BoP Lab / Buttonwillow Raceway Park

P vs GTX vs B Spec pace at Buttonwillow Raceway Park

Quickest here: P 1:32.872 Jim Devenport, Cal Club 2025 qualifying · GTX 1:49.596 Rob Scholl, Cal Club 2025 race

Lap times% of P

PGTXB Specsolid race · dashed qualifying · slower is lower

PGTXB Specsolid race · dashed qualifying · each class's best lap as a share of P's at the same event (the reference class, changeable above); 100% is level, higher is quicker

	Event	P			GTX					B Spec
	Event	Qual best	Race best	Trap	Qual best	Race best	Trap	vs P	% of P	Qual best	Race best	Trap	vs P	% of P
	Cal Club 2026 CALCL262026-02-21	1:38.716Kevin Mitz · fastest of 3 · top 3 within 3.1s+5.844s (+6.29%)	1:37.287John Manfroy · fastest of 3 · top 3 within 3.5s+3.315s (+3.53%)	160.4John Manfroy+18.7 mph (+13.2%)	1:54.892Moze Cowper · only car	1:55.330Moze Cowper · only car+5.734s (+5.23%)	146.0Moze Cowper+29.6 mph (+25.4%)	+18.043squal +16.176s	118.5%qual 116.4%
9 rule changes (P: 6, GTX: 3)3 cars added · 2 engine · 1 induction · 1 suspension & brakes · 2 wording · GTX Misc Table 4 adds RCR T70 Coupe with 2200 lbs minimum weight, no restrictor specified. · Prototype carbon-carbon and carbon-ceramic brake rotors now permitted instead of prohibited. · P class 13B rotary engine restrictor changes to 40mm SIR fuel injection or 41.5mm venturi carburetor. · Prototype class adds Radical SR3 spec line to Table 1 effective 9/1/25. · Prototype P2 cars may now run P2 spec or modified Prototype spec in Prototype class; clarified language and added Radical Cup series table. · Prototype Engine Table A 2-cycle restrictor reduces from 40mm to 38mm venturi size. · GTX Ligier LMP3 now allows any normally aspirated LS Chevrolet engine. · GTX Porsche GT2 RS Clubsport classified with factory specifications required at all race events. · Class P adds clarification notes on restrictor requirements, throttle bodies, Mazda 12A engine spec, and P2 auto-based engine rules.showhide 2026-01-01 GTX Please Consider Adding a Spec Line to GTX Table 4 for the RCR T70 #39470cars addedneutralGTX Misc Table 4 adds RCR T70 Coupe with 2200 lbs minimum weight, no restrictor specified. 2026-01-01 P Request to Continue to Allow Carbon Brakes #39476suspension & brakesneutralPrototype carbon-carbon and carbon-ceramic brake rotors now permitted instead of prohibited. 2025-09-01 P 13B Rotary Engine Rules Change Request #38856engineunclearP class 13B rotary engine restrictor changes to 40mm SIR fuel injection or 41.5mm venturi carburetor. 2025-09-01 P Add Radical Cup series Radical SR3 spec line to Table 1 #38916cars addedneutralPrototype class adds Radical SR3 spec line to Table 1 effective 9/1/25. 2025-09-01 P Clarify spec line cars language #38943wordingneutralPrototype P2 cars may now run P2 spec or modified Prototype spec in Prototype class; clarified language and added Radical Cup series table. 2025-08-01 P RM 25-05 - Prototype Engine Table A, 2 Cycle Restrictor Change #38929inductionslowerPrototype Engine Table A 2-cycle restrictor reduces from 40mm to 38mm venturi size. 2025-06-01 GTX Ligier P3 LS Swap #38164engineunclearGTX Ligier LMP3 now allows any normally aspirated LS Chevrolet engine. 2025-05-01 GTX Request to Classify Porsche GT2 RS Clubsport #37972cars addedneutralGTX Porsche GT2 RS Clubsport classified with factory specifications required at all race events. 2025-05-01 P Add missing punctuation marks #38150wordingneutralClass P adds clarification notes on restrictor requirements, throttle bodies, Mazda 12A engine spec, and P2 auto-based engine rules.
	Cal Club 2025 CALCL252025-02-22	1:32.872Jim Devenport · fastest of 3 · top 3 within 8.1s	1:33.972Jim Devenport · fastest of 3 · top 3 within 7.7s	141.7Jim Devenport		1:49.596Rob Scholl · only car	116.4Rob Scholl	+15.624s	116.6%
