Truck Aerodynamics - cost effective mods?

[Joenavy85]

not sure where it's available, if at all, i googled "angled truck bed cap" and it popped up.

[fjasper]

I found the thread on EM for this top:

http://ecomodder.com/forum/showthrea...d-cap-583.html

[slowmover]

One way to help answer the question asked is what percentage of time the truck spends above 50 mph. If it is only the commute to the yard, or to the jobsite, some idea must be had where aero will play a part in the reduction of costs.

I saw a recent post on engine hours that the new 2011 Ford diesel breaks out idle time as a separate reading from overall run time. One would like to see even more info on time-in-a-given-speed-range.

Nationwide the average metro speed is 15 mph. Truck companies plan cross-country trips at 50 mph. The range between is useful, IMO. At a 39-mph average I have a lot of highway driving included in my overall fuel use. If my per tank average falls below 27 mph I see a decline in FE that is related to the overall slower travel around a metro area.

For the OP what is the average mph at present? Something below 30 mph suggests mainly urban/suburban; below 25 mph little aero advantage gain is to be had (my guess) as so little time is spent at highway speeds.

Otherwise the generic suggestion of a partial grill block, bed cover and only a partial cover below (from body edge inwards to frame rail) may suffice for pickup truck aero and ROI. A "metro" truck will benefit more from a winter front, LRR tires for summer, fresh fluids/filters, etc. Driver skill versus add-ons past that.

More, and specific, information on truck use could be useful to the thread. What is the present average mph? A log over one week showing time-in-transit, perhaps, for urban versus rural would help. Same for a scaled weight (full fuel, driver plus the usual stuff onboard; and compared to the DODGE Towing Guide Specs). The advantage of a Dakota is in it's smaller size per in-town agility, not necessarily weight reduction or FE over a full-sized truck. It can tow a substantial trailer, for example, well bigger than a Ranger.

And a business vehicle has IRS deductible miles and/or can be depreciated on a schedule. This is a vastly different relationship to fuel use than a private vehicle. The best savings may well lay in a full suite of devices to fully warm the vehicle prior to morning departure, and in maintaining that warmth (where ROI is best, IOW).

A concerted effort to reduce/eliminate idle time would be my focus if for no other reason than longevity (like-new performance over the longest time & miles). I'm all for DIY on this forum, it's fantastic, but it follows the same pitfalls seen on vehicle-specific enthusiast boards where sending money to strangers will magically reduce my op costs. Let's see more of what we're starting with. (Pics, too!).



.

[Blu3Z3rg]

Sorry I didn't go into detail about the truck use. I have a thread on the dodge forums where i go into it in much more detail.
Sadly I cannot yet post it!
Anyways, I live out in the country a bit, so I drive for like 4 minutes through my little town, and then it's a 15 minute hike at 55-60 mph, and then it's like a half-mile between lights most places I go from there. Also, Probably once every couple of months we travel a 3 hour trip to Michigan that is all Highway.
I would say my overall speed average is probably 40 mph. It's a 15 minute drive to like, go to the grocery store out here, lol.

As for "the jobsite", it varies... Sometimes it's an hour and a half drive, sometimes it's only 20. Right now, the shop is 15 minutes away and only 2 stops in that with all 55+ mph. The job I'm going to typically is 40 minutes away, and my average is probably 40 mph. I'm just taking average guesses at all this btw, as I don't actually record it or anything.

[SlideWRX]

high res pics of the 2005 quad cab:
Dodge Dakota Quad Cab (2005) with pictures and wallpapers

I would say a belly pan, just because the truck sits high enough that there is a lot of air going underneath, even if you add an air dam. Do you have the tow hooks sticking out of the two front openings in the bumper? probably a good idea to close those off. They might feed the radiator though. A grill block will help with the short trips to the shop; I'll bet it takes 5-10 minutes (depending on season) to warm up on that trip.

Changing a final drive on a 4x4 isn't cost effective (gotta do it twice, hehe), but I'll bet that would be a big help as well.

[redneck]

The first thing you need is a Scanguage or Ultraguage to help track fuel use so the nut behind the wheel can be recalibrated. Then aero mods.

>

[slowmover]

This looks like the other forum discussion thread.

Looks like records should be established (if not already done). Fuel log here at EM.

5,260-lbs configured (same weight as my 1/2T 2WD 2001 high option Ram V8-318) against what specific drivetrain (drive, engine, trans, rear gears, tire height, etc)?

