iRacing has revealed its 2026 Season 3 Week 13 schedule, giving members their first detailed look at how the Aston Martin Valkyrie, Caterham 420R, Caterham Academy, Gen 4 Grand National and rebuilt pavement Sprint Car will be used immediately after the Season 4 build arrives.
Published on September 4, the schedule covers the traditional transition week between iRacing’s quarterly championships. Week 13 combines ranked racing with experimental and deliberately unusual unranked series, while also giving members an opportunity to try newly released cars, updated tracks and features before 2026 Season 4 begins.
The current Season 3 Week 12 runs from September 1-7, placing Week 13 from September 8-14, 2026. iRacing notes that all series specifically using new content and features will begin only after the Season 4 build has been deployed.
New Season 4 content gets dedicated Week 13 series
The most interesting part of the schedule is the group of championships specifically designed around new Season 4 content.
| Week 13 Series | Cars / Content |
|---|---|
| iTested | GTP including Aston Martin Valkyrie, LMP2 and GT3 — 17 car types on track |
| Left Turn It Up | Gen 4 Grand National |
| Super Slide | Rebuilt pavement Sprint Car |
| Shiny New Shakedown | Caterham 420R and Caterham Academy |
| Prototype Challenge – Fixed | GTP, Radical SR10 and Spec Racer Ford |
The headline event is undoubtedly iTested. The series will combine GTP, LMP2 and GT3 machinery with as many as 17 different car types on the same track, including the new Aston Martin Valkyrie AMR-LMH.
The Valkyrie is one of iRacing’s biggest new cars for Season 4. iRacing says it has spent more than a year developing the LMH using real telemetry, chassis information and engineering support rather than rushing the car to release.
Its appearance alongside the existing prototype and GT fields should also provide one of the first major opportunities to experience Season 4’s evolving multiclass systems under heavy traffic.
Caterham 420R and Academy make their Week 13 debut
The 13th Week Shiny New Shakedown will be dedicated to the two Caterhams arriving with Season 4: the Caterham Academy and the more powerful Caterham 420R.
Both cars are being sold together as a single iRacing package. The Academy is intended to occupy a more accessible Class D position, combining lightweight handling with strong slipstream effects, while the 420R steps up the performance significantly and is initially planned for Class C competition.
Week 13 will therefore provide a useful opportunity to drive both before their regular Season 4 championships begin.
Gen 4 Grand National joins the oval roster
Oval racers will get a dedicated 13th Week Left Turn It Up series for the new Gen 4 Grand National. The car represents the second-tier stock car machinery from the pre-Car of Tomorrow era and sits underneath iRacing’s existing Gen 4 Cup car.
Importantly, iRacing is adding the Grand National directly to the existing [Legacy] ARCA Menards Chevrolet and Gen 4 Cup package. Current owners will receive the new car automatically when the Season 4 build arrives, while the package will lose its Legacy designation and receive a dedicated Grand National official series.
Both the Gen 4 Cup and Grand National are also receiving an updated drafting model.
The pavement Sprint Car gets a complete rebuild
The 13th Week Super Slide series will showcase iRacing’s heavily reworked pavement Sprint Car.
This is considerably more than a visual refresh. iRacing has rebuilt the car from front to rear with a revised engine model, more low-end torque, reduced engine braking, the latest tire model, new suspension geometry, updated hydraulic brakes and specifications based around the 2026 rulebook.
The garage adjustment range has also been revised to more closely match the real car.
For drivers familiar with the existing Sprint Car, Week 13 should therefore provide an immediate way to compare the old and new driving behaviour before the updated version enters regular competition.
Rebuilt Road America and Mid-Ohio appear in Prototype Challenge
The new 13th Week Prototype Challenge – Fixed combines GTP machinery with the Radical SR10 and Spec Racer Ford.
iRacing specifically notes that the series includes Mid-Ohio and Road America, two circuits that have been completely rebuilt from new laser scans for Season 4.
Road America gains two additional configurations using the Turn 5 bypass road, while Mid-Ohio has also been reconstructed from its latest scan. Existing owners receive the rebuilt versions automatically rather than having to purchase the tracks again.
Milwaukee Mile is the third circuit receiving a complete new scan for Season 4, including a new road-course configuration.
Week 13 still has ranked racing
Week 13 is often associated with chaotic combinations and relaxed racing, but iRacing now offers a substantial selection of ranked series where both iRating and Safety Rating remain active.
