Jack Myers wrote:


I have seen a suggestion that the onboard computer takes note of the
fact that the rear wheels are rotating and the front wheels are
stationary. That seems plausible to me.
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
detection software.

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.

Jon