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BoP Lab / Buttonwillow Raceway Park

P vs GTL pace at Buttonwillow Raceway Park

Class · click a class to switch, + to compare alongside (up to 4)
Reference class · the others' laps as a share of this one's at the same event, so years compare despite weather; + a class above to measure against it
Track configuration

Quickest here: P 1:32.872 Jim Devenport, Cal Club 2025 qualifying

1:331:341:351:361:371:381:396 rule changes between Cal Club 2025 and Cal Club 20266 ▾P race best at Cal Club 2025: 1:33.972 (Jim Devenport)P race best at Cal Club 2026: 1:37.287 (John Manfroy)P qualifying best at Cal Club 2025: 1:32.872 (Jim Devenport)P qualifying best at Cal Club 2026: 1:38.716 (Kevin Mitz)Cal Club 20252025Cal Club 20262026
PGTLsolid race · dashed qualifying · slower is lower
100%6 rule changes between Cal Club 2025 and Cal Club 20266 ▾P race best at Cal Club 2025: 100.0% of P's (Jim Devenport)P race best at Cal Club 2026: 100.0% of P's (John Manfroy)P qualifying best at Cal Club 2025: 100.0% of P's (Jim Devenport)P qualifying best at Cal Club 2026: 100.0% of P's (Kevin Mitz)Cal Club 20252025Cal Club 20262026
PGTLsolid 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
EventPGTL
Qual bestRace bestTrapQual bestRace bestTrapvs P% of P
Cal Club 2026 CALCL262026-02-211:38.716Kevin 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%)
6 rule changes (P: 6)1 cars added · 1 engine · 1 induction · 1 suspension & brakes · 2 wording · 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. · Class P adds clarification notes on restrictor requirements, throttle bodies, Mazda 12A engine spec, and P2 auto-based engine rules.showhide
  • P Request to Continue to Allow Carbon Brakes #39476suspension & brakesneutralPrototype carbon-carbon and carbon-ceramic brake rotors now permitted instead of prohibited.
  • P 13B Rotary Engine Rules Change Request #38856engineunclearP class 13B rotary engine restrictor changes to 40mm SIR fuel injection or 41.5mm venturi carburetor.
  • 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.
  • 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.
  • 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.
  • 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 CALCL252025-02-221:32.872Jim Devenport · fastest of 3 · top 3 within 8.1s1:33.972Jim Devenport · fastest of 3 · top 3 within 7.7s141.7Jim Devenport
69 earlier rule changes on record, in force before Cal Club 2025 (from 2019)21 cars added · 7 induction · 7 weight · 6 aero · 3 engine · 1 removed · 24 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. · GTL Toyota G16E-GTS removes direct injection ban wording, effective 11/1/2024. · GTL Nissan L16 limited prep gains alternate 32mm choke option at 1910 lbs minimum weight. · GTL adds Toyota GR86 2021-2023, 2dr RWD, 101.3 in wheelbase. · GTL adds Spec Miata 1990-2005 with legal Spec Miata engine and intake system. · Mazda MX5 RF 2017- added to GTL with 91.0 inch wheelbase. · GTL added to GT3 choke option line for induction control. · GT2-ST Acura NSX minimum weight raised to 3000 lbs, restrictor increased to 45mm TIR. · GTL Datsun 510 L16 Limited Prep allows 34 mm chokes, minimum weight rises to 2000 lbs. · 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. · GTL Mazda 12A rotary engines may machine and use 13B housing to O.E. 12A specifications. · GTL Toyota GR86 (DR86, 2021-2024, 2-door RWD, 101.3-inch wheelbase) newly classified. · GTL BMW Mini years corrected to 2002-2013. · GTL small unrestricted engines under 1399cc lose 40-50 lbs across Alfa, AMC, Triumph, Mini, Sprite, Fiat, Ford, Honda, Mazda, Nissan, Subaru, Toyota, Volkswagen. · GTL Honda Fit 2009-13 2-door FWD classified with wheelbase options 94.0, 97.0, or 99.0 inches. · GTL spec lines moved to contiguous position with GT2 and GT3; GTA category and spec lines renumbered and moved behind GTL. · GTL Nissan Sentra/200SX A14 engine