Vehicle: Wheeled Simulation
Input (Controller)
SCR_CarControllerComponent
General
Param  Type  Unit  Description 

Type 
Type of gearbox
 
Transmission RND 
bool  Transmission have three settings: reverse, neutral and drive 
Steering speed coefficients
The following are properties for smoothing the digital or small range/insensitive analog input (gamepad thumbstick). The setup should be quick and responsive enough while allowing the player to keep a smooth ride (e.g. by tapping the keys), without having to constantly counter compensate.
Param  Type  Unit  Description 

Steering Forward Speed 
pairs of floats  [vehicle speed in km/h, steering speed in °/s]

Pairs of velocity and steering speed at the given velocity 
Steering Backward Speed 
pairs of floats  [vehicle speed in km/h, steering speed in °/s]

Pairs of velocity and countersteering speed (recentering via input) at the given velocity 
Steering Center Speed 
pairs of floats  [vehicle speed in km/h, centering speed in °/s]

Pairs of velocity and recentering speed (when no steering input is given / caster effect) at the given velocity 
Throttle
Param  Type  Unit  Description 

Throttle Curve 
pairs of floats  [engine rpm, amount of throttle]

Throttle application with respect to engine's RPM 
Reverse Curve 
pairs of floats  [engine rpm, amount of throttle]

Throttle application with respect to engine's RPM while in reverse 
Throttle Reaction Time 
float  s

Time (in seconds) it takes to get wanted value of throttle  e.g. to interpolate from 0.0 to 1.0 throttle input 
Throttle Turbo Time 
float  s

Time (in seconds) to reach wanted value of throttle in turbo mode 
Throttle Turbo 
float  Amount of throttle that is reserved for turbo mode. For instance 0.2 means that without turbo, vehicle will be moving with maximum 0.8 throttle 
Brake
Param  Type  Unit  Description 

Braking Curve 
pairs of floats  [time in seconds, amount of braking force]

Brake application over time 
Brake Turbo Time 
float  s

Time to reach wanted value of brake in turbo mode 
Engine
Param  Type  Unit  Description 

Max Startup Time 
float  seconds

Failsafe time for the engine to start (it can also bypass animations if it is shorter) 
Max Startup Attempts 
float  How many times you can be "stuck" in the startup loop animation  
Engine Startup Chance 
float  %

Probability that each startup attempt has to turn on the engine (0  100) (should be tied to engine below "damaged" threshold) 
Air Intakes 
float  array of PointInfo classes

Air intake positions in local vehicle space 
Drowning Time 
float  s

Amount of time needed to completely drown the engine when all air intakes are underwater 
Shutdown Time 
float  s

Amount of time (some) vehicle systems automatically toggle off after the shutdown 
Max Lights Time 
float  s

Maximum amount of time the light toggle should take (or if there are no animations) 
Clutch
Param  Type  Unit  Description 

Clutch Uncouple Time 
float  seconds

Time to disengage clutch before switching gears 
Clutch Couple Time 
float  seconds

Time to engage clutch after switching gears 
Clutch Uncouple Rpm 
float  RPM

Engine RPM at which clutch is fully uncoupled while moving off 
Clutch Couple Rpm 
float  RPM

Engine RPM at which clutch is fully coupled while moving off 
Clutch Uncouple Factor 
float  Clutch uncouple RPM factor while moving off uphill or downhill  
Clutch Couple Factor 
float  Clutch couple RPM factor while moving off uphill or downhill  
Clutch Minimum Position 
float  Minimum clutch position while moving off  
Clutch Minimum Factor 
float  Minimum clutch position factor while moving off uphill or downhill 
Shifting
Param  Type  Unit  Description 

Slope Smoothing 
float  Factor of filter that smooths out upshift and downshift RPMs  
Latency 
float  seconds

Minimum time between gear switches 
Up Shift Factor 
float  Upshift RPM factor while going uphill or downhill  
Up Shift Rpm 
float  RPM

Engine RPM required for upshifting 
Down Shift Factor 
float  Downshift RPM factor while going uphill or downhill  
Down Shift Rpm 
float  RPM