The commute can be figured with the trucks elapsed time counter (if so equipped) for travel time versus miles. Miles from the shop to the jobsite and back should be deductible.

Tire pressure set according to load?

Truck has hard tonneau cover.

As above, some instrumentation needed. The CAI may hurt more than help, so hold off on other mods until records baseline established for time, distance, fuel and use.

[Joenavy85]

Originally Posted by slowmover

Miles from the shop to the jobsite and back should be deductible.

if you're talking about taxes then yes, any mileage from your shop (place of work) to the jobsite counts as work related driving, but is only deductible if you aren't provided a vehicle by the company (forced to use your own). be sure to keep a log of all those miles and you can use that when tax season comes around. also note it is an itemized deduction, unless the IRS decides to change something

[Blu3Z3rg]

Originally Posted by Joenavy85

if you're talking about taxes then yes, any mileage from your shop (place of work) to the jobsite counts as work related driving, but is only deductible if you aren't provided a vehicle by the company (forced to use your own). be sure to keep a log of all those miles and you can use that when tax season comes around. also note it is an itemized deduction, unless the IRS decides to change something

ABSOLUTELY! I keep a pretty detailed log for all those miles actually, much more than I probably need to.

The Truck has the 4.7 V8, which is basically a small Hemi, without the cylinder cut off. This is mated to the 545 Mercedes Transmission which then goes to the 4x4 with 3.55 gears.

I won't be putting on any boat-tails, lol I'm looking for more cost effective and realistic things obviously. And of course I watch my driving.

I like the idea of the grill blocking, especially where they leave holes for the tow hooks, which I don't have. I'm thinking of doing a chin spoiler type of thing, and underbelly pan to a certain extent.

As for setting tires to load... well, the load sure can vary, but i'm trying to make a good couple of weeks without hardly carrying anything to get a good baseline and get the info up on this site.

OH! and thanks slowmover, for linking for me, lol I"ll be putting that link in first post probably tomorrow. For right now, I'm just trying to get a good solid baseline of where i'm at now to get my log started (excellent idea - glad I found it right away!!!)

As for the Cold Air intake... Surprisingly, you're right! I am getting the feeling that it wants me to get on it for it to really free anything up. We'll see though, since guys on the dodge forums are suggesting that a CAI, exhaust, and tuner gets them to the 17mpg range pretty easily. Currently, those are in the plans as that will help with mileage towing anyways, but I think when i tuned the CAI, I did so at too high of an rpm for mileage. 3" puts my motor (believe me, lots of calculating here) with a max power band in the 3500-4500 range. Only downside is that the low end suffers some, so being light on the throttle isn't very helpful in moving a 5260lb truck. If I find 2 3/4" piping, I may switch to that...

[slowmover]

OH! and thanks slowmover, for linking for me, lol I"ll be putting that link in first post probably tomorrow. For right now, I'm just trying to get a good solid baseline of where i'm at now to get my log started

You're quite welcome. It was a lot harder 35-40 years ago to find enthusiasts of a similar stripe. We all wanted a wider performance envelope (acceleration and economy) but it was hard, very hard, to find out just where the otherwise similar efficiency gains necessary to both branched apart without money, time & expertise. Some mods worked and some didn't.

Today one is faced with the consumer culture that sees, "buy my product for FE and throttle-stomp with no overall penalty!!" endemic to aftermarket advertising. And is reinforced in this self-deception by enthusiast forums, ad nauseum. Main problem is lack of records. No indication of average mpg much less average speed, etc. Hard to know who to trust.

When in doubt: ask for the calendar year numbers, both average mpg and average mph. Those without don't truly have a leg to stand on.

As to tire pressures: the big truck tire folks will tell you to get per wheel readings and use the heaviest tire as the across-axle tire load X2.
My suggestion is to weigh it with a really heavy load this way so you know how things are; remember, springs settle over time at different rates. And masons never overload their trucks, lol. Then, a separate set of readings for a light and normal load.

In both cases check pressure the following morning to see what actual pressure was when cold. Record, and then inflate/deflate to proper numbers. Work trucks & tires are a special. Done right you'll come out close to a commuter for life, relatively. Done poorly and tires will eat you. (As you already know). I imagine you have easy access to an air compressor.

With one or two or three scale weights to compare against, truck tire pressure can be kept in accordance -- quickly changed -- for long life and safe operation. FE is just part of overall Economy. And is always trumped by safety. No one wants to "give" us the time to keep the vehicle at it's best, we have to make it.