lglamb

FWIW, about a year ago there was a 2500 or 3500 on ebay that
claimed 29mpg at 55mph. Had a box (don't remember) and injectors
and lowered 2 inches. I've always figured the lowering was a big
part of the mpg.

Tv just had a commercial for "on demand" karioki cable channel.
Gotta go barf.

Lowell

chuxtruk

Cmon....common sense says that drag is reduced by lowering the tailgate. Maybe some dipwit engineer or halfwit on TV would say something different but what would they know? I'm not buying it...



With the tailgate up....I agree with you on this one completey!!
Chuck

big jimmy

There was a respected test group that used several pickups, from little ricers to 3500's, using gate up, gate down, and those goofy net things.

They found most trucks got better mpg with the gate up or had no better MPG with it down or with a net.

The upshot was its pointless to bother dropping the gate or getting a net.

They did not do wind tunnel tests to find out why the gate up did not reduce MPG. They just found that having them up did not hurt MPG.


I can't say whether they were this or that, or engineers, but thankfully we have those types in this world or we'd still be using stone axes.

Big Jimmy

blord

The best that I can recall of the test, they said that with the tailgate UP it created a high pressure bubble in the bed. Wind then followed the contour of the bubble.

With the tailgate down, it just creates turblulence in the back of the bed which causes drage.

sled4fun

Exactly! It was an air bubble and the air flowed over it = less drag and better fuel economy. With the tailgate down it had more surface area for the air to grab and drag the vehicle down.

big jimmy

I pity the poor bugger who bites at this topic next "cocktail" party I have to make smalltalk at...

I'll whip out the "air bubble" like an old single action- after the appropriate ambush has been fashioned naturally. Or maybe DEADFALL TRAP would be a better description...thump.

Big Jimmy

Raspy

I'm glad we have chuxtruk's "common sense" to live by. All the engineers and testers have been leading us astray! For years this has been talked about. And those Dodge wind tunnel guys will probably now be fired. Help, Im losing my balance.


Wetspirit

sled4fun

Ok guys, I looked around a little to help enlighten us all on how these results were found related to airflow over the truck. Tailgate up or down.

Draw your own conclusions!

http://www.cartalk.com/content/colum...ctober/05.html

http://blog.kevindonahue.com/archive...s_mileage_.php

http://kwc.org/mythbusters/2005/11/e...s_cures_f.html

http://www.aberdeennews.com/mld/aber...e/14266948.htm

http://www.aberdeennews.com/mld/aber...printstory.jsp

http://experts.about.com/q/Dodge-777...efficiency.htm

http://www.trucktrend.com/features/c...tailgate_myth/

IrishND

I did kinda of an experiment over the last 2-3 weeks.

One week I ran 70mph for a week running cruise control to keep it at 70 or lower for a week and did about 13.5mpg and ran the tank to half a tank. Took a week to get to half a tank

Weeks 2 and 3 I ran 65mph and kept the cruise on when I could and ran the tank to half again....I was suprised to see the increase. 15.1-15.5mpg and 300 miles to a half a tank. Took a week and a day to get to half a tank.

Trust me it sucked driving 65mph, but if it saves me fuel, oh well for right now.

Bob
05 dodge ram QC 4x4 CTD Auto

C/E

I think that you will find that it was your RPM that was the real saver. The lower the RPM the less fuel burnt. IE less times the injector puts fuel in engine. This on it's own will save your fuel. Of course driving down hill will help as well and drafting behind a big rig will help but I would not reccomend it they tend to get testy bout it.

chuxtruk

I'll stick by my words there Ace and say again COMMON SENSE. Think about this now.... It took a bunch of aerodynamics engineers with time on their hands and these "professional" automotive authors writing all these articles to tell you what? That if you had any common sense, that the tailgate up will maybe give you a better miles per gallon figure by reducing drag? No! Apparently very few of us were that smart as common sense (if you have any) says put it down or better yet, take it off TO REDUCE DRAG. But the experts, after extensive testing on newer trucks, say otherwise. First I've heard about of any of this, honestly. Intersting reading...did you notice they say "modern" trucks in every test/article?? I don't consider my 93 very modern as there's not even a cup holder in it and me & my common sense says it has the aerodynamics of a brick. I don't need anyone to point out the obvious but I doubt they were talking about my truck in any of those tests and I'll be keeping the tailgate off, thanks. Common sense says that, if nothing else, at least the inside of the bed will be cleaner....and my mileage WILL improve as that thing weighs a TON!!

Shovelhead

Also don't discount the tailgate as a structural member across the rear of the truck bed.
I've seen reports of beds cracking at the welds due to running for extended periods with the tailgate removed, or with one of those cargo nets.

SoTexRattler

AMEN! I try to "fly it by the trim tabs" on the steering wheel whenever I'm on the Interstate and I always see some very satisfying MPG's I don't see when using my foot.
Made a round trip run to Pensacola Fl this past weekend and I got 22.58mpg on the outbound leg using the Cruise Control at 72-74MPH. Coulda got more if I kept it between 65/70mph but that wasn't fun.
Homebound leg had lots of stops, detours and town driving.. 20.5mpg.

The boost guage tells me if I'm getting good economy or not. anything below 5psi at 2000rpm = , 5psi = , 5psi+ = . Headwinds cost money. Hey!, it's a high profile chunk of steel being pushed through the air... Even brush guards deduct ~2mpg from what I've been told.

Did I say I love my truck? I love my truck...
It sure makes a great long-legged cruising vehicle. Easily getting well over 600miles on a tankfull. Daughter said my truck was quieter than my Wife's Minivan at highway speeds. (It helps to have it stuffed full of clothes too)

K.

Jon Gibbs

With all my vehicles I have found at highway speeds I get about three extra miles per gallon if I'm following somebody, at a safe distance of course, but the vehicle in front of you creates a little tunnel basically , where the wind is already agitated.
High divers use the same principle by smacking the water with flat Palms to create a tunnel and a smaller splash.

SIXSLUG

Resurrection:

I need to add that all these ideas and tests and opinions are all performed at very different conditions and with very different trucks and drivers...The best I have ever seen with my slightly modified 4x4 HO is just under 21 mpg, in Wyoming at about 5,000 feet above sea level running flat out to Colorado at 70 mph, little to no wind and after ULSD became the law for road diesel.

Limiting factors or drag adders= 2" level kit, larger "off road" tires, 350 lb cab hi canopy, tow mirrors, (can't remember if a/c or windows up or down...), standard load for a week out of town to include wife, luggage and a dog with supplies.

Drag reducers= Altitude, little to no wind added turbulence....level, slightly downhill running.

I worked with a guy that claimed his stock dually duramax regularly pulled 27-28 mpg. Also a 4x4.

I'm proud and in love with my truck still, but c'mon.... I am currently seeing 16.4, EZ on 1, don't break 70 mph 50/50 city/highway travel with slight fluctuation to average between fill ups, Power Service white bottle at .32 oz/gal, air check every weekend, at sea level, currently at 7950 gvw, winds variable, traffic light to moderate, temps 55-75F...

These kinds of threads make me glad we all don't live closer together.....

PS: The NV5600 is not an overdrive trans, 6th gear is the same ratio as 5th in an NV4500.... the "6th" gear is actually ratio'd between 2nd and 3rd for a 1,2,2.5,3,4,5 if you will, no overdrive.