BoP Lab / Buttonwillow Raceway Park
FM vs SRF vs F6 vs GT2 pace at Buttonwillow Raceway Park
Quickest here: GT2 1:42.698 Tim Carroll, Super Tour Feb 2026 qualifying
| Event | FM | SRF | F6 | GT2 | ||||||||||||||||
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| Qual best | Race best | Trap | Qual best | Race best | Trap | vs FM | % of FM | Qual best | Race best | Trap | vs FM | % of FM | Qual best | Race best | Trap | vs FM | % of FM | |||
| Super Tour Feb 2026 CALCL262026-02-21 | 1:42.698Tim Carroll · fastest of 8 · top 5 within 7.4s-3.120s (-2.95%) | 1:44.128Tim Carroll · fastest of 8 · top 5 within 4.3s-2.798s (-2.62%) | 155.7Rocky Crocker+37.8 mph (+32.1%) | |||||||||||||||||
11 rule changes (SRF: 3, GT2: 8)5 cars added · 2 aero · 1 engine · 2 wording · 1 other · GT2 Porsche 911 SC gains 4.0L air-cooled engine option at 2275 or 2350 lbs depending on valve count. · M3 E92 classified in GT2 with 3999cc V8, 35mm restrictor, 3300 lb minimum weight. · GT2 adds Cadillac CTS, Chevrolet Impala/Malibu/Monte Carlo/SS, Dodge Intrepid, Ford Fusion/Taurus, Lincoln MKS, Pontiac G8/GTO/Grand Prix, Toyota Camry, and Gen late Model Stock Car bodies Camaro/Mustang/Camry. · GT2 Mazda BP 1839cc DOHC classified with 2250 lbs minimum weight, 46mm restrictor, EFR6258 or EFR7163 turbo allowed. · SRF3 adds HD Oil Cooler P/N G1148500 option alongside standard P/N G480503, no fan permitted. · GT2 Porsche 911, 963, 994 may use 993 3.8 RSR rear deck lid or faithful aftermarket reproductions. · SRF drivers with disabilities may modify seat and controls for safety and comfort with SCCA approval, noted in logbook, for that driver only. · SRF SADEV-SRF3 6-speed sequential transmission: effective date clarified to 1 April 2025 onward. · GT2 Pontiac Fiero drivetrain changed to RWD and hood bulge permitted for front engine relocation. · TA2 OEM wing height rule exemption removed; STO permits factory aero but bans it with aftermarket wings.show
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| Super Tour Feb 2025 CALCL252025-02-22 | 1:45.818Brad McAllister · fastest of 6 · top 5 within 14.6s | 1:46.926Brad McAllister · fastest of 6 · top 5 within 13.3s | 117.9Guy Laidig | |||||||||||||||||
127 rule changes (SRF: 28, GT2: 99)30 cars added · 25 engine · 19 weight · 6 tyres & wheels · 5 aero · 3 induction · 2 suspension & brakes · 24 wording · 13 other · GT2 STO aftermarket ABS weight penalty reduced from 100 lbs to 50 lbs. · GT2 Panoz Esperante GTS adds 2013-2016 Ford EcoBoost Twin Turbo V-6, 3496 cc, 2600 lbs, twin turbo induction. · TA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof height limit. · GT2 Sunbeam Tiger gains Holly 650 cfm carburetors PN #80541-1 and PN #80541-2 as alternate options. · SRF3 air filter rule removes K&N RC-9160 option, specifies Weems P/N WM301020 only. · SRF Wilwood vented rotor minimum thickness increases to 13.25mm, 0.522 inches. · SRF3 Hoosier decal placement changed from four logos on nose and tail to three logos on sides and center front. · FE and SRF protest fee rules redirected to GCR section 8.3.1.D for fees and procedure. · SRF Hoosier contingency decal requirement reduced from four decals in specific locations to three decals with simplified placement. · SRF wet tyres: front P185/60R13 H20 or W2 and rear P205/60R13 H20 or W2 removed; front P185/65R13 W2 and rear P205/60R13 W2 now required. Hoosier decal placement specified. · GT2-ST: aftermarket replacement differential housings