EcoModder Forum Calculator: Determine Horsepower @ specific speed

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 08-21-2008, 01:15 PM #1 (permalink) Administrator     Join Date: Dec 2007 Location: Germantown, WI Posts: 11,171 CM400E - '81 Honda CM400E 90 day: 51.49 mpg (US) Daox's Grey Prius - '04 Toyota Prius Team Toyota 90 day: 49.53 mpg (US) Daox's Insight - '00 Honda Insight 90 day: 64.33 mpg (US) Swarthy - '14 Mitsubishi Mirage DE Mitsubishi 90 day: 56.69 mpg (US) Thanks: 2,469 Thanked 2,537 Times in 1,529 Posts Calculator: Determine Horsepower @ specific speed I put this excel file together a while back after reading an article on Autospeed called Real World Measurement of Drag and Lift. He had a calculation to measure Cd. I was more interested in reversing the calculation to get horsepower at a specific speed, so I made a calculator. The downside is that it does not take into account rolling resistance. To use it, you will need the Cd of your vehicle, length and width (or just frontal area), and input a speed. Horsepower at Speed Calculator __________________ Current project: A better alternator delete
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Master EcoModder

Join Date: Jun 2008
Location: Northwest Lower Michigan
Posts: 1,006

Red Car - '89 Chevrolet Celebrity CL 4 door
Team Chevy
90 day: 36.47 mpg (US)

Winter Wagon - '89 Pontiac 6000 LE Wagon
90 day: 28.26 mpg (US)
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Interesting.

Daox, here is something I got a couple years ago from an RV forum. It was made not necessarily for saving fuel, but for estimating if you had enough engine power to tow the trailer depending on expected grades, speed, and wind. Im not sure of the accuracy of any of it though, you would probably know better.
Attached Files
 Horsepower.xls (19.0 KB, 46 views)
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Winter daily driver, parked most days right now

Summer daily driver

 08-22-2008, 12:58 PM #3 (permalink) EcoModding Lurker   Join Date: Jul 2008 Location: illinois Posts: 72 EP3 - '03 Honda Civic Si 90 day: 31.73 mpg (US) Scooter - '93 Honda Elite 80 90 day: 74.87 mpg (US) Ape - '07 Aprilia Sportcity 250ie 90 day: 66.97 mpg (US) Thanks: 0 Thanked 2 Times in 2 Posts I just look at a dyno graph to see what it is at an rpm and translate that to the speed in 5th gear may be a little off, but it works for me.(i get the dyno from guys who have done it with the stock version of my car online) __________________
 08-22-2008, 01:00 PM #4 (permalink) Master EcoModder   Join Date: Jun 2008 Location: London, Ontario Posts: 1,096 2k2Prot5 - '02 Mazda Protege5 90 day: 33.82 mpg (US) Thanks: 0 Thanked 12 Times in 9 Posts dyno graphs are only for full throttle. You aren't using NEARLY that much power to cruise.