P vs STU vs AS vs STL pace at Buttonwillow Raceway Park
Quickest here:P 1:32.872 Jim Devenport, Cal Club 2025 qualifying · STU 1:50.913 Tony Rivera, Cal Club 2026 qualifying · AS 1:55.849 Roger Eagleton, Cal Club 2025 race · STL 1:54.845 Gavin Wardle, Cal Club 2026 race
PSTUASSTLsolid race · dashed qualifying · slower is lower
PSTUASSTLsolid 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
STU
AS
STL
Qual best
Race best
Trap
Qual best
Race best
Trap
vs P
% of P
Qual best
Race best
Trap
vs P
% of P
Qual best
Race best
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% 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%)
1:50.913Tony Rivera · fastest of 6 · top 5 within 14.1s-4.488s (-3.89%)
1:52.737Tony Rivera · fastest of 7 · top 5 within 7.7s-0.903s (-0.79%)
135.2Tony Rivera+21.8 mph (+19.3%)
+15.450squal +12.197s
115.9%qual 112.4%
1:56.812Ross Murray · fastest of 2+0.367s (+0.32%)
1:56.314Ross Murray · fastest of 2+0.465s (+0.40%)
135.2Ross Murray+26.5 mph (+24.4%)
+19.027squal +18.096s
119.6%qual 118.3%
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%)
+17.558squal +18.810s
118.0%qual 119.1%
37 rule changes (P: 6, STU: 17, AS: 11, STL: 3)11 weight · 5 induction · 4 cars added · 3 tyres & wheels · 2 engine · 1 suspension & brakes · 11 wording · AS Chevy LS adds Edelbrock Performer RPM 71187 intake manifold with MSD 6014 ignition and 4776 Holly carburetor as spec line option. · AS Ford Mustang Restricted Prep engines lose 3 mm restrictor plate, from 64 mm to 61 mm. · Prototype carbon-carbon and carbon-ceramic brake rotors now permitted instead of prohibited. · STL minimum weights increase across all classes, 1300 cc gains 195 lbs to 1950, up to 1850 cc at 2500. · STU Mazda MZR (LF, L3, L5) Turbo classified; Jack Spania Racing 70 mm intake manifold and Fab9 Tuning bottom-mount turbo kit approved. · AS Ford Mustang GT 94-04 Restricted Prep Engine now permits Ford Motorsport M-6250-F303 camshaft. · STU 36mm restrictor allows 2830 lbs (up 10 lbs from 2820); 37mm allows 2980 lbs (down 5 lbs from 2985). · STU cars over 3150 lbs lose 275-tire option with 2% weight adder. · STU Honda K20 and K24 engines lose 2% minimum weight penalty. · AS Cadillac CTS-V 04-07 Restricted Prep weight reduced 50 lbs to 3400. · STU Honda K24 engine swap weight increases by 2% effective November 1, 2025. · 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. · STU Lotus Elise SC and Exige SC weight reduced from 2450 to 2250 lbs. · Prototype Engine Table A 2-cycle restrictor reduces from 40mm to 38mm venturi size. · STL/STU Lotus weight reduced: Evora GT4 to 2700 lbs, Elise Cup R to 2250 lbs, Elise/Exige SC to 2450-2550 lbs. · STU-TCR tire width increases to 275 with weight adder raised from 100 to 150 pounds. · STL/STU Lotus weight reduced: Evora GT4 to 2700 lbs, Elise Cup R to 2250 lbs, Elise/Exige SC to 2450-2550 lbs. · AS Ford Mustang GT 5.0 2018- weight reduced from 3600 to 3525 lbs. · STU 2.8-3.2L N/A engines now allow 245 max tire width; over 3150 lbs may run 275 with 2% weight penalty. · STU Mazda MZR may use Goodwin 61-2510 or Gato Performance 31972 intake manifold. · STU Honda JDM H23a added, 2259cc displacement, minimum weight per Chart, must meet ST engine regulations. · AS Ford Mustang GT 05-14 Restricted Prep Engine gains alternative gear ratios: 3.66, 2.43, 1.69, 1.32, 1.00, .65 · AS Ford Mustang GT 5.0L (15-17) flat plate restrictor reduced from 67mm to 64mm. · AS LS1/LS6 5.3L truck engine gains four approved intake part numbers: 12561269, 88894095, 89017363, 89017364. · Class P adds clarification notes on restrictor requirements, throttle bodies, Mazda 12A engine spec, and P2 auto-based engine rules. · STL Mazda MX5 Challenge minimum weight now references GCR 9.1.7.1 instead of 2500 lbs; spec components removed, only alternative tires allowed. · STU wheel width rules clarified: cars ≤2,850 lbs max 8 inches, cars >2,850 lbs max 9 inches. · STU Spec Line GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tire options clarified with weight adjustments. · AS Flotek Head plunge cut dimensions figure updated in GCR Section 9.1.6. · AS class notes cleanup: multiple Camaro, Firebird, CTS-V, Challenger, Mustang specs and fuel cell/ECM/head restrictions removed. · AS Spec Lines removes ECM flexibility restriction from five Cadillac and Chevrolet/Pontiac V8 models. · STU BMW N54/N55 3.0L classified at Chart +3% minimum weight; N54 twin turbo not allowed. · STU Mini Cooper S SC supercharger pulley diameter reduced from 2.285 to 2.185. · STU Honda K20C1 Turbo I4 exempted from 3% DI weight adder in Spec Lines Table A. · STU GT3U minimum weight increases 150 to 250 pounds.showhide
AS Edelbrock manifold (& timing kit) to Chevy LS Spec Lines Request #39055cars addedneutralAS Chevy LS adds Edelbrock Performer RPM 71187 intake manifold with MSD 6014 ignition and 4776 Holly carburetor as spec line option.