permitted if exact equivalent. · GT4 cars now permitted in GT2-ST with factory power stick or Pro Series restrictor, 100-pound weight penalty for slicks. · GT2-ST Acura NSX minimum weight rises to 3000 lbs, restrictor increases to 45mm TIR. · GT2-ST Spec Corvette (14-19) LS2 restrictor increases from 78mm to 80mm flat plate. · Chevrolet Corvette C8 (2020–) classified in GT2-ST: 6162 cc, 3300 lbs minimum, 71 mm restrictor, flat plate. · Mitjet ST 2015 added to GT2, must run per VTS specs with FIA form CdM008. · GT1-GTX rear blade spoiler: angle 50–75°, max 59.0 wide by 5.0 high inches; total area limit removed. · GT1, GT2, GT3, GTL, GTX Direct Injection now permitted if original equipment. · GT2 Chevrolet Corvette 7011 OEM 7-liter minimum weight reduces to 3125 lbs, down 150 lbs. · GT2 Nissan and GT3 Mazda, Mitsubishi 4G93, Nissan QR25DE/DD, QE25DE/DD now permit Direct Injection per 9.1.2.F.7.5.E. · GT2 Dodge Viper Gen 3 hybrid kit restrictor reduced from 50mm to 45mm flat plates in 8300 class. · SRF rain/brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24; secondary filament must connect to rain light switch. · SRF brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24, with SCCA Enterprises P/N 180427A pigtail and strobing rain light kit. · SRF adds mandatory front brake ducts 12–36 inches, throttle pedal heel-toe extension, braided stainless flex lines, camber limit 5.0 degrees, radiator opening height 3½ ± ½ inches, rear shift cable clamp P/N WM302007A. · GTL spec lines moved contiguous with GT2 and GT3; GTA category and specs renumbered behind GTL; P2 engine tables reorganised with restrictor and weight specifications clarified. · GT2-ST Dodge Viper including Comp Coupe, ACR/ACR-X adds VRL front fascia, 100 lbs weight reduction. · SRF radiator options expanded: Enterprises P/N 480465 with baffle 480464, 480466, or Automotive 1R698 and CU698 allowed if cross-reference equivalent. · GT2 Mazda 20B rotary minimum weight reduced to 2280 lbs, with 100-lb penalty for Grand Am transaxle and independent rear suspension. · GT2 BMW E46 M3, E36, Z3, 5000cc V8: 3.4L at 2575 lbs, 4.0L at 2900 lbs, 4.5L at 2950 lbs, 5.0L at 3000 lbs; S54 97mm stroke permitted at 2800 lbs. · GT2 Corvette C7 restrictor increases from 73mm to 77mm flat plate. · SRF wet front tyre changes to Hoosier P/N 46100 P185/60R13 H20 or W2 with 2.5" ground clearance. · GT2 adds 2009-2012 Porsche Cayman S, 3.4L, RWD, no PDK transmission. · Fields Cardinal V8 added to GT1 with Ford V8 engine, 4.9L, 2100 lbs, fuel injection. · SRF front W2 rain tyre Hoosier part number changes from 46100 to 46101 P185/65R13. · GT2 Ginetta G56 GTA may use Factory installed ProMap ECU Map. · SRF removes 1985 Renault Alliance solid front rotor option; restrictor sizes decrease 1mm for newer Kawasaki and multi-brand engines; minimum weights increase to 1100 lbs. · GT2 Mazda 13B Street Port turbo changes from EFR 76/70 to BW7670 or Garrett G30-660 with 46mm TIR at 2280 lbs. · GT2 Porsche SOHC 2478/2681/2992 turbos: EFR 76/70 compressor 42mm to 44mm, SIR to TIR designation. · GT2-ST Chevrolet Corvette 14-19 restrictor increases from 70 to 73 mm. · GT2 and GTL add Toyota 4A-F and 4A-FE 1.6L DOHC 16V engines as permitted options. · GT2 Mazda 13B turbocharger part number changed from EFR 70/76 to 76/70, compressor 42mm to 46mm. · GT2-ST BMW E36/46 spec line adds MA Shaw carbon/composite door and body kit options to notes. · GT3 normally aspirated cars may now