The 2026 Season 3 Week 13 ranked schedule includes:
| Discipline | Ranked Series |
|---|---|
| Oval | NASCAR iRacing Series, Street Stock Challenge, NASCAR iRacing Truck Series, Mini Stock Cup |
| Sports Car | Mazda MX-5 Cup, BMW M2 Cup, Ferrari 296 Challenge, Porsche Cup Series, GT3 Challenge – Fixed |
| Formula Car | FF1600, Formula Vee Series, FIA F4 Challenge |
| Dirt Oval | Dirt Street Stock Challenge, Dirt Mini Stock Challenge, Sprint Car Series |
| Dirt Road | iRacing Rallycross Lite, Cross Car Cup |
The Week 13 NASCAR Truck Series will run a 100% race distance at New Hampshire, making it considerably more substantial than the short novelty races traditionally associated with the week.
Weather rerolls will be tested during Week 13
Several ranked sports car series will also be used to experiment with one of iRacing’s new Season 4 weather features.
The Ferrari 296 Challenge and GT3 Challenge – Fixed will reroll weather conditions once per day at 00:00 GMT, while the Porsche Cup Series will generate a new weather roll for every individual session.
That matches the weather experiments outlined in iRacing’s August Development Update. The company is evaluating both per-session and per-day weather rerolls as it continues refining how dynamic conditions are used in official racing.
The goal is to create more variability without immediately applying major changes across the entire service.
The unranked Week 13 schedule gets much stranger
As usual, some of the most entertaining combinations sit on the unranked side, where iRating and Safety Rating are not affected even though the Sporting Code still applies.
- 13th Week Ridiculousness puts GTP and GT3 cars together on Bristol, Dover and Milwaukee, while Figure GR8 returns with GT4 machinery.
- Battle of the Little Wings combines FIA F4, Super Formula Lights and Skip Barber cars, while The Doctor’s Office uses the Dallara P217, Ligier JS P320 and Ferrari 296 Challenge.
INDYCAR fans can take the Dallara IL-15 onto street circuits in To The Streets, while Manufacturer Madness puts seven different Ford Mustangs together.
Other combinations include the Toyota GR86 at Lime Rock’s chicane layouts in the Incident Limit Challenge and the BMW M2 at Oulton Park International in Storm Chasers, where rain probability will sit between 45% and 55%.
Track Day returns with the new Caterham
The unranked 13th Week Track Day also gains the Caterham 420R alongside the Renault Clio, BMW M2, Radical SR8, Radical SR10, Spec Racer Ford, Toyota GR86, Global Mazda MX-5 Cup and RUF RT 12R Track.
Rather than operating as a normal race, Track Day uses an open qualifying format, giving drivers a lower-pressure environment to experiment with different machinery.
For anyone buying the Caterham package primarily to learn the 420R before entering Class C racing, this may be one of the easiest ways to start.
Week 13 is the first public test of a huge Season 4 build
The Week 13 schedule is notable because the underlying 2026 Season 4 build is considerably larger than the list of new cars alone suggests.
Season 4 introduces Physics Islands, iRacing’s new multithreaded physics architecture. iRacing says the system can reduce physics CPU overhead by 50% or more in heavily populated sessions on a wide range of hardware, while providing the foundation for future increases in physics tick rates, input sampling and force feedback update frequency.
The build also soft-launches separate pace cars and independent green flags for multiclass racing, alongside new Pit Summary and Car Damage interfaces, Reference Car telemetry, improved particles and smoke, weather experiments and major car physics updates.
Our full overview of those changes is available in the iRacing August 2026 Development Update and our dedicated iRacing 2026 Season 4 guide.
What happens after Week 13?
Week 13 remains a transition rather than a normal championship week. Tracks typically rotate daily instead of weekly, new content can be tested in unusual combinations, and many of the unranked events deliberately prioritize experimentation over conventional competition.
Drivers should therefore check whether a series is ranked before entering if they are concerned about iRating or Safety Rating.
Once Week 13 concludes, the normal 12-week 2026 Season 4 championship structure begins with the new cars, rebuilt circuits, physics updates and revised systems fully integrated into the service.
iRacing has also said that more information about some of the new features and Week 13 fun series will be published in the coming days, meaning the schedule may not be the final Season 4 announcement before the build arrives.
New drivers who want to join ahead of Season 4 can view the current iRacing membership options here.
The full Week 13 schedule is available through iRacing’s official announcement.
See you on the track!
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