SRF3 vs STL vs P2 pace at Buttonwillow Raceway Park
Quickest here:SRF3 1:50.233 Caleb Shrader, Cal Club 2025 qualifying · STL 1:54.845 Gavin Wardle, Cal Club 2026 race · P2 1:09.928 Tim Day Jr, Cal Club 2023 qualifying
SRF3STLP2solid race · dashed qualifying · slower is lower
SRF3STLP2solid race · dashed qualifying · each class's best lap as a share of SRF3's at the same event (the reference class, changeable above); 100% is level, higher is quicker
Event
SRF3
STL
P2
Qual best
Race best
Trap
Qual best
Race best
Trap
vs SRF3
% of SRF3
Qual best
Race best
Trap
vs SRF3
% of SRF3
Cal Club 2026 CALCL262026-02-21
1:50.913Asad Nikadambaev · fastest of 27 · top 5 within 1.1s+0.680s (+0.62%)
1:52.070Asad Nikadambaev · fastest of 27 · top 5 within 0.8s+1.245s (+1.12%)
138.9Paul Marino+20.7 mph (+17.5%)
1:57.526Jared Korth · fastest of 10 · top 5 within 1.2s+2.563s (+2.23%)
1:54.845Gavin Wardle · fastest of 11 · top 5 within 4.7s-0.837s (-0.72%)
136.6Bryce Johnson+26.2 mph (+23.7%)
+2.775squal +6.613s
102.5%qual 106.0%
1:37.278Tim Day Jr · only car+27.350s (+39.11%)
1:39.758Tim Day Jr · only car
155.4Tim Day Jr
-12.312squal -13.635s
89.0%qual 87.7%
7 rule changes (SRF3: 4, STL: 3)2 weight · 4 wording · 1 other · STL minimum weights increase across all classes, 1300 cc gains 195 lbs to 1950, up to 1850 cc at 2500. · SRF3 adds HD Oil Cooler P/N G1148500 as alternative to standard cooler P/N G480503. · SRF3 brakes restructured: Hawk Blue 801993 pads, Wilwood 800065 rotors only; adds Girling 880358, Wilwood 880357, Tilton 880360 master cylinders. · STL/STU Lotus weight reduced: Evora GT4 to 2700 lbs, Elise Cup R to 2250 lbs, Elise/Exige SC to 2450-2550 lbs. · STL Mazda MX5 Challenge minimum weight now references GCR 9.1.7.1 instead of 2500 lbs; spec components removed, only alternative tires allowed. · SRF drivers with disabilities may modify seat and controls for safety and comfort with approval and logbook notation. · SRF SADEV-SRF3 6-speed sequential transmission gear ratios wording clarified, effective 2025-04-01.showhide
STL Weight adjustment for STL #39579weightslowerSTL minimum weights increase across all classes, 1300 cc gains 195 lbs to 1950, up to 1850 cc at 2500.
SRF3 Add HD Oil Cooler #38979otherneutralSRF3 adds HD Oil Cooler P/N G1148500 as alternative to standard cooler P/N G480503.
STL Lotus Weight Reduction #38772weight -50 lbsfasterSTL/STU Lotus weight reduced: Evora GT4 to 2700 lbs, Elise Cup R to 2250 lbs, Elise/Exige SC to 2450-2550 lbs.
STL E&O: SMX Allowance in STL #37945wordingunclearSTL Mazda MX5 Challenge minimum weight now references GCR 9.1.7.1 instead of 2500 lbs; spec components removed, only alternative tires allowed.
SRF3 Driver Safety & Comfort #37966wordingneutralSRF drivers with disabilities may modify seat and controls for safety and comfort with approval and logbook notation.