use chokes instead of SIRs, same size as listed SIR, one per carburetor barrel. · GT3 2.0L 4-valve non-turbo engines may run unrestricted at 2060 lbs minimum weight. · GT2 TA2 and GTA throttle body part numbers updated to GM 12570790 or Edelbrock 33869/3870. · GT2 Ginetta G56 GTA may now use optional 18" x 9" and 18" x 10" wheels. · GT2/ST BMW E36/E46 Z3 5000cc V8 now permits MAShaw body kit: wide body, M3 front bumper with splitter, fenders, rockers, flairs, rear bumper. · GT2 Chevrolet Corvette L76 5967 restrictor increases from 73 mm to 74 mm. · GT1, GT2, GT3, GTL, GTX tail lights may now be original style or custom panel graphic with functioning red LED brake lamps. · Ginetta GTA G56 added to GT2 as spec car, 2600 lbs, 3.7L Ford V6 sealed, 6-speed Quaife sequential. · GT2 adds approved carbon roof suppliers and part numbers for BMW E36 and E46 models to Notes. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 may use 95mm S54 crankshaft at +150 lbs. · Audi R8 GT4 added to GT2 at 5.2L, 3000 lbs minimum weight, factory restrictor. · SRF tire rule wording clarified: tires must be run as delivered. · SRF brake rotor minimum thickness reduced from 13.25 mm to 12.20 mm; seals and air filter specs clarified. · GT2 shock absorber attachment points clarified as movable; wording correction only. · GT2 Porsche 104.0 x 88.0 SOHC minimum weight increases to 2090 lbs; EFR 76/70 turbo allowances added for three Porsche engines at specific weights. · Ginetta G40 added to GT2 with Mazda MZR/L5-VE engine, 2488cc or 2399cc, 1950 lbs base weight. · Toyota Supra GT4 added to GT2-ST with 3000cc displacement, 3000 lb minimum weight, factory restrictor. · GT2 Porsche 944/924 may use ERC 76/70 Turbo instead of Jayco super 50. · GT2-ST Porsche Cayman 05-15 throttle body restrictor increased from 70mm to 75mm. · GT2 Porsche Cayman 05-15 4.0L and 4.2L swap flat plate restrictor for throttle body restrictor at 2700 lbs. · SRF wet tyres front P185/65R13 W2 option added; air box clarified as-delivered; SRF3 restrictor plate G301048 mandatory Jan 1 2022; P2 motorcycle engines up to 1005cc with 35mm restrictor, 2009+ stock 1075 lbs, 2008 stock 1025 lbs, modifie… · GT2 Mazda 13B street port gains EFR 70/76 turbocharger with 42mm inlet restrictor at 2280 lbs minimum. · GT3 Volkswagen Fun Cup Beetle EVO3 classified, sealed SOHC 1984cc engine, 2060 lbs minimum weight. · GT2 Dodge Viper ACR/ACR-X8300 front fascia loses 100 lbs, to 3175 VRL. · GT2 adds 04-06 World Challenge Pontiac GTO, 6062 cc, 3000 lbs minimum, World Challenge rules. · GTA part numbers updated: 0-80541-1 to 0-80541-2 in two locations and 6010 to 6014X in TA2 Appendix. · Grullon GT 2.0L Acura K20 moved from GTX to GT2-ST class at 2350 lbs unrestricted. · SRF wet tyres add Hoosier W2 option alongside existing H20 from October 4, 2021. · SRF adds SADEV-SRF3 6-speed sequential transmission option with ratios 3.0–0.92:1 and 3.20 final drive. · SRF seal requirements clarified: seals now must be on driveline components in designated locations; unsealed components removed and inspected by CSR or Enterprises rather than engine shipped for testing. · GT2-ST Porsche Cayman restrictor increases from 65mm to 75mm flat plate at 2700 lbs. · GT2 Dodge Viper VRL Spec minimum weight reduced 100 lbs to 3275. · TA2 cars may run prior generation rules or current Trans Am rules at 2930 lbs minimum weight with free tire make and size. · SRF3 alternator pulley specified as P/N G902130 or