What we have

That’s curious. Until the moment I stumbled upon on this one, I’ve never asked myself what is in the game and what isn’t. Something similar should have felt Dave G Lancaster trying to explain a customer why iRacing should be consider as a realistic sim. To solve it, he made an extensive list which has been improved over the last five months showing us the current status of the sim. Here it is.

Currently Modelled

Some items are only available for certain vehicles, tracks, etc.

Vehicles – Officially licensed and modelled using CAD drawings, photos (1000 to 3000) and 3D laser scanning.

• cockpit modelled – including switches, dials, lights, steering wheel, shifters etc.
• exterior modelled
• colour
• working gauges
• body shape/design
• textures
• headlights
• paintwork, graphics and sponsor decals
• dirt accumulation
• dirty windshield – it will get dirty as you drive. Driving behind other cars will make the windshield get dirtier faster. Driving through smoke, dust, clouds of oil from blown motors will make the windshield get really dirty really fast.
• grime – cars accumulate grime as a race progresses. The amount is based upon both time and circumstances of the race. This grime effect causes a dulling of the car, which combines with the dirt accumulation effect.
• Vehicle positioning (longitude and latitude

Gauges & Controls

• fuel level- user adjustable
• fuel pressure
• oil temperature
• water temperature
• engine RPM
• shift lights
• warning lights
• speedometer. GPS vehicle speed
• gear indicator
• pit speed limiter
• clutch
• brake
• accelerator
• ignition

Vehicle Dynamics

• Lateral, longitudinal and vertical acceleration (including gravity)
• heave & roll
• weight transfer
• mass
• inertia
 engine
 wheel
 driveline
 chassis – 3 axes (roll, pitch, yaw)
• kinematics
• slip
• wheel hop
• pitch, roll & yaw orientation
• pitch, roll & yaw rate
• static weight distribution
• weight on each corner of car
• cross weight/wedge
• ballast – user adjustable
• nose weight – user adjustable
• loss of traction

Flex – not everything flexes, while in real life there is no such thing as a rigid piece. The following are modelled for flex.

• sway bars
• suspension mounting points
• drive shaft
• chassis torsion
• steering column
• body
• a-arms
• tyres


• power steering
• steering wheel angle
• output torque on steering shaft. Force feedback (FFB)
 loss of traction
 bumps
 curbs
 collisions
• steering ratio – user adjustable
• steering offset – user adjustable

Engine Physics – Each engine has the proper bore and stroke along with properly sized valves so that engine drag is modelled exactly when you are off throttle (and models how much air goes through the system to figure out the air/fuel mixture, etc). And that is coupled with realistic air pressures and densities based on track altitude and weather.

• torque curves – matched to dyno sheets
• bore
• stroke
• engine RPM
• valve size
• air/fuel mixture – user adjustable
• oil level
• oil temperature
• oil pressure
• engine voltage
• coolant level
• coolant temperature
• turbo boost pressure
• manifold pressure
• turbo lag
• turbo – affected by altitude
• rev limiter
• starter motor
• throttle pedal response – user adjustable
• engine braking – user adjustable
• engine power – user adjustable
• throttle shaping – user adjustable
• Push To Pass (P2P)- gives you sightly more power and revs when pressed. You only get 10 for a race and it stays on for 10 seconds, regardless of taking your foot off the gas or braking. You need the turbos to be wound up for it to work, as that is where the boost is applied.
• F1 Energy Recovery System (ERS) which harvests thermal energy from the turbo and braking system.
• F1 Motor Generator Unit (MGU) that provides a bank of extra electrical power that you will be able to use for overtaking.


• fully automated sequential
• dog-box sequential
• dog-box sequential with throttle cut
• dog-box h-pattern
• synchromesh h-pattern
• gearing – user adjustable
• RPM of shifter grinding noise
• Friction torque applied to gears when shifting or grinding


• diff locking – All diffs that use spider gears (cars with open diffs, Salisbury diffs, or viscous diffs) generate a small amount of diff locking from spider gear friction itself.
• preload
• ratios
• diff ramp angle