Engine RPM required for downshifting 
Turbo Shift Factor 
float  Upshifting and downshifting RPM ratio in Turbo mode 
Simulation
VehicleWheeledSimulation
General
Param  Type  Unit  Description 

Solver Type 
Solver selector  only V1 solver is available right now  
Solver Update Rate 
Hz

Solver update rate in Hz (number of ticks per second) 
Engine
Controls engine power and its other properties. All values must be greater than 0 to be accepted as valid.
The engine is simulated as rotating cylinder around its central axis (simplification of crankshaft).
Param  Type  Unit  Description  References 

Inertia 
float  kg.m^{2}

Moment of inertia 
https://www.researchgate.net/publication/258176892_Evaluation_of_variable_mass_moment_of_inertia_of_the_pistoncrank_mechanism_of_an_internal_combustion_engine 
Max Power 
float  kW

Maximum power that the engine can provide 
You can use this calculator to visualize RPM curve

Max Torque 
float  Nm

Maximum torque that engine can provide (peak torque)  
Rpm Max Power 
float  RPM

RPM where engine outputs maximum power  
Rpm MaxT orque 
float  RPM

RPM where maximum torque is produced  
Rpm Idle 
float  RPM

RPM when engine is idling, e.g. in neutral  
Rpm Redline 
float  RPM

Redline RPM
This parameter is currently ignored  
Rpm Max 
float  RPM

Maximum RPM  
Steepness 
float  Controls how fast engine can reach max torque. It can be used to flatten the torque curve before max torque rpm are reached  
Friction 
float  Engine's braking torque  
Output 
Powertrain part driven by the engine (clutch) 
Clutch
Param  Type  Unit  Description 

Max Clutch Torque 
float  Nm

Maximum torque that clutch can provide. (1.6*MaxTorque can be a good starting point)
This parameter is currently ignored 
Output 
Powertrain part driven by the clutch (gearbox) 
Gearbox
Param  Type  Unit  Description 

Reverse 
float  Reverse gear ratio  
Forward 
array of floats  Array of forward gear ratios, order of the values are mapped to gears respectively  
Efficiency 
float  Transmission efficiency  scales the engine output passed down  
Output 
Powertrain part driven by the gearbox (differential) 
Differentials
Param  Type  Unit  Description 

Type 
Open  Same torque on both outputs, different rotational speeds  
LSD  Limited slip differential  limiting rotational difference between outputs. Opens Anti slip and Anti slip torque parameters.  
Ratio 
float  Differential ratio (sometime "final drive")  
Strength 
float  Determines the magnitude of the extra force that is applied to the gripping wheel  
Output0 
Powertrain parts driven by the differential (other differential or axle differential)  
Output1 
Axles
Param  Type  Unit  Description 


float  Defines how much torque is delivered to this axle. Sum of Torque Share for all axles should be equal to 1  
Has Handbrake 
bool  Determines whether this axle is used for handbrakes. Handbrake force is same as Brake Torque 
(Axle) Differential
Param  Type  Unit  Description 

<same as differentials>  
Output0 
Driven wheels  
Output1 
Suspension
Accelerating/braking/turning should noticeably shift the weight of the vehicle. Weight shifting affects the grip of the tires  allowing more grip on the side with more weight. Center of mass should be set realistically high and the tendency to roll should be limited by a sway (antiroll) bar if necesary, not by setting the CoM below the vehicle or just the wheel center.
Param  Type  Unit  Description 

Max Steering Angle 
float  degrees

Specifies the maximum steering angle of this axle, if negative value is given, the axis will steer in opposite direction of the steering wheel. 
Spring Rate 
float 
N/mm 
Spring force per mm. 
Compression Damper 
float 
Ns/m 
Compression damper force per 1m/s. 
Relaxation Damper 
float 
Ns/m 
Relaxation damper force per 1m/s. 
Max Travel Up 
float  m

Maximum distance that the suspension can be compressed from modeled position. Standard cars 0.06  0.1 m. Offroad cars >0.1 m. 
Max Travel Down 
float  m

