The Amocat- 2005 Tacoma

[aardvarcus]

Freebeard,
Yeah I should have done something like that, I should have known "clear" wouldn't turn out as hoped. I still might mask over and paint the outside edges, not as good but it would be something.


I was examining the shell yesterday, and I think it is a touch too low. When you tighten down on the bolts holding the shell to the track, it compresses the weatherstripping and drops the whole shell down I am guessing around half an inch, which I had not accounted for since I was mocking it up without actually bolting it down. I think I will get some pipe insulation I have lying around and put it under there to try to get it more flush.

Anyway, I ran a full tank through the truck and filled up this morning and got right at 28 MPG (28.00168). Note this tank was far from ideal, just a routine tank. Looking back through my fuel log, I have to toss out my prior tank numbers because it was 93 octane 100% gas which throws the MPG way off (about 2MPG). Averaging the prior five tanks (random number, five sounded good) I drove 1617.304 miles using 60.528 gallons resulting in 26.720 MPG.

I consider these results just preliminary until I get a couple more to average out, but comparing the initial results, it shows about a 1.28 MPG increase, or 4.79% improvement. I don’t think that’s too shabby for a half shell, hopefully with a few tweaks it will get a bit better.

[aardvarcus]

Had a second tank with the half shell, using the same methodology as before for calculating I now show an average 1.456 MPG increase or a 5.45% improvement.

I removed the shell to fix some of the issues with it, so I guess since I am driving without it I am doing a form of ABA testing, just with tanks. Prior to removal, I examined the roofline transition between the truck cab and the shell leading edge, and sure enough the shell was about ½” too low. This was certainly hampering performance. I have some ½” XPS foam, so I plan to cut a few strips to replace the compressible rubber weather stripping between the shell and the bed rails.

I removed the window and the bad looking adhesive, which was already starting to let go. That took quite a while. I masked off the center of the lexan windows and painted them from the outside, hopefully that will turn out ok since I didn’t use “plastic” primer. I then promptly ran out of time to work on the shell, hopefully today I can glue the windows back in place.

[aardvarcus]

So, since I am never content with leaving things alone, I took off the half shell to redo it again. The adhesive I had used on the window was coming lose, so I scraped that off. I masked off the window center and painted the outside of the lexan to hide the adhesive seam. I also did more bondo work on the shell, and trimmed the front edge of the shell to better integrate against the cab of the truck. I then painted the shell with primer followed by rustoleum hammered silver paint, looks much nicer.

I reglued the window in place, but that glue failed as well within a day or two. In desperation, I bought the most expensive polyurethane based construction adhesive I could find at lowes, and did lots of prep work, rough sanding to mar the surfaces, and then cleaned the two surfaces. I used my usual jack stand clamp routine, and this time I think the window is glued in there good, but time will tell.

Anyway, the silver paint almost matches the truck paint, and the black ring around the window hiding the adhesive makes it look nicer than before. I also shimmed up the shell by ½”, getting the transition closer and better matching AST-II.

Last week, I also mounted some bolt on steel truck steps (aka rock sliders) to the truck, not yet an aero mod, but makes it easier to get in and out. I hope to skin the bottom of them with something smooth, probably aluminum or UHMW (HDPE). This will be the start of my belly pan.

You will notice in my fuel log, most of last week was a-typical driving and I had my aggressive offroad tires on the truck, as I did a little exploring. I did have a tank early this week without the shell, and I will get a tank this week with the shell and re-look at MPG differences.

[freebeard]

It looks good. Time to update your avatar pic?

Have you thought about a half-tonneau on the length of the bed that's left?

[aardvarcus]

FreeBeard,
I updated the avatar photo (which was from the day I bought the truck), thanks for the reminder and for the encouragement.

Honestly I have been daydreaming about building the other half of the aeroshell and having it hinged off of what I already built, but I need to get some other projects wrapped up before I embark on something that involved. A half tonneau would be a lot easier, but the AST-II overlay shows the air wanting to be about 6” or so above the tailgate. I know it would improve the flow some, but I don’t really know how much.

[aerohead]

Originally Posted by aardvarcus

FreeBeard,
I updated the avatar photo (which was from the day I bought the truck), thanks for the reminder and for the encouragement.

Honestly I have been daydreaming about building the other half of the aeroshell and having it hinged off of what I already built, but I need to get some other projects wrapped up before I embark on something that involved. A half tonneau would be a lot easier, but the AST-II overlay shows the air wanting to be about 6” or so above the tailgate. I know it would improve the flow some, but I don’t really know how much.

From the Texas Tech research they would have us expect about a 12% additional drag reduction from completing the shell.6% more mpg on the highway.

