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Determine how well your engine will run under certain meteorological and geological conditions
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README.rdoc

EngineTune

Interested in determining how well your engine will run under certain meteorological and geological conditions?

This is the gem for you! (And I am sure there are a lot of you out there.)

EngineTune returns the following calculations when supplied with altitude, altimeter (barometric pressure), temperature and dew point:

  • AE Relative Horsepower

  • Dyno Correction Factor

  • Air Density

  • Density Altitude

  • ICAO Relative Air Density

  • Virtual Temperature

  • Absolute Air Pressure

  • Vapor Pressure

  • Relative Humidity

The calculations in this gem are modeled after Richard Shelquist's Engine Tuner's Calculator, but have been re-factored to be more ruby-like. I urge you to read his technical articles on Density Altitude and Corrected Horsepower for detailed explanations of these concepts.

wahiduddin.net/calc/calc_hp_dp.htm

Standard Usage

Note that all observations must be supplied using the metric system of measurement.

observations = Hash.new
observations[:temperature] = 32.0 # Celsius
observations[:dew_point] = 22.0 # Celsius
observations[:altitude] = 149.0 # Meters
observations[:altimeter] = 1013.4 # Millibars

calculations = EngineTune.calculate(observations)

calculations.relative_horsepower
  #=> 96.2 (as percentage)

calculations.density_altitude
  #=> 876 (as meters)

Calculations are returned in metric units, but if you prefer your calculations using the English system of measurement, do this:

calculations.metric = false

calculations.density_altitude
  #=> 2874 (as feet)

And if you forget what system of measurement your calculations object is using, just ask it:

calculations.metric = false

calculations.metric?
  #=> false

calculations.english?
  #=> true

The Calculator

You can also bypass the calculations object and directly use the calculator:

temperature = 32.0 # Celsius
dew_point = 22.0 # Celsius
altitude = 149.0 # Meters
altimeter = 1013.4 # Millibars

EngineTune::Calculator.relative_horsepower(altimeter, altitude, dew_point, temperature)
  #=> 96.2 (as percentage)

Convenience methods to convert between metric and English units are provided as well:

EngineTune::Calculator.meters_to_feet 1054
  #=> 3458.0052546

EngineTune::Calculator.inches_to_millibars 1223
  #=> 41415.3694298

Copyright

Copyright © 2012 twmills LLC. See LICENSE for details.

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