Maximum distance that the suspension can be expanded from modeled position. Standard cars 0.07  0.12 m. Offroad cars >0.1 m. 
Wheel
Param  Type  Unit  Description 

Radius 
float  m

Radius of the wheel 
Ratio 
float  Wheel reduction ratio  
Mass 
float  kg

Mass of the wheel on this axle 
Brake Torque 
float  Nm

Amount of brake torque applied to each wheel on this axle 
Tyre
Param  Type  Unit  Description 

Rolling Resistance 
float  Currently not used in game
Linearly proportional to speed. Acts against the wheel torque. For limiting acceleration. (in addition to surface property)  
Rolling Drag 
float  Currently not used in game
Proportional to speed squared. For limiting high speeds. (in addition to surface property)  
Roughness 
float  m

Bumpiness height  how bumpy is the wheel itself (in addition to surface property) 
Longitudinal Friction 
float  Directly affects tyre grip in longitudinal direction  
Lateral Friction 
float  Directly affects tyre grip in lateral direction  
Tread 
float  Ratio of the "Thread"  related to how well wheel performs on specific surface. 
Swaybar
Param  Type  Unit  Description 

Stiffness 
float  N

Sway bar stiffness ( antiroll force ) 
WheelPositions
Inertia
 InertiaOverrideEnable
 Enables manual override of vehicle inertia  the way how to "simulate" mass distribution on the vehicle.
 InertiaOverride
 Inertia values around each axis. Copy initial values from diag or via context menu opened on
VehicleWheeledSimulation
on the Entity instance (you have to Apply to prefab later)
 Inertia values around each axis. Copy initial values from diag or via context menu opened on
Aerodynamics
Param  Type  Unit  Description 

Reference Area 
float  m^{2}

Drag reference area  see following page for more details https://en.wikipedia.org/wiki/Automobile_drag_coefficient#Drag_area 
Drag coefficient 
float  Drag coefficient  see following page for more details https://en.wikipedia.org/wiki/Automobile_drag_coefficient#Typical_drag_coefficients 
Pacejka
 https://www.edy.es/dev/docs/pacejka94parametersexplainedacomprehensiveguide/
 http://www.racer.nl/pacejka/pacplay.htm
Fill in initial values via context menu opened on VehicleWheeledSimulation
on the Entity instance (you have to Apply to prefab later)
Longitudinal
b0
Param  Role  Units  Typical range  Sample  Description  Dependency 

Shape factor  1.4 .. 1.8

1.5

General shape of the curve. Defines the amount of falloff after the peak.
The Pacejka model defines b0 = 1.65 for the longitudinal force. 
Loadindependent  
b1 
Load influence on longitudinal friction coefficient (*1000)  1/kN

80 .. +80

0

Change of the friction coefficient at the peak.
Positive = more friction with more load. Negative = less friction with more load. 
Loaddependent 
b2 
Longitudinal friction coefficient (*1000)  900 .. 1700

1100

Friction coefficient at the peak (vertical coordinate) *1000.  Loadindependent  
b3 
Curvature factor of stiffness/load  N/%/kN^2

20 .. +20

0

Change of the peak’s horizontal position.
Positive = increases ascent rate with load (moves to the left). Negative = decreases ascent rate with load (moves to the right). 
Loaddependent 
b4 
Change of stiffness with slip  N/%

100 .. 500

300

Peak’s horizontal position specified as “ascent rate”.  Loadindependent 
b5 
Change of progressivity of stiffness/load  1/kN

1 .. +1

0

Lineal change of the peak’s horizontal position. Similar to b3 but more lineal and with reverse effect positivenegative.
Positive = decreases ascent rate with load. Negative = increases ascent rate with load. 
Loaddependent 
b6 
Curvature change with load^2  0.1 .. +0.1

0

Quadratic change of the curvature at the peak.
Positive = more flat with load. Negative = sharper with load. 
Loaddependent  
b7 
Curvature change with load  1 .. +1