1:50.233Caleb Shrader · fastest of 33 · top 5 within 0.4s
1:50.825Caleb Shrader · fastest of 32 · top 5 within 0.8s
118.2John Black
1:54.963Nick Leverone · fastest of 16 · top 5 within 3.3s
1:55.682Nick Leverone · fastest of 17 · top 5 within 2.6s
110.4Ryan Gutile
+4.857squal +4.730s
104.4%qual 104.3%
30 rule changes (SRF3: 14, STL: 6, P2: 10)3 engine · 3 tyres & wheels · 2 induction · 2 suspension & brakes · 2 weight · 17 wording · 1 other · P2 2000cc Pinto engine car minimum weight set to 1335 lbs. · STL/STU: 90-05 Mazda Miata alternate front wheel hubs moved from General to specific part approval. · SRF3 air filter rule removes K&N RC-9160 option, leaving only P/N WM301020 allowed. · SRF brake rotor minimum thickness increases from 12.20mm to 13.25mm, Wilwood vented rotor P/N 800065. · SRF3 Hoosier logo placement changes from four decals to three decals in different locations. · SRF Hoosier decal requirement reduced from four decals in specific locations to three decals with simpler placement rules. · SRF wet tires: P185/60R13 H20/W2 option removed; P185/65R13 W2 front now required with P205/60R13 W2 rear. · SRF3 alternator pulley minimum weight reduced from 12 oz to 11 oz. · P2 Spec ECU engine modifications clarified: oil system, ECU, and exhaust unrestricted only. · P2 FIA Group CN spec notes clarified: Series changed to Challenge, documentation requirement moved to online link. · STL and STU power steering rules clarified to permit electric-assisted and hydraulic-assisted steering systems. · STL Acura/Honda B-series and Mazda MZR restrictors reduced 2mm; minimum weights down 25–75 lbs for 1900–2000cc engines. · STL Mazda 12A must keep 5th and 6th intake port actuators and valves, no longer allowed removal or disabling. · P2 AMAC modified engine range clarified to 2008 and older stock engines only, restrictor 38mm, weight 1025 lbs. · P2 Suzuki GSX-R1000 07/08 engine crankcase may swap to GSX-S1000 16/19 part #11301-04840. · SRF rain/brake light now requires Super Bright LEDs Inc. P/N PT-STRB-R24 with specific connector and rain light switch. · SRF requires Super Bright LEDs P/N PT-STRB-R24 rain/brake light with strobing capability and specific wiring. · SRF adds brake duct and pedal extension rules, rear shift cable clamp option, camber limit to 5.0°, radiator opening height 3.5" ±0.5", and P2 engine restrictor changes. · STL Mazda RX-7 12A (79-85) now allows auto-type 2 bbl with 42mm choke(s) on dual-y manifold as alternate to stock Nikki 4 bbl. · P2 Table 1 corrects engine date ranges and brand specifications for Stock and Modified engines across multiple car models. · SRF radiator rule clarified: P/N 480466 replaceable with Automotive P/N 1R698, CU698 or manufacturer equivalent with documentation. · SRF Hoosier wet front tire updated to P/N 46100 P185/60R13 H20 or W2. · STL ITA/ITS RX7 and 1985+ ITA/ITS/ITB/ITC vehicles clarified to conform to section 9.1.4.2 tire specifications. · P2 side body height requirement clarified: outermost surface between wheel openings must equal front axle centerline height. · P2 closed cockpit single seat cars now prohibited unless specifically allowed in Table 1. · SRF Hoosier front rain tyre part number changes from 46100 to 46101 P185/65R13 W2. · P2 engine table wording updated; redundant effective date language removed. · P2 motorcycle engines: 2011+ Kawasaki restrictor reduced to 34mm, minimum weight raised to 1100 lbs; 2009+ other brands weight raised to 1100 lbs. · SRF Renault Alliance solid front rotors banned; restrictor reduced 35mm to 34mm for 2011+ Kawasaki; minimum weight increased to 1100 lbs for 2009+ stock engines. · SRF3 tail sections allowed on SRFs with GEN3 airbox shimming up to 19 mm; alternate dash panel P/N 180100 or 180101 relocated in rules.showhide
P2 2000 cc Pinto Engine Car Weight #37187weightslowerP2 2000cc Pinto engine car minimum weight set to 1335 lbs.
STL Request to Remove Miata Hubs from General category #37138wordingneutralSTL/STU: 90-05 Mazda Miata alternate front wheel hubs moved from General to specific part approval.
SRF3 Update SRF3 Air Filter Rule #36681wordingunclearSRF3 air filter rule removes K&N RC-9160 option, leaving only P/N WM301020 allowed.
SRF3 Hoosier Tire Decal Placement #36739wordingneutralSRF3 Hoosier logo placement changes from four decals to three decals in different locations.
SRF3 Update to Letter 36619 with new Hoosier Contingency Decal Info #36624wordingneutralSRF Hoosier decal requirement reduced from four decals in specific locations to three decals with simpler placement rules.
SRF3 Update Rain Tire Rule and Hoosier Decal Placement #36436tyres & wheelsslowerSRF wet tires: P185/60R13 H20/W2 option removed; P185/65R13 W2 front now required with P205/60R13 W2 rear.
SRF3 SRF3 Alternator Pulley Update In #36095weightfasterSRF3 alternator pulley minimum weight reduced from 12 oz to 11 oz.
P2 E&O - Correct FIA Group CN spec line notes #35900wordingneutralP2 FIA Group CN spec notes clarified: Series changed to Challenge, documentation requirement moved to online link.
STL ST Electric-Assisted Steering Systems #35066wordingneutralSTL and STU power steering rules clarified to permit electric-assisted and hydraulic-assisted steering systems.
STL BOP Adjustments #35112inductionfasterSTL Acura/Honda B-series and Mazda MZR restrictors reduced 2mm; minimum weights down 25–75 lbs for 1900–2000cc engines.
STL Mazda 12A #35320engineslowerSTL Mazda 12A must keep 5th and 6th intake port actuators and valves, no longer allowed removal or disabling.
P2 E&O - Clarify B.1 modified engine range in AMAC spec lines #35225wordingneutralP2 AMAC modified engine range clarified to 2008 and older stock engines only, restrictor 38mm, weight 1025 lbs.
P2 Replacement Engine Crankcase for 07/08 Suzuki GSX-R1000 Engines #35340engineunclearP2 Suzuki GSX-R1000 07/08 engine crankcase may swap to GSX-S1000 16/19 part #11301-04840.