weight reduced from 1850 lbs to 1800 lbs. · Fields Cardinal V8 classified in GT1 with Ford V8 engine, 4.9L displacement, 2100 lbs minimum weight. · GTL Toyota 3K, 4K, 5K engines now permitted to use 4Y block only. · GT2 Toyota 4A-F and 4A-FE 1.6L DOHC 16V engines newly classified in spec line. · GTL Fiat 1500 Limited Prep X1/9 weight increases to 2000 lbs. · GT2 TA2 and GTA throttle body part numbers updated to GM 90mm electronic #12570790 or Edelbrock 90mm mechanical #33869 or #3870. · Ford Festiva 1988-1993 added to GTL with Mazda B3 1324cc engine. · GTL Toyota G16E-GTS 3-cylinder engine added: 1618cc, 1945 lbs, naturally aspirated with SIR fuel induction. · GT taillights may now be original style or a panel graphic with functioning red LED brake lamps; wording change only. · Ginetta G40 classified in GTL with Ford Zetec 1796cc engine at 2050 lbs, plus 51 lbs for IRS or 26 lbs for sequential. · GT3 Fun Cup Beetle EVO3 classified with 1984 cc sealed SOHC engine, 2060 lbs minimum weight. · GTA part numbers updated: 0-80541-1 to 0-80541-2 in two sections and 6010 to 6014X in TA2 Appendix. · GTL Honda B18a,b vs B18c: new split classifies B18a,b at 2050 lbs, B18c at 2065 lbs. · GTL Nissan B13 Sentra allowed hood bulge maximum 1.5 inches high, 10.0 inches long, 6.0 inches wide. · GTL BMW E21 added to GT Cars - BMW classification. · GTL Mazda 12A SIR increases to 29mm, minimum weight rises to 2000 lbs. · Fiat X-1/9 Bertone 1500 added to GTL with 2000 lbs minimum weight, SOHC, fuel induction options, Level 2 prep. · GTL Nissan MRA8DE 1797cc engine classified with 2050 lbs minimum weight and 22.5mm restrictor. · GTL Mazda 13B SIR increases from 26mm to 28mm; 27mm plus 175 lbs option removed. · GT1, GT2, GT3, GTL, GTX now permit turbocharging/supercharging if listed on spec line. · GTL Mazda 13B restrictor increases to 26mm SIR, minimum weight rises to 2125 lbs. · GTL Toyota MR2 Spyder 1999-2007 newly classified. · 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. · GTL Mazda 13B restrictor size clarification issued; refer to letter 28518 for details. · GTL stall test procedure clarified: intake system must pass SIR test as raced, no air bypass allowed. · GTL wing mount openings excluded from square inch limit. · GTL wing mounting posts limited to 85 square inches exposed area each, measured flat from side view. · GTL wing mounting posts limited to 85 square inches exposed area each, measured flat from side. · GTL wing endplates change from 8.5×3.0 inch rectangle to maximum 64 square inches. · GTL Mazda 12A Street Port minimum weight reduced to 1950 lbs from 2000 lbs. · 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. · GTL adds Jetta Mk1 two door classification effective 2020-01-01. · GTL Honda CRX 84-87 and 88-91 remove IRS option with 2.5% weight penalty. · GTL Fun Cup Beetle engine weight specified at 1850 lbs with sealed SOHC 1780cc specification. · GTL Fun Cup Beetle removes reference to VW engine table; Fun Cup engine spec remains 1.8L at 2040 lbs. · GTL Honda CRZ 10-14, CRZ 15-16, and Insight 00-06 gain alternate wheelbase option of 90.6 in. · GTL adds VW Fun Cup Beetle, all model years, 2-door RWD, 94.5-inch wheelbase. · 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. · GTL Mazda 13B may use 25mm SIR with 175 lbs weight penalty added. · 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. · GTL Mazda 12A may use 28mm SIR plus 175 lbs. · GTL Mustang 94-04 newly classified in GTL. · GTL Mini 1275-1399 Iron and Aluminum Crossflow gain 75 lbs weight reduction to 125 lbs with OE common sump gearbox. · GTL BMC thru Rover Group removes long inactive Mini engines: 948, 970, 1071, 1098. · GTX FIA GT3: Audi R8 40mm restrictor 2900 lbs, BMW Z4 70mm 2800 lbs, Ferrari 488 35mm restrictor 3025 lbs classified.showhide
  • P Correct text in engine table notes #37606wordingneutralPrototype Staudacher and unrestricted engine notes corrected for minimum weight wording.
