Will Mandatory dyno testing kill quattro and 4wd?

[Dan Cordon]

> Efraim Gavrilovich <egav at wireless2000.com> writes:
>
> > I live in Vancouver, Canada and I have to take my Q-car every year
> > through a mandatory emission test. There are two dyno's there, one
> > for regular cars and one designated for 4WD vehicles. Test is done in
> > Neutral at 60mph with front and rear wheels being spinned by test
> > machine. By the way, my 15 years old 5KTQ passed with a huge margin
> > last time I went through this test. This is with original muffler.
>
> Neutral? Dyno spinning the tires?  That makes no sense.
>

I had the same thought when reading the post. Working frequently with
chassis dynos, I think I understand what's going on. In order to
determine the power requirements that a vehicle needs to maintain a
speed, a coastdown test must be performed. For instance - A sleek, light
audi may only require 35 hp to maintain 60 mph on level ground, while a
boxy hummer (or H2) may require over 60 hp. So to properly load the dyno
for a given speed, a coastdown test is done. Usually this entails
driving the vehicle up to speed (on a real road) and collecting data
while coasting from 60-20 mph. Then, this data is replicated on the dyno
*before* a dyno test is actually done. The dyno operators will adjust
parameters so that coasting down on the machine replicates coasting on a
road.

However, the above usually just applies to FTP driving cycle testing.
I'm guessing that none of the local emissions stations are so elaborate.
So in conclusion, I have no idea what Efraim was talking about by dyno
testing in neutral at 60 mph.

--
Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility