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FORDF250HDXLT 05-19-2011 10:29 PM

aerodynamic improvements; diesel,dually,dump
3 Attachment(s)
aerodynamics improvements.
can someone help with just a couple basic tips.
did my idea on placing a custom tool holder (the culvert,now with end caps to secure tools inside) help,hurt,or not really change anything?
if that did help,would placing a section of 8" PVC pipe on each side vertically (as that's all that would fit,and still allow me to open and close the doors of the cab) help round out the corners some more to reduce wind drag?

question two;
should i enclose the rear gates or leave them open like in the pics?
and or any other suggestions i should do with the rear.
iv looked around here,and saw the "boat tail" mods.
i really think thats like to stay away from that,but im open to suggestions and opinions,and will consider at least a few short sections on the sides and or top.
if anyone is good with photo editing,have at it to help show me what to do.

with diesel over $4 per gallon,i really need to help out all i can.

current MPG:
14.45 over the course of 53 tanks.

id like 30 lol.but id settle for 16 if i can reach it.;)

the engine mods and tweaks iv got covered.e-fans etc.:thumbup:
id like to just focus on aerodynamic tweaks please.
thank you for reading.

cleanspeed1 05-20-2011 05:28 AM

You made your body essentially into a box and want to keep the utility for work.

Given that you said that you didn't want to drastically affect the looks of the truck, and that you want to get to 16 mpg with an IDI without going into the mechanicals, it may come down to driving technique. The fact that you got 14.45 mpg out a combo that does 10 - 12 mpg most of the time is not bad.

I know you wanted to keep things relegated to aero, but given the constraints and the type of truck you have, it will be hard.

If it were me, and I just wanted to get another 1.5 mpg out of it, and I am not towing heavy or anything like that, here's what I'd do:

Regear the axle. The best cruise rpm is 1600 - 1800 rpms and most of the HDs and Super Duties are geared with 4.10s, 4.88s, sometimes 5.13s. IH intentionally set up the engine to fall off the efficiency cliff past 1800 rpms. Going to 3.55s will make a big improvement with either a stick or automatic. 3.08s would be even better, but without a turbo it will be slow going. ( See Big Dave's Powerstroke pickup and see what he did )

Synthetic lubricant: Front to back, but at least do the rear axle. Lot of drag back there.

Evans Coolant: I am a big advocate of this stuff just because it'll allow you to run hotter, eliminate the need for SCAs ( 7.3 IDI blocks are bad for cavitation when the levels are not proper ), and save the head gaskets. Higher, more stable operating temps = mpg bump.

If the injectors and pump haven't been done, they'll be sorted.

euromodder 05-20-2011 05:41 PM


Originally Posted by FORDF250HDXLT (Post 239613)
did my idea on placing a custom tool holder (the culvert,now with end caps to secure tools inside) help,hurt,or not really change anything?

Rounding off the corners could help a bit .
Don't make the tube sit higher than the top of the dumpster box - it'll increase frontal area, and you've already got plenty of that.

The top tube is also deflecting air down into the gap between the cab and the box. Try to prevent that - with small deflectors on the cab.
Same applies if you add something similar to the sides.

Close the gap aft of the tube


if that did help,would placing a section of 8" PVC pipe on each side vertically (as that's all that would fit,and still allow me to open and close the doors of the cab) help round out the corners some more to reduce wind drag?
You'd still be pushing air as much in the gap aft of the cab as what you're pushing aside.

If you cut a pipe with twice the diameter in 4 parts, the 4 pies will only be as wide and deep as the full tube what you were planning to use .
Additionally, the whole width of the 90 pie would be rounding off the sides of the box.


should i enclose the rear gates or leave them open like in the pics?
If the sides and front are closed off, it won't matter.
Kammbacks and boattails are also left open at the rear.

You could clean up the sides and make it flush like the top.


iv looked around here,and saw the "boat tail" mods.
i really think thats like to stay away from that,but im open to suggestions and opinions,and will consider at least a few short sections on the sides and or top.
Ugly as they may be, boattails are effective - especially on square boxes.

Smoothing out airstream on the sides would help a boattail to function properly.

Those dual wheels are very much exposed.
Fairing them in, or putting a bulbous deflector in front of them would very likely help as well.
Maybe you could fabricate a streamlined toolbox that fits along the chassis, that's directing the air away from the rear wheels.

Do you really need all those mirrors ?

FORDF250HDXLT 05-20-2011 10:27 PM

1 Attachment(s)
thanks for the replies.

the truck has 3:55's with LT 225/75/R16 (29.3X8.9) Effective Gear Ratio Change: 3.84:1
i haul HEAVY very often,so that was my main focus.
the truck is my business truck,setup for my tree service.hauling wood and wood chips.
there was a lot of time spent deciding on the shorter tires.
yes i could have gone with 215's,but i load wood by hand,and NEED the truck to sit as low as possible.
i drive an average of 45 MPH,which puts me around 1400 RPM in OD most of the time.
anyway,back to my focus;aero.

yes,that's what i figured about the tube.but i needed the tube type tool carrier and was the perfect place.i guess i should have an RV deflector on the cab roof now.

as for pushing half and half on the sides with the 8"'s the best idea i could come up with that would fit.
it's got to be better than just leaving the wind smashing a flat wall,so i guess i'll start there since you agree it could help a bit.
id like to add some typ of deflector on the sides of the cab,but i just don't see enough room for anything.
if only i had a super cab.......ah well.

clean up the sides.
so cover up the stakes somehow.
the drawback to this,is weight though.any suggestions?
what type of improvement would that make on a scale of 1-10,would you guess?

oh yes.very much needed.
besides the large ones being required by law,the small round mirrors eliminate my blind spots so i can change lanes.otherwise id never know if there was a car,or even a large truck there.
i have a rear view cam as well,but the mirrors.....oh yes,must haves.

priority is function for work.otherwise i wouldn't even be driving anything like this.i wouldn't have a pickup at all actually with these fuel prices.
im just looking for the obvious aero mods that will for sure lead to more MPG's.
i'll study the truck some more,and try to think of a way to deflect air away from the cab-dump body.this sounds pretty important i take it?

so no simple/basic air deflectors of any sort for the rear of the dump then?
it's either a full boat tail (not going to happen/besides not liking that look,the rear gates need to swing open,so i can dump fast and easy day in,and day out) or don't waste my time type of thing?

below is a pic of the underbody toolbox.
there is another just like it on the other side.
(yes these where needed.they do not lift with my dump.they hold my gear and chain saws/other tools etc.that i use daily.)

Maine is very rural,and if i want to stay busy,i need to be prepared to travel.yet i need to stay as competitive as the other tree services who may be just across the street from the place on bidding on.i drive approx 20k miles per any little aero mod,isn't so little in my case.:)

Bill in Houston 05-20-2011 11:15 PM

can the culvert tube be lowered? if you could lower it so the top of it is even with the top of the box, that would be good.

the toolbox is interesting. some kind of deflector under it could keep a lot of air off those tires.

some coroplast would smooth out the sides of the box, and would weigh too much.

and then? belly pan!

great work and great results so far.

aerohead 05-21-2011 01:46 PM

dump truck
FORD,you've had a lot of good suggestions worth acting are a few thoughts:
* if your grille opening is larger than the actual dimensions of the radiator,that opening can be reduced.If there is distance between the grille and face of radiator,if closed in with an air-tight duct,as all NASCAR racers do,you can reduce the area even more.
* if you don't have a wrap-around airdam which extends down as low as your lowest suspension member,which would still not get knocked off at jobsites,that would help.
* any gaps,like between bumper top and grille bottom at the nose of the truck could be sealed.
* with access to oxyacetylene of wire-welder,a very light and strong framework of Electrical Metal Tubing (EMT), to close in the flanks of the truck could be welded up and covered with doped fabric,as is done with vintage and experimental aircraft.
* the EMT could also provide for a very lightweight tail frame,fabric covered boat tail as well,which if hinged above the tail gates,could be winched up and out of the way with a 12-VDC Warn winch and simple cable/pulley setup.I know you don't like 'em,but they're a real money-maker.
* the box is' covered' when your driving? If not,a tarp,pulled down snug will cut drag there.
If you'll look at small delivery box trucks today,you'll see subtle 'softening' that their doing to every leading edge which might snag and trip up the air.Any of these tricks would cut your Diesel bill.

david85 05-22-2011 06:04 PM

Oh no, I really shouldn't be here LOL.