Suspension Geometry

• suspension travel – compression (i.e. bump) & rebound
• damping (shock absorbers)
• suspension bottoming out – causes a loss of downforce and sparks
• shock deflection
• spring deflection
• track bar height
• truck arm mount position
• corner spring
• heave spring
• spring perch offset – user adjustable
• shock collar offset – user adjustable
• front & rear anti-roll bars (ARB) – user adjustable
 front and rear anti-roll bar (ARB) asymmetry – user adjustable.
 diameter – user adjustable
 arm asymmetry – user adjustable preload – user adjustable
 attack – user adjustable
• ride height – user adjustable
• camber – user adjustable
• castor – user adjustable
• toe-in – user adjustable
• spring rate – user adjustable
• bump stop gap – user adjustable
• packer/shim – user adjustable
• bump stiffness- user adjustable
• rebound stiffness- user adjustable
• sway bar – user adjustable
 diameter – user adjustable
 arm length – user adjustable
 left bar end offset – user adjustable
 sway bar gap – user adjustable

Brake Systems

• dynamic braking friction – If the brakes get too hot, pad friction reduces and braking performance degrades. Also in fact, most of the pads in iRacing’s models start out with relatively lower grip until they come up to temperature.
• many cars have a full hydraulic model from foot force all the way through to pad-rotor interface modelled, which include temperature effects.
• anti-lock braking system (ABS)
• traction control
• brake rotor glow
• overheating brakes transfer heat into the rim which in turn can increase tyre pressures
brake bias – user adjustable
• brake line pressure – user adjustable

Tyres/Wheels – modelled items that affect grip – tire parameters such as number of plys, side wall thickness, rubber mixture etc are all modelled

• contact patch
• wheel speed
• wear – reduces grip and increases fuel usage
• damping forces
• pressure – last hot pressure reading
• temperature – along with temperature variations from friction etc, heat can even be transmitted from the brake calipers through the rim and into the tyre. Heat also convects through the air into the air inside the tire, flowing through the sidewalls and rim (as well as the inner liner, and the air inside the inner liner, if there is one.
• tyre temperature readings – inside, middle and outside of tyre (based on a tyre’s load and pressure)
• tyre carcass – stiffness/flex
• curvature of the tread and sidewalls
• rim and tire radii
• tyre compound materials (molecular bond of the rubber) the amount of carbon black, silica filler and/or extender oils that might be in the tread compound.
• glass transition temperature of the tread rubber – i.e. the temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material (reversible).
• tyre curing
• pressure – user adjustable
• loss of traction
• tyre warmers
• tyre smoke
• tyres collect, hold, and discard debris over the course of a race, including dust particles, blades of grass, pebbles, and rubber marbles.


• aero push
• draft – reduces your car’s downforce, not just drag
• bump drafting
• downforce
• rear spoiler
• drag
• rear wing angle
• front dive planes (winglets that attach to the front fenders)
• wings – user adjustable
• grille Tape – user adjustable
• front flap angle – user adjustable
• rear wing wicker – user adjustable
• Drag Reduction System (DRS). Basically there are one or two zones around each track where, if you are within a second of a car in front of you, you are allowed to open a flap on your rear wing to reduce drag.

Damage – affects car behaviour and reliability

• engine
 coolant leaks
 oil leaks
 fuel leaks
 over revving – especially on early downshifts but there also may be very rare engine failures even without significant abuse
• body – affects aerodynamic drag, downforce and balance, and can affect engine cooling on some cars.
• engine smoke
• suspension
• transmission
• sparks from contact with cars


• force feedback
• lap analysers
 split times
 delta times


• reflections
• shadows
• texture
• animated drivers
• day/night racing

Sounds – recorded from the actual real life vehicle in most cases. Multiple microphones are used (exhaust, intake, cockpit, around track etc)

• engine
• engine warble – this is driven by the physics. The gear shift puts strain on the engine (a mismatch between the tires and engine) and that creates the noise you hear (if any). Drive shaft flex and some other components between the tires and engine are modelled, but the modelled clutch plate is overly perfect and does not chirp when you mess up the shift and therefore gives too clean of a sound. Drive train flex (a very small flex) was added and gave some cars a really nice shift sound (warble), without having to fake something up. As with everything, the tires make a difference as well. They act as springs between the engine and the road and that also allows the engine to warble.
• exhaust
• tyre noise
• wind
• impacts/collisions
• transmission clunks
• gear shifts – the volume of the “clunk” corresponds to force of the gears hitting each other (basically how well you rev match the shift). This is only subtle and is recognised as requiring improvement.
• gear grinding
• flat tyre
• bottoming out
• backfires -many cars will spit out backfire flames when appropriate. Some cars backfire when off throttle, depending on their engine tuning. Others will backfire if you hit the rev limiter or upshift if their engine tuning implements these features via an ignition cut (which passes unburned fuel through to the exhaust). Some cars don’t make flames at all, typically the lower level cars.

