Mr. Gasket 8703 Hot Rod Calculator - Manual (Page 21)

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ImPoRtAnt teRms And defInItIons
Motorsports Standard Atmosphere (MSA)*
Motorsports Standard Atmosphere, MSA, is a term defined
by Drag Racing Pro’s Patrick Hale, and is a methodology
implemented in this calculator. Simply stated, it is a standard,
reference set of ambient weather conditions. Engine and race
car performance can be corrected back to MSA in order to
understand the effects of environmental changes.
As a rule, if the local weather changes, so does your vehi-
cle’s performance. Some basic guidelines to know are that
the higher the absolute Pressure, the faster your vehicle will
go, but the higher the temperature, the slower it will go. More
specifically, engine performance is impacted by the ambient
air’s density.
MSA includes three parameters: absolute Pressure (29.92
inHg), temperature (60° F), and relative humidity (0% RH, or
“dry air”).
Horsepower Correction Factor (HPc)*
The Horsepower Correction Factor is calculated and imple-
mented within HP, ET and speed estimations on the Hot Rod
Calc
. The current local weather conditions and/or Elevation
entered into the calculator are used to calculate HPc.
As a guideline, the closer the HPc is to 1.0, the faster the
vehicle will run (more Horsepower is produced). Conversely,
the higher the HPc, the slower it will run (less Horsepower is
produced).
* Patrick Hale, “Motorsports Standard Atmosphere and Weather
Correction Methods”, Arizona: DRPro, 2008.
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