AS Restrictor Plate Change for Gen 2 Ford Coyote Engine #39501inductionslowerAS Ford Mustang Restricted Prep engines lose 3 mm restrictor plate, from 64 mm to 61 mm.
P Request to Continue to Allow Carbon Brakes #39476suspension & brakesneutralPrototype carbon-carbon and carbon-ceramic brake rotors now permitted instead of prohibited.
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.
STU Request for Permission on Aftermarket Turbo Kit and Intake #39529cars addedfasterSTU Mazda MZR (LF, L3, L5) Turbo classified; Jack Spania Racing 70 mm intake manifold and Fab9 Tuning bottom-mount turbo kit approved.
AS 1994 Mustang Spec Line Request #39104wordingunclearAS Ford Mustang GT 94-04 Restricted Prep Engine now permits Ford Motorsport M-6250-F303 camshaft.
STU Turbo Inlet Restrictor Table #38961inductionslowerSTU 36mm restrictor allows 2830 lbs (up 10 lbs from 2820); 37mm allows 2980 lbs (down 5 lbs from 2985).
STU 275 Tire Rule #38983tyres & wheelsslowerSTU cars over 3150 lbs lose 275-tire option with 2% weight adder.
STU STU Honda Engine weight penalty #39375weightfasterSTU Honda K20 and K24 engines lose 2% minimum weight penalty.
AS Cadillac CTS-V BOP Weight Change #38640weight -50 lbsfasterAS Cadillac CTS-V 04-07 Restricted Prep weight reduced 50 lbs to 3400.
STU Non-Homologated Engine Swaps - Specifically K24A2 w/ Honda CRZ #38746weightslowerSTU Honda K24 engine swap weight increases by 2% effective November 1, 2025.
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.
STU Lotus Weight Reduction E&O #38919weightfasterSTU Lotus Elise SC and Exige SC weight reduced from 2450 to 2250 lbs.
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.
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.
STU STU-TCR Adjustments #38723tyres & wheelsslowerSTU-TCR tire width increases to 275 with weight adder raised from 100 to 150 pounds.
STU 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.
AS RE: Previous Letter 37695 Update #38245weight -75 lbsfasterAS Ford Mustang GT 5.0 2018- weight reduced from 3600 to 3525 lbs.
STU 2.8-3.2L N/A Engine Allowances #38007tyres & wheelsunclearSTU 2.8-3.2L N/A engines now allow 245 max tire width; over 3150 lbs may run 275 with 2% weight penalty.
STU 2006-2015 Mazda Miata Intake Manifold #38422wordingneutralSTU Mazda MZR may use Goodwin 61-2510 or Gato Performance 31972 intake manifold.
STU Requesting Approval of the JDM Honda h23a #38489cars addedneutralSTU Honda JDM H23a added, 2259cc displacement, minimum weight per Chart, must meet ST engine regulations.
AS Errors and Omissions #38234wordingneutralAS Ford Mustang GT 05-14 Restricted Prep Engine gains alternative gear ratios: 3.66, 2.43, 1.69, 1.32, 1.00, .65
AS Errors and Omission #38055inductionslowerAS Ford Mustang GT 5.0L (15-17) flat plate restrictor reduced from 67mm to 64mm.
AS Request to Add LS1/LS6 Intakes for 5.3L Truck Engine EnO #38197wordingneutralAS LS1/LS6 5.3L truck engine gains four approved intake part numbers: 12561269, 88894095, 89017363, 89017364.
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.
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.
STU Wheel Size Inconsistency #38018wordingneutralSTU wheel width rules clarified: cars ≤2,850 lbs max 8 inches, cars >2,850 lbs max 9 inches.
STU Table C: STU-GT3U Clarification #38268weightfasterSTU Spec Line GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tire options clarified with weight adjustments.
AS Flotek Head Plunge Cut Inconsistencies #37502wordingunclearAS Flotek Head plunge cut dimensions figure updated in GCR Section 9.1.6.
AS Notes clean up #37693wordingneutralAS class notes cleanup: multiple Camaro, Firebird, CTS-V, Challenger, Mustang specs and fuel cell/ECM/head restrictions removed.
AS Race memo #37902wordingunclearAS Spec Lines removes ECM flexibility restriction from five Cadillac and Chevrolet/Pontiac V8 models.
STU BMW N54/N55 Engine Allowance Follow Up #37447engineneutralSTU BMW N54/N55 3.0L classified at Chart +3% minimum weight; N54 twin turbo not allowed.
STU STU Mini Cooper pulley size clarification re: letter #36980 #37717inductionfasterSTU Mini Cooper S SC supercharger pulley diameter reduced from 2.285 to 2.185.
