Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Coast down test methods and determining cD?

wwkayaker · 05-15-2009, 06:16 PM

I am going to be doing some coast downs for my car in an A-B-A fashion. Here are my questions

.

1) How do I determine cD off of a coast down test? Sometimes, I find it hard to believe that my car starts with a cD of 0.30. Especially, since the same year Eclipse starts with a cD of .34.

that is horrible for a sporty car!

2) How far? Even in central Indiana it can be hard to find a paved side road that doesn't have a stop sign every mile.

3) Exactly, step by step, how is a coast down conducted? Should I use cruise and step on the clutch at the same spot?

4) Can I accurately do this without a SGII or other device? My speedo shows every 5mph. I don't have a measuring wheel either.

I already know to use weather dot com and record all of the weather conditions for the nearest town to the test site. Also, I have a few good flat roads to use that are miles long with a couple stop signs.

I think I have all of my questions in here.

05-15-2009, 06:16 PM	#1 (permalink)
wwkayaker EcoModding Lurker Join Date: Jul 2008 Location: Carmel, IN Posts: 61 Kayak hauler - '05 Mitsubishi Lancer ES 90 day: 33.88 mpg (US) Thanks: 3 Thanked 3 Times in 3 Posts	Coast down test methods and determining cD? I am going to be doing some coast downs for my car in an A-B-A fashion. Here are my questions . 1) How do I determine cD off of a coast down test? Sometimes, I find it hard to believe that my car starts with a cD of 0.30. Especially, since the same year Eclipse starts with a cD of .34. that is horrible for a sporty car! 2) How far? Even in central Indiana it can be hard to find a paved side road that doesn't have a stop sign every mile. 3) Exactly, step by step, how is a coast down conducted? Should I use cruise and step on the clutch at the same spot? 4) Can I accurately do this without a SGII or other device? My speedo shows every 5mph. I don't have a measuring wheel either. I already know to use weather dot com and record all of the weather conditions for the nearest town to the test site. Also, I have a few good flat roads to use that are miles long with a couple stop signs. I think I have all of my questions in here.