GetMore
Veteran Member
I've seen some posts that mentioned that the origin of the current defeat device was a noise reduction measure. (I forget the name: audible something, or something like that.)
As it turns out, to quiet the noise from ignition, they use "pilot injection", or inject some fuel before the main injection. (Overly simplified, but hopefully good enough.) The side effect is increased NOx.
Now, some people have commented on the fact that BMW and Mercedes have managed to pass emissions without the defeat device. Nobody has mentioned that the Chevy Cruze is able to boost an extra 10 hp for 10 seconds, but I think it is relevant.
I don't know how the Mercedes runs, but reading the reviews of the BMW, they mention that there are times, when under heavy acceleration, that it gets louder, or more dieselly.
I suspect that MB and BMW allow more noise, and are possibly better insulated to counter it. By using less of a pilot injection they would be louder, but emit less NOx.
In the case of the Cruze, I'll bet the car is normally 140 hp, and got a waiver from the EPA to allow additional pollution for only the 10 seconds. So, you can merge onto a crowded highway, or make that two-lane-road passing maneuver, but generally keep the emissions clean.
We know that VW has been fighting against the ghosts of the old GM diesel atrocities, and telling people that diesels are not loud, clanky, smoke blowing turds, but quiet, clean, and quick.
I can only imagine that they wanted to make sure the automotive press would be impressed by how quiet and not at all what they expected of a diesel these new cars were.
Most people also appreciate the quiet nature of these cars, and that was one of the selling points for some.
I am positing that this is the real reason VW used the defeat devices. If so, I am not sure why they couldn't just allow it to be a little louder and pass.
Unfortunately, I doubt we will ever know why they did what they did.
As it turns out, to quiet the noise from ignition, they use "pilot injection", or inject some fuel before the main injection. (Overly simplified, but hopefully good enough.) The side effect is increased NOx.
Now, some people have commented on the fact that BMW and Mercedes have managed to pass emissions without the defeat device. Nobody has mentioned that the Chevy Cruze is able to boost an extra 10 hp for 10 seconds, but I think it is relevant.
I don't know how the Mercedes runs, but reading the reviews of the BMW, they mention that there are times, when under heavy acceleration, that it gets louder, or more dieselly.
I suspect that MB and BMW allow more noise, and are possibly better insulated to counter it. By using less of a pilot injection they would be louder, but emit less NOx.
In the case of the Cruze, I'll bet the car is normally 140 hp, and got a waiver from the EPA to allow additional pollution for only the 10 seconds. So, you can merge onto a crowded highway, or make that two-lane-road passing maneuver, but generally keep the emissions clean.
We know that VW has been fighting against the ghosts of the old GM diesel atrocities, and telling people that diesels are not loud, clanky, smoke blowing turds, but quiet, clean, and quick.
I can only imagine that they wanted to make sure the automotive press would be impressed by how quiet and not at all what they expected of a diesel these new cars were.
Most people also appreciate the quiet nature of these cars, and that was one of the selling points for some.
I am positing that this is the real reason VW used the defeat devices. If so, I am not sure why they couldn't just allow it to be a little louder and pass.
Unfortunately, I doubt we will ever know why they did what they did.