Hi Brett -
First: let me say I have huge respect for what you're doing and I hope you become a zillionaire because of your cap. I praise it to everyone I talk to about pickup truck aero.
The Cd info you provided is fantastic:
Quote:
Originally Posted by bondo
The wind tunnel testing I have had done on the Aerolid is all I can offer. In the A2 wind tunnel test the Aerolid achieved a delta Cd of -0.062. This test was with the lid on my 2006 F150 which Ford says has a baseline coefficient of drag of .42.
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Quote:
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let's work together to get closer to the truth.
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Regarding Fubeca's number, don't forget we have to compare apples to apples, and we're not in this case. This is important:
1) He tested at a
much lower speed than you did! At 55 mph, this is reflected in the smaller % difference he measured vs. the % difference you will see at 75 mph. If he had tested at a slower speed it would have been
even lower (less than 4%), and if you had tested at 85 mph, your % results would have been even greater.
2) He's using a different truck,
3) His cap design is different from yours
4) Neither your or Fubeca's tests is "lab quality", so let's not get hung up on the decimal points, if you know what I mean.
All of these things make it impossible to directly compare his results to yours. (Also I don't think the home page suggests that all caps are created equal or that everyone should expect only 4% from an aeroshell.)
Unless you're testing the same truck at the same speed(s), in the same conditions, it's apples & oranges.
But we can work with your numbers:
If we plug the values for your truck into the
aero/rolling drag formula for calculating power requirements across a range of speeds, here's what we find:
Using your vehicle (Brett's 2006 F-150)...
Weight:
4,840 lbs
Base Cd: 0.42
Cd with aeroshell: 0.358
Frontal area: 33 sq. feet (* this is an estimate: I couldn't find the value online, and EcoModder's
CdA list has a value of 31.5 sq. feet for the previous generation 2004 F150 Lightning, lowered and probably slightly smaller. For comparison, a 2002-2008 Ram 1500 is listed at 35.1 square feet.)
Crr: .0125 (estimate)
Based on the Cd difference (and adding 150 lbs - est. - for the aero shell), let's calculate power requirements (in Watts) and look at the % differences to travel at 55 mph and 75 mph, at 25C and -10C (taking air density changes into account):
- Stock truck Cd 0.42 (open bed)
@ 30 C / 86 F on summer fuel (click the links to open the tool with all values entered)
55 mph requires 17,758 Watts (~21.7 MPG US)
75 mph requires 37,271 Watts (~14.1 MPG US)
@ -10 C / 14 F on winter fuel
55 mph requires 19,452 Watts (~19.5 MPG US)
75 mph requires 41,566 Watts (~12.4 MPG US)
- With aeroshell Cd 0.358 (plus 150 lbs - est.)
@ 30 C / 86 F on summer fuel
55 mph requires 16,319 Watts, 8.1% better than stock in same conditions (~23.6 MPG US)
75 mph requires 33,381 Watts, 10.4% better than stock in same conditions (~15.8 MPG US)
@ -10 C / 14 F on winter fuel
55 mph requires 17,763 Watts, 8.6% better than stock in same conditions (~21.3 MPG US)
75 mph requires 37,042 Watts, 10.9% better than stock in same conditions (~14.0 MPG US)