  • P Update Prototype class designation #37653wordingneutralPrototype class renamed from P1 to P, affecting designation throughout rules with no performance changes.
  • GTL Correct language regarding OEM Areo Devices #37137wordingneutralTA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof requirement.
  • GTL G16E-GTS Fuel Injection Spec Line Change #36588wordingunclearGTL Toyota G16E-GTS removes direct injection ban wording, effective 11/1/2024.
  • GTL GTL Alternate Weight and Choke Option for L16 engine #36653inductionfasterGTL Nissan L16 limited prep gains alternate 32mm choke option at 1910 lbs minimum weight.
  • GTL Request to Include Toyota GR86 in GTL #36324cars addedneutralGTL adds Toyota GR86 2021-2023, 2dr RWD, 101.3 in wheelbase.
  • GTL Inclusion of Modified Spec Miata for GTL competition #36325cars addedneutralGTL adds Spec Miata 1990-2005 with legal Spec Miata engine and intake system.
  • GTL Include Mazda MX5 RF 2017- in GTL #36428cars addedneutralMazda MX5 RF 2017- added to GTL with 91.0 inch wheelbase.
  • GTL Add GTL to GT3 choke option line. #36236wordingunclearGTL added to GT3 choke option line for induction control.
  • GTL Request for Spec Line 1010 Reconsideration #35009weight +300 lbsslowerGT2-ST Acura NSX minimum weight raised to 3000 lbs, restrictor increased to 45mm TIR.
  • GTL Allow 34 mm chokes for the Datsun 510 #35661weight +50 lbsslowerGTL Datsun 510 L16 Limited Prep allows 34 mm chokes, minimum weight rises to 2000 lbs.
  • GTL Rear Blade Spoiler Clarification #35261aerofasterGT1, GT2, GT3, GTL, GTX rear spoiler maximum surface area limit of 295.0 square inches removed.
  • GTL GT Direct Injection allowance and rules #35437enginefasterGT1/GT2/GT3/GTL/GTX Direct Injection now permitted if OE, using only OE pump, hoses, injectors.
  • GTL 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.
  • GTL Rotary Engine 12A Rotor Housings #35131wordingneutralGTL Mazda 12A rotary engines may machine and use 13B housing to O.E. 12A specifications.
  • GTL Request to Include Toyota GR86 in GTL #35198cars addedneutralGTL Toyota GR86 (DR86, 2021-2024, 2-door RWD, 101.3-inch wheelbase) newly classified.
  • GTL Errors and Omissions, GTL engines & Cars #35226wordingneutralGTL BMW Mini years corrected to 2002-2013.
  • GTL Small Engines in GT Lite #34842weightfasterGTL small unrestricted engines under 1399cc lose 40-50 lbs across Alfa, AMC, Triumph, Mini, Sprite, Fiat, Ford, Honda, Mazda, Nissan, Subaru, Toyota, Volkswagen.
