The Amocat- 2005 Tacoma

[aardvarcus]

Edit:
To make this thread easier to follow and so that you can bypass my rambling, I decided to post an index up at the front for you to link to completed major projects on the truck. Also I have the original and a recent picture of the truck so you can see the changes that have been made.


Rubber Air Dam:
http://ecomodder.com/forum/showthrea...tml#post454423

Initial Half-Aeroshell Construction:
http://ecomodder.com/forum/showthrea...tml#post473102

Finished Half-Aeroshell:
http://ecomodder.com/forum/showthrea...tml#post480010

HVAC Air Intake Pest Screen:
http://ecomodder.com/forum/showthrea...tml#post481678

Electric Fan Construction/Swap:
http://ecomodder.com/forum/showthrea...tml#post483654

Fender Flare Removal:
http://ecomodder.com/forum/showthrea...tml#post494844

Full Aeroshell:
http://ecomodder.com/forum/showthrea...tml#post511880

Back to the regularly scheduled post:
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Hello all,

Figured it was time to start my own build thread for this truck. Truck is a 2005 Toyota Tacoma Access Cab, 2.7L 4 Cylinder, 5 Speed Manual, 4x4. The truck is my daily driver, which includes long commutes to work, trips hauling construction materials, and driving off road. I engage 4x4 an average of 3 times a day to navigate unpaved roads. My current baseline from my fuel log is 26.7 MPG, based on 23 fill ups.

My first goal is to consistently exceed 30 MPG, while maintaining or improving the truck’s capabilities. I plan on achieving most of this through aerodynamics, as the truck has a factory Cd of Cd 0.394.

Mods that I have already done are: First mod was switching all long term fluids to Amsoil synthetic, including front diff, rear diff, transmission, and transfer case, and changing engine oil to Mobil 1 synthetic. Second mod was changing the tires, went to Michelin LTX M/S2 LT 235/85R16 mounted on factory Toyota 16” alloys. (Note factory was P 245/75R16 on steel wheels.) This nets about 0.5” ground clearance, 4% gearing reduction, and corrects the speedometer to within 1MPH at 55MPH. Going from P rated tires and steel wheels to LT rated tires and alloys only netted a 5lb increase in weight, but it increased the rotational inertia of the wheel tire combo by 15% due to the weight being farther from the center.

The next step for this truck is an aerodynamic bed cover.

[Daox]

Nice to see a build thread for your vehicle. Have you thought about a grill block or air dam?

[aardvarcus]

Wow, fast reply. Those are both on my list, just a little farther down. I am going to do an air dam, but it is part of a bigger project on the front end because I want to make it quickly removable for rough roads/trails. I don't want to do the grill block until after I swap to electric fans, and get a feel for the temperature baseline.

Let’s jump right into the bed cover. I have run through many options on bed covers, and have admired all the great looking aeroshells that members on here have made. Truck has a factory Cd 0.394. I am leaning towards doing a cab wing and tonneau cover combination. That would give me the most flexibility as far as still loading tall things in the back half of the bed that a full aeroshell would not allow. I think it would also retain the best visibility.

I will present my initial plan below, and then I would like your comments on how to make it better and/or easier to construct.

The Tacoma has a 6’-ish bed. The “cab wing” would be built similar to a half aeroshell, and only cover about 3’ worth of bed. What I have to start with is a snugtop xtr bed cover in rough shape I picked up for cheap. It was designed for a 5’ bed, and I am going to hack up into the half cover. You can see from an attached photo, it has a two part window; my plan is to remove the back window and end the cover right after the current fiberglass divider between the windows, forming a 3’ish bedcover. The front window and good visibility will be retained.

Next the roof will get removed, the front most part with the bump up will be removed, and the middle and back of the roof will be reinstalled starting in the front on a curve following the AST-II template in side view. The sides and front of the cover will be left intact. This will form a gap between the top sides of the cover above the windows and the lowered roof. This gap will be prepped and fiberglassed, tying the two together. I have attached a sketch of what I am proposing.

