Aerodynamics

Configure your vehicle's aerodynamic characteristics including downforce, drag, and aerodynamic balance. Choose between fixed coefficients, ride height-dependent maps, or percentage-based adjustments.

Overview

The Aerodynamics setup defines:

• Aerodynamic Mode - Fixed, Map (Standard/Split), Percentage, or Expression (Beta) configuration
• Core Parameters - SCx (drag area), SCz (lift area), CoP (center of pressure)
• Ride Height Sensitivity - How aero changes with front/rear ride heights (Map and Percentage modes)
• Offset Settings - Offset angle adjustments using polynomial or map-based offsets

Positive Downforce Convention

In motorsport, positive SCz values represent downforce (negative lift). This is opposite to aerospace convention but standard in vehicle dynamics.

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Aerodynamic Modes

Choose the mode that best fits your available data and tuning needs.

Mode 1: Fixed (Coefficient)

Simple fixed values for drag, downforce, and balance. Best for initial setup or when aero data is limited.

Use when: - You have single-point aero data (e.g., manufacturer specs) - Testing baseline vehicle behavior - Ride height sensitivity is negligible

See also: Standard vs Split Modeling for input parameter options.

Mode 2: Map (map2d)

Full 2D maps defining how aero changes with front and rear ride heights. Most accurate for advanced setups.

Use when: - You have CFD or wind tunnel data across ride height ranges - Modeling ride height-sensitive aero platforms - Maximum accuracy is required

See also: Standard vs Split Modeling for input parameter options.

Mode 3: Percentage

Reference values modified by percentage maps based on ride height. Convenient for relative adjustments.

Use when: - You have a baseline configuration and want to model percentage changes - Exploring aero sensitivity studies - Easier to understand percentage changes vs absolute values

See also: Standard vs Split Modeling for input parameter options.

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Standard vs Split Modeling

All four modes (Fixed, Map, Percentage, Expression) support two modeling approaches:

Standard Modeling

In Standard modeling, the inputs are defined as: - SCx - Drag area - SCz - Total downforce area
- CoP - Center of pressure (front axle proportion)

The standard approach uses a single 2D grid where both front and rear ride heights index into the same map.

Use when: - You have CFD or wind tunnel data across ride height ranges - Modeling ride height-sensitive aero platforms - Maximum accuracy is required

Split Modeling

In Split modeling, the inputs are defined as: - SCx - Drag area - SCzF - Front downforce area - SCzR - Rear downforce area

The split approach uses separate maps for front and rear aero coefficients. Front aero is indexed by front ride height only; rear aero is indexed by rear ride height only.

Use when: - You have front and rear aero data from different sources (e.g., front wing tunnel, rear wind tunnel) - Modeling asymmetric aero platforms where front and rear behave independently - Simplified mapping when front-rear interaction is negligible

Output: - Total downforce is calculated as: SCz = SCzF + SCzR

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Mode 4: Expression (Beta)

Expression mode allows you to define aero parameters using mathematical expressions that reference other channels (e.g., ride heights, velocity, steering angle). This enables dynamic aero modeling where coefficients change based on vehicle state.

Use when: - Modeling aero that responds to vehicle dynamics (e.g., ride height + speed effects) - Complex interactions between multiple parameters - Custom aero curves that don't fit standard polynomial or map approaches

See also: Standard vs Split Modeling for input parameter options.

Configuration:

1. Define Input Channels - Which vehicle state channels to reference (e.g., h_ride_f, h_ride_r, a_roll, a_slip_car, a_steer)
2. Write Expressions - Mathematical formulas using the input channels
3. Define Operating Range - Valid ranges for inputs to prevent extrapolation

Expression Syntax: - Basic math: +, -, *, /, ^ - Functions: sin(), cos(), sqrt(), abs(), min(), max(), clamp() - Channel references: h_ride_f, h_ride_r, a_roll, a_slip_car, a_steer, etc.