  • GTL Request to Classify Honda Fit body in GTL #35020cars addedneutralGTL Honda Fit 2009-13 2-door FWD classified with wheelbase options 94.0, 97.0, or 99.0 inches.
  • GTL 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.
  • GTL Weight for Nissan Sentra/200SX A 1400's #34918weight -50 lbsfasterGTL Nissan Sentra/200SX A14 engine weight reduced from 1850 lbs to 1800 lbs.
  • GTL Please classify Fields Cardinal V8 #33784cars addedneutralFields Cardinal V8 classified in GT1 with Ford V8 engine, 4.9L displacement, 2100 lbs minimum weight.
  • GTL Toyota 4Y Engine Classification Request #33562engineneutralGTL Toyota 3K, 4K, 5K engines now permitted to use 4Y block only.
  • GTL Toyota 4A-F and 4A-FE 1.6L DOHC 16V Engine Request #33415cars addedneutralGT2 Toyota 4A-F and 4A-FE 1.6L DOHC 16V engines newly classified in spec line.
  • GTL Fiat HP Limited Prep X1/9 Weight in GTL #33297weightslowerGTL Fiat 1500 Limited Prep X1/9 weight increases to 2000 lbs.
  • GTL 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.
  • GTL Request to add Ford Festiva to GTL #33335cars addedneutralFord Festiva 1988-1993 added to GTL with Mazda B3 1324cc engine.
  • GTL Engine Request #33064cars addedneutralGTL Toyota G16E-GTS 3-cylinder engine added: 1618cc, 1945 lbs, naturally aspirated with SIR fuel induction.
  • GTL 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.
  • GTL Request to Classify Ginetta G40 in GTL #31599cars addedneutralGinetta G40 classified in GTL with Ford Zetec 1796cc engine at 2050 lbs, plus 51 lbs for IRS or 26 lbs for sequential.
  • GTL Request car classification #31032cars addedneutralGT3 Fun Cup Beetle EVO3 classified with 1984 cc sealed SOHC engine, 2060 lbs minimum weight.
  • GTL 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.
  • GTL Request clarification for the Honda B18a,bVS B18c #30482wordingneutralGTL Honda B18a,b vs B18c: new split classifies B18a,b at 2050 lbs, B18c at 2065 lbs.
  • GTL Request to Allow Hood Bulge on Nissan B13 Sentra #30504aeroneutralGTL Nissan B13 Sentra allowed hood bulge maximum 1.5 inches high, 10.0 inches long, 6.0 inches wide.
  • GTL Request BMW E21 Classing #30582cars addedneutralGTL BMW E21 added to GT Cars - BMW classification.
  • GTL Request for Help for Mazda 12A #29754induction +50 lbsslowerGTL Mazda 12A SIR increases to 29mm, minimum weight rises to 2000 lbs.
  • GTL Request LP HP Fiat X1/9 & Bertone 1500 to GTL #30058cars addedneutralFiat X-1/9 Bertone 1500 added to GTL with 2000 lbs minimum weight, SOHC, fuel induction options, Level 2 prep.
  • GTL Please Add GTL Nissan 1.8L Engine MRA8DE #29805cars addedneutralGTL Nissan MRA8DE 1797cc engine classified with 2050 lbs minimum weight and 22.5mm restrictor.
  • GTL Increase 13b SIR size #29867inductionfasterGTL Mazda 13B SIR increases from 26mm to 28mm; 27mm plus 175 lbs option removed.
  • GTL GT Category Wording #29193wordingunclearGT1, GT2, GT3, GTL, GTX now permit turbocharging/supercharging if listed on spec line.
  • GTL Request to change the Mazda 13b restrictor size #28518induction +175 lbsfasterGTL Mazda 13B restrictor increases to 26mm SIR, minimum weight rises to 2125 lbs.
  • GTL Request to classify 1999-2007 Toyota MR2 Spyder body #28870cars addedneutralGTL Toyota MR2 Spyder 1999-2007 newly classified.
  • GTL 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.