Obvious downsides are little plan taper and the vertical extension on each side of the cover is less than ideal. Upside is ease of construction, and a “more normal” appearance, as you will not see the tapering roof section from the side, only from the back.

I am unsure on the best way to address the tonneau cover, as presently the template AST-II does not touch the back of the tailgate when overlaid. Also any half tonneau would need to be quickly removed and stowed. Options are to install a half tonneau at present elevation, raise it up to touch the template, or extend it back to touch the template.

Edit: The template looks off in the front, but it will be correct when I replace my front shocks and raise it up a bit, plus I am accounting for additional dead load in the back of the truck.

[BamZipPow]

Since you off-road, you'll need to account fer frame/bed flex so the shell doesn't impact the cab. On my aero cap journey, I made some gap covers that slide over the cab and cap. I ended up incorporating the covers into my aero cap.

Can't wait to see how you progress!

[aerohead]

Does the Taco have holes in the rail tops? If so,you could attach stanchions in those,then attach the tonneau to the stanchions.Air Force button-release lock pins would be ideal.Fast!
If you blistered the tonneau you could loft the upper surface up close to the AST.Without it,or some kind of spoiler,the air may overshoot the tailgate area completely.

[freebeard]

Given your materials and goals, that looks like a reasonable approach.

How about a full tonneau that overhangs the tailgate; but has a sliding track with roller bearings, like a high-end cabinet drawer; so it unlocks, pulls back and locks to make a half-tonneau/Bonneville spoiler?

[oldtamiyaphile]

Simple first mod, use pipe lagging to fill in the gap between the cab and bed.

[aardvarcus]

BamZipPow,
Since I am reusing the front part of the original shell, I believe it will hold the shell about an inch or so away from the back of the truck, so that should allow sufficient room for flexing side to side. I saw what you did in one thread with the flexible baseboard as gap filler and would like to do something similar.

Aerohead,
No holes in the bed rail tops unfortunately, but it has a factory track on the inside of the bed that I can mount a bracket to. That bracket could hold a quick release. I would like to not inhibit visibility too much in the back, so I don’t think a blister would work for me. Since the tonneau needs to touch the template in the back it needs to go rearward, up, or both.

Freebeard,
Thanks for the encouragement on the cap design. I hadn’t thought of a sliding track, that is a good idea, but I don’t want to go to a full tonneau for bed utility reasons.

Oldtamiyaphile,
Yeah, I have done pipe insulation as a gap filler on one of my other trucks, need to cut pieces for this one.

What I am thinking now is I could do two tonneau pieces flush and have one just in front of the tailgate covering the last part of the bed and one sticking out just over a foot behind the tailgate to touch the template, but then I have the overhang to contend with. Alternatively I could do just the piece in front of the tailgate if I raised it up about 5” and leaving it open below I could still see above and below it, so visibility wouldn’t be that bad. Either way they would be hinged or quick released so that I could transition to a fully open bed in the back as necessary.

[t vago]

Nice!

I have found that a tonneau cover, by itself, effectively did nothing for aero on my Dakota. Looking at the template overlay, it would appear to be because the airflow over the Dakota does not come near the tailgate.

You might want to experiment with the cab wing by itself, first. Then, once you demonstrate an improvement in aero with the cab wing, you can experiment with a partial tonneau.

[aardvarcus]

Thought I would update this thread with my progress. I took some measurements of the truck and the cap. I stripped all the unnecessary windows, liner, and hardware off of the cap. I then chopped the majority of the roof section off of the cap. I still need to chop the front bump-up off, just ran out of time. Also the side cuts are not finished; I will trim those to make one straight line. I ran into one snag, as the roof section was doubled and reinforced. I was expecting it to just be a single sheet of fiberglass that I could coax into a gentle curve. I will either have to remove the reinforcement or just use another material for the roof. Anyway, here are some shots of the progress, ignore the dust from the sawzall.