G902130A, minimum 12oz. · GT2 Sunbeam SBF engine firing order 1,3,7,2,6,5,4,8 now available for Boss 302 variants. · GT2-ST Corvette (-2019) LS2 and L76 5967 gain 100 lbs minimum weight to 3100; 6162 and 7011 variants gain 50–100 lbs; L76 restrictor opens 70 to 73 mm. · GT2 rear engine opening position requirement removed. · GT2 Ford Mustang/Thunderbird Boss 302 firing order changes from unrestricted to optional later SBF 302 order 1,3,7,2,6,5,4,8. · SRF and SRF3 mandatory identification revised: removed Ford Performance and Blue Oval decals, added Hoosier logo placement. · GT2 allows ABS braking systems if shown on the individual Spec Line. · GT2 Corvette C6 and C7 spec lines split for clarification; C7 LS2, L76, LS3, LT1, LS7 weights raised 100–150 lbs effective 3/1/2021. · GT2 Ford Mustang/Thunderbird Boss 302 firing order becomes unrestricted. · GT2 BMW E46 M3 and E36, Z3, and 5000cc V8 minimum weight reduced to 2500 lbs. · GT2 Chrysler/Dodge/Plymouth DOHC 2429cc engine classified, 1950 lbs minimum weight. · SRF rear springs limited to P/N 280390 only, previous part numbers no longer allowed; ground clearance wording clarified. · GT2 stock car bodies removal rescinded; 1997-current year commercially available stock car bodywork allowed. · GT2 Appendix L section 4.8.4.2.10.3.6 renumbered, eliminating subsections .17–.19. · GT2 TA2 wing width maximum clarified to 65 -5/16 inches, including end plates. · GT1/GT2/GT3/GTL/GTX turbocharging and supercharging now permitted if listed on spec line. · Chevrolet Corvette (-2019) GT2-ST permitted LS1/LS6 alternate intake manifold, DORMAN part # 615-900. · GT2 997.2 GT3 Cup minimum weight reduced from 3000 to 2900 lbs. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 gain Trans Am SGT option: regular shifter 3000 lbs., paddle shifter plus 150 lbs. · GT2 allows up to four hood/fender louvered panels, max 600 sq inches total, min five slots each, ahead of windscreen. · TA2 Gurney flap wording clarified: replace 'wicker bill' and 'wicker' with 'Gurney flap' throughout wing specifications. · STO rear wing rules clarify that wicker is called Gurney flap in two places; no performance change. · GT Gurney flap wording clarified: wickerbill and tab terminology replaced with Gurney flap throughout sections 9.1.2.F.7.b. · GT2 Dodge Viper 8.4 OEM minimum weight reduced to 3275 lbs. · GT2 Chevrolet Corvette -2019 OEM minimum weight reduced to 3275 lbs. · GT2 Corvette -2019 LS6 allowed to reduce weight by 50 lbs. · SRF Penske shock P/N 280396 bump stop P/N 280407 becomes mandatory, maximum one per shock, effective 05/01/2020. · GT2 Panoz GT-S may use TA2 Choice Engine with any 5-speed H-shift transmission. · GT2-ST Corvette LS2 restrictor increases from 70mm to 75mm flat plate; LSX block option added. · GT2-ST Corvette L76 added: 5967cc displacement, 3000 lb minimum weight, 70mm flat plate restrictor. · GT2 Porsche 991.2 GT3 Cup Car engine displacement corrected to 4.0L from 3.8L. · GT1, GT2, GT3, GTL, GTX may use bonded-glass factory windshields without clips or straps if attached per original specifications. · GT2 Chevrolet SS replaces Dodge Charger; all stock car bodies removed from GT2 in 2021. · GTX Misc. adds Factory Five Type 65 Coupe R Ford 302/351 and 5.0/5.2L NA at 2600 lbs, plus Ferrari 458/488 Challenge, Ford FP350S, Chevrolet C6, Lamborghini Super Trofeo. · 991.2 GT3 Cup Car added to GT2 at 3100 lbs with 63mm throttle body restrictor. · GT2 Acura NSX minimum