  • GTL STO Gurney flap wicker clarification #28883wordingneutralSTO rear wing wording clarified: 'wicker' changed to 'Gurney flap' in maximum chord and mounting height rules.
  • GTL GT Gurney flap wicker clarification #28909wordingneutralGT classes clarify Gurney flap wording, replacing wickerbill/tab terminology with flap; specifications unchanged.
  • GTL Mazda 13b Restrictor Size Follow up to Letter 28518 #29015wordingunclearGTL Mazda 13B restrictor size clarification issued; refer to letter 28518 for details.
  • GTL Stall Test #28709wordingneutralGTL stall test procedure clarified: intake system must pass SIR test as raced, no air bypass allowed.
  • GTL GTL Wing Rule #28754aeroneutralGTL wing mount openings excluded from square inch limit.
  • GTL Wing Mounting Upright Size #27641aeroneutralGTL wing mounting posts limited to 85 square inches exposed area each, measured flat from side view.
  • GTL Wing Mounting Upright Size #27641aeroneutralGTL wing mounting posts limited to 85 square inches exposed area each, measured flat from side.
  • GTL GTL wing end plates addition #28243aerofasterGTL wing endplates change from 8.5×3.0 inch rectangle to maximum 64 square inches.
  • GTL Clarification to letter #27406 #28309weight -50 lbsfasterGTL Mazda 12A Street Port minimum weight reduced to 1950 lbs from 2000 lbs.
  • GTL Windshield Clips #27323wordingneutralGT1, GT2, GT3, GTL, GTX may omit windshield clips if factory glass is bonded per original specifications.
  • GTL 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.
  • GTL Request to Classify the MK1 two door Jetta #27648cars addedneutralGTL adds Jetta Mk1 two door classification effective 2020-01-01.
  • GTL 88-91 Honda CRX Spec Line Correction #27233wordingneutralGTL Honda CRX 84-87 and 88-91 remove IRS option with 2.5% weight penalty.
  • GTL Fun Cup Beetle #27334wordingneutralGTL Fun Cup Beetle engine weight specified at 1850 lbs with sealed SOHC 1780cc specification.
  • GTL GTL #26960wordingneutralGTL Fun Cup Beetle removes reference to VW engine table; Fun Cup engine spec remains 1.8L at 2040 lbs.
  • GTL Request CRZ wheelbase change #26896wordingunclearGTL Honda CRZ 10-14, CRZ 15-16, and Insight 00-06 gain alternate wheelbase option of 90.6 in.
  • GTL Request to Classify VW Fun Cup Beetle #25986cars addedneutralGTL adds VW Fun Cup Beetle, all model years, 2-door RWD, 94.5-inch wheelbase.
  • GTL Request GTX Fuel injection for previous GT-1 tube frame cars #26141inductionfasterGTX tube frame cars gain fuel injection with 90mm maximum throttle body size.
  • GTL Request to Classify Ligier JS2 R #26535cars addedneutralLigier JS2 R classified in GTX, no performance parameters specified in filing.
  • GTL Request for GTL Mazda 13B SIR Increase with Penalty #26572engineslowerGTL Mazda 13B may use 25mm SIR with 175 lbs weight penalty added.
  • GTL 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.
  • GTL Request Mazda 12a Rotary SIR Increase #26081inductionfasterGTL Mazda 12A may use 28mm SIR plus 175 lbs.
  • GTL Request to Classify Mustang 2 Body in GTL #26222cars addedneutralGTL Mustang 94-04 newly classified in GTL.
  • GTL Request for GTL Mini Adjustments #25754weightfasterGTL Mini 1275-1399 Iron and Aluminum Crossflow gain 75 lbs weight reduction to 125 lbs with OE common sump gearbox.
  • GTL BMC thru Rover Group remove long inactive mini #25771removedneutralGTL BMC thru Rover Group removes long inactive Mini engines: 948, 970, 1071, 1098.
  • GTL 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.