in the test sequence. It doesn't just affect diesel cars either; they tend to over-estimate the fuel efficiency of all cars and presumably under-estimate their pollution levels too.
DanBC 11y ago
Some manfs were cheating - they increased tire pressure to levels that would be dangerous on roads, for instance. Some manfs were building to the type approval test, but not for real world driving. A car needs to accelerate from 0 kph to 100 kph over a certain time. Normal road drivers would accelerate faster than this test, and acceleration is when the vehicles emit a lot of stuff. The tests are run on engines at their normal operating temperature. So cold engines are allowed to emit more stuff to protect the engine. Many engines in real world use would be at this cold temperature. The US has particularly stringent testing, and it might not be possible to meet those tests. They should probably have done other stuff to reduce diesel vehicles - taxes and duties on the vehicles and the fuel, with exemptions for commercial operators. It's clear now that manfs build to the test, and that type approval testing needs to include better real world driving testing.
lb1lf 11y ago
Also, the number of car manufacturers outnumber the number of car engine manufacturers - so if one company which actually makes engines (cough) optimizes their engines for testing, several car manufacturers may be caught with their trousers down. (Which, I am sure, will lead to all sorts of interesting lawsuits.) For instance, the engine in cars as different as the Land Rover Defender (sadly, no longer among us) and the Volvo, say, S80 is basically the same Ford-engineered unit.

I thought it was more a case of "some car manufacturers cheated" and not "almost all diesel cars emit several times more than they should". How is this possible?

Spare_account 11y ago

The test is accurate and measures emissions very well. The cars emit NOX at levels lower than the legal limits during the test. There is no mistake during the test and no cheating (apart from VW). However, when the cars are used by normal drivers, the usage patterns are so significantly different than the test sequences that the emissions profile changes. In the majority of cases the NOX emissions from cars used by normal people exceed the EU limits. This does not, as I understand it, mean that the cars are illegal. The cars all passed the tests in the test environment. That is the requirement and they met the requirement. No law is being broken but that is only because the law is not fit for purpose.

makomk 11y ago

The tests simply don't match modern real-world driving patterns. For example, apparently real-world drivers tend to accelerate much more rapidly than in the test sequence. It doesn't just affect diesel cars either; they tend to over-estimate the fuel efficiency of all cars and presumably under-estimate their pollution levels too.

DanBC 11y ago

Some manfs were cheating - they increased tire pressure to levels that would be dangerous on roads, for instance. Some manfs were building to the type approval test, but not for real world driving. A car needs to accelerate from 0 kph to 100 kph over a certain time. Normal road drivers would accelerate faster than this test, and acceleration is when the vehicles emit a lot of stuff. The tests are run on engines at their normal operating temperature. So cold engines are allowed to emit more stuff to protect the engine. Many engines in real world use would be at this cold temperature. The US has particularly stringent testing, and it might not be possible to meet those tests. They should probably have done other stuff to reduce diesel vehicles - taxes and duties on the vehicles and the fuel, with exemptions for commercial operators. It's clear now that manfs build to the test, and that type approval testing needs to include better real world driving testing.

lb1lf 11y ago

Also, the number of car manufacturers outnumber the number of car engine manufacturers - so if one company which actually makes engines (cough) optimizes their engines for testing, several car manufacturers may be caught with their trousers down. (Which, I am sure, will lead to all sorts of interesting lawsuits.) For instance, the engine in cars as different as the Land Rover Defender (sadly, no longer among us) and the Volvo, say, S80 is basically the same Ford-engineered unit.