Home Dyno (was) Datalogging RPM signal

[Glen Beard]

Steve.Flanagan at VerizonWireless.com wrote:
> 
> 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.

Here is a list of the required inputs:
Engine type: 2/4 stoke
Total vehicle weight
A/M transmission and stall speed (if app)
Axle gear ratio
Trans gear ratio
Tire width, aspect ratio, and diameter
Drag coefficient
Frontal Area
Drivetrain loss (%)
Ambient Temp
Relative Humidity
Barometric Pressure
Elevation above sea level

> I would love to see some of the formulas being used.

I don't know what the formulas are, but I know I have seen
them scattered on the web.  The only ones that ever really
gave me trouble were drag coefficient, frontal area,
drivetrain loss, and tire diameter (because it grows from 15
mph to 70 mph and is not accounted for).  It only takes
being off by a little to really throw your curves off. 
Other than that...  If you don't look at the output numbers
themselves, but instead keep everything constant and look at
the trends, it's a fairly repeatable tool for tuning.

-- 
Glen Beard  95 T/A conv M6
355, Vortech, heads, cam...
http://home.nycap.rr.com/gbeard1/TransAm.html
http://home.nycap.rr.com/gbeard1/Impala/Impala.html

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