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P1 is rooted in a merger of the European Group C cars and the IMSA GT series GTP cars. Prototype chassis with ambitious ground effects provide exceptional aerodynamics with lower resistance then most open wheel cars. International endurance races including LeMans, Daytona and Sebring put thes cars on track both day & night. Lighting for all cars works very well.

The 21 30 models provided in the IMSA GT P1 class consists of cars constructed for prototype racing over the last 20 years. Physics for each car has been developed to preserve the unique personality from a driver's perpective yet remain competitive with all the other cars in the P1 class.

Default setups are in the middle ranges for most settings to maintain consistency for AI racing. Cars respond very well to tuning. Common adjustments include:

  • Larger Front Ant-Roll Bars
  • Lower Front Spring Rates
  • Lower Ride heights - Rear should be 1/2" - 3/4" higher then front for most cars
  • Differential settings - everyone is different here, just depends on your driving style
  • Gear Ratios - plenty to choose from
  • Front & Rear Wing settings

25 models are complete in Version 1.5. Work In Progress (WIP) cars include:

  • Dome S102
  • Audi R18
  • Lancia LC2
  • Riley & Scott MkIII
  • Spice GTP

See the P1 Class Lineups below for each car. Download Links for the IMSA GT mod are provided to registered members of rFactor-League. These files are hosted on our server for high speed downloads. Files are not in an executable and require manual installation. Note that MAS files reside in a common folder rather then the folder for each car.

