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Whoops · 02-19-2008, 07:14 PM

I can't say much, although if you check out the link on trailer aerodynamics, that was posted recently, it might give you some practical ideas.

I can tell you something I once did that enhanced things substantially, in a very conter-intuitive fashion. We once had a 82 Plymouth Reliant station wagon. It is a fairly boxy shape, but we typically got 22 mpg or so, on trips. I built a car top where the front of the car top followed the windshield angle. I modified it so it was about 18 inches tall because at the 24 inches I initially had built, it got about 15 mpg and I couldn't go over 60. The top and rear were just square.

I later added a shape similar to a the top half of an airplane, oriented with what would be the trailing edge, to the front. What would have been the leading edge was aligned with the back edge of the car top.

When I made this change, I went from 16-17 mpg back up to about 21 mpg. Additionally, it made a substantial improvement in our ability to accelerate and I could drive 65, before I could feel the aerodynamics starting to really drag the car down, where previously this had occurred at 35 or 40.

I initially discovered this when I had loaded a stack of fire wood on top of the cargo top, at the back 1/3 of the top. I put about 4 inches or so of wood, across the top, for about 18 inches or so, at the back. The difference it made was noticable upon acceleration, and when I had to purchase gas. However, the car only had a 2.5 liter engine and it was a 3 speed automatic, with no torque lockup.

I don't know if it would help, but I would get about 10 2*4 boards, stack them on top, at the back and give it a try.

Sounds weird, can't really explain it, just know it worked, on that car.

02-19-2008, 07:14 PM	#17 (permalink)
Whoops EcoModding Apprentice Join Date: Dec 2007 Location: Ventura, Ca Posts: 112 Whoop's Wheels - '89 Honda Civic Wagovan 90 day: 39.09 mpg (US) Thanks: 1 Thanked 9 Times in 7 Posts	I can't say much, although if you check out the link on trailer aerodynamics, that was posted recently, it might give you some practical ideas. I can tell you something I once did that enhanced things substantially, in a very conter-intuitive fashion. We once had a 82 Plymouth Reliant station wagon. It is a fairly boxy shape, but we typically got 22 mpg or so, on trips. I built a car top where the front of the car top followed the windshield angle. I modified it so it was about 18 inches tall because at the 24 inches I initially had built, it got about 15 mpg and I couldn't go over 60. The top and rear were just square. I later added a shape similar to a the top half of an airplane, oriented with what would be the trailing edge, to the front. What would have been the leading edge was aligned with the back edge of the car top. When I made this change, I went from 16-17 mpg back up to about 21 mpg. Additionally, it made a substantial improvement in our ability to accelerate and I could drive 65, before I could feel the aerodynamics starting to really drag the car down, where previously this had occurred at 35 or 40. I initially discovered this when I had loaded a stack of fire wood on top of the cargo top, at the back 1/3 of the top. I put about 4 inches or so of wood, across the top, for about 18 inches or so, at the back. The difference it made was noticable upon acceleration, and when I had to purchase gas. However, the car only had a 2.5 liter engine and it was a 3 speed automatic, with no torque lockup. I don't know if it would help, but I would get about 10 2*4 boards, stack them on top, at the back and give it a try. Sounds weird, can't really explain it, just know it worked, on that car.