SRF3 Update SRF Rain / Brake Rule #34706wordingneutralSRF rain/brake light now requires Super Bright LEDs Inc. P/N PT-STRB-R24 with specific connector and rain light switch.
SRF3 Update SRF Brake Light Rule v1 #34853wordingneutralSRF requires Super Bright LEDs P/N PT-STRB-R24 rain/brake light with strobing capability and specific wiring.
STL Alternate Carburetor Request for 79-85 RX7 12a #35181inductionunclearSTL Mazda RX-7 12A (79-85) now allows auto-type 2 bbl with 42mm choke(s) on dual-y manifold as alternate to stock Nikki 4 bbl.
P2 Correct Table 1 for Engine Date Range Specifications #35182wordingneutralP2 Table 1 corrects engine date ranges and brand specifications for Stock and Modified engines across multiple car models.
SRF3 SRF Radiator Rule Update #34805wordingneutralSRF radiator rule clarified: P/N 480466 replaceable with Automotive P/N 1R698, CU698 or manufacturer equivalent with documentation.
SRF3 Hoosier SRF Wet Front Tire Rule Update #34189tyres & wheelsunclearSRF Hoosier wet front tire updated to P/N 46100 P185/60R13 H20 or W2.
STL Clarify STL table B - IT spec notes on Tires #34187wordingneutralSTL ITA/ITS RX7 and 1985+ ITA/ITS/ITB/ITC vehicles clarified to conform to section 9.1.4.2 tire specifications.
P2 Clarify minimum side body height requirement #34143wordingneutralP2 side body height requirement clarified: outermost surface between wheel openings must equal front axle centerline height.
P2 Clarify closed cockpit single seat car allowance #34144wordingneutralP2 closed cockpit single seat cars now prohibited unless specifically allowed in Table 1.
SRF3 Update SRF Front W2 Rain Tire Part Number #34118tyres & wheelsneutralSRF Hoosier front rain tyre part number changes from 46100 to 46101 P185/65R13 W2.
P2 Remove redundant effective date language and update engine table #34012wordingneutralP2 engine table wording updated; redundant effective date language removed.
P2 E&O - Correct dimensional equivalents #34038engineslowerP2 motorcycle engines: 2011+ Kawasaki restrictor reduced to 34mm, minimum weight raised to 1100 lbs; 2009+ other brands weight raised to 1100 lbs.
SRF3 Update SRF Brake Rule #33469suspension & brakesslowerSRF Renault Alliance solid front rotors banned; restrictor reduced 35mm to 34mm for 2011+ Kawasaki; minimum weight increased to 1100 lbs for 2009+ stock engines.
SRF3 Update SRF Bodywork Fitment Rule #33765wordingneutralSRF3 tail sections allowed on SRFs with GEN3 airbox shimming up to 19 mm; alternate dash panel P/N 180100 or 180101 relocated in rules.
Cal Club 2023 CALCL232023-02-24
1:09.928Tim Day Jr · fastest of 2
99 earlier rule changes on record, in force before Cal Club 2023 (from 2019)17 induction · 11 cars added · 8 engine · 6 weight · 5 aero · 4 tyres & wheels · 3 suspension & brakes · 44 wording · 1 other · Sebeco NP01-EVO and Elan NP01 Mazda 2.0L MZR added to P2, 1600 lb minimum, no restrictor required. · P2 Radical SR3/SR4/Cup/Club Sport/Pro-Sport/PR6 removes assisted shifting requirement across all spec lines. · P2 chassis rules clarified to allow composite materials in non-fully-composite construction; anti-intrusion panel attachment standardized; Stohr and converted F600 cars added with specific allowances. · Unable to summarize: the change to P2 Engine Table Spec Line B.1 is not detailed in the provided text. · STL Spec MX5 clutch, wheels, and tyres specified: ACT 0000-02-5004-G6, 17x8 wheels, Toyo RR and RA1 235-40-17. · SRF tire rule wording changed from 'Tires: must be run as delivered' to 'Tires must be run as delivered.' · SRF brake rotor minimum thickness reduced from 13.25 to 12.20mm; seal and air filter rules clarified. · P2 chassis construction rules clarified: fully composite or partially composite requiring composite for mobility allowed; partial composite must roll without composite parts. · P2 classification wording cleaned up in GCR section 9.1.8.C and Contents. · P2 Oldsmobile cam rules clarify aftermarket manufacturer requirements; wording only. · P2 adds Beasley B2 spec line with 1350 lbs, Mazda 12A, 40.5mm venturi, 16.5in wing. · P2 wing specs correct terminology from 'cord' to 'chord' for 16.5in single or dual element wings. · P2 Converted F5 cars reclassified as Converted F500 cars; suspension must comply with F500 requirements, minimum width 55 inches. · STU normally aspirated engines: minimum weights reduced up to 310 lbs; single throttle body weight reduction removed. · STL and STU Improved Touring vehicles must conform to 9.1.4 Tires & Wheels requirements. · P2 motorcycle engines increase to 1505cc max, two-stroke to 1205cc max; automotive engines gain 50 lbs minimum weight to 1350. · P2 Control Area definition narrowed; aerodynamic attachments and vertical structures like turning vanes now prohibited. · STL and STU piston engines clarified: intake manifold and