Drivetrain Components
Table of Contents
- Drivetrain Components
- Power Flow Overview
- RCCP_Engine
- Editable in Lite
- Locked in Lite (Available in Pro)
- Runtime Behavior
- RCCP_Clutch
- Editable in Lite
- Locked in Lite (Available in Pro)
- RCCP_Gearbox
- Editable in Lite
- Locked in Lite (Available in Pro)
- Transmission Types
- RCCP_Differential
- Editable in Lite
- Locked in Lite (Available in Pro)
- Differential Types
- RCCPAxles / RCCPAxle
- Editable in Lite
- Locked in Lite (Available in Pro)
- Axle Filtering
- RCCP_WheelCollider
- Editable in Lite
- Locked in Lite (Available in Pro)
- Drivetrain Configuration in Lite
- Next Steps
Power Flow Overview
RCCP simulates a realistic drivetrain where power flows from the engine through each component in sequence. Components communicate torque downstream via outputEvent fields:
RCCP_Engine (torque generation via NM curve)
↓ outputEvent
RCCP_Clutch (engagement modulation)
↓ outputEvent
RCCP_Gearbox (gear ratio multiplication)
↓ outputEvent
RCCP_Differential (power distribution)
↓ connectedAxle
RCCP_Axle (per-axle: steer / brake / power flags, anti-roll)
↓ leftWheelCollider / rightWheelCollider
RCCP_WheelCollider (tire physics, traction, skidmarks)
↓ forces applied to
Rigidbody (vehicle movement)
Each component receives torque from upstream, processes it, and passes the result downstream. This chain ensures that changes at any point (gear shift, clutch slip, differential lock) propagate realistically through the entire drivetrain.
RCCP_Engine
The engine generates torque based on a Newton-Meter (NM) curve evaluated at the current RPM. It handles idle RPM, rev limiting, acceleration and deceleration rates, and optional features like turbocharging, variable valve timing (VVT), knock detection, and temperature simulation.
Editable in Lite
| Parameter | Description |
|---|---|
maximumSpeed | Top speed of the vehicle (km/h) |
maximumTorqueAsNM | Peak engine torque in Newton-Meters |
maxEngineRPM | Maximum RPM before rev limiter |
minEngineRPM | Idle RPM |
engineRunning | Whether the engine is currently running |
engineRevLimiter | Toggle rev limiter on/off |
Locked in Lite (Available in Pro)
Torque curve editing (NMCurve), turbocharger settings, engine friction and inertia, dynamic acceleration rates, engine temperature simulation, VVT configuration, knock detection, and output event wiring.
Runtime Behavior
At runtime, the engine fully simulates all features regardless of Lite editor locks. The NM curve, turbo, VVT, and temperature systems all function — they simply use their default values which cannot be modified in the Lite inspector.
RCCP_Clutch
The clutch modulates power transfer between the engine and gearbox. It supports both automatic and manual clutch modes, with configurable engagement RPM and inertia.
Editable in Lite
| Parameter | Description |
|---|---|
automaticClutch | Toggle automatic clutch engagement |
Locked in Lite (Available in Pro)
Clutch inertia, engagement RPM, force to press, behavior during gear shifts and handbraking, output event wiring.
RCCP_Gearbox
The gearbox multiplies engine torque through gear ratios. It supports three transmission types: Automatic, Manual, and CVT (Continuously Variable Transmission). Automatic mode handles gear selection based on RPM thresholds; Manual mode requires player input for shifts.
Editable in Lite
| Parameter | Description |
|---|---|
transmissionType | Automatic, Manual, or CVT |
Locked in Lite (Available in Pro)
Gear ratios (individual values per gear), shift timing, shift RPM thresholds, automatic gear selector logic, gear preset buttons, output event wiring.
Transmission Types
| Type | Behavior |
|---|---|
| Automatic | Shifts gears automatically based on RPM thresholds |
| Manual | Player shifts using gear up/down inputs |
| CVT | Continuously adjusts ratio for optimal RPM range |
RCCP_Differential
The differential distributes torque from the gearbox to the driven axle(s). RCCP supports multiple differential types that affect how power is split between left and right wheels, which significantly impacts handling characteristics.
Editable in Lite
| Parameter | Description |
|---|---|
differentialType | Open, Limited Slip, Full Locked, or Direct |
Locked in Lite (Available in Pro)
Limited slip ratio, final drive ratio, axle connection buttons.
Differential Types
| Type | Behavior |
|---|---|
| Open | Power goes to the wheel with least resistance (realistic for road cars) |
| Limited | Partially locks wheels together, prevents one-wheel spin (sporty) |
| FullLocked | Both wheels always rotate at the same speed (off-road, drift) |
| Direct | Direct torque pass-through without distribution logic |
RCCP_Axles / RCCP_Axle
RCCP_Axles is a container that holds all RCCP_Axle components. Each axle represents a pair of wheels (left and right) and defines whether that axle provides steering, braking, handbrake, and/or power.
A standard car has two axles (front and rear), but RCCP supports any number for trucks, buses, or custom configurations.
Editable in Lite
| Parameter | Description |
|---|---|
isSteer | This axle provides steering |
isBrake | This axle has brakes |
isHandbrake | This axle is affected by handbrake |
Locked in Lite (Available in Pro)
Wheel model and collider references, auto-align, anti-roll force, max steer angle, steer speed, brake torque, power multiplier, all per-axle tuning, axle creation/removal.
Axle Filtering
The RCCP_CarController provides filtered axle lists for quick access:
PoweredAxles— Axles that receive engine powerBrakedAxles— Axles that have brakesSteeredAxles— Axles that steerHandbrakedAxles— Axles affected by handbrake
RCCP_WheelCollider
Each wheel has an RCCP_WheelCollider that handles tire physics, including grip calculation, slip detection, traction control interaction, skidmark generation, and tire wear simulation.
RCCP_WheelCollider extends Unity's built-in WheelCollider with additional physics for realistic tire behavior, including separate forward and sideways friction curves.
Editable in Lite
Wheel colliders have no directly editable parameters in Lite. Their behavior is determined by the axle configuration, stability settings, and global behavior preset.
Locked in Lite (Available in Pro)
Tire stiffness (forward and sideways), friction curve editing, deflation settings, wheel deformation, camber and toe angles.
Drivetrain Configuration in Lite
While detailed parameter tuning is locked in Lite, you can still configure meaningful drivetrain variations:
| What You Can Do | How |
|---|---|
| Set top speed and torque | Engine inspector: maximumSpeed, maximumTorqueAsNM |
| Choose transmission type | Gearbox inspector: Automatic / Manual / CVT |
| Change differential behavior | Differential inspector: Open / Limited / Locked / Direct |
| Configure drive layout | Axle inspectors: toggle isSteer, isBrake, isPower per axle |
| Toggle automatic clutch | Clutch inspector: automaticClutch |
| Set RPM range | Engine inspector: minEngineRPM, maxEngineRPM |
These options give you meaningful control over how the vehicle feels and performs, while advanced tuning (curves, ratios, friction) is available in RCCP Pro.
Next Steps
- 05_VehicleSystems.md — Stability, damage, audio, and more
- 03_VehicleSetup.md — Vehicle architecture overview