STU Question About a Weight Modifier #37782weightfasterSTU Honda K20C1 Turbo I4 exempted from 3% DI weight adder in Spec Lines Table A.
STU Increase Minimum Weight #37919weight +100 lbsslowerSTU GT3U minimum weight increases 150 to 250 pounds.
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
1:55.401Wilson Powell · fastest of 4 · top 4 within 8.7s
1:53.640Rylan Hazelton · fastest of 5 · top 5 within 8.0s
113.3Rylan Hazelton
+19.668squal +22.529s
120.9%qual 124.3%
1:56.445Roger Eagleton · fastest of 3 · top 3 within 4.0s
1:55.849Roger Eagleton · fastest of 4 · top 4 within 5.3s
108.7Roger Eagleton
+21.877squal +23.573s
123.3%qual 125.4%
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
+21.710squal +22.091s
123.1%qual 123.8%
198 earlier rule changes on record, in force before Cal Club 2025 (from 2019)28 cars added · 23 induction · 23 weight · 20 engine · 10 tyres & wheels · 7 aero · 4 suspension & brakes · 81 wording · 2 other · 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. · AS Ford Mustang Coyote engines increase restrictor to 80mm from 64mm or 67mm. · AS Mustang GT 05-14 4.6L loses 300 lbs; 15-17 and 2018+ models lose 61mm and 60mm restrictors respectively. · AS class gear ratio options specified for multiple American muscle cars, including Cadillac CTS-V, Chevrolet Camaro, Ford Mustang, Dodge Challenger, and Pontiac GTO. · AS LS-engine cars gain ECU freedom; Camaro/Firebird 93-02 LS1 removes fuel cell location restriction. · STU Audi 1.8T wagon deleted; Porsche 944 1800 weight to Chart, turbo inlet restrictor removed. · STU-GT3 reclassified as STU-GT3U effective January 1, 2026. · STU GT3 TCR gains 275-width tire option with 100 lb weight penalty, but not in A compound. · STL/STU: 90-05 Mazda Miata alternate front wheel hubs moved from General to specific part approval. · STL/STU: 90-05 Mazda Miata alternate front wheel hubs moved from General to specific part approval. · STU BMW N54/N55 turbo inlet restrictors now required per GCR definition; turbo swapping prohibited. · STU Mini Cooper S SC 1900 restricts to 2.565 diameter pulley; 2100 allows 2.285 diameter pulley. · AS Ford Mustang GT models gain alternate transmission ratio options for 2024-09-01. · STU RWD turbo cars no longer required to reduce restrictor by 1 mm from table. · AS Ford Mustang GT 5.0L (2018-) classified at 3600 lbs with 60mm restrictor, Brembo BBK permitted. · AS Chevrolet Camaro 1LE (2016-) classified with 3600 lbs minimum weight, 60mm restrictor, 275 tires. · AS Chevrolet/Pontiac Camaro & Firebird 82-92 5.7L LS1 classified at 3200 lbs with 65mm restrictor plate required. · AS Chevrolet Camaro, Firebird, and Ford Mustang models permitted to use Flo Tek cylinder heads. · AS Camaro/Firebird and GTO LS1 connecting rods approved: Callies CSC6100DS6A2AH, Scat 2-1CR6100-944, GM 12649190. · AS Cadillac CTS-V, Chevrolet Camaro SS, Dodge Challenger, Ford Mustang GT, Pontiac GTO allowed 11" wheels until 3/1/25. · Chevrolet Camaro, Pontiac Firebird 70-81 Full Prep classified AS at 3400-3600 lbs with 250 lb weight reduction. · AS class: multiple cars gain fuel cell placement note allowing 24 inches from standard tank, unrestricted filler location. · Chevrolet Camaro 16- Full Prep classified into AS at 3400 lbs with 250 lb weight reduction. · AS adds Ford Mustang GT 05-14 Restricted prep Engine with 62mm FPR, 3400 lbs minimum, 18-inch wheels. · STU Mini Cooper S SC: alternate LEAP OMICRON hood scoop LEP-OMICRON3 permitted. · STU BMW S54 B32 OEM now permits dry sump oiling system. · 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. · STL and STU power steering rules clarified to permit electric-assisted and hydraulic-assisted steering systems. · 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. · AS crate motor part number specified: GM Performance CT400 P/N 19370604 engine assembly for GM vehicles. · AS Spec Lines Ford Mustang GT 5.0L (15-17) max wheel size increases to 19.0 inches. · AS Dodge Challenger 5.7L/6.1L/6.4L V8 now permits SPC-66045 alternate front upper control arms. · AS Dodge Challenger 5.7L/6.1L/6.4L V8 allows alternate front brake caliper adapters for updated or backdated components. · Toyota GR Cup and GR86 Cup (2022-) newly classified in STU at 2700 lbs with 2387 cc engine. · STL ITA/ITS RX7 and 1985+ ITA/ITS/ITB/ITC vehicles clarified to conform to section 9.1.4.2 tire specifications. · STU Mazda BP5A classified at 1839 cc maximum displacement, 2023-04-01. · STU minimum weight chart updated: 2450cc to 2595lbs, 2600cc to 2710lbs. · STL Spec MX5 clutch, wheels, and tyres specified: ACT 0000-02-5004-G6, 17x8 wheels, Toyo RR and RA1 235-40-17. · AS allows Hoosier W2 tyre option in addition to R7, R6, WET/H20. · AS Dodge Challenger 08-20 adds two transmission ratio options: 2.97, 2.10, 1.45, 1.00, 0.74, 0.50 or 2.26, 1.58, 1.19, 1.00, 0.77, 0.63. · STU Mazda 13B Turbo classified, streetport only, stock turbos prohibited, alternatives allowed. · STU OEM louver vents now exempt from vent count and 200 square inch