No. That is not a practical solution anyway. If you can only test
cars on 70 degree/50%RH calm wind days, you are going to have a severe
backlog of testing after the first year.
I think the new test drives the car a little more aggressively. What
it should include is a full throttle acceleration from 10 to 75 mph.
The current test assumes that you bought a 200hp engine because you
want to drive like a little old lady.
Makes sense. Still not clear that this would produce more realistic
results than a dyno test. And you would need a very big indoor track
to accommodate my 10 - 75 mph test.
The truth is that no matter how you test it, the results will be wrong
for most drivers. Most drivers will be either more or less fuel
efficient than any number you put on the sticker. It clearly could be
more accurate than it is now.
I assume that the frontal area is factored in. Surprised there would
be no consideration of aerodynamic efficiency. I remember when there
used to be a lot of bragging rights for lowest Cd. Haven't heard much
about that in years.
not that big, and by indoor, i guess you could replace that will
walled/sheltered. OR, you cuold just use a circular test-track, and as
long as the windspeed is within a range (say 0-10mph) it would be
acceptable, since you're going circularly, so what you lose from the
headwind you gain from the tailwind.
Right now its very inaccurate. Almost useless i'd say, espcially as
modern cars will often have their software 'tuned' for the EPA tests.
Its not just frontal aea though, its shape, flow etc. We did start
talking about it a few days ago on #honda on the Efnet network though.
most cars were in the 0.3 range.
(top posting is generally frowned upon, but i'll let it pass this
wind tunnels are expensive, just in rental fees. second, they're just
no that big. third, all wind tunnels are static, the vehicle is held
in place with force bars, which record the forces acting ont he
vehicle when the tunnel is active (info courtesy a riend of the wifes,
who runs the windtunnel at Cranfield university) There is no way to
measure the effect the wind would have on the load of the carthe car
is not progressing, and as such having to work against the wind force.
if its not moving, the winds not affecting the milage, and its
basically the same deal as with any other static test.
nice idea though, good thinking.. a half mile wind tunnel might be
more the answer.
It sounds like drag (not just coefficient, but entire magnitude) of drag is
already factored in. http://www.fueleconomy.gov/feg/how_tested.shtml says:
"The energy required to move the rollers can be adjusted to account for
aerodynamic forces and the vehicle's weight."
The coefficient of drag is just that, a coefficient relative to a "bluff
body" (flat surface) of the same frontal area. Drag is the actual retardive
On Thu, 23 Feb 2006 18:35:15 -0700, "Michael Pardee"
Another unnecessary limitation of current tests is that cars are
placed in weight categories instead of factoring in their actual
weight. Apparently this is why the Accord Hybrid previously had no
spare tire in 2005 and when they added one in 2006 the milage
estimates dropped noticeably. The extra weight put it into the next
category and it was severely punished.
I've heard this argument before, but when I went to the EPA site that
describes the testing protocol (http://www.fueleconomy.gov /), it made
no mention of weight classes (other than being exempted altogether if
your vehicle weighs more than 8500 lbs). It does mention different
classes based on interior volume, but the testing protocol appears to
be the same for all classes.
Do you have any reference material/website link that can give me info
on the different weight classes?
On Sun, 26 Feb 2006 01:59:08 GMT, Gordon McGrew
This is from a Road & Track article on the 2005 Accord Hybrid:
Less sun and storage. No sunroofs allowed, because when it came down
to crunch time, the Accord Hybrid was on the verge of being bumped up
another EPA weight class and something had to go. [Goes on to note
absence of spare tire also.]
EPA documents refer to weight classes in this description of the
Inertia weight class means the class, which is a group of test
weights, into which a vehicle is grouped based on its loaded vehicle
weight in accordance with the provisions of part 86 of this chapter.
Here is the table itself. Note that at around 3500 pounds the classes
are in increments of 125 pounds. So, at some point, one more pound
counts as 125.
On Sun, 26 Feb 2006 15:34:44 -0500, Spazpop2000
It all depends on how far, how fast, and most importantly of all, just
plain HOW you're driving.
Smooth fluid driving at or around the optimal speed will result in
best MPG. lots of short drives, or ones which big speed variations
will result in poor MPG.
Driving agressively wll give poor mpg, and thinking and driving ahead
will do better. Its all about you. Geting a hybrid is no magic bullet
*BANG* yuo're getting high mpg figures. I can ease 50 out of my van on
a long highway run, I can get low double figures out of my 88 civic if
i really tried.
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