cylinder head porting remains free. · STL Mazda Renesis flat plate restrictor increases from 55mm to 60mm. · STL Mazda RX-7 12A 79-85 clarifies carburetor, emissions, and water jacket modification rules. · P2 Engine Table Spec Line B.1 changed effective 1-1-22, details not provided in excerpt. · P2 Control Area definition clarified: floor extensions and aerodynamic attachments on bottom or top side now explicitly included. · SRF front wet tire changes from P185/60R13 H20 to P185/65R13 W2; SRF3 adds mandatory G301048 restrictor plate Jan. 1, 2022. · P2 CN Honda K20A-FD2 engine rebuild rules clarified: machining prohibition replaced with specific restrictions on balancing, porting, polishing, valve jobs, cylinder honing. · STL Spec MX-5 removes redundant specification line; no performance change. · Converted F5 cars in P2 minimum width reduced to 55 inches from F5 spec. · P2 clarifies minimum body width requirement between front and rear wheels for Ralt RT40, RT41, Swift 008, 014. · SRF wet tyres add Hoosier P185/60R13 W2 front and P205/60R13 W2 rear as alternatives to H20. · SRF adds SADEV-SRF3 6-speed sequential option with final drive 3.20 versus OEM 5-speed 3.85. · SRF seal procedures clarified: unsealed components need CSR inspection and logbook notation instead of engine removal. · SRF3 alternator pulley restricted to P/N G902130 or G902130A, 12oz minimum weight. · STL Volkswagen 2.0L TFSI 1984cc classified with turbocharger removal required, meeting all other STL specs. · P2 tonneau covers now allowed to meet minimum dimensions; equipment attachment requirements clarified. · P2 multiple chassis models remove effective dates from Table 1 specifications. · P2 engines limited to 4 valves per cylinder maximum across all three spec lines. · STL Pontiac Solstice/Saturn Sky allowed 4" ride height. · STL Mazda B5 DOHC added to classification with standard STL regulations. · STL Honda B16A JDM restrictor reduced from 54mm to 53mm. · ST oil coolers and filters now explicitly allowed to be added or substituted; wording clarifies existing permissions. · P2 adds new spec line for 2-cycle 3-cylinder engine up to 820cc with 10 front and 14-15 rear wheel width. · SRF and SRF3 mandatory identification simplified: removed Ford Performance and Blue Oval decals, kept Hoosier logo placement. · STL GM Ecotec engines now permit any combination within the family, must use 55mm flat plate restrictor. · STL/STU 90-05 Mazda Miata gains approval for Mazda Motorsports Development alternate front wheel hubs. · ST cars may relocate ABS actuation hardware and wiring anywhere in engine compartment. · STL rear wing trailing edge, including end plates and gurney flap, maximum rearward mounting clarified to center of rearmost bodywork. · STL allows OEM gear sets from same manufacturer transmissions with input shaft modifications for fitment. · STL RWD strut suspension weight penalty cut to 0.5%, other RWD cut to 2.5%. · STL Honda F20C loses 2% weight penalty, minimum weight reduced by approximately 35 lbs. · STL Honda B16/B17/B18C1 restrictor tightened to 53mm; B18C variants and Mazda MZR to 52mm. · P2 Honda K20A-FD2 intake restrictor reduced from 55mm to 50mm, making cars faster. · SRF shocks, springs, bump stops sealed; rear springs 412-429 lbs/in P/N 280390 only; previous parts no longer allowed. · ST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch. · P2 rear wing requirements clarified: standard wing 6×12 inches, end plates 14-inch square; alternate 110cm width wing 9×18 inches, end plates 14×18 inches. · STL and STU clarify weight adjustment calculation order: engine adjustments first, then chassis adjustments. · STL and STU rear wing rules clarify that wicker is a Gurney flap; no performance change. · GT3 and STU add Borg-Warner EFR6258 to approved turbocharger list. · Elan NP01 classified in P2 Table 1 as Spec Line car with 2000cc displacement and P2 Engine Table restrictor. · SRF3 shock absorber brand restriction removed; all shocks must be sealed by Enterprises. · STL adds 2016-2019 Mazda MX-5 Global Cup at 2000cc, 2450-2550 lbs minimum weight. · STL Mazda MX-5 Club Model 06-15 allows Mazda header part number 0000-06-5407-NC. · STL Honda/Acura B18 non-C gets 54mm restrictor; B18C variants drop B18C1, get 53mm restrictor. · P2 Enterprises Sports Racer adds 55mm flat plate intake restrictor Part # WM303013 as alternative to SIR. · SRF3 bump stop now must be SCCA P/N 280407 only, no modifications, optional, max one per shock. · SRF shock absorber bump stop clarified: only SCCA P/N 280407 allowed as delivered, maximum one per shock, effective 05/01/2020. · STL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor. · P2 Enterprise Sports Racer 2.3L engine now requires SIR or Flat Plate restrictor sized in 0.5mm increments. · STU GM Ecotech LNF now allowed with turbo