allowance. · STU 2400cc non-4-valve engines gain 9% base weight reduction; DI turbo prep limits removed. · AS Cadillac CTS-V 6.0L V8 removes 50 lbs weight penalty for 295 tire size. · STU normally-aspirated 2976–3200 cc single-throttle engines lose 10% base engine weight reduction. · ST redundant language removed from balance shaft and pulley modification rules. · STU cars that qualified for 9 inch wheels in 2021 may continue through 2022 only. · STU splitter definition clarified: must be single-plane with no vertical deviations, attached to lowest front point. · STU BMW S52B32 minimum weight drops 90 lbs to 3110; max displacement cut to 3152 cc. · STU BMW S50B32 Euro classified at 3201 cc displacement, 3300 lbs minimum weight. · ST engine swap origin country requirement changes from North America to the United States for case-by-case approval. · STU Honda CRX (84-91) and Civic Del Sol (93-97) ineligible for front wheel drive weight reductions. · STU vehicles at or over 2950 lbs base weight may use 9 inch wide wheels instead of 8.0 inch maximum. · STU minimum weights reduced: 2450cc to 2596 lbs, 2500cc to 2635 lbs, 2550cc to 2675 lbs. · 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. · STU normally aspirated engines: minimum weights reduced up to 310 lbs; single throttle body weight reduction removed. · STU Audi A4 1.8T minimum weight fixed at 3050 lbs, VF30 turbo with 35mm restrictor now required only. · STL and STU Improved Touring vehicles must conform to 9.1.4 Tires & Wheels requirements. · STU engines may delete balance shafts and plug openings; alternate pulleys allowed for timing belt or chain operation only. · STU hood vents allowed to include louvers within 200 sq. inch area. · SMG long tube headers: Borla PN 17237 discontinued, Kooks PN 11312000 and American Racing PN MT3-05134300LSNC approved alternatives. · AS Mercury Capri (79-86) removed as individual spec line, merged into Ford Mustang (79-93) spec line. · AS Spec Mustang SMG loses 3.73 gear ratio and 355/300 mm brake specification. · AS Chevrolet, Pontiac, Ford full prep engines now permit alternate cylinder heads with restrictor plate ALL26180 and 1.250 inserts ALL26186 for regional competition. · 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. · STU adds Honda K23 with 2354cc displacement and minimum weight per chart, K24 block allowed with K23 internals and head. · STU Honda K23 internals rule relaxed to require only K23 crankshaft, allowing other internal modifications. · STL and STU piston engines clarified: intake manifold and cylinder head porting remains free. · AS Chevrolet/Pontiac Camaro & Firebird 93-02 now allow BMR AA004 or UMI 2310 adjustable front upper control arms. · AS Pontiac GTO 04-06 LS1 to 3300 lbs, LS2 to 3350 lbs on 295 tire. · STL Spec MX-5 removes redundant specification line; no performance change. · STU fender flare wording clarified: exterior contour of any wheel opening may not change opening size, location or shape from side view. · STU Mazda 12A Bridge Port Miata weight reduced from 2550 lbs to 2350 lbs. · AS Cadillac CTS-V 6.0L V8 removes 50 lbs tire size penalty, making it lighter. · AS consolidates seven SN95 Mustang spec lines into three: 94-04 including Cobra, 94-95 5.0/5.8, and 96-04 4.6L two/four valve. · AS Camaro/Firebird LT1/LS1 transmission code changes to 6362; Mustang GT 4.6L/5spd changes to 5.0L/6spd with 300 lbs weight reduction. · AS Camaro/Firebird and Mustang GT gear ratio specifications restored with alternate sets permitted. · AS Chevrolet Camaro & Firebird, Ford Mustang variants, Mercury Capri minimum weights increase 50 lbs across all model years. · STL Volkswagen 2.0L TFSI 1984cc classified with turbocharger removal required, meeting all other STL specs. · 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. · STU fender flare rules clarified: maximum 2 inches, must cover tire contact patch from above, cannot alter body configuration or wheel opening geometry. · ST oil coolers and filters now explicitly allowed to be added or substituted; wording clarifies existing permissions. · STU Honda S2000 allows F20/F22 K24 crankshaft with chart weight for achieved displacement. · ST oil coolers and filters now explicitly allowed to be added or substituted; wording clarifies existing permissions. · AS Mustang 4.6L/5spd loses 300 lbs; 5.0L/6spd gains 56mm restrictor requirement. · AS CTS-V LS6 and LS2 may now use Driveshaft Shop carbon fiber driveshaft for durability. · AS Chevrolet Camaro SS V8 6.2L model years extended from 10-13 to 10-15. · 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. · 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. · ST cars may relocate ABS actuation hardware and wiring anywhere in engine compartment. · STU Porsche PDK automatic transmission limited to 8 forward speeds instead of torque converter restriction. · STU Mazda 13B Street Port 2400 removes choke location restriction, allows auto-type 2bbl with dual-Y manifold. · STU driveshaft and half-shaft materials