The Amocat- 2005 Tacoma

[aardvarcus]

Sven and BamZipPow,

Support did have something to do with it, but a forward projecting flat lip (splitter) on the bottom of an air dam was shown in Hucho’s book in one example as achieving a slight reduction in drag. I am assuming because it is helping to contain the increased pressure from flowing under the dam and instead directing it around the side.

This tube acts like a lip, only with a radius in the leading edge. This also mimics a design I have seen on some OEM air dams that have a radiused bulge near the bottom, as well as some OEM designs for a front splitter that lead with a radiused edge. It also gives the air going around the car and under the dam a small radius to follow, which I would think would be better than a square edge.

But at the end of the day I don’t have a wind tunnel so this is just guess and check based on what I have seen and read from those who do.

[wdb]

Have you driven with it long enough to form any opinions yet? Any MPG differences, driving experience, wind/road noise, blahblahblah? Enquiring fellow Taco owners want to know!

[aardvarcus]

Wdb,

Good questions, I’ll address the MPG first. I have not done ABA, but I have been watching my fuel log intently to discern a FE difference. Unfortunately, my timing could not have been worse, as I installed the air dam right as the temperature dropped dramatically. Also my fuel log contains some tricky data, as most of the time I fill my truck with 87 Octane 90 Gasoline 10% Ethanol, but occasionally I get access to some 93 Octane 100% Gasoline, so many of the peaks on my FE graph are associated with that. Many of the dips on my FE graph are due to unusually large amounts of offroad driving.

Looking back through my fuel data, to avoid the 100% gas and offroad outliers, I will use six tanks from October 2nd through October 18th (next tank had 100% gas) as the baseline, and six tanks from November 5th (first tank with it installed) through 13th (today) as the test data. Note the temperature has dropped 20 degrees, from having morning lows in the 50s and 60s down to lows in the 30s and 40s. Also some of those tanks had V1.0 not V1.2 of the air dam.

In October, traveling 1812.928 miles using 70.015 gallons is 25.893 MPG. In November traveling 1114.568 miles using 42.633 gallons is 26.143 MPG. So the air dam is showing a roughly 1% increase which is within measurement noise, but given the 20 degree temperature drop, I don’t think the results are too shabby. So basically I like it, but let’s face it I am biased to it.

As for wind/road noise, there is a noticeable reduction in wind noise coming from air hitting the tires up front. The Tacoma’s had stock tire air deflectors which did ok when traveling straight, but the second I would cut my wheel very far, the noise would greatly increase. That has all but gone away. Note I am running 235/85R16 (32”) tires on stock wheels and have the front shocks raised up 1.75” so your results may vary.

For driving experience, the truck certainly feels more planted around turns, but that may just be my brain extrapolating a reduction in noise to better handling. According to popular literature, the truck should be experiencing reduced front axle lift, which is equivalent to increased downforce, and the handling isn’t all in my head. Anyway I feel better about taking the same turns at the same speeds.

In other news, I am refining my aero shell design, so that will get posted when I get something worth posting.

[aardvarcus]

Well, I don’t know that I have an idea worth posting yet, but I started last night gluing pieces of foam together to make my aero shell. I cut a few wooden 2x4s into the gentle arch shape I needed for the top section, laid plywood over that, and started layering on ½” XPS foam using gorilla glue to hold them together. I then stacked weight on the assembly to hold the foam tight together, since the glue should expand as it dries. After it dries, the foam should hold the arched shape when removed from the form.

Also, the cold weather has killed my MPG. My last tank was my worst ever. Definitely need to check my tire pressures when I get home today, I am sure they are at least a little low due to the temperature swing.

[windy]

Conveyer is such a neat idea. I scoured the junkyard to find a good fit my 74 wagoneer, but not a single air dam was in a good shape, ended up buying one on-line that match my width, and need to figure out the best way to attach it.
The hose at the bottom is good too, the same idea is present on OEM civic crx from the 80's.

The other try was the underbelly pan on the 85 Grand wagoneer, seen here during install, I used the bungee around the block...




I used a drip pan fastened to the frame under the transmission and transfer case and covered a bit of the cat, great idea, but not so good when it is over 90F, the cat slowly warmed up the gas tank , and in the afternoon with temp in the near 100, the gas was so hot that the electric fuel pump could not draw gas due the restricted air flow under the carriage, pull over and chill out in the middle of Utah beetween Green River and Wellington... on the way back to SF....

But as you mentioned at the beginning the biggest improvement was the synthetic oil for the rear differential which netted a good 2 to 3 mpg, so from 12.5 to almost 15 and even 16 cruising on the highway 80 going East or West over a few tank refill.

[aardvarcus]

As an update, I have gone back and forth fifty times on exactly how to do my aeroshell, which frustrates me to the point of ignoring it. I have finally decided on a path forward, which is to use as much as I can from the original shell I chopped up to put together a 1/3 shell right behind the cab. This uses the original pieces of the shell from the front, back, and roof trimmed down to size. This will also cover only the part of the bed that my toolbox currently occupies, and gives me enough room to easily access it. I got the pieces all cut out, but I need to change some lengths to make the cover follow my template overlay (AST-2). Anyway I posted up a mockup picture showing the modified front and back, the roof section bridges the two but I don’t have a picture of it yet.

The long term plan is to build a cover to cover the rest of the bed and hinge it off of this cover, but I need to just get something built and done so I am not focusing on this at all until the first part is installed and done.

Hey Windy,
Sorry I never saw your post until now. I can't take credit for the conveyor idea, I borrowed that from others on this site. The drip pan you used is a neat idea, hopefully you have resolved the gas tank heating issue. (I had a similar issue on my old car.)

[aardvarcus]

Continued to work on my partial shell mock up. I changed the angle (steeper) and height (shorter) of my back piece to raise the back corner to hit on an AST-2 overlay. I cut the old roof section out some more to match and got the front, back, and roof all temporarily bolted together. After some tweaking and adjusting, I threw the mock up on the truck to double check the overlay.

Ignore how bad the overlay pictures are, it was dark out and I had to really wack out the camera settings to make the shell show up against the background. Also the camera was too close to the truck so the perspective was off.

The rough shape seems to basically follow AST-2, so I am decently happy with the results. The cab to shell transition could be smoother as it looks to be a fairly abrupt 6.5 degree change.

Next steps are:
Adjusting the side window openings to be larger.
Fiberglassing these three pieces together to remove the bolts.
Making something to transition between the window sides pieces and the roof.
Getting a more distant side picture of the shell.

[wdb]

Looks interesting to say the least! It may just be me but it looks as though yYour design study validates the flying buttresses on some Chevy pickups, and the Honda Ridgeline.

[aardvarcus]

Did a little more on this over the weekend. I got a more distant side photo in good light where you can actually see the shell. Did the requisite AST-2 overlay and it looks like the back of my shell is a little low and the front a tad high. I attached the overlay photo.

I removed a bit more material from the front, maybe dropped it 3/8” to ½”-ish. I also cut some more material out around the windows. I was getting it mocked up to make the back part steeper to raise the back up around an inch when I ran out of time. I also found another piece of the original shell that I may be able to adapt into the window to roof transition piece. If all goes well, I hope to get a final mockup done and maybe start the fiberglass patching next weekend.

[aardvarcus]

Well, I got my initial fiberglass patching done over the weekend and it has set up nicely. This was my first time using epoxy resin with fiberglass, it seems sturdy. The remaining tasks to do on this project are:

1. Make a curved transition from the top to the sides and finish making a lip for the side windows out of fiberglass.

2. Prep and paint the shell.

3. Install some acrylic/lexan windows.