removed or with LE5 head and intake manifold, meeting STL specs. · STL Mazda MZR restrictor reduced from 54 mm to 53 mm. · STL Mazda MZR restrictor reduced from 55 mm to 53 mm. · P2 fly-by-wire throttle control wording clarified: stock ECUs with drive-by-wire must activate original throttle shaft mechanism. · STL Mazda Spec MX5 Challenge adds approved wheel part numbers 0000-04-5706-GM, 0000-04-5706-SL. · P2 adds BMW to motorcycle-based engine options in 4-cycle line alongside Kawasaki, Suzuki, Yamaha, Honda. · SRF rain and brake rule wording updated; supersedes GCR 9.3.32.B.2 effective 1/1/202 through 12/31/2024. · SRF bans tire warmers and cooling methods other than natural air convection or conduction. · SRF front nose weight minimum reduced from 35 to 32 lbs. · SRF3 reclassified as Spec Racer Ford 3 with 1.6L conversion; SRF2 becomes Regional Only Class. · P2 Honda K20A-FD2 non-composite chassis must use 55mm flat plate intake restrictor at 1500 lbs minimum weight. · Mazda Spec MX-5 Challenge classified in STL with 2000cc displacement and 2500 lbs minimum weight. · P2 motorcycle engines: Stock restrictor 36.5mm to 35mm, modified 37.5mm to 34mm; B.5 restrictor 37.5mm to 33mm. All weights increase 25 lbs. · P2 cars limited to power application on maximum two wheels, effective 2019-07-01. · SRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102. · STU alternate intake manifolds now allowed case-by-case instead of prohibited. · P2 Enterprise minimum weight increases to 1375 lbs; peak horsepower of sealed ESR engine reduced per CRB specification. · SRF3 nose assembly must use approved multi-piece design; no modifications allowed except as specified. · STL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate. · SRF3 brakes now allow Hawk Blue 9012 pads P/N 801993 only; shocks simplified to Penske P/N 280396 sealed assembly only, with optional SCCA Enterprises bump rubber P/N 280407 from 05/01/2020. · STL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld. · P2 stock engine restrictor shrinks to 35.0mm and weight rises to 1025 lbs; modified engine restrictor to 34.0mm, weight to 1125 lbs; line B.5 restrictor to 33.0mm, weight to 1185 lbs. · P2 Line A.1 restrictor reduced from 40mm to 38mm. · STL adds VW 1.8L R4 20VT 1781cc, 1 minimum weight, turbo removed permitted. · STL Mazda Renesis minimum weight reduced from 2800 to 2700 lbs. · STL Mazda MX-5 Cup brake pad compound changed to open. · STL adds Acura/Honda B18C1 GSR with 54mm flat plate restrictor and port matching limited to 1 inch. · STL Mazda 12 and 13B now permit port matching; previous ban removed. · P2 Spec Line cars now allow 1345cc Hayabusa stock engines at 1050 lbs with 30mm restrictor. · P2 Group CN Honda K20A-FD2 55mm restrictor implementation delayed from 1/1/2019 to 3/1/2019. · P2 Honda K20A-FD2 in CN chassis must use stock intake manifold with 64mm throttle body and 55mm restrictor at 1500 lbs minimum weight. · STL B18C Type R variants get 54mm flat plate restrictor; B17 also gets 54mm restrictor. · STL Mazda Miata removes maximum displacement limit and adjusts minimum weight.showhide
P2 Request to Classify Sebeco NP01 #33378cars addedneutralSebeco NP01-EVO and Elan NP01 Mazda 2.0L MZR added to P2, 1600 lb minimum, no restrictor required.
P2 Radical spec line clarifications #33485wordingneutralP2 Radical SR3/SR4/Cup/Club Sport/Pro-Sport/PR6 removes assisted shifting requirement across all spec lines.
P2 E&O original class intent #33519wordingneutralP2 chassis rules clarified to allow composite materials in non-fully-composite construction; anti-intrusion panel attachment standardized; Stohr and converted F600 cars added with specific allowances.
P2 Update Engine Table Spec Line B.1 #33608engineunclearUnable to summarize: the change to P2 Engine Table Spec Line B.1 is not detailed in the provided text.
STL Spec MX5 in STL #33473wordingneutralSTL Spec MX5 clutch, wheels, and tyres specified: ACT 0000-02-5004-G6, 17x8 wheels, Toyo RR and RA1 235-40-17.
SRF3 SRF Tire Rule Update #32614wordingneutralSRF tire rule wording changed from 'Tires: must be run as delivered' to 'Tires must be run as delivered.'
SRF3 Brake, seal, and air filter clarifications #32670suspension & brakesfasterSRF brake rotor minimum thickness reduced from 13.25 to 12.20mm; seal and air filter rules clarified.
P2 E&O Clarification of Chassis Construction Requirements #32469wordingneutralP2 chassis construction rules clarified: fully composite or partially composite requiring composite for mobility allowed; partial composite must roll without composite parts.
P2 Clean up P2 wording #32525wordingneutralP2 classification wording cleaned up in GCR section 9.1.8.C and Contents.
P2 After Market to Aftermarket #32373wordingneutralP2 Oldsmobile cam rules clarify aftermarket manufacturer requirements; wording only.