change from OEM-type to steel or aluminum. · Ford Mustang GT 5.0L 15-17 Restricted Preparation classified in AS with 55mm flat plate restrictor required. · AS underhood bracing on stock hoods, trunks, and rear decks may be modified or removed. · AS Cadillac CTS-V 04-07 with 295 tire drops to 3450 lbs; Camaro SS V8 10-13 275 tire removed; Challenger 08-20 gains 315 tire option at 3600 lbs. · AS Camaro & Firebird (93-02) and Mustang GT (05-14) specifications restored with 200 lb weight reduction for permitted heads. · 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. · STU Mazda 13B Street Port classified at 2400 lbs minimum weight, replacing peripheral and bridge port variants. · AS Dodge Challenger 08-20 gains 6.1L and 6.4L V8 options; 5.7L weight rises to 3500 lbs on 295 tyres, 3600 on 315 tyres. · AS Camaro/Firebird (93-02) and Mustang Coupe GT (05-14) consolidated into single specs with 100 lb and 300 lb weight reductions respectively. · ST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch. · ST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch. · STU fender flare rules reworded: up to 2" per corner allowed with 1% weight penalty total. · AS Dodge Challenger 5.7L V8 gets iron block requirement, 10.5:1 compression max, intake valve 12.7 mm, exhaust 12.3 mm, intake duration 188°, exhaust duration 205°. · AS Dodge Challenger 08-14 rear spoiler part number changes from 1GL20RXF to 1GL20TZZAB. · 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. · 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. · AS class pursues specified list of eligible tires; details of tire changes not provided in letter. · AS class pursuing specified list of eligible tires; details pending further communication. · No restrictor plate change implemented; 2021 AS Mustang Coyote under evaluation. · AS 2005-2009 Restricted Prep 4.6 3V now permits conversion to 2 valve configuration. · AS Ford Mustang Coupe GT 4.6L 3V Restricted Prep now permits Ford Performance camshaft kit P/N-M-6550-3V. · 2010-2014 Camaro reclassified to AS; full preparation classification approved effective 2020-07-01. · AS class cylinder head replacement options under review; implementation planned for 2021 season. · AS Mustang, Camaro, Firebird, Capri max brake rotor diameter increases from 12.2 to 13.1 inches. · AS rotor diameter increase approved; see Fastrack letter #28748 for details. · GT3 and STU add Borg-Warner EFR6258 to approved turbocharger list. · STU request for alternate intake manifold denied; no rule change issued. · GT3 and STU add Borg-Warner EFR6258 to approved turbocharger list. · STU large displacement turbo engines limited by GCR turbo list; non-turbo trim suggested as more competitive. · STU sequential shifters referred to Board of Directors for approval; no change implemented yet. · 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. · STU Mazda 13B Bridge Port and Street Port engines added with 2550 and 2250 lbs minimum weights respectively. · AS Chevrolet/Pontiac Camaro & Firebird (82-92) loses 50 lbs, to 3500. · STL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor. · 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. · STU Honda S2000 adds HKS Supercharger kits 12001-AH006 and 12001-AH010 as allowed. · STU Lotus Elise Cup R and SC models, plus Exige SC, gain 100–200 lbs minimum weight. · STU Volkswagen GTI/GLI MK5 and Jetta Mk4 may install turbo inlet restrictor in OEM turbo inlet housing. · STU Honda K20C1 Turbo I4 restrictor reduces from 36mm to 35mm. · STU GM Ecotech LNF now allowed with turbo removed or with LE5 head and intake manifold, meeting STL specs. · STU Porsche 944 now permits VW/Audi 1.8L and 2.0L turbo engines as alternates. · STL Mazda Spec MX5 Challenge adds approved wheel part numbers 0000-04-5706-GM, 0000-04-5706-SL. · STU vehicles over 2951 lbs base weight may use 9 inch wide wheels, up from 2950 lbs. · STU turbocharged engines now use base weight instead of minimum weight, with 3% DI increase applied to base weight. · AS rear trailing arms may be replaced with tubular arms maintaining stock length and axle location purpose only. · AS Ford and GM full-prep cars get 200 lb weight reduction, up from 150 lb. · 05-10 Ford Mustang Coupe GT 4.6L OHC classified AS with 3200 lbs minimum weight, HR cam restricted prep. · AS 10-15 Chevrolet Camaro Full Prep classified with 3400 lbs base weight, over 313 CID engine 3700 lbs maximum. · STU cars with manual OEM throttle bodies may convert to OEM electronic throttle body of same inner diameter. · AS Spec Mustang (SMG) added as Restricted Prep class. · Mazda Spec MX-5 Challenge classified in STL with 2000cc displacement and 2500 lbs minimum weight. · STU wing assembly wording corrected: no part higher than roof height. · AS class minimum ride height clarified to 5 inches measured at rocker panel, excluding seams and cladding. · STU alternate intake manifolds now allowed case-by-case instead of prohibited. · STU Nissan SR20DET removes -2mm penalty in Table