Example (Standard Modeling):

SCx = 0.75 + 0.005 * abs(h_ride_f - h_ride_r)
SCz = 2.5 + 0.02 * h_ride_f + 0.01 * h_ride_r
CoP = 0.42 - 0.001 * h_ride_f + 0.001 * h_ride_r

Example (Split Modeling):

SCx = 0.75 + 0.005 * abs(h_ride_f - h_ride_r)
SCzF = 1.5 + 0.02 * h_ride_f + 0.001 
SCzR = 1.0 + 0.01 * h_ride_r + 0.001 

Available Input Channels: | Channel | Description | |---------|-------------| | h_ride_f | Front ride height | | h_ride_r | Rear ride height | | a_roll | Roll angle | | a_slip_car | Slip angle | | a_steer | Steering angle |

Expression Mode Beta

Expression mode is in beta. Performance may vary for complex expressions. Use Standard or Split map modes for production simulations where maximum performance is critical.

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Core Aerodynamic Parameters

SCx (Drag Area)

The drag coefficient multiplied by frontal area: Cd × A

Used in drag force equation: Drag = ½ρv²(CdA) where ρ is air density and v is velocity.

Typical values: - Formula cars (high downforce): 0.8-1.2 m² - GT cars: 0.6-0.9 m² - Touring cars: 0.6-0.8 m² - Road cars: 0.5-0.7 m²

Positive Values Only

Drag always opposes motion. SCx values are always positive.

SCz (Lift Area)

The lift coefficient multiplied by reference area: Cl × A

Used in lift force equation: Lift = ½ρv²(ClA) where ρ is air density and v is velocity.

In motorsport: Positive values = Downforce (negative lift)

Typical values: - Formula cars (high downforce): 2.5-4.0 m² - GT cars (LMP, GTE): 1.5-3.0 m² - Touring cars: 0.3-0.8 m² - Road cars: 0.0-0.2 m²

Negative SCz = Lift (Undesirable)

Negative SCz values indicate lift instead of downforce. The platform will warn if this occurs, as it's usually unintended in racing.

CoP (Center of Pressure)

The proportion of total downforce acting on the front axle, expressed as a decimal (0-1) or percentage (0-100%).

Formula: - Front downforce = Total downforce × CoP - Rear downforce = Total downforce × (1 - CoP)

Examples: - CoP = 0.7 (or 70%) → 70% front, 30% rear (forward balance) - CoP = 0.5 (or 50%) → 50% front, 50% rear (neutral balance) - CoP = 0.35 (or 35%) → 35% front, 65% rear (rearward balance)

Typical values: - Formula cars: 0.40-0.50 (balanced to slight rear bias) - GT cars (front-engine): 0.45-0.55 (more forward) - GT cars (mid-engine): 0.35-0.45 (more rearward)

Aero Balance and Handling

• Higher CoP (>0.5): More front downforce, reduces understeer at high speed
• Lower CoP (<0.5): More rear downforce, reduces oversteer at high speed
• Adjust CoP to tune high-speed balance without changing total downforce

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Configuration: Fixed Mode

The simplest configuration for constant aerodynamic properties.

Setup Steps

1. Select Fixed mode from the radio buttons
2. Enter SCx (drag area)
3. Enter SCz (downforce area)
4. Enter CoP (front downforce proportion)

Example Configuration

GT3 Car - Fixed Aero: - SCx: 0.75 m² - SCz: 2.8 m² - CoP: 0.42 (42% front, 58% rear)

At 200 km/h (55.56 m/s) with air density 1.225 kg/m³: - Total downforce: ½ × 1.225 × 55.56² × 2.8 = 5,308 N (541 kg) - Front downforce: 5,308 × 0.42 = 2,229 N (227 kg) - Rear downforce: 5,308 × 0.58 = 3,079 N (314 kg) - Drag force: ½ × 1.225 × 55.56² × 0.75 = 1,420 N (145 kg)

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Configuration: Map Mode

Full ride height-dependent aero maps for maximum accuracy.