40 earlier rule changes on record, in force before Cal Club 2025 (from 2019)20 cars added · 3 induction · 1 aero · 1 engine · 1 weight · 14 wording · Prototype Staudacher and unrestricted engine notes corrected for minimum weight wording. · Prototype class renamed from P1 to P, affecting designation throughout rules with no performance changes. · TA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof requirement. · GT2-ST Acura NSX minimum weight raised to 3000 lbs, restrictor increased to 45mm TIR. · GT1, GT2, GT3, GTL, GTX rear spoiler maximum surface area limit of 295.0 square inches removed. · GT1/GT2/GT3/GTL/GTX Direct Injection now permitted if OE, using only OE pump, hoses, injectors. · GT2/3 Nissan, Mazda, Mitsubishi 4G93, QR25DE/DD, QE25DE/DD Direct Injection now permitted per 9.1.2.F.7.5.E. · GTX adds KTM X-Bow classification with restrictor and weight specifications effective 2024-01-01. · GTL spec lines moved to contiguous position with GT2 and GT3; GTA category and spec lines renumbered and moved behind GTL. · GTX Ligier LMP3 3.7L NA classified at 2203 lbs with 22 mm restrictor. · GTX Ligier JSP4 newly classified as GTX Misc with restrictor and weight specified. · Fields Cardinal V8 classified in GT1 with Ford V8 engine, 4.9L displacement, 2100 lbs minimum weight. · GT2 TA2 and GTA throttle body part numbers updated to GM 90mm electronic #12570790 or Edelbrock 90mm mechanical #33869 or #3870. · GT taillights may now be original style or a panel graphic with functioning red LED brake lamps; wording change only. · Porsche 992 GT3 Cup Car newly classified in GTX. · GTX Wolf GB08 F1 Ford 52XS V8 added to classification at 1725 lbs minimum weight. · C7 Corvette Grand Sport classified in GTX Misc at 3200 lbs with option to remove displacement on demand valve train. · GTX eligible prototypes expanded: IMSA GTP years changed to 1981-1993, five prototype categories added. · GTX McLaren 720s GT3 newly classified at 3000 lbs with 3000 mm restrictor. · GTX-FIA GT3 removes all intake restrictor requirements for fifteen car models; McLaren name corrected. · GT3 Fun Cup Beetle EVO3 classified with 1984 cc sealed SOHC engine, 2060 lbs minimum weight. · GTX SRO-GT4 Porsche 718 Club Sport MR GT4 classified, unrestricted, 2900 lbs minimum weight. · GTA part numbers updated: 0-80541-1 to 0-80541-2 in two sections and 6010 to 6014X in TA2 Appendix. · Grullon GT with 2.0L K20 moved from GTX to GT2-ST, minimum weight 2350 lbs, unrestricted. · GTX Grullon GT added, unrestricted, 2350 lbs, factory spec required. · GT1, GT2, GT3, GTL, GTX now permit turbocharging/supercharging if listed on spec line. · GTX Chevrolet Camaro ZL1 LT4 with factory supercharger classified at 3400 lbs minimum weight. · GTX adds KTM X-Bow GT4, turbocharged 2.5L Audi TFSI I5, 2000 lbs minimum weight. · TA2 Gurney flap wording clarified: terminology standardized to 'Gurney flap', height limits and thickness specifications remain 0.50 inch / 0.625 inch or 0.375 inch / 0.0625 inch depending on configuration. · STO rear wing wording clarified: 'wicker' changed to 'Gurney flap' in maximum chord and mounting height rules. · GT classes clarify Gurney flap wording, replacing wickerbill/tab terminology with flap; specifications unchanged. · GTX tube frame cars must weigh 2780 pounds; stock car bodies now permitted. · GTX adds Lotus Evora GTS with 3.5L 2GR-FE engine, no restrictor, 2950 lbs minimum weight. · GT1, GT2, GT3, GTL, GTX may omit windshield clips if factory glass is bonded per original specifications. · Factory Five Type 65 Coupe R with Ford 302/351 or 5.0/5.2L NA added to GTX-MISC at 2600 lbs. · GTX tube frame cars gain fuel injection with 90mm maximum throttle body size. · Ligier JS2 R classified in GTX, no performance parameters specified in filing. · GT1 and GT2/GT3/LITE ride height requirements removed from GCR sections 9.1.2.D.5.a.1 and 9.1.2.F.7.b. · GTX replaces all FIA GT4 references with SRO GT4. · GTX FIA GT3: Audi R8 40mm restrictor 2900 lbs, BMW Z4 70mm 2800 lbs, Ferrari 488 35mm restrictor 3025 lbs classified.showhide 2025-02-01 P Correct text in engine table notes #37606wordingneutralPrototype Staudacher and unrestricted engine notes corrected for minimum weight wording. 