0

Change of the curvature at the peak. Same as b6 but more lineal.
Positive = more flat with load. Negative = sharper with load. 
Loaddependent  
b8 
Curvature factor  20 .. +1

2

Curvature at the peak. The more negative = more “sharp”. Has influence on the falloff afterwards.  Loadindependent  
b9 
Load influence on horizontal shift  %/kN

1 .. +1

0

Change of the horizontal shift.
Positive = shifts to the left with more load. Negative = shifts to the right with more load. 
Loaddependent 
b10 
Horizontal shift  %

5 .. +5

0

Curve’s horizontal shift  Loadindependent 
Lateral
a0
Param  Role  Units  Typical range  Sample  Description  Dependency 

Shape factor  1.2 .. 18

1.4

General shape of the curve. Defines the amount of falloff after the peak.
The Pacejka model defines a0 = 1.3 for the lateral force. 

a1 
Load influence on lateral friction coefficient (*1000)  1/kN

80 .. +80

0

Change of the friction coefficient at the peak.
Positive = more friction with more load. Negative = less friction with more load. 
Loaddependent 
a2 
Lateral friction coefficient (*1000)  900 .. 1700

1100

Friction coefficient at the peak (vertical coordinate) *1000.  
a3* 
Change of stiffness with slip  N/deg

500 .. 2000

1100

Peak’s horizontal position at the reference load, specified as “ascent rate”.  
a4* 
Change of progressivity of stiffness / load  1/kN

0 .. 50

10

Change of the peak’s horizontal position with load. Smaller value = bigger change with load.  
a5 
Camber influence on stiffness  %/deg/100

0.1 .. +0.1

0

Change of the peak’s horizontal position.
Positive = decreases ascent rate with camber (moves to the right). Negative = increases ascent rate with load (moves to the left). 
Camberdependent 
a6 
Curvature change with load  2 .. +2

0

Change of the curvature at the peak.
Positive = more flat with load. Negative = sharper with load. 
Loaddependent  
a7 
Curvature factor  20 .. +1

2

Curvature at the peak. The more negative = more “sharp”. Has influence on the falloff afterwards  
a8 
Load influence on horizontal shift  deg/kN

1 .. +1

0

Change of the horizontal shift.
Positive = shifts to the left with more load. Negative = shifts to the right with more load. 
Loaddependent 
a9 
Horizontal shift at load = 0 and camber = 0  deg

1 .. +1

0

Curve’s horizontal shift  
a10 
Camber influence on horizontal shift  deg/deg

0.1 .. +0.1  0  Change of the horizontal shift.
Same sign as camber = shifts to the left. Opposite sign as camber = shifts to the right. 
Camberdependent 
a11 
Vertical shift  N

200 .. +200  0  Curve’s vertical shift  
a12 
Vertical shift at load = 0  N

10 .. +10  0  Vertical shift when approaching zero load.
Must be verified for coherency at the configured minimum load. 
Loaddependent 
a13 
Camber influence on vertical shift, load dependent  N/deg/kN

10 .. +10  0  Change of the vertical shift according to camber and load.
Same sign as camber = shifts upwards. Opposite sign as camber = shifts downwards. The more load the more camber effect. 
Camberdependent 
a14 
Camber influence on vertical shift  N/deg

15 .. +15  0  Change of the vertical shift.
Same sign as camber = shifts upwards. Opposite sign as camber = shifts downwards. 
Camberdependent 
^{* Configure the horizontal behavior with load}
Aligning
Param  Role  Units  Typical range  Sample  Description  Dependency 

c0 

c1 

c2 

c3 

c4 

c5 

c6 

c7 

c8 

c9 

c10 

c11 

c12 

c13 

c14 

c15 

c16 

c17 

c18 
RaycastLayer
 LayerPreset in which the wheel raycast is performed (should be "Vehicle")
RigidBody and Center of Mass
 All vehicles are set to curb weight (assuming dynamic weight could happen at some point in the future)
 Center of Mass plays a crucial role in vehicle handling  it should be high enough to allow for weight shifting and changes in the wheel grip due to the changing pressure.