Setup Steps

Step 1: Define Ride Heights

1. Click Ride Heights button
2. Enter Front RH array - e.g., [20, 30, 40, 50] mm
3. Enter Rear RH array - e.g., [30, 40, 50, 60] mm
4. Platform creates a grid: 4 front × 4 rear = 16 combinations

Step 2: Create Aero Maps

For each of SCx, SCz, and CoP:

1. Click the parameter button (e.g., SCx)
2. Fill in the 2D table with values at each (front RH, rear RH) combination
3. Values are interpolated during simulation

Example Configuration

Formula Car - Ride Height Sensitive:

Ride Heights: - Front: [20, 30, 40] mm - Rear: [30, 40, 50] mm

SCz Map (downforce area, m²):

Front RH →	20mm	30mm	40mm
Rear 30mm	3.8	3.5	3.2
Rear 40mm	3.5	3.3	3.0
Rear 50mm	3.2	3.0	2.8

Pattern: Lower ride height = more downforce (ground effect)

CoP Map (front proportion, decimal):

Front RH →	20mm	30mm	40mm
Rear 30mm	0.45	0.42	0.40
Rear 40mm	0.48	0.45	0.43
Rear 50mm	0.50	0.48	0.46

Pattern: Lower front RH or higher rear RH = more forward CoP

Aero Map Strategy

• Lower ride heights typically generate more downforce (ground effect)
• Rake (front low, rear high) often increases downforce but shifts CoP forward
• Use CFD or wind tunnel data when available
• Start with conservative maps and refine based on track data

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Configuration: Percentage Mode

Reference values modified by percentage changes based on ride height.

Setup Steps

Step 1: Define Ride Heights

Same as Map mode - define front and rear ride height arrays.

Step 2: Set Reference Values

1. Enter Reference SCx - Baseline drag area
2. Enter Reference SCz - Baseline downforce area

Step 3: Create Percentage Maps

For each parameter: 1. Click the parameter button 2. Fill percentage changes relative to reference 3. Final value = Reference × (1 + Percentage/100)

Example Configuration

GT Car - Percentage Adjustments:

References: - Reference SCx: 0.75 m² - Reference SCz: 2.5 m²

Ride Heights: - Front: [40, 50, 60] mm - Rear: [50, 60, 70] mm

SCz Percentage Map (%):

Front RH →	40mm	50mm	60mm
Rear 50mm	+15%	+5%	0%
Rear 60mm	+10%	0%	-5%
Rear 70mm	+5%	-5%	-10%

At Front 40mm, Rear 50mm: - SCz = 2.5 × (1 + 15/100) = 2.5 × 1.15 = 2.875 m²

At Front 60mm, Rear 70mm: - SCz = 2.5 × (1 - 10/100) = 2.5 × 0.90 = 2.25 m²

CoP Percentage Map: Direct CoP values (0-1), not percentages of reference.

CoP in Percentage Mode

The CoP map in percentage mode contains direct CoP values (0-1), not percentage changes. This is because CoP represents a proportion, not a multiplied quantity.

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Offset Settings

Add polynomial-based or map-based offsets to model aerodynamic surface adjustments (e.g., rear wing angle, front flap trim, DRS).

Understanding the Parent-Child Relationship

The Aerodynamics component uses a parent-child structure where offset components are optional children that modify the parent's base aerodynamic values.

graph TD
    Aero[Aerodynamics<br/>Base: SCx, SCz, CoP<br/>Mode: Fixed/Map/Percentage]
    Aero -->|Optional| W1[Rear Offset]
    Aero -->|Optional| W2[Front Flap]
    Aero -->|Optional| W3[DRS Offset]

    W1 -->|Polynomial Offsets| W1_Data[Angle: 5°<br/>Type: Relative<br/>SCz: +22.5%<br/>SCx: +15%<br/>CoP: -5%]
    W2 -->|Polynomial Offsets| W2_Data[Angle: 3°<br/>Type: Absolute<br/>SCz: +0.15<br/>SCx: +0.05<br/>CoP: +0.02]

    style Aero fill:#6366f1,color:#fff
    style W1 fill:#10b981,color:#fff
    style W2 fill:#10b981,color:#fff
    style W3 fill:#10b981,color:#fff
    style W1_Data fill:#f3f4f6,color:#000
    style W2_Data fill:#f3f4f6,color:#000

How it works:

1. Aerodynamics (Parent) contains the base aero data configured in one of three modes (Fixed, Map, or Percentage)
2. Offsets (Children) are optional offset components, each representing an adjustable aerodynamic surface
3. Final values = Base aero + Sum of all offsets:

   Final SCz = Base SCz × (1 + Σ relative offsets) + Σ absolute offsets
   Final SCx = Base SCx × (1 + Σ relative offsets) + Σ absolute offsets
   Final CoP = Base CoP × (1 + Σ relative offsets) + Σ absolute offsets
   