P1 Class Lineup & Car Briefs
Car: Acura ARX P1
Description: Acura 4.0 liter engine allows a 50 lb reduction in weight to larger displacement engines making the Acura a little more nimble into and out of turns.
Engine: Acura V8 4.0 liter engine
Release Level: 1.5
Car: Audi R8
Description: Like the Acura the Audi has a smaller displacement engine with less weight and a low center of gravity.
Engine: Audi V8 3.6 liter
Release Level: 1.5
Car: Audi R10
Description: Audi rocked the sports car world with a diesel powerplant as allowed by IMSA rules. Very successful although a bit heavy with a higher center of gravity.
Engine: Audi V12 TDI 5.5 Liter
Release Level: 1.5
Car: Audi R15
Description: Audi engineers reduced the engine mass with a 10 cylinder version that provided a little more power, and revised the chassis to the new engine allowing improved handling.
Engine: Audi V12 TDI 5.5 Liter
Release Level: 1.5
Car: Audi R18
Description: WIP - Audi R18 is scheduled for release in November. Both turbo diesel and V8 versions will be released.
Engine: 1 2 3 4 5 6
Release Level: 1.5
Car: Bentley Speed 8
Description: After a 70 year absence, Bentley returned to motorsports in 2001 with the Speed 8. Classic British design with clean green aerodynamic bodywork, superb drivability and of course equipped with British electronics that were prone to failure.
Engine: Audi 3.6 litre turbocharged V8
Release Level: 1.5
Description: BMW commissioned Williams to build the LMR to be fitted with the compact 6.1 Liter V12 from the 850i series sedans. Awesome car, smooth power.
Engine: BMW S70 V12 6.1 Liter All Aluminum
Release Level: 1.5
Car: Dallara P1
Description: Originally developed for Ferrari as the platform for the 333SP the Dallara evolved into a privateer market chassis.
Engine: Judd GV4 V10 4.0 Liter
Release Level: 1.5
Car: Dome S101M
Description: Dome cars (Japan) remained out of the spotlight for several years until just after they constructed Dan Gurney's "All American Racing" Toyota GTP cars. The S101M is mostly a privateer market chassis and offers several engine options.
Engines: (Std) Judd V10 5.0 Liter :: Chevrolet V8 6.6 Liter :: Aston Martin V12 :: Mazda 26B ::Cosworth DFX V8 2.6 Liter Turbo
Release Level: 1.5
Car: Eagle Mk III
Description: Eagle Mk III is a model of Dan Gurney's "All American Racing" Toyota GTP cars. Powered by a Toyota 2.1 Liter Turbo, IMSA rules allowed unrestricted throttle body size in turn enabling the small displacement motor to crank out "big bore" horsepower. Reliable and fuel efficient with low aero effects in traffic.
Engine: Turbocharged Toyota 2.1 Liter 4 cylinder
Release Level: 1.5
Car: Ferrari 333 SP
Description: Making a 1993 debut the 333SP breathed new life into prototype racing as Porsche, Toyota, Jaguar & Nissan had all but pulled the plug on prototypes. Dallara designed and built a short wheelbase chassis and Ferrari installed a stroked F1 engine. The 333SP enjoyed an 11 year run with the final apperance in 2003 at Monza.
Engine: Ferrari F310E 3997 cc V12
Release Level: 1.5
Car: Jaguar XJR
Description: Throght the late 80's & early 90's the late Tom Walkinshaw managed a spectacular racing program for Jaguar based on both 3.5 Liter V6 Turbo and a mighty 7 liter V12. One of each is included.
Engines: #901 is equipped with the 3.5 L V6 Turbo, and #902 is equipped with a 7 liter V12.
Release Level: 1.5
Car: Kudzu Mazda P1
Description: Jim Downing designed & built this GTP chassis out of his carbon fiber shop in Atlanta area. Mazda used the Downing car as a rolling test bed to evolve the 3 rotor 20B into the 4 rotor 26B. The car has exceptional braking and handling.
Engine: Mazda 26B
Release Level: 1.5
Car: Lola B09 P1
Description: Developed jointly with Aston Martin, there were about a dozen assembled tubs that were never delivered with an AM engine and Xtrac gearbox; these cars are rumored to have been intended for an AM supercar that was abandoned. Now these cars are included in the IMSA GT mod with optional engines.
Engine: (Std) AM V12 6.0 Liter :: Chevrolet V8 6.6 Liter :: Judd V10 5.5 Liter :: Mazda 26B ::Cosworth DFX V8 2.6 Liter Turbo
Release Level: 1.5
Car: Lola EX264 P1
Description: Lola EX264 is an evolution of the EX257, both cars having exceptional aerodynamics. Originally developed for MG some of the cars found their way into the hands of privateers with various engines.
Engine: (Std) Judd V10 5.0 Liter :: Chevrolet V8 6.6 Liter :: Aston Martin V12 :: Mazda 26B ::Cosworth DFX V8 2.6 Liter Turbo
Release Level: 1.5
Car: Mazda 787B P1
Description: Mazda commission Nigel Stroud to design and construct this car for GTP/Gruppe C competition with some significant success in the early 90's. The newly developed 26B engine was capable of over 900HP but was restricted to 705 HP in race trim.
Engine: Mazda 4 rotor 26B
Release Level: 1.5
Car: Mazda Furai P1
Description: Mazda developed this car on the Courage C65 platform as a concept car using it as a test mule for various engine configurations. The latest engine is the X-generation of rotaries with 3 rotors having 2.4 liters displacement. While not entered into IMSA racing, lap times at Suzuka show this car to be dead equal with current P1 cars at that track.
Engine: Mazda 3 rotor 24X
Release Level: 1.5
Car: Mercedes Benz CLR
Description: Mercedez Benz designed and built this car for the 1999 LeMans race. Mark Webber made the car famous with a 360° end-over flip at 254 MPH on the LeMans Mulsanne straight.
Engine: Mercedes Benz 4 cam V8 5.7 Liter
Release Level: 1.5
Car: Sauber-Mercedes C9 P1
Description: Sauber developed the chassis for Mercedes to be fitted with the venerable Benz V8 4 cam 5.7 liter engine to compete in the GTP class in 1989.
Engine: Mercedes Benz Turbocharged V8 5.0 Liter
Release Level: 1.5
Car: Nissan NPT 90 P1
Description: In the hands of Geoff Brabham this car was on a roll dominating the IMSA GTP class. The model has an unresolved issue with the nose disappearing only in cockpit view, otherwise its a sheer joy to drive. Model will be updated at a later date.
Engine: Nissan Turbo V6 3.5 Liter
Release Level: 1.5
Car: Cadillac Northstar LMP02 P1
Description: Cadillac commissioned Nigel Stroud to construct the LMP02 chassis to be fitted with their twin turbo Northstar engine. Typical for GM of that era, fabulous engineers developed great stuff only to have the capabilities wrecked by poor management. Great car none the less, its a gotta-try car.
Engine: Northstar twin turbo V8 4.0 Liter
Release Level: 1.5
Car: Pescarolo C60 P1
Description: Born in LeMans Pescarolo is a small constructor focusing on LeMans prototypes; featuring a low center of gravity and slippery aerodynamics these cars do slightly better on long tracks then short tracks.
Engine: (Std) Judd V10 5.0 Liter :: Chevrolet V8 6.6 Liter :: Aston Martin V12 :: Mazda 26B ::Cosworth DFX V8 2.6 Liter Turbo
Release Level: 1.5
Car: Peugeot 908 P1
Description: Peugeot watch the success of Audi diesel technology and brought their own dog to the fight - except this was no dog! Using 100° cylinder bank angle allowed the V12 diesel a lower center of gravity while the sleek enclosed cockpit pierced the wind with ease. The sound of the diesel is a bit unique.
Engine: Peugeot V12 twin turbo diesel 5.5 Liter
Release Level: 1.5
Car: Porsche 962 P1
Description: The 956 chassis was extended for driver safety becoming the 962. Continuing Porsche's race winning heritage it was powered by a reliable turbo flat 6 providing a low center of gravity. The engine was capable of 1000 HP but restricted to 700HP in race trim. The 962 was the last full factory effort from Porsche to dominate IMSA GTP/P1 racing.
Engine: Porsche air cooled flat 6 "boxer" twin turbo 3.5 Liter.
Release Level: 1.5
Car: Reynard 01Q P1
Description: Reynard built a handful of prototypes that were evolved in house and by privateers. This particular car is one of the lightweights powered by a 4 cylinder turbo engine. Blistering on the short tracks.
Engine: VW A59 turbo 2.0 Liter
Release Level: 1.5
Car: Riley Technologies Mark XI P1
Description: Bill Riley designed and built great cars for the privateer market which were equipped with a variety of engines by the customers. 3 of the 4 cars is equipped with a different engine.
Engine: BMW 5.0 Liter V8 :: Lexus 5.0 Liter V8 :: Pontiac 5.7 Liter V8
Release Level: 1.5