Tailgate Up (closed) or Tail gate Down (open)
Senior User
Joined: Oct 2003
Posts: 418
Likes: 1
From: Nice, California
I've heard you can't even notice a difference with having the tailgate up or down while driving the older trucks. They are designed to have the tailgate up, otherwise they would not have one. So why have the tailgate down? If you want it down, just take the whole tailgate off....
Dan
Dan
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Bdox has it right, must have heard it from the engineers themselves just like I did. 
Maybe even BOTH Ford and GM types like I did...
Engineering is SO much fun. For mileage they even look at a few grams here and there, corrosion allowances, high $$ materials, reduced fluid capacities, "extra" fasteners, even eliminating wear allowances on brake rotors, etc.
Maybe even BOTH Ford and GM types like I did...Engineering is SO much fun. For mileage they even look at a few grams here and there, corrosion allowances, high $$ materials, reduced fluid capacities, "extra" fasteners, even eliminating wear allowances on brake rotors, etc.
Hotshot
Joined: Dec 2003
Posts: 18,423
Likes: 9
From: iowa
Originally Posted by Torque1st
The OEM's in general will jump on anything that will provide 0.1MPG difference nowadays.
Elder User
Joined: Feb 2002
Posts: 987
Likes: 2
From: East Bend, Carolina, U.S
Yep, I've been convinced that they work their tails off for every .1 mpg to be gained by aerodynamic designing. You guys are actually looking at the same trucks I see on the road today right?
Elder User
Joined: Jul 2005
Posts: 969
Likes: 1
From: North Texas
Originally Posted by Purely Ford
You guys are actually looking at the same trucks I see on the road today right?
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
None the less, aerodynamic principles hold for older trucks the same as newer one. With any of them, the tailgate issue is so small that you would probably have to do some testing to notice it. However, just to observe the effects, you could sprinkle some flour in the bed of your truck and watch how it behaves with the tailgate up. Then lower the gate and see what it does then.
Elder User
Joined: Jul 2005
Posts: 969
Likes: 1
From: North Texas
The flour would tell you about wind directions and speed, but I'm more interested in the net result(or lack of same). For example not all laminar flows are good. Porsche actually has this problem. They are so streamlined that the wind does not want to break loose from the rear curve and creates drag. Their solution... a little ripple just above the rear glass or the nifty automatic wing depending on the year. You know that little fin on the Volkswagen... Passat? Beetle? It has the same problem as Porsche, and solves it by adding a vortex. High confidence level modeling is expensive and requires multiple degrees that I don't have. However there is one way to know for sure, even for a layman like me, TEST IT!
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Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
Those aerodynamic cars you are describing with their little aero mods are primarily fighting lift at high speeds. A 911 has a flat bottom and a down sloping back which naturally creates lift.
The flour in the truck bed will demonstrate the difference in turbulance between the gate up or gate down. Turbulance equals drag.
The flour in the truck bed will demonstrate the difference in turbulance between the gate up or gate down. Turbulance equals drag.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
I suggested flour because it is light, unlike sand which would take quite a bit more air to disturb it. Also, flour is pretty harmless, washes off easily and is biodegradable.
Mil, does it always rain in Innisfail?
Mil, does it always rain in Innisfail?
Elder User
Joined: Jul 2005
Posts: 969
Likes: 1
From: North Texas
Preliminary data:
Baseline - 10.85mpg, speedlimit +4, light acceleration, hold speed up hills.
Test 1 - vacuum guage run 1 - 11.79mpg, 13inhg max accel hwy, 14 cruise, 15 max accel city, 16 max cruise city.
Currently running test 2 on vacuum. If the MPG is really close I'll move on to the bed cover test. If there's some variation I'll do vac test run 3 first.
Baseline - 10.85mpg, speedlimit +4, light acceleration, hold speed up hills.
Test 1 - vacuum guage run 1 - 11.79mpg, 13inhg max accel hwy, 14 cruise, 15 max accel city, 16 max cruise city.
Currently running test 2 on vacuum. If the MPG is really close I'll move on to the bed cover test. If there's some variation I'll do vac test run 3 first.
Elder User
Joined: Jul 2005
Posts: 969
Likes: 1
From: North Texas
Test 1 - vacuum guage run 2 - 11.70mpg. Not gonna get much more consistant than that.
So, on to Test 2, bed cover. I'm using a 1x3 frame and a medium weight tarp with a total cost of about $23. It will be sat on top of the bed with a slight bow up in the middle to get rain to run off. Pics as soon as completed.
Test 3 will probably be the stock 2v carb and intake reinstalled.
So, on to Test 2, bed cover. I'm using a 1x3 frame and a medium weight tarp with a total cost of about $23. It will be sat on top of the bed with a slight bow up in the middle to get rain to run off. Pics as soon as completed.
Test 3 will probably be the stock 2v carb and intake reinstalled.