[freebeard]

I'm curious whether a lower 'cab' height and shorter open bed might have the same effect. That's as close as you could get to that 12% with an open bed.

[aerohead]

Originally Posted by freebeard

I'm curious whether a lower 'cab' height and shorter open bed might have the same effect. That's as close as you could get to that 12% with an open bed.

GM's Holden Commodore ute is kinda doing this,although it does have a OEM tonneau,like the lower drag RAM.
At Cd 0.309 it's the lowest drag production 'pickup',although mighty men would argue whether it's a truck at all.
http://goautomedia.cdn.on.net/galler...den_ute_07.jpg

[aardvarcus]

Got some new data with the newly adjusted shell, so I decided to try to run some new numbers for percent improvement. I am only going to use the most recent figures between the last time I removed the shell to now to try to reduce variability. Most of my trips are to the same few places, and most of the time I know any outliers that would skew the data and can throw them out. I know this isn’t the ABA quality everyone would like, but it is the best I can do right now given time constraints I am under.

For my “shell off” baseline, I am going to use the 5/8 and 5/19 tanks. These are both very typical routine tanks. The 5/17 shell off tank was way off as I was running different tires and making short trips so it is out. These two tanks sum 480.168 miles using 17.52 gallons so 27.407 MPG.

For my “shell on” comparison, I am going to use the 5/20 and 5/22 tanks. The 5/20 is a very typical routine tank (first tank at over 30MPG!) but the 5/22 tank was slightly a-typical and in worse conditions. These two tanks sum to 404.56 Miles using 14.123 gallons so 28.6455 MPG or 4.52% improvement.

I know one of the trips from the 5/22 tank was way off my usual driving routine, if I factor out that one trip by removing 28.4 miles at 25 MPG per the Ultra Gauge so 1.136 gallons, that would make the figures 376.16 miles at 12.987 gallons or 28.964 MPG or 5.68% improvement. This would make this tank more typical in terms of destinations of the other three tanks. Note I am not trying to “cherry pick” figures, just trying to get an apples to apples comparison and minimize variability.

The first data set showed 5.45%, so any way you slice it, it looks like the half shell gave around a 5.5% improvement to which I would assign a +/- 1% tolerance given the inaccuracies of my measurement procedure, weather, and variations in even my “routine” trips. So between 4.5% and 6.5% FE improvement would imply a roughly 9%-13% drag improvement.

Utilizing Phil’s drag as a function of aft body truncation table and the AST-II overlay, I was predicting a 11.2% reduction in drag. So it looks like the theoretical landed right in the middle of the measured results range. So once again thank you Phil and everyone else on this site who have shared such a wealth of knowledge.

[aardvarcus]

I had an opportunity to do some design work on a few things on the truck and have made some progress on a few fronts.

Electric fan conversion: I just ordered the last of the parts. I have a final wiring diagram that gives me all the functionality and control I could ever want. I got a spare Tacoma fan shroud and have begun cutting and fitting the shroud to accept my two Camry fans. FYI, they don't fit very well but I am going to make them work anyway. Basically the two fans are more of a rectangle and the Tacoma shroud is more of a square, but after over-analyzing it, I figured out a way to get them mounted by putting them in opposite corners and angling one out so that they slightly overlap. Note I am rebuilding the shroud so that each fan vents a portion of the radiator, so functionally the “overlap” doesn't matter due to the ducting. It was either overlap or extend out past. Anyway I have been using a soldering iron to heat weld the plastic from the Tacoma shroud to the plastic from the Camry E-fan shroud. Once I am done, I will remove all the stock parts and be able to install the newly welded up Tacoma shroud with E-fans already integrated in place.

HVAC Blower Motor: The blower motor started making an awful noise on high, sounded like it was out of balance or the bearings were shot. Doing a bit of research, looked like bearings going out was fairly common, to the extent Toyota redesigned the part. Ordered the new part, went in to replace it and to my surprise what do I see when I drop the old fan and motor but a nut sitting in the fan blades. I had a mouse living in the air intake and had built a nest on top of the air cleaner. The mouse decided to carry some nuts into his home, one of which made it through the air filter and was on my fan blower. I cleaned the mess out and scared the mouse away. I just put the old blower motor back in the truck for now, need to order a new filter. To prevent recurrance, I took some perforated aluminum I had lying around and made a cover for the air intake. Toyota, why was this not installed from the factory? This could have been a $5 part at most, plus you even had mounting holes for me to bolt into stamped in the sheet metal of this part. I don't know that my design is the best as it blocked off about half of the net clear opening, but it was what I had on hand. A heavy duty welded mesh with 1/2" or so openings would have been better.