2025-02-01 P Update Prototype class designation #37653wordingneutralPrototype class renamed from P1 to P, affecting designation throughout rules with no performance changes. 2025-01-01 GTX Correct language regarding OEM Areo Devices #37137wordingneutralTA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof requirement. 2024-05-01 GTX Request for Spec Line 1010 Reconsideration #35009weight +300 lbsslowerGT2-ST Acura NSX minimum weight raised to 3000 lbs, restrictor increased to 45mm TIR. 2024-02-01 GTX Rear Blade Spoiler Clarification #35261aerofasterGT1, GT2, GT3, GTL, GTX rear spoiler maximum surface area limit of 295.0 square inches removed. 2024-02-01 GTX GT Direct Injection allowance and rules #35437enginefasterGT1/GT2/GT3/GTL/GTX Direct Injection now permitted if OE, using only OE pump, hoses, injectors. 2024-02-01 GTX GT2/3 remove Direction Injection not allowed in Spec line notes #35439inductionfasterGT2/3 Nissan, Mazda, Mitsubishi 4G93, QR25DE/DD, QE25DE/DD Direct Injection now permitted per 9.1.2.F.7.5.E. 2024-01-01 GTX KTM X Bow GTX #34956cars addedneutralGTX adds KTM X-Bow classification with restrictor and weight specifications effective 2024-01-01. 2023-12-01 GTX Errors in GTCS Headings and Use of the Terms Category and ClassChange existing GTL and GTA Rules #34453wordingneutralGTL spec lines moved to contiguous position with GT2 and GT3; GTA category and spec lines renumbered and moved behind GTL. 2023-07-01 GTX Request Ligier LMP3 Classification #34043cars addedneutralGTX Ligier LMP3 3.7L NA classified at 2203 lbs with 22 mm restrictor. 2023-07-01 GTX Ligier JSP4 Request #34173cars addedneutralGTX Ligier JSP4 newly classified as GTX Misc with restrictor and weight specified. 2023-05-01 GTX Please classify Fields Cardinal V8 #33784cars addedneutralFields Cardinal V8 classified in GT1 with Ford V8 engine, 4.9L displacement, 2100 lbs minimum weight. 2022-12-01 GTX GT2 (TA2)/GTA Part Number Update #33315wordingneutralGT2 TA2 and GTA throttle body part numbers updated to GM 90mm electronic #12570790 or Edelbrock 90mm mechanical #33869 or #3870. 2022-09-01 GTX Tail lights on all GT category race cars. #32799wordingneutralGT taillights may now be original style or a panel graphic with functioning red LED brake lamps; wording change only. 2022-06-01 GTX Classify 992 GT3 Cup #32649cars addedneutralPorsche 992 GT3 Cup Car newly classified in GTX. 2022-05-01 GTX Add Classification to the accepted Model Table #31981cars addedneutralGTX Wolf GB08 F1 Ford 52XS V8 added to classification at 1725 lbs minimum weight. 2022-05-01 GTX Request to classify C7 Corvette Grand Sport IN GTX Misc #32254cars addedneutralC7 Corvette Grand Sport classified in GTX Misc at 3200 lbs with option to remove displacement on demand valve train. 2022-05-01 GTX E&O list of eligible prototypes #32511cars addedneutralGTX eligible prototypes expanded: IMSA GTP years changed to 1981-1993, five prototype categories added. 2022-03-01 GTX McLaren 720s GT3 #31955cars addedneutralGTX McLaren 720s GT3 newly classified at 3000 lbs with 3000 mm restrictor. 2022-02-01 GTX Remove restrictions from GTX-FIA GT3 #32039inductionfasterGTX-FIA GT3 removes all intake restrictor requirements for fifteen car models; McLaren name corrected. 2021-10-01 GTX Request car classification #31032cars addedneutralGT3 Fun Cup Beetle EVO3 classified with 1984 cc sealed SOHC engine, 2060 lbs minimum weight. 2021-09-01 GTX Request to classify 2020 Porsche 718 GT4 Clubsport MR #30956cars addedneutralGTX SRO-GT4 Porsche 718 Club Sport MR GT4 classified, unrestricted, 2900 lbs minimum weight. 