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Old 01-08-2010, 04:46 PM   #69 (permalink)
aerohead
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cold

Quote:
Originally Posted by Fubeca View Post
Phil,

If you get a second to put some mental work in my direction - could you answer a quick question?

I've read your post on ambient temperature and its effect on drag and fuel efficiency.

I noticed when I did my initial ABA style testing that my cap only increased my mileage by about 4%. Does the cold dense air increase the skin friction significantly? Would this cause the mileage increase with the topper to be less in the cold than it might be in hot air?

Or, is the opposite true, does an aerodynamic improvement with a lot of surface area have an increased effect on MPG improvement in the cold because aerodynamic drag is more pronounced in the cold air?

I'm curious as to whether my mpg difference will be consistent as the weather warms up or if when the weather is warmer I might see something more like 10% increase with the topper.

I do understand the non-aero effects of the cold, and during my test tried to mitigate them by testing with and without the topper as fast as I could make the change, and ensuring the truck was fully warmed up before the test. I also do not think the test was definitive and look forward to further testing.
Fubeca,the additional skin friction of the cover is completely over shadowed by the reduction in profile drag.
The colder denser air this winter is going to cut significantly into your mpg.
In addition,your tire's rolling resistance is up a tick.All your lubricants require greater "pumping" power,and even when fully "warmed" may still be way below SAE "cold" temps.
I waited a whole winter for my bellypan to show up on the radar.
Winter modification can be really frustrating.
A topper like bondo has done is going to provide about a 10% mpg improvement on the highway in "normal" weather.
I'd tough it out 'til Spring and see if your mpg doesn't creep up with the warmer temps.
My T-100 will lose almost 9% HWY mpg in the winter.If you're seeing 4% in "nasty" weather,you may be ecstatic come May.
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