B. · STU alternate intake manifolds now allowed case-by-case instead of prohibited. · AS Ford Mustang (79-93) 313 CID and under loses 100 lbs to 3150; over 313 CID loses 100 lbs to 3450. · STL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate. · STU aftermarket side skirts must meet 3-inch ride height, no openings except jacks or side exhaust, no wider than fascias, not higher than door bottom, no chassis reinforcement. · STU fender flare wording clarified: each fender may be flared up to 2" for tire clearance with 1% weight penalty. · STL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld. · STL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld. · STU Mazda 13B Bridge Port may use ELITE ROTARY SHOP FD V2.0 intake manifold instead of stock. · STU Mazda MZR LF/L3/L5 may use Goodwin Part #61-2510 intake manifold with stock or Acura throttle body. · STU suspension rules clarified: alternate components from same manufacturer moved from section E to section D. · STU Honda/Acura B20 classified at 1973 cc, now permits VTEC B16 or B18 cylinder head and intake manifold. · STU flared fenders up to 2" with 1% weight penalty moved from base to Advanced Aero rules. · TCA Honda Civic Si (2017-) must run 37mm TIR maximum as of June 1, 2019. · STU BMW S54B32 OEM reclassified from E46 designation, 3246 cc, 3300 lbs minimum weight. · 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. · Honda Civic Si 2017- classified STU at 1500cc, 2800 lbs minimum with OEM engine and bodywork. · STU BMW E46 S54 OEM 3246cc added at 3300 lbs minimum weight, no Super Touring allowances. · STU Mazda 13B and 13B Bridge Port may use RE or REW housings and intake with turbo removed. · STU Honda K24 may use intake part #s 17100-RRB-A00 or 17100-PRB-A10. · STU Mazda 12A Bridge Port engine classified at 2550 lbs minimum weight with specified carburetor induction options. · STU World Challenge car weight calculation method removed; new basis unclear from text provided. · STU AWD cars no longer required to reduce restrictor 1 mm from table. · STU rear wing maximum cord length set to 12 inches, end plates to 72.0 square inches each. · AS Spec Mustang (SMG) newly classified with 107.1 wheelbase, 3.73 gears, 355mm front brakes, 300mm rear. · 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. · STU Honda K20C1 Turbo I4 1996cc added at 3025 lbs minimum weight with 36mm TIR.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.
AS Increase Coyote Engine Restrictor to 80mm #36177inductionfasterAS Ford Mustang Coyote engines increase restrictor to 80mm from 64mm or 67mm.
AS Performance Pack for 2015+ Mustang #36867enginefasterAS Mustang GT 05-14 4.6L loses 300 lbs; 15-17 and 2018+ models lose 61mm and 60mm restrictors respectively.
AS Gear Ratios #37131wordingneutralAS class gear ratio options specified for multiple American muscle cars, including Cadillac CTS-V, Chevrolet Camaro, Ford Mustang, Dodge Challenger, and Pontiac GTO.
AS ECU specs for LS engine #37208enginefasterAS LS-engine cars gain ECU freedom; Camaro/Firebird 93-02 LS1 removes fuel cell location restriction.
STU Audi 1.8t Wagon STU Table B #36685cars addedfasterSTU Audi 1.8T wagon deleted; Porsche 944 1800 weight to Chart, turbo inlet restrictor removed.
STU Merger GT3 to STU #37486wordingneutralSTU-GT3 reclassified as STU-GT3U effective January 1, 2026.
STU GT3 TCR Tire allowance #37494tyres & wheelsslowerSTU GT3 TCR gains 275-width tire option with 100 lb weight penalty, but not in A compound.
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.
STU 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.
STU BMW N54/N55 Engine Allowance #37146inductionslowerSTU BMW N54/N55 turbo inlet restrictors now required per GCR definition; turbo swapping prohibited.
STU R53 15% Pulley Request #36980inductionslowerSTU Mini Cooper S SC 1900 restricts to 2.565 diameter pulley; 2100 allows 2.285 diameter pulley.
AS Mustang transmission ratios #36662wordingunclearAS Ford Mustang GT models gain alternate transmission ratio options for 2024-09-01.
STU RWD Turbo Disadvantage #36255inductionfasterSTU RWD turbo cars no longer required to reduce restrictor by 1 mm from table.
AS Request for Classification of 2018-2023 mustang In #35764cars addedneutralAS Ford Mustang GT 5.0L (2018-) classified at 3600 lbs with 60mm restrictor, Brembo BBK permitted.
AS 6th gen Camaro limited prep #35733cars addedneutralAS Chevrolet Camaro 1LE (2016-) classified with 3600 lbs minimum weight, 60mm restrictor, 275 tires.
AS Chevrolet/Pontiac Camaro & Firebird (82-92) 5.7L V8 LS1 Alum BLK #35825cars addedneutralAS Chevrolet/Pontiac Camaro & Firebird 82-92 5.7L LS1 classified at 3200 lbs with 65mm restrictor plate required.
AS Full Prep Head #35891otherneutralAS Chevrolet Camaro, Firebird, and Ford Mustang models permitted to use Flo Tek cylinder heads.
AS Restricted Prep Aftermarket Parts Request #35682wordingneutralAS Camaro/Firebird and GTO LS1 connecting rods approved: Callies CSC6100DS6A2AH, Scat 2-1CR6100-944, GM 12649190.
