Home Dyno was RE: Datalogging RPM signal

[Stephen Andersen]

Home Dyno uses the acceleration rate of the vehicle, and 
the vehicle mass to determine the horsepower based on simple
linear acceleration equations that you will find in any
basic 1st year college Physics text.  You need to know 
accurately the weight of the vehicle, as well as the gear
ratios and tire size.  This will allow the program to 
correlate engine rpm with road speed fairly accurately.

The power to accelerate the car in a vacuum is calculated based
on the above info.  Then the software ADDS in the power required to 
overcome aero drag vs. speed.  This is based on the following 
equation:

DRAG = 1/2 * Rho * V^2 * Cd * A

Where Rho is the density of the air
V is the velocity
Cd is the drag coefficient for the vehicle
A is the frontal area of the vehicle.

Also, the software then does an air density correction where
it takes you current temperature and humidity conditions, calculates
the air density, and then factors the results relative to STP conditions.

I have found Home Dyno to work quite well.  It is extremely consistent,
and overall, matches quite closely to actual chassis dyno numbers...

Steve


> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> Behalf Of Steve.Flanagan at VerizonWireless.com
> Subject: RE: Datalogging RPM signal
> 
> 
> Glen
> 
> Do you have any incite as to the physics being used with that device.
> 
> What inputs are used to calculate the HP / TQ numbers?  And 
> how is the drag
> from wind added to the equation.
> 
> How about the actual vs corrected values on the web site, 
> what is used to
> calculate them?
> 
> I would love to see some of the formulas being used.  I am 
> sure its all
> basic physics, but I am not sure where those books are 
> anymore.  Think there
> in a box at my parents place?
> 
> Steve
> 
> 

----- End of forwarded message from owner-diy_efi at diy-efi.org -----
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