P2 Add spec line for Beasley B2 #32147cars addedneutralP2 adds Beasley B2 spec line with 1350 lbs, Mazda 12A, 40.5mm venturi, 16.5in wing.
P2 E&O Table 1 spec line wing terminology #32148wordingneutralP2 wing specs correct terminology from 'cord' to 'chord' for 16.5in single or dual element wings.
P2 E&O class name #32196wordingneutralP2 Converted F5 cars reclassified as Converted F500 cars; suspension must comply with F500 requirements, minimum width 55 inches.
STL Single TB Weight Modifiers #31449weightfasterSTU normally aspirated engines: minimum weights reduced up to 310 lbs; single throttle body weight reduction removed.
STL Improved Touring Tires #32063tyres & wheelsneutralSTL and STU Improved Touring vehicles must conform to 9.1.4 Tires & Wheels requirements.
P2 E&O Engine section #31969enginefasterP2 motorcycle engines increase to 1505cc max, two-stroke to 1205cc max; automotive engines gain 50 lbs minimum weight to 1350.
P2 E&O letter #31539 – Control Area definition #31783aeroslowerP2 Control Area definition narrowed; aerodynamic attachments and vertical structures like turning vanes now prohibited.
STL Throttling Device Clarification #31323wordingneutralSTL and STU piston engines clarified: intake manifold and cylinder head porting remains free.
STL Mazda Renesis Restriction #31467inductionfasterSTL Mazda Renesis flat plate restrictor increases from 55mm to 60mm.
STL Clarification of 79-85 RX7 Spec line #31621wordingneutralSTL Mazda RX-7 12A 79-85 clarifies carburetor, emissions, and water jacket modification rules.
P2 BoP adjustment effective 1-1-22 #31538wordingunclearP2 Engine Table Spec Line B.1 changed effective 1-1-22, details not provided in excerpt.
P2 E&O clarification of "Control Area" definition #31539wordingneutralP2 Control Area definition clarified: floor extensions and aerodynamic attachments on bottom or top side now explicitly included.
SRF3 Three Updates to SRF Rules #31523tyres & wheelsunclearSRF front wet tire changes from P185/60R13 H20 to P185/65R13 W2; SRF3 adds mandatory G301048 restrictor plate Jan. 1, 2022.
P2 P2 CN Engine Rebuild Clarification #31000wordingneutralP2 CN Honda K20A-FD2 engine rebuild rules clarified: machining prohibition replaced with specific restrictions on balancing, porting, polishing, valve jobs, cylinder honing.
STL Request to clean up Spec MX-5 Redundancy #31069wordingneutralSTL Spec MX-5 removes redundant specification line; no performance change.
P2 F5 P2 Conversion #30856aerofasterConverted F5 cars in P2 minimum width reduced to 55 inches from F5 spec.
P2 Clarify minimum body width requirement #30859wordingneutralP2 clarifies minimum body width requirement between front and rear wheels for Ralt RT40, RT41, Swift 008, 014.
SRF3 SRF Wet Tires #30849tyres & wheelsneutralSRF wet tyres add Hoosier P185/60R13 W2 front and P205/60R13 W2 rear as alternatives to H20.
SRF3 SADEV-SRF3 Transmission #30926cars addedunclearSRF adds SADEV-SRF3 6-speed sequential option with final drive 3.20 versus OEM 5-speed 3.85.
SRF3 SRF Update Maintenance, Repairs and Seals #30961wordingneutralSRF seal procedures clarified: unsealed components need CSR inspection and logbook notation instead of engine removal.
SRF3 SRF3 Alternator Pulley #30684engineslowerSRF3 alternator pulley restricted to P/N G902130 or G902130A, 12oz minimum weight.
STL VW Engine Request #30625engineslowerSTL Volkswagen 2.0L TFSI 1984cc classified with turbocharger removal required, meeting all other STL specs.
P2 E&O tonneau cover provision in cockpit opening section #30459wordingneutralP2 tonneau covers now allowed to meet minimum dimensions; equipment attachment requirements clarified.
P2 Remove effective dates in Table 1 #30468wordingneutralP2 multiple chassis models remove effective dates from Table 1 specifications.
P2 E&O Maximum Valves Per Cylinder #30560engineneutralP2 engines limited to 4 valves per cylinder maximum across all three spec lines.
STL Request Mazda B5 DOHC #30420cars addedneutralSTL Mazda B5 DOHC added to classification with standard STL regulations.
STL Honda B16A (JDM) Restrictor change #30531inductionslowerSTL Honda B16A JDM restrictor reduced from 54mm to 53mm.
STL ST Oil Coolers E&O Correction to 9.1.4.2.H #30388wordingneutralST oil coolers and filters now explicitly allowed to be added or substituted; wording clarifies existing permissions.
P2 Add a new spec line for a 2-cycle, 3-cylinder engine up to 820cc #30272cars addedneutralP2 adds new spec line for 2-cycle 3-cylinder engine up to 820cc with 10 front and 14-15 rear wheel width.
SRF3 Mandatory identification: #30223wordingneutralSRF and SRF3 mandatory identification simplified: removed Ford Performance and Blue Oval decals, kept Hoosier logo placement.
