Well, I couldn't make it to The Rock since a transmission pump blew on my way home from work.

As for the times, once it hits about 65 or so, it takes off and it's gone.

 

hey, i saw an episode of myth busters (i know i'm a dork) and they did that test and they proved that it was actually creating less drag with it up. who would have thunk it.

 

for those interested:

http://www.hellerauto.com/faqs.htm

http://www.findarticles.com/p/articl...39015#continue

http://makeashorterlink.com/?I17A2100D

http://web.archive.org/web/200208032...332270,00.html

 

Had by tonneau off AND tailgate up for about 2 months now. Don't notice a diff in drag or fuel economy. I think it's all bulls***. Of course, IMO....

 

It is challenging to do an accurate MPG test that can spot things that make only small changes like
tonneaus, tailgate up/down, thermostat settings, tires & air pressure, acetone in gasoline, tornados swirlygigs, etc.

But in the 18 wheel trucking industry MPG is a profit or bankruptcy maker.

They figured out how to do a reliable MPG test years ago when hundreds of experienced and smart people got together:
---
Got a buddy with a Dodge Ram with the overhead trip computer?
(His truck does not have to be exactly the same as yours, but the closer the
better)

Since you are making a modification with hopes of getting better MPG
why not do a "before & after" test?

Do a 'before test' with both trucks
* you and your buddy fill up at the same gas station and put the same air
pressure in all tires
* Pick a highway without too much traffic and hopefully where the wind is a
head wind or tailwind (side winds mess things up)
* Your Ram and your buddy's Ram follow one another staying at least 6 vehicle
lengths apart
* talk to one another with cell phones or walkie talkies
* drive at the same speed
* reset the overhead computers at the same time
* drive at least long enough to burn up 2.5 gallons
* exit highway, turn around, and continue the test in opposite direction
(this is to partially cancel out wind direction)
* write down average MPG on overhead computers at end of run
and compare this to the gas pump numbers and odometer mileages.

After doing your modification
redo the test the same way as above,
hopefully at a time of day where the temperature is about the same as the
'before' test and the wind speed & direction is not a problem - which you
can check here:

http://tribunewx.wunderground.com/US...WindSpeed.html

Note that in the above weblink you can type in your zip code and get exact
wind, temperature and other weather data.

The value of your buddy's pickup being along on is that on this 'after' test
if his MPG is greatly different you should suspect something has gone wrong
like strong cross winds, a change in temperature, tire air pressure, etc.

If you want to test two trucks against one another that are already modified
like comparing 3.55 differential gears to 4.56 gears
or an underdrive pulley, syn versus dino oil, tire air pressure, thermostat,
SuperChips, etc......
you can modify this test slightly for even better accuracy.
Swap two tires from one truck to the other.
Now both trucks have the same 'average' tires.
Weigh the trucks and add weight to the lighter truck to make them even.

If you really want 'gold standard' accuracy that you can trust
(or if you are measuring a small effect like a thermostat)
then swap the mod over to your buddy's truck
and do the tests another time with your truck as the 'control'.

If you are presently thinking:

"Wow, who would be that careful for a lousy MPG test?"

then just think about a dragstrip
which will have:
carefully measured distances,
highly accurate timing trigger by light beams,
know its altitude,
have a weather station,
and have a computer program to 'adjust' results for weather conditions.

All this type of MPG test is doing is applying the same standards to MPG
that is expected when someone brags about their vehicle's ET or MPH in the
quartermile.

By doing a test this way you are doing a simplified version of a
SAE/TMC Type IV fuel economy test RP 1109.

Here the SAE stands for Society of Automotive Engineers and
TMC stands for Truck Maintenance Council which is a group
of professional 18 wheel truckers who have banded together to share
information. RP stands for recommended procedure.

Credit for inventing a 'reliable' MPG test like this goes to many, but
especially Claude Travis, known to his peers at TMC as "Mr. MPG,"
who has spent 37 years managing the operation, maintenance and testing
of heavy-duty, on-highway vehicles. Highly regarded for his exhaustive
research in the field of heavy-vehicle fuel-economy, he is principal of
Claude Travis and Associates, Fleet Consultants, Grand Rapids, Mich.

In the actual SAE/TMC type IV test they also take the temperature of the
fuel both before and after, because a gallon of fuel coming out of an
underground tank at 57 degrees F will expand/contract several percent
as it approaches that day's air temperature.

If you are interested in learning more about this
there are also SAE/TMC tests I, II and III
and no doubt someday an even better test V will be invented.

 

ya, or you could just fill your tank... wait till its empty... fill again....
little bit of math..... done!!![sm=smiley20.gif]

 

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Sorry but, that was a little long winded. jager is right.