Example: - Base aero: SCz = 2.5 m², SCx = 0.75 m², CoP = 0.42 - Rear Offset: +22.5% SCz, +15% SCx, -5% CoP (Relative) - Front Flap: +0.15 SCz, +0.05 SCx, +0.02 CoP (Absolute) - Final SCz = 2.5 × 1.225 + 0.15 = 3.21 m² - Final SCx = 0.75 × 1.15 + 0.05 = 0.91 m² - Final CoP = 0.42 × 0.95 + 0.02 = 0.419

Component Hierarchy

See Component Hierarchy for more details on how parent-child relationships work throughout ARD.

What Offsets Do

Offsets adjust the base aero properties (from Fixed/Map/Percentage modes) based on aerodynamic surface angle changes.

Formula:

offset = a₄x⁴ + a₃x³ + a₂x² + a₁x + a₀

Where x = current_angle - reference_angle

Offset Types: - Absolute: Final = Base + Offset - Relative: Final = Base × (1 + Offset/100)

Map-Based Offsets

In addition to polynomial-based offsets, you can define offsets using 2D lookup tables. Map-based offsets interpolate values from a grid of reference angles versus another variable (e.g., ride height or velocity).

Use when: - You have test data mapping angle to aero at multiple conditions - Polynomial curves don't fit your data well - Offsets vary with operating conditions

Configuration: 1. Enable Map-Based toggle on an offset 2. Define Reference Angles - Array of angle values 3. Define Map Variables - Second dimension (e.g., ride height, velocity) 4. Fill the 2D table with offset values at each combination

Hub vs Chassis Application Points

Aero offsets can be applied at different reference points, affecting how they interact with the suspension and vehicle dynamics:

Hub Application: - Offsets are applied at the wheel hub - Aero forces act directly on the hub not affecting the sprung geometry. - Better for modeling unsprung aerodynamic elements.

Chassis Application: - Offsets are applied at the sprung components. - Aero forces are transferred through the suspension geometry - Better for modeling overall chassis attached elements

Configuration: - Select Application Point in offset settings: Hub or Chassis - Default: Chassis

Choosing Application Point

Use Hub for unsprung components (e.g., tyres). Use Chassis for overall vehicle aero changes or when the aero element is mounted to the chassis structure.

Adding an Offset

1. Click Add Offset button
2. Name the offset (e.g., "Rear Offset", "Front Flap")
3. Click the gear icon to configure

Configuring an Offset

Angle Settings: - Reference Angle - Base angle where offset is zero (e.g., 0°) - Current Angle - Actual wing angle (e.g., 5°)

Offset Type: - Absolute - Adds/subtracts directly from base values - Relative - Adds/subtracts as a percentage

Polynomial Coefficients:

For each of SCz, SCx, and CoP, enter the 5 coefficients (a₄, a₃, a₂, a₁, a₀).

The platform plots the polynomial curve in real-time.

Example: Rear Offset Adjustment

Scenario: Increase rear wing from 0° (reference) to 5° (current).

Offset Type: Relative (percentage)

SCz Polynomial (more downforce with higher angle): - Coefficients: [0, 0, 0.5, 2.0, 0] - At 5°: offset = 0(5⁴) + 0(5³) + 0.5(5²) + 2.0(5) + 0 = 12.5 + 10.0 = 22.5%

SCx Polynomial (more drag with higher angle): - Coefficients: [0, 0, 0.3, 1.5, 0] - At 5°: offset = 0(5⁴) + 0(5³) + 0.3(5²) + 1.5(5) + 0 = 7.5 + 7.5 = 15.0%

CoP Polynomial (shifts rearward with more rear wing): - Coefficients: [0, 0, -0.1, -0.5, 0] - At 5°: offset = 0(5⁴) + 0(5³) - 0.1(5²) - 0.5(5) + 0 = -2.5 - 2.5 = -5.0%

If base values are SCz=2.5 m², SCx=0.75 m², CoP=0.42: - Final SCz = 2.5 × (1 + 22.5/100) = 3.0625 m² (+22.5% downforce) - Final SCx = 0.75 × (1 + 15/100) = 0.8625 m² (+15% drag) - Final CoP = 0.42 × (1 - 5/100) = 0.399 (39.9% front, shifted rearward)

When to Use Offsets

• Modeling adjustable rear wings or front flaps
• Simulating setup changes without recreating entire aero maps
• Testing wing angle sensitivity
• DRS (Drag Reduction System) modeling

Multiple Offsets

You can add multiple offsets (e.g., front + rear wing). The platform sums all absolute offsets and all relative offsets separately, then applies both.

