Based on discussions with knowledgeable sources, we surmise that once an
emissions test was detected, VW got the affected TDI engines to meet the
Tier 2, Bin 5 NOx limits by reducing the fuel flow rate.
This would reduce performance, but most likely not to the point where the
car couldn't complete the emission cycles.
Lowering fuel flow would also reduce combustion temperatures and/or the
duration of high-temperature operation enough to keep NOx emissions barely
within EPA limits.
If the car detected that it was no longer in "testing mode" but had
returned to "driving mode," it would restore fuel flow to the regular
level--which would send NOx emissions soaring.
On Sat, 19 Sep 2015 00:19:10 +0000, Ewald Böhm wrote:
The best answer to the question seems to be here, as noted by Sofa Slug:
"How can the program tell the difference? By noting the position of the
steering wheel, variations in speed and other data that suggest no one
is driving the car, and thus it is likely being tested."
Apparently VW lied at first, & apparently they can no longer sell the cars:
"The cheating came to light when the California Air Resources Board and
the EPA pressed Volkswagen for an explanation for disparities found between
lab tests and road tests of its vehicle emissions. The agencies didn't
find the technical reasons offered by VW to be convincing and said they
would not issue certificates allowing 2016 models to be sold until the
automaker offered an adequate explanation. "Only then did VW admit it
had designed and installed a defeat device in these vehicles," the EPA
said. VW said it was cooperating with the investigation but otherwise
had no comment."
It's interesting that VW didn't fess up until they were forced to.
That's pretty much human nature going back to the Garden of
Eden. The next trick is to blame someone else. A TV show from long
ago had comedian Flip Wilson on. His line was "The devil made me
Using Opera's mail client: http://www.opera.com/mail/
Staying on topic, this article says the cheat only worked when there was a
Here are the contiguous quotes:
VW used secret software — an algorithm that detects when cars are being
tested on treadmill-like devices called dynamometers, and stealthily
switches the engines to a cleaner mode.
Because *smog tests are almost always done on dynamometers*, VW got away
with the scheme for seven years, until the "clean transportation" advocates
went to West Virginia University, which tests emissions using equipment
that fits in car trunks.
On Mon, 21 Sep 2015 21:44:12 -0700, Sam Wilhelm wrote:
(4) What exactly did VW do?
Volkswagen has admitted that it equipped the control software for its
2.0-liter TDI diesel vehicles with a "defeat device" that detected when the
car was undergoing emissions testing and significantly changed the
operations of its powertrain to reduce emissions during the tests.
That detection was likely based on a combination of sensor data from the
car, which might include steering angle (since cars on dynamometer tests
don't make turns), front-wheel versus rear-wheel rotation speed, and a
variety of other factors.
It appears that a combination of the factors above plus extremely gentle
acceleration and braking might alert the car that it wasn't on the road but
being tested in a lab.
On Tuesday, September 22, 2015 at 8:42:32 AM UTC-4, CRNG wrote:
Seems to me that's a failed algorithm. Aren't these cars front wheel
drive, ie he has it backwards? Heard on the news last night mention
of the steering wheel remaining stationary was an input used too.
Not all dynos work that way. I would expect such a dyno to drive the
stability/ABS systems crazy, possibly SLAMMING on the brakes or other
actions. (Most cars today are FRONT wheel drive, so the case would be the
front wheels turning and the back stationary. For rear wheel drive trucks,
of course, it is the opposite case. on these, it would be VERY hard to keep
the truck on the rear wheel only dyno. If it started to drift to either
side, the steering wheel could not get the tires centered back on the
treadmill.) On such vehicles, it might be necessary to shut down the
stability/ABS systems to even do these tests, which would clue in any test
As for how the software could tell, this gives me an idea! The dynos have
some considerable inertia, but it is likely much less that the inertia
involved in accelerating the car to 60 MPH. So, the software might detect
VERY easy acceleration to highway speed as a sign of a dyno test. This
might also look like accelerating down a long hill, but if it goes on too
long, it indicates minimal wind resistance. If you are cruising at 60 MPH
with 4 HP effort, that would be a DEAD GIVEAWAY you are on a dyno! The
emissions test dynos probably cannot absorb the output of a big car's engine
to give it the normal highway load. That can be a LOT of power that you
have to absorb for several minutes.
| > My question is HOW did the car *know* it was being *tested* for
I'm more curious about how the EPA didn't
figure it out earlier. Reports say the EPA saw a
discrepancy between testing and on-road
results. But they've been haggling with VW
all this time and somehow never thought to look
at the software. Is the software accessible to
EPA? Do they have developers who could
How the test is faked is just a technical issue.
How the EPA didn't figure it out seems to be the
important issue. They only found out because they
threatened to hold up sales and at that point the
VW execs admitted what they were doing.
(Have they disclosed everything? Surely if there's
more dirty dealing they're not going to tell if they
don't have to.)
... Then of course there's the question that begs
to be asked: How could all of those executives,
in a company whose clientelle tend to be liberal
environmentalists, have possibly decided it was
a good idea to be so dishonest and shortsighted?
There should be arrests. Either way, it's likely
to be a serious, perhaps fatal, blow to the company.
If it were Chevy I'm sure rednecks would come out
of the woodwork to support "the company that denies
global warming". But VW customers are almost a
cult following, and mostly liberal.
Should there have been arrests of EPA miscreants (or the environmentalists
that petitioned them to do so) for the hatchet job they did on DDT? This
resulted in millions of third-world deaths from malaria due to other
countries following our lead:
Roger Blake (Change "invalid" to "com" for email. Google Groups killfiled.)
This article is not exactly accurate.
In the fifties, DDT was amazing, it worked great. We put it between our
sheets. You could spray it in the air and see insects dropping out right
But... by the seventies, mosquitoes (at least in Hawaii where I lived)
had pretty much become immune to the stuff. Enormous, absolutely enormous
amounts were necessary to kill insects. This is why there were environmental
effects. My father had a gadget that would drop a mix of diesel and DDT into
the muffler of the lawnmower and the smoke would kill mosquitoes, but by
the seventies it wasn't killing them any more, even with a couple pounds of
the stuff being burned.
Give it another forty years or so and we might be able to start using DDT
in a small way again. But it was the massive overuse and abuse of DDT that
got us to the point where it was banned, not some crazy left-wind conspiracy.
And yes, it WAS one of the big weapons in the fight against malaria, and it
was a crime to lose that weapon. But it wasn't politicians that lost it.
"C'est un Nagra. C'est suisse, et tres, tres precis."
The point is that government malfeasance, which can and does result
in massive death, rarely if ever goes punished. I don't know how much
additional pollution is being caused by VW diesels or if the effect
is even measurable given their relatively low numbers. I do know that
governments routinely lie, cheat, steal, and kill (sometimes en masse)
all in a day's work. There's no doubt that what VW did was bad, but
the outcry seems out of proportion given the routine misdeeds of
Roger Blake (Change "invalid" to "com" for email. Google Groups killfiled.)
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