[Diy_efi] Wind resistance calculator

[Hugh Keir]

Here is a great set of worked calculations that take you through it step by
step.

http://members.home.net/rck/phor/06-Speed.html titled The Physics of Racing,
Part 6: Speed and Horsepower

I have been using them to produce a spreadsheet to calculate BHP, torque etc
using a datalogged RPM and vehicle speed signal.

The density of air changes with humidity / pressure which I also added to
the calculations.

I also have a column for AFR from my DIY wideband to look for the best
acceleration against which AFR

My spreadsheet is 95% finished, I still have some problems with the numbers
in the dyno sheet.

What have you used to obtain your datalog?

Hugh


----- Original Message -----
From: "Derek" <derek_obanion at yahoo.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, December 16, 2002 10:44 PM
Subject: [Diy_efi] Wind resistance calculator


> Does anyone know of an equation, or maybe a online calculator, that can
tell me
> how much HP is required to maintain a given speed, given the drag
coefficient of
> the vehicle?
>
> I can calculate the g forces at any speed based upon my RPM rate of
change, and
> therefore, acceleration (assuming no tire spin), which I have in 30
samples/sec
> in my log files.
>
> I can calculate horsepower from g-force and road speed (also constantly
logged).
> I just need to add the horsepower lost through wind resistance. I want to
keep
> drivetrain losses, I want a RWHP figure, not FWHP.
>
>
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> Diy_efi at diy-efi.org
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>


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