AS Allowance of 11 #35824tyres & wheelsfasterAS Cadillac CTS-V, Chevrolet Camaro SS, Dodge Challenger, Ford Mustang GT, Pontiac GTO allowed 11" wheels until 3/1/25.
AS Request to Classify 1970-1981 Camaro and Firebird in AS #33659cars addedneutralChevrolet Camaro, Pontiac Firebird 70-81 Full Prep classified AS at 3400-3600 lbs with 250 lb weight reduction.
AS Fuel Cell 12 #34194wordingneutralAS class: multiple cars gain fuel cell placement note allowing 24 inches from standard tank, unrestricted filler location.
AS Please Classify the 6th Gen Into AS. #35448cars addedneutralChevrolet Camaro 16- Full Prep classified into AS at 3400 lbs with 250 lb weight reduction.
AS spec lines #35713cars addedneutralAS adds Ford Mustang GT 05-14 Restricted prep Engine with 62mm FPR, 3400 lbs minimum, 18-inch wheels.
STU Letter #35397 addendum #35453wordingneutralSTU Mini Cooper S SC: alternate LEAP OMICRON hood scoop LEP-OMICRON3 permitted.
STU S54 Drysump #35464wordingneutralSTU BMW S54 B32 OEM now permits dry sump oiling system.
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.
STU ST Electric-Assisted Steering Systems #35066wordingneutralSTL and STU power steering rules clarified to permit electric-assisted and hydraulic-assisted steering systems.
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.
AS Crate Motor Part Numbers #32944wordingneutralAS crate motor part number specified: GM Performance CT400 P/N 19370604 engine assembly for GM vehicles.
AS Request wheel size change #33007tyres & wheelsfasterAS Spec Lines Ford Mustang GT 5.0L (15-17) max wheel size increases to 19.0 inches.
AS Alternative Upper Front Control Arms for Dodge Challenger #33352wordingneutralAS Dodge Challenger 5.7L/6.1L/6.4L V8 now permits SPC-66045 alternate front upper control arms.
AS Front Brake Caliper Adapters for Dodge Challenger #33353wordingneutralAS Dodge Challenger 5.7L/6.1L/6.4L V8 allows alternate front brake caliper adapters for updated or backdated components.
STU 2022 Toyota GR Cup for STU #34449cars addedneutralToyota GR Cup and GR86 Cup (2022-) newly classified in STU at 2700 lbs with 2387 cc engine.
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.
STU Alternate OEM Miata Intake Manifold #33827wordingneutralSTU Mazda BP5A classified at 1839 cc maximum displacement, 2023-04-01.
STU E&O STU NA Weight Chart. #33737weightfasterSTU minimum weight chart updated: 2450cc to 2595lbs, 2600cc to 2710lbs.
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.
AS Request to add Hoosier W2 #33031tyres & wheelsneutralAS allows Hoosier W2 tyre option in addition to R7, R6, WET/H20.
AS correction of Dodge Challenger specification line #33151wordingneutralAS Dodge Challenger 08-20 adds two transmission ratio options: 2.97, 2.10, 1.45, 1.00, 0.74, 0.50 or 2.26, 1.58, 1.19, 1.00, 0.77, 0.63.
STU Request Mazda 13 B turbo #32668cars addedneutralSTU Mazda 13B Turbo classified, streetport only, stock turbos prohibited, alternatives allowed.
STU Hood Vents and Intercooler Scoops #32733aerofasterSTU OEM louver vents now exempt from vent count and 200 square inch allowance.
STU Non 4 valve weight reduction removed #32808enginefasterSTU 2400cc non-4-valve engines gain 9% base weight reduction; DI turbo prep limits removed.
AS Request CTS-V Spec Line Error Correction #30242weightfasterAS Cadillac CTS-V 6.0L V8 removes 50 lbs weight penalty for 295 tire size.
STU Error in new minimum weight table when combined with other text #32711engineslowerSTU normally-aspirated 2976–3200 cc single-throttle engines lose 10% base engine weight reduction.
STU Redundant Language in May GCR #32713wordingneutralST redundant language removed from balance shaft and pulley modification rules.
STU Opposed to the Proposed STU Weight Chart #32381wordingneutralSTU cars that qualified for 9 inch wheels in 2021 may continue through 2022 only.
STU Clarification request for GCR 9.1.4.D.3.a Splitter Definition #32414wordingneutralSTU splitter definition clarified: must be single-plane with no vertical deviations, attached to lowest front point.
STU Request Adjustment to Min Weight for STU BMW E36 M3 (95-99) #31535weight -90 lbsfasterSTU BMW S52B32 minimum weight drops 90 lbs to 3110; max displacement cut to 3152 cc.
STU BMW E36 M3 Canadian (North American) S50B32 engine #31866cars addedneutralSTU BMW S50B32 Euro classified at 3201 cc displacement, 3300 lbs minimum weight.
STU Engine Swap Origin Country #32209wordingneutralST engine swap origin country requirement changes from North America to the United States for case-by-case approval.
STU CRX/Civic Del Sol #32214weightslowerSTU Honda CRX (84-91) and Civic Del Sol (93-97) ineligible for front wheel drive weight reductions.
