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Ambient Conditions

Ambient Conditions Options

Configure the atmospheric and environmental conditions that affect aerodynamic performance and engine output.

Overview

Ambient Conditions is an independent library component located on the Track page. It has its own save/load functionality separate from the track configuration.

Changes to ambient conditions affect:

  • Aerodynamic forces — air density directly scales drag and downforce
  • Engine performance — air density affects volumetric efficiency of internal combustion engines
  • Vehicle weight and traction — gravitational constant affects normal loads

Parameters

Parameter Unit Description
Air Temperature °C Ambient air temperature. Affects calculated air density.
Air Pressure bar Atmospheric pressure. Affects calculated air density.
Air Humidity 0–1 (0–100%) Relative humidity as a fraction. Affects calculated air density.
Gravitational Constant m/s² Acceleration due to gravity. Affects weight, traction, and all force calculations.

Air Density

Air density is calculated automatically from temperature, pressure, and humidity using the Magnus formula (WMO standard).

The calculation uses the ideal gas law for a mixture of dry air and water vapor:

ρ = p_dry / (R_d × T) + p_vapor / (R_v × T)

Where:

  • R_d = 287.058 J/(kg·K) — specific gas constant for dry air
  • R_v = 461.495 J/(kg·K) — specific gas constant for water vapor
  • T — temperature in Kelvin
  • p_dry — partial pressure of dry air (total pressure minus vapor pressure)
  • p_vapor — partial pressure of water vapor, derived from humidity and the saturation vapor pressure (Magnus formula)

Override

You can toggle an override to enter a custom air density value directly. When overriding, the auto-calculated value is shown alongside for reference.

When to Override

Override air density when you have a measured value from the track (e.g., from a weather station or data logger) rather than relying on the formula.

Validation: Air density must be > 0 when overridden.

Engine Efficiency Multiplier

The engine efficiency multiplier models how changes in air density affect internal combustion engine power output.

It is calculated as the ratio of the current air density to a reference air density:

Efficiency Multiplier = ρ_current / ρ_reference

Reference conditions:

  • Temperature: 25 °C
  • Pressure: 100 kPa
  • Humidity: 30%

At reference conditions the multiplier is 1.0 (100%). At higher altitudes or hotter temperatures, air density drops and the multiplier falls below 1.0, reducing engine power proportionally.

Disable Toggle

A toggle allows you to disable the engine efficiency multiplier, which sets it to 1.0 (100%). This effectively ignores altitude and weather effects on engine output.

Electric Vehicles

The engine efficiency multiplier only affects internal combustion powertrains. It has no effect on electric motors.

Validation

Constraint Rule
Air Temperature Must be above absolute zero (> -273.15 °C)
Air Pressure Must be positive (> 0)
Air Humidity Must be between 0 and 1
Air Density (override) Must be positive (> 0)
Gravitational Constant Must be positive (> 0)