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:
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AE Relative Horsepower
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Dyno Correction Factor
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Air Density
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Density Altitude
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ICAO Relative Air Density
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Virtual Temperature
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Absolute Air Pressure
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Vapor Pressure
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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
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
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 © 2012 twmills LLC. See LICENSE for details.