STL GM Ecotec engines in STL #30247wordingneutralSTL GM Ecotec engines now permit any combination within the family, must use 55mm flat plate restrictor.
STL Super Touring Alternate Miata Hubs #30345wordingneutralSTL/STU 90-05 Mazda Miata gains approval for Mazda Motorsports Development alternate front wheel hubs.
STL Brake Component Relocation #29990wordingneutralST cars may relocate ABS actuation hardware and wiring anywhere in engine compartment.
STL Super Touring Wing Clarification #30111aeroneutralSTL rear wing trailing edge, including end plates and gurney flap, maximum rearward mounting clarified to center of rearmost bodywork.
STL Transmission Options #30118wordingneutralSTL allows OEM gear sets from same manufacturer transmissions with input shaft modifications for fitment.
STL Request for FWD and RWD Parity #29728weightfasterSTL RWD strut suspension weight penalty cut to 0.5%, other RWD cut to 2.5%.
STL Request to Remove Honda F20C 2% Weight Penalty #29815weightfasterSTL Honda F20C loses 2% weight penalty, minimum weight reduced by approximately 35 lbs.
STL Request for FWD and RWD Parity #30023inductionslowerSTL Honda B16/B17/B18C1 restrictor tightened to 53mm; B18C variants and Mazda MZR to 52mm.
P2 Balance of Performance adjustments effective 01-01-2021 #29822inductionfasterP2 Honda K20A-FD2 intake restrictor reduced from 55mm to 50mm, making cars faster.
SRF3 SRF Shocks, Springs and Ride Height. #29688suspension & brakesneutralSRF shocks, springs, bump stops sealed; rear springs 412-429 lbs/in P/N 280390 only; previous parts no longer allowed.
STL Request clarification on wing measurement #29640aeroneutralST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch.
P2 E&O clarification of P2 rear wing requirements #29205aeroneutralP2 rear wing requirements clarified: standard wing 6×12 inches, end plates 14-inch square; alternate 110cm width wing 9×18 inches, end plates 14×18 inches.
STL Minimum Weight Determination #27695wordingneutralSTL and STU clarify weight adjustment calculation order: engine adjustments first, then chassis adjustments.
STL ST Gurney flap Wicker clarification #29012wordingneutralSTL and STU rear wing rules clarify that wicker is a Gurney flap; no performance change.
STL Request for Addition to GT3 Approved Turbo List #27576wordingneutralGT3 and STU add Borg-Warner EFR6258 to approved turbocharger list.
P2 Classify Elan NP01 in P2 Table 1 #28812cars addedneutralElan NP01 classified in P2 Table 1 as Spec Line car with 2000cc displacement and P2 Engine Table restrictor.
SRF3 SRF Shocks #28791wordingneutralSRF3 shock absorber brand restriction removed; all shocks must be sealed by Enterprises.
STL Request to add 2016-2019 GMX-5 Spec line #28604cars addedneutralSTL adds 2016-2019 Mazda MX-5 Global Cup at 2000cc, 2450-2550 lbs minimum weight.
STL Request to update PN for MX-5 #28622wordingunclearSTL Mazda MX-5 Club Model 06-15 allows Mazda header part number 0000-06-5407-NC.
STL Correction - Clarification Honda/Acura B18B engine Letter # 26209 #28873inductionunclearSTL Honda/Acura B18 non-C gets 54mm restrictor; B18C variants drop B18C1, get 53mm restrictor.
P2 SCCA Enterprises ESR / P2 engine restrictor testing #28669engineneutralP2 Enterprises Sports Racer adds 55mm flat plate intake restrictor Part # WM303013 as alternative to SIR.
SRF3 Update Bump Stop Rule #28712suspension & brakesneutralSRF3 bump stop now must be SCCA P/N 280407 only, no modifications, optional, max one per shock.
SRF3 SRF Bump Stop Correction #27019wordingneutralSRF shock absorber bump stop clarified: only SCCA P/N 280407 allowed as delivered, maximum one per shock, effective 05/01/2020.
STL STL Honda B18 restrictor changes #28794inductionfasterSTL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor.
P2 Add ESR inlet restrictor #27869inductionslowerP2 Enterprise Sports Racer 2.3L engine now requires SIR or Flat Plate restrictor sized in 0.5mm increments.
STL Change GM LNF 2.0 Allowance to LSJ Engine for Viable STL 2.0 #27884engineslowerSTU GM Ecotech LNF now allowed with turbo removed or with LE5 head and intake manifold, meeting STL specs.
STL Acura/Honda B18C engine chart. Reduce the current 54 mm flat plat #28663inductionslowerSTL Mazda MZR restrictor reduced from 54 mm to 53 mm.
STL Mazda MZR engine chart. Reduce the current 55 mm flat plate to 53 #28664inductionslowerSTL Mazda MZR restrictor reduced from 55 mm to 53 mm.
P2 Request for Fly by Wire Rule Wording Change #28247wordingneutralP2 fly-by-wire throttle control wording clarified: stock ECUs with drive-by-wire must activate original throttle shaft mechanism.