Weather – affects tyres, engine and aerodynamics and therefore car performance. Cool and dry weather makes an engine perform better but will result in more downforce and more drag.
while the opposite is true for hot, humid weather.

• dynamic – variable aspects of weather (i.e. realistic)
• temperature
• altitude – at higher altitude tracks there will be properly reduced engine power and aerodynamics effects.
• humidity
• air density
• wind speed
• wind direction
• wind gusts
• fog
• cloud cover
• sun

Race Conditions

• officially sanctioned and regulated races
• official racing rules
• road racing
• oval racing
• point scoring and championships – e.g. The NASCAR iRacing.com Series World Championship uses the NASCAR-Sanctioned Points system without averaging
• advisory boards – e.g. NASCAR Competition Advisory Board members include iRacing.com Staff and NASCAR Staff.
• practise sessions
• qualifying
• endurance racing
• team racing
• mixed class racing
• real race stewards – live officiating
• championships
• protest system
• appeals – e.g NASCAR iRacing.com Series World Championship appeals are heard by the F.I.R.S.T. Appeals Committee that contains at least one NASCAR official.
• post race review system
• penalties
 speeding in the pits
 unsafe pit entry
 unsafe pit exit
 cut course
 gained time
 jump start
 passing the pace car
 passing on the inside
 passing the leader
 passing under yellow
• sponsorship
• pace car
• flags – yellow, black, white, chequered, green, blue
• spotters – sim or real
• full course cautions
• lucky dog
• fuel limiting
• pit stops and garage
 tyre changes
 pit stalls
 refuel
 damage repair
 driver swaps
 windscreen tear offs
 external cooling fans
 tyre warmers
 tech inspections

Tracks – officially licensed 3D laser scanned tracks that are accurate to within millimetres. GPS points and thousands of photos are used to model and place items accuratley.

• bumps
• seams & cracks
• curbs
• different surface types such as asphalt, concrete, grass, astro-turf are modelled, including the thermal conductivity of asphalt aggregates etc.
• elevation changes
• stadiums, trees, leaves on the track, fencing, houses etc. Even distant hills, drainage systems, power lines and letterboxes at the front of actual houses are modelled accurately.
• people
• dynamic tracks – variable aspects of the track surface that affect the level and characteristics of tyre grip available and the wear rate. Generally, a rubbered-in but cool track free of marbles will offer the most grip.

 track temperature – is variable across the track and is influenced by weather, the position of the sun in the sky, surface type, the surface angle of the track, albedo (colour), track rubber, shadows, and interaction with cars (heat is absorbed by the ground as it comes in contact with the tire surface). The actual average race-line temperature at the start of the session is displayed as the track temperature, to simulate a crew member taking some sample measurements with a temperature gun pointed at the track a few minutes before the session begins.

 track rubber – Track rubber is built up under the tires in rough proportion to how hard they are working. A clean track will increase in rubber more quickly than a track that already has rubber. The rate at which rubber will be added tapers off and eventually reaches zero when the track is effectively saturated with usable rubber (at least it helps to think of it this way).
 rubber marbles – Tires generate marbles and these can accumulate on tires and be thrown off and redistributed on the track. They are influenced by both the player car and opponent cars to simulate the effect of following a car closely through debris. A clean track is going to produce very, very few marbles, but if there is a lot of track rubber, marbles will be produced at a healthy rate.

 debris – such as grass, gravel, dirt and marbles will collect on tires of the player car and then be flung off when appropriate. This means tires will continue to emit debris even after leaving the associated surface. Debris from the track colliding with vehicles causes a matching set of sound effects.

 grip levels change throughout race

 DRS Zones

Currently Not Modelled

engine stalling
debris from collisions/crashes
day/night cycle
moving sun
moving clouds
no tyre flatspots
continuing vulcanization
ambient sounds when in pits
smooth hand/wheel movement when watching other cars

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