2021-08-01 GTX Request to Update GTA Obsolete Part Numbers #30615wordingneutralGTA part numbers updated: 0-80541-1 to 0-80541-2 in two sections and 6010 to 6014X in TA2 Appendix. 2021-08-01 GTX GTX class correction to GT2/ST #30973cars addedneutralGrullon GT with 2.0L K20 moved from GTX to GT2-ST, minimum weight 2350 lbs, unrestricted. 2021-07-01 GTX Request classification of Grullon #30481cars addedneutralGTX Grullon GT added, unrestricted, 2350 lbs, factory spec required. 2020-09-01 GTX GT Category Wording #29193wordingunclearGT1, GT2, GT3, GTL, GTX now permit turbocharging/supercharging if listed on spec line. 2020-08-01 GTX Request Car classification #28935cars addedneutralGTX Chevrolet Camaro ZL1 LT4 with factory supercharger classified at 3400 lbs minimum weight. 2020-08-01 GTX X-Bow GT4 #29088cars addedneutralGTX adds KTM X-Bow GT4, turbocharged 2.5L Audi TFSI I5, 2000 lbs minimum weight. 2020-07-01 GTX TA2 Gurney flap wicker clarification #28874wordingneutralTA2 Gurney flap wording clarified: terminology standardized to 'Gurney flap', height limits and thickness specifications remain 0.50 inch / 0.625 inch or 0.375 inch / 0.0625 inch depending on configuration. 2020-07-01 GTX STO Gurney flap wicker clarification #28883wordingneutralSTO rear wing wording clarified: 'wicker' changed to 'Gurney flap' in maximum chord and mounting height rules. 2020-07-01 GTX GT Gurney flap wicker clarification #28909wordingneutralGT classes clarify Gurney flap wording, replacing wickerbill/tab terminology with flap; specifications unchanged. 2020-06-01 GTX Request to Re-classify SP Stock car to GTX #28333cars addedneutralGTX tube frame cars must weigh 2780 pounds; stock car bodies now permitted. 2020-05-01 GTX Request to Classify Lotus Evora GTS #27057cars addedneutralGTX adds Lotus Evora GTS with 3.5L 2GR-FE engine, no restrictor, 2950 lbs minimum weight. 2020-02-01 GTX Windshield Clips #27323wordingneutralGT1, GT2, GT3, GTL, GTX may omit windshield clips if factory glass is bonded per original specifications. 2020-01-01 GTX Request Factory Five Daytona coupe classification #26308cars addedneutralFactory Five Type 65 Coupe R with Ford 302/351 or 5.0/5.2L NA added to GTX-MISC at 2600 lbs. 2019-05-01 GTX Request GTX Fuel injection for previous GT-1 tube frame cars #26141inductionfasterGTX tube frame cars gain fuel injection with 90mm maximum throttle body size. 2019-05-01 GTX Request to Classify Ligier JS2 R #26535cars addedneutralLigier JS2 R classified in GTX, no performance parameters specified in filing. 2019-04-01 GTX Request Ride Height Clarification #26600wordingneutralGT1 and GT2/GT3/LITE ride height requirements removed from GCR sections 9.1.2.D.5.a.1 and 9.1.2.F.7.b. 2019-03-01 GTX Replace FIA references with SRO #26427wordingneutralGTX replaces all FIA GT4 references with SRO GT4. 2019-01-01 GTX GTX Homologation table update #26034cars addedneutralGTX FIA GT3: Audi R8 40mm restrictor 2900 lbs, BMW Z4 70mm 2800 lbs, Ferrari 488 35mm restrictor 3025 lbs classified.

Best is the class's fastest lap in that event's qualifying or race sessions, with the driver who set it, how many cars set a time that session and how close the top five were; a best from fewer than three cars is greyed. With two or more classes, "vs" is the gap of each class's best to the first class's at the same event. "% of P" is the class's best as a share of P's best at the same event (100% is level, less is quicker): weather and track condition move every class together, so this compares across years where the raw times do not. It still breaks when P's own field changes or one session was wet and another dry. Newest event first. The coloured figure under each value is the change from the previous event that has one (green is quicker, red slower). Whole laps only, so events with different sector layouts still compare. Weather and track condition are not accounted for.