STL Request to add wheel part numbers #28342wordingneutralSTL Mazda Spec MX5 Challenge adds approved wheel part numbers 0000-04-5706-GM, 0000-04-5706-SL.
P2 Request for addition of BMW Engine in P2 Engine Table #27821cars addedneutralP2 adds BMW to motorcycle-based engine options in 4-cycle line alongside Kawasaki, Suzuki, Yamaha, Honda.
SRF3 SRF Rain / Brake Rule - BoD approved as follows #34958wordingneutralSRF rain and brake rule wording updated; supersedes GCR 9.3.32.B.2 effective 1/1/202 through 12/31/2024.
SRF3 SRF Tire Warmer Rule #27622tyres & wheelsslowerSRF bans tire warmers and cooling methods other than natural air convection or conduction.
SRF3 SRF / SRF3 Nose Weight Reduction #27706weightfasterSRF front nose weight minimum reduced from 35 to 32 lbs.
SRF3 SRF / SRF3 Majors & Regional Class Updates #27723wordingneutralSRF3 reclassified as Spec Racer Ford 3 with 1.6L conversion; SRF2 becomes Regional Only Class.
P2 Update Engine Table Line E notes #27414inductionslowerP2 Honda K20A-FD2 non-composite chassis must use 55mm flat plate intake restrictor at 1500 lbs minimum weight.
STL Request to Classify Spec MX-5 Challenge in STL #27399cars addedneutralMazda Spec MX-5 Challenge classified in STL with 2000cc displacement and 2500 lbs minimum weight.
P2 Update P2 Engine Table spec lines to reflect 3/1/2019 #27254inductionslowerP2 motorcycle engines: Stock restrictor 36.5mm to 35mm, modified 37.5mm to 34mm; B.5 restrictor 37.5mm to 33mm. All weights increase 25 lbs.
P2 E&O Transmissions #27006otherslowerP2 cars limited to power application on maximum two wheels, effective 2019-07-01.
SRF3 SRF Dash Windscreen Kit #27028wordingneutralSRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102.
STL Request clarification for manifold and throttle in STU #27004inductionfasterSTU alternate intake manifolds now allowed case-by-case instead of prohibited.
P2 Request to restrict all cars #26246weightslowerP2 Enterprise minimum weight increases to 1375 lbs; peak horsepower of sealed ESR engine reduced per CRB specification.
SRF3 New SRF Sectional Nose Rule Addition #26914wordingneutralSRF3 nose assembly must use approved multi-piece design; no modifications allowed except as specified.
STL Request Restrictor Plate correction #26779inductionfasterSTL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate.
SRF3 SRF Brakes and Shock Rule Changes #26629wordingneutralSRF3 brakes now allow Hawk Blue 9012 pads P/N 801993 only; shocks simplified to Penske P/N 280396 sealed assembly only, with optional SCCA Enterprises bump rubber P/N 280407 from 05/01/2020.
STL Request Ride Height Clarification #26597wordingneutralSTL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld.
P2 Change Engine Table Lines B.1 & B.5 #25777inductionslowerP2 stock engine restrictor shrinks to 35.0mm and weight rises to 1025 lbs; modified engine restrictor to 34.0mm, weight to 1125 lbs; line B.5 restrictor to 33.0mm, weight to 1185 lbs.
P2 Change Line A.1 restrictor size #26429inductionslowerP2 Line A.1 restrictor reduced from 40mm to 38mm.
STL Request to reduce weight of RX8 with Renesis rotary #25781weight -100 lbsfasterSTL Mazda Renesis minimum weight reduced from 2800 to 2700 lbs.
STL Request for Open Brake Pads On Mazda MX-5 Cup NC #25821wordingneutralSTL Mazda MX-5 Cup brake pad compound changed to open.
STL Request to clarify B18C1 GSR Honda B motor table #26209cars addedneutralSTL adds Acura/Honda B18C1 GSR with 54mm flat plate restrictor and port matching limited to 1 inch.
STL Port Matching #26415wordingfasterSTL Mazda 12 and 13B now permit port matching; previous ban removed.
P2 Request to Allow 1345cc Hayabusa Engines for Spec Line P2 Cars #25595enginefasterP2 Spec Line cars now allow 1345cc Hayabusa stock engines at 1050 lbs with 30mm restrictor.
P2 Change CN inlet restrictor implementation date #25816wordingneutralP2 Group CN Honda K20A-FD2 55mm restrictor implementation delayed from 1/1/2019 to 3/1/2019.
P2 Clarify Honda K20A-FD2 parts requirement #25950inductionslowerP2 Honda K20A-FD2 in CN chassis must use stock intake manifold with 64mm throttle body and 55mm restrictor at 1500 lbs minimum weight.
STL Request to equalize FPR Reduction on all B-Series Vtec Engines #24746inductionslowerSTL B18C Type R variants get 54mm flat plate restrictor; B17 also gets 54mm restrictor.
STL Request E&O for Mazda Miata Spec Line #25955wordingunclearSTL Mazda Miata removes maximum displacement limit and adjusts minimum weight.
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 SRF3" is the class's best as a share of SRF3'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 SRF3'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.