Bellypan was something I've been considering for my truck but never got around to it.

Looking at your utility box, a few things jump out at me.

1; the steel frame on is exposed on the outside of the plywood sheeting. This creates a lot of extra surface area and air drag on the sides of the box. I noticed that a lot when hauling railings on my truck. Its quite noticeable how much it slowed the truck down even with a single length on top. (which is one of many reasons I tow a trailer these days instead).

2; The cover you have on there. What you could try is removing the rear wall and storing it at home when not needed, then slant the cover down to the bed to simulate the "boat tail" effect. Better yet, the rear gate could still be hauled inside in a folded down position perhaps...

3; rear skirts. I've started to notice big rigs using these lately. (it seems I can't post images or links yet but just google big rig aerodynamics skirt on an image search and you'll see the filler panels they hang on either side of the longer trailers)

FORDF250HDXLT 05-22-2011 08:02 PM

hey David! great to see you here too man!
thanks for the suggestions.
while googling big rig aerodynamics skirt,i found a cool avy lol.
i can see how i can copy that aero mod, no problem.
i didn't realize i had so many aero improvements that i could make.
i figured this big box was a hopeless write glad to see iv got much room for improvement.
looks like my focus right off is going to be;
smooth out the sides.
round out the front corners some.
probably not a whole belly pan,but at least a custom bumper valance.
then work on enclosing the rear tires in,and perhaps some air deflectors on the under side of my toolboxes.i probably wont go too steep with those,because i haul heavy,and need the air to keep my tires cool between the duals.but im sure i can direct most of it to hit more down on them.
this should keep me busy for a while.
i had no idea really that those stake sides were causing much this is great to hear it will help free up quite a bit just in that.
im so happy no ones written my setup off as a hopeless,lost cause,areo brick lol.:)
thanks a mill guys!
i'll get working on some ideas and have pics of my progress within the month.

rigging up the back section of my hinged roof so it slants down some (at least when im not hauling stuff and don't need the room) not going to write that idea it really does sound like it could make quite a difference by many here.i'll need to keep an open mind.after all my wallet is much more important than looks:),and with the slant in the bed like that,it wouldn't be like something hanging off the end anyway,and really not alter the looks much anyway.

while searching the big rig aero kits some more,something called a "Trailer Tail" came up.
with some impressive results.
www(add the . here lol)
i think i could live with incorporating these onto my rear french door style gate.hinged as well,so i could still open the gates to dump easily.hmmmm
search this on youtube:
TrailerTail - Fuel savings of 6.5%+ for tractor-trailers
i could build one of these for my bed.

david85 05-22-2011 09:51 PM

I've actually admired this forum for a while and followed the odd thread but never registered until now. I probably know some of the members here who also frequent (where I am an admin).

Yeah, I found that trailer tail too although I didn't realize it was designed to collapse like that. Neat idea.

I'm not sure how easy this would be to do, but one thing I thought of on one of many drives in the rain (it rains a lot here......) was to try and either videotape or photograph a vehicle while it drives in light rain and use the image as a reference for where the drag comes from. The water mist tends to highlight any vortex as well as the airstream as it passes over the vehicle. Its also easy to see the big trailing wake behind the vehicle along with the typical stalled bubble in the pickup bed that mythbusters made famous a few years back (my 24~25 MPG runs were all with the gate up:thumbup:). Although I suspect many here already knew that effect was real.

With a chase vehicle in the next lane and a good quality camera, it might be possible to use this as a reference for what works or what doesn't when trying different aeromods. Never tried this myself though, just thinking aloud. The other way is to simply tape small strings at several places all over the vehicle which wind tunnels still use to this day AFAIK.

slowmover 05-23-2011 07:59 PM

Look forward to seeing how it works out.

The least aerodynamic big truck is the car carrier in a 3/4 crosswind.

I know that this is about aero, but I'd make even the smallest steering slop disappear.

I'm impressed by the mpg at present with that big box. The hotshot guys I work around would like to have an IFTA average that high (the combination of loaded and deadhead miles for tax purposes) for their flatbed chassis cab trucks & flatbed trailers in the oilfield.

I'd be thinking about side skirts/front air dam where conditions permit.

A boat-tail would be "the answer", IMO, once the rest is covered/smoothed/melted/radiused.


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