weight cut from 3000 lbs to 2700 lbs. · GT2 Porsche 991.1 GT3 Cup restrictor size increases from 67 mm to 70 mm. · GT2 Porsche 996/997.1 GT3 Cup minimum weight drops to 2800 lbs. · GT2 Corvette -2019 restrictor reduced from 75 mm to 70 mm. · SRF rain and brake rule supersedes GCR 9.3.32.B.2 effective 1/1/2024 through 12/31/2024. · SRF adds tire warmer prohibition and specifies Hoosier dry and wet tire part numbers. · SRF front nose weight minimum reduced from 35 to 32 lbs. · SRF2 becomes Regional Only; SRF3 nomenclature changed from GEN3 to Ford 1.6L conversion; SRF and SRF3 no longer compete together for points. · GT2 TA2 cars must meet 2930 lbs minimum weight per current Trans Am rules or Appendix L. · SRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102. · GT2-ST Toyota Supra 3SGTE added: 2.0L, 2900 lbs minimum weight, 43mm restrictor. · Acura NSX all years classified to GT2-ST: 3.5L turbocharged, 3000 lbs minimum, 43mm restrictor, specific aero and turbo required. · GT2 TA2 minimum weight increases 100 lbs to 2930 pounds. · GT2 BMW E36/E46 M3 and Z3: 4.5L V8 permitted at 2950 lbs, 5.0L V8 at 3000 lbs, plus Flossman body kit allowed. · GTX tube frame cars now allowed fuel injection with maximum 90mm throttle body. · GTX adds Ligier JS2 R classification with restrictor and minimum weight.show
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| Super Tour Apr 2019 ST19APR262019-04-26 | ||||||||||||||||||||
14 earlier rule changes on record, in force before Super Tour Apr 2019 (from 2019)6 cars added · 3 weight · 1 aero · 3 wording · 1 other · GT2 Ford Mustang 5.2L classified at 3300 lbs minimum weight, 82mm single throttle body, carbon fiber body parts allowed. · GT1 and GT2/3/Lite remove ride height ground clearance rules; cars may now touch ground when tires deflate. · GT2/ST Porsche Cayman eligible model years extended from 2005–2011 to 2005–2015. · GT2 Porsche Cayman adds 4.0L with 65mm flat plate restrictor at 2700 lbs minimum weight. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 may now use Flossman body kit. · GT2 TA2 clarifies rules; shock caps to $850, brake calipers to $550, pads to $250/axle, wheels to $175 each; allows carbon fiber rear wing; engine setback 21.75 inches max (A–F) or 24 inches (G); carbureted engine displacement 366 cubic in… · GT2 adds BMW 1 Series E82 2008–2012 with N52B30 engine, 2996 cc, 2140 lbs minimum weight. · GT2 Porsche Cayman 05-11 minimum weight drops to 2800 lbs; STO and X51 motor variants noted at 2950 and 2850 lbs. · GT2 Ford Mustang 05- with Ford Racing 5.2l Aluminator engine classified: 5200cc displacement, 3400 lbs minimum weight, 2×41mm flat plate restrictor. · GT2 Porsche 996/997.1 GT3 Cup: add 3.6L displacement and 2900 lbs minimum weight; remove aftermarket exhaust header allowance for 996. · GT2 Ford Mustang FP350S minimum weight reduced 100 lbs to 3400. · GT2 Ford Mustang 05- EcoBoost added: 3500 cc, 3200 lbs minimum, 41 mm restrictor. · GT2 Mazda RX7 Downing GTS body kit allowed without 75 lbs. weight penalty. · GTX FIA GT3: Audi R8 now 40 mm restrictor and 2900 lbs; BMW Z4 now 70 mm restrictor and 2800 lbs; Ferrari 488 now 35 mm restrictor, TIR, and 3025 lbs.show
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About this data
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 FM" is the class's best as a share of FM'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 FM'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.