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How Aerodynamics Relates to Other Components

Chassis

Chassis reference ride height defines the baseline. Initialization race-ready ride height is used to lookup values in aero maps during simulation.

Suspension

Suspension compression/extension during cornering, braking, and acceleration changes ride heights dynamically. Aero maps model how downforce and balance shift with these ride height changes.

Track

Different tracks require different aero setups: - High-speed tracks (Monza, Spa) → Lower drag, moderate downforce - Twisty tracks (Monaco, Hungary) → Maximum downforce, higher drag acceptable - Balanced tracks (Silverstone, Barcelona) → Compromise between drag and downforce

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Configuration Workflow

Recommended Workflow

1. Start with Fixed Mode

   • Use manufacturer data or estimates
   • Get baseline vehicle behavior

2. Choose Your Mode

   • Fixed: If aero is not ride height sensitive
   • Map: If you have CFD/wind tunnel data
   • Percentage: If you want relative adjustments

3. Configure Base Aero

   • Fixed: Enter SCx, SCz, CoP
   • Map: Define ride heights, create 2D maps
   • Percentage: Set references, create percentage maps

4. Add Offsets (Optional)

   • Model wing angle adjustments
   • Configure polynomials for each offset
   • Use Absolute or Relative as appropriate

5. Review Quick Stats

   • Check calculated downforce at typical speeds
   • Verify aero balance (front/rear distribution)
   • Review on desktop (Quick Stats panel, right side)

1. Validate Configuration
   • Check Tree View for warnings
   • Address any flagged issues
   • Test in simulation

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Validation Warnings

The platform validates aerodynamic parameters and warns for:

Offset/Offset Warnings: - Offset angle >20° (unusually high) - Offset angle differs >15° from reference (large delta) - Absolute offsets: SCz >1.0, SCx >0.5, CoP >0.2 (very large) - Relative offsets: >25% (very large percentage change)

System Warnings: - Combined offsets too large (all offsets summed) - Negative SCz values (lift instead of downforce) - SCx <0.15 (unrealistically low drag) - SCx >2.0 (unrealistically high drag) - CoP <0.2 or <20% (very rearward aero balance) - CoP >0.8 or >80% (very forward aero balance)

Viewing Warnings

Warnings appear in the Tree View next to the Aero component. Click the warning icon to view details.

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Tips & Best Practices

Start Simple, Add Complexity

Begin with Fixed mode to establish baseline behavior. Add Map mode only when you have validated data and need ride height sensitivity.

CoP Tuning for Balance

Adjust CoP (not total downforce) to tune high-speed understeer/oversteer. Increase CoP to reduce high-speed understeer, decrease to reduce oversteer.

Drag vs Downforce Trade-off

More downforce usually means more drag. Balance corner speed gains (downforce) vs straight-line speed losses (drag) based on track layout.

Use Percentage Mode for Sensitivity Studies

Percentage mode makes it easy to explore "what if" scenarios: "What if I lose 10% downforce at low ride height?"

Offset Offsets for Quick Adjustments

Use offsets to model wing angle changes without recreating entire aero maps. Great for setup optimization.

Validate CFD/Wind Tunnel Data

Always cross-check simulation results with real-world testing. CFD and wind tunnel data can have errors or not account for on-track conditions.

Negative Downforce is Usually Wrong

If you see negative SCz warnings, verify your data. Racing cars should generate downforce (positive SCz), not lift.

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Related Topics

• Chassis Setup - Reference ride heights for aero baseline
• Initialization Setup - Race-ready ride heights used in aero lookups
• Suspension Setup - How suspension affects ride height dynamically
• Track Selection - Track-specific aero requirements
• Coordinate System - Understanding positive/negative conventions

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Aerodynamics is one of the most powerful tuning tools in modern motorsport. Master aero balance to unlock lap time gains.