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AndrewJ · 01-04-2008, 07:32 PM

I went out to do some more testing today and while I didn't get to do all of the testing I had planned to do, the intrigue continues.

I did 2 of 6 runs of coastdown testing in "stock" form to verify that the Excel spreadsheet was giving me decent numbers. By comparing the Cd that the spreadsheet gave me with Honda's Cd of 0.33 for a stock 5th generation Civic hatchback, I can see how far off (if any) the numbers in the spreadsheet are.

Now, I only got to do 2 runs, one in each direction, before I had to quit due to the sudden appearance of a fierce crosswind. I didn't want my data corrupted by any wind, so I just used those two sets of data to plug into Excel.

I know, I know... two points of data isn't much, in fact, it's probably safe to consider it flawed.

But then again...

Guess what Excel came up with based on my 2 data points?

Cd = 0.33

Grrr....more testing....damn wind.

Given the windyness situation I headed on over to my "calibrated" hill for a little session of A-B-A. The hill is usually windy, but today it was on the leeward side of the wind, so it was unusually calm on the downhill side.

I brought the car to 55mph at the top of the hill, and at the same point in all 3 runs, cut the engine reset the trip odo. I then kept track of speed and at what distance on the trip odometer those speeds were reached. The runs ended when I coasted back down to 55mph at the bottom of the hill.

---------------------------A(stock)----B(aero)---A(stock)
Initial speed-------------55mph-----55mph-----55mph
Slowed to----------------52mph-----55mph-----52mph
Miles@lowest speed-----0.375------0-0.4------0.375
Top speed---------------66mph-----71mph-----65mph
Miles@top speed--------1.1---------1.05-------1.05
Miles@55mph (end)-----1.35-------1.45-------1.25

Also, on the "B" run, 66mph was reached at 0.75 miles.

Looks like this aerodynamics stuff might actually work

01-04-2008, 07:32 PM	#32 (permalink)
AndrewJ Awesomeness personified Join Date: Dec 2007 Location: Columbia, MO Posts: 642 Harold - '94 Honda Civic CX 90 day: 54.51 mpg (US) Margot - '08 Surly Big Dummy Thanks: 0 Thanked 28 Times in 18 Posts	The testing drags on.... I went out to do some more testing today and while I didn't get to do all of the testing I had planned to do, the intrigue continues. I did 2 of 6 runs of coastdown testing in "stock" form to verify that the Excel spreadsheet was giving me decent numbers. By comparing the Cd that the spreadsheet gave me with Honda's Cd of 0.33 for a stock 5th generation Civic hatchback, I can see how far off (if any) the numbers in the spreadsheet are. Now, I only got to do 2 runs, one in each direction, before I had to quit due to the sudden appearance of a fierce crosswind. I didn't want my data corrupted by any wind, so I just used those two sets of data to plug into Excel. I know, I know... two points of data isn't much, in fact, it's probably safe to consider it flawed. But then again... Guess what Excel came up with based on my 2 data points? Cd = 0.33 Grrr....more testing....damn wind. Given the windyness situation I headed on over to my "calibrated" hill for a little session of A-B-A. The hill is usually windy, but today it was on the leeward side of the wind, so it was unusually calm on the downhill side. I brought the car to 55mph at the top of the hill, and at the same point in all 3 runs, cut the engine reset the trip odo. I then kept track of speed and at what distance on the trip odometer those speeds were reached. The runs ended when I coasted back down to 55mph at the bottom of the hill. ---------------------------A(stock)----B(aero)---A(stock) Initial speed-------------55mph-----55mph-----55mph Slowed to----------------52mph-----55mph-----52mph Miles@lowest speed-----0.375------0-0.4------0.375 Top speed---------------66mph-----71mph-----65mph Miles@top speed--------1.1---------1.05-------1.05 Miles@55mph (end)-----1.35-------1.45-------1.25 Also, on the "B" run, 66mph was reached at 0.75 miles. Looks like this aerodynamics stuff might actually work __________________ "I got 350 heads on a 305 engine. I get 10 miles to the gallon. I ain't got no good intentions." - The Drive By Truckers.