STU Error correction #32383tyres & wheelsfasterSTU vehicles at or over 2950 lbs base weight may use 9 inch wide wheels instead of 8.0 inch maximum.
STU Single TB Weight Modifiers Add to Chart #32393weightfasterSTU minimum weights reduced: 2450cc to 2596 lbs, 2500cc to 2635 lbs, 2550cc to 2675 lbs.
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.
STU Single TB Weight Modifiers #31449weightfasterSTU normally aspirated engines: minimum weights reduced up to 310 lbs; single throttle body weight reduction removed.
STU Request to Remove A4 1.8t from STU Spec Line Tables #31465weightslowerSTU Audi A4 1.8T minimum weight fixed at 3050 lbs, VF30 turbo with 35mm restrictor now required only.
STU Improved Touring Tires #32063tyres & wheelsneutralSTL and STU Improved Touring vehicles must conform to 9.1.4 Tires & Wheels requirements.
STU Request Allowance for Balance Shaft Delete in STU #31434enginefasterSTU engines may delete balance shafts and plug openings; alternate pulleys allowed for timing belt or chain operation only.
STU Request Louvers in hood vents #31916aeroneutralSTU hood vents allowed to include louvers within 200 sq. inch area.
AS Proposed Revisions to SCCA GCR 2021 Appendix M, Part 3 #30295wordingneutralSMG long tube headers: Borla PN 17237 discontinued, Kooks PN 11312000 and American Racing PN MT3-05134300LSNC approved alternatives.
AS specification line consolidation and correction #31846wordingneutralAS Mercury Capri (79-86) removed as individual spec line, merged into Ford Mustang (79-93) spec line.
AS correction of SMG specification line #31847wordingunclearAS Spec Mustang SMG loses 3.73 gear ratio and 355/300 mm brake specification.
AS Alternate cylinder heads for full prep engine builds - Evaluation #31851engineunclearAS Chevrolet, Pontiac, Ford full prep engines now permit alternate cylinder heads with restrictor plate ALL26180 and 1.250 inserts ALL26186 for regional competition.
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.
STU Request to Add Honda K23 Spec Line #30682cars addedneutralSTU adds Honda K23 with 2354cc displacement and minimum weight per chart, K24 block allowed with K23 internals and head.
STU RE: Aug FT letter 30682 #31060enginefasterSTU Honda K23 internals rule relaxed to require only K23 crankshaft, allowing other internal modifications.
STU Throttling Device Clarification #31323wordingneutralSTL and STU piston engines clarified: intake manifold and cylinder head porting remains free.
AS Request for adjustable Front Upper Control Arms on 4th Gen F-Body #30457suspension & brakesneutralAS Chevrolet/Pontiac Camaro & Firebird 93-02 now allow BMR AA004 or UMI 2310 adjustable front upper control arms.
AS Request Pontiac GTO tire size change #30881weightslowerAS Pontiac GTO 04-06 LS1 to 3300 lbs, LS2 to 3350 lbs on 295 tire.
STL Request to clean up Spec MX-5 Redundancy #31069wordingneutralSTL Spec MX-5 removes redundant specification line; no performance change.
STU STU Fender flares #30696wordingneutralSTU fender flare wording clarified: exterior contour of any wheel opening may not change opening size, location or shape from side view.
STU Request weight reduction for 12A bridgeport motor in Miata #30751weight -200 lbsfasterSTU Mazda 12A Bridge Port Miata weight reduced from 2550 lbs to 2350 lbs.
AS Request CTS-V Spec Line Error Correction #30242weightfasterAS Cadillac CTS-V 6.0L V8 removes 50 lbs tire size penalty, making it lighter.
AS Request to consolidate SN95 Mustang '94-'04 Mustang spec lines #30428wordingneutralAS consolidates seven SN95 Mustang spec lines into three: 94-04 including Cobra, 94-95 5.0/5.8, and 96-04 4.6L two/four valve.
AS American Sedan Transmission Rule Change Request #30595enginefasterAS Camaro/Firebird LT1/LS1 transmission code changes to 6362; Mustang GT 4.6L/5spd changes to 5.0L/6spd with 300 lbs weight reduction.
AS Correction to specifications inadvertently deleted #30691wordingneutralAS Camaro/Firebird and Mustang GT gear ratio specifications restored with alternate sets permitted.
AS weight adjustments #30700weight +50 lbsslowerAS Chevrolet Camaro & Firebird, Ford Mustang variants, Mercury Capri minimum weights increase 50 lbs across all model years.
STL VW Engine Request #30625engineslowerSTL Volkswagen 2.0L TFSI 1984cc classified with turbocharger removal required, meeting all other STL specs.
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.
STU Request for Fender Flare Clarification #30375wordingneutralSTU fender flare rules clarified: maximum 2 inches, must cover tire contact patch from above, cannot alter body configuration or wheel opening geometry.
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.
STU Provision for Interchangeable Engine Components Already Allowed #30342engineunclearSTU Honda S2000 allows F20/F22 K24 crankshaft with chart weight for achieved displacement.
STU 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.
AS AS Mustang LP 4.6 3V Classification Transmission Request #29886weightfasterAS Mustang 4.6L/5spd loses 300 lbs; 5.0L/6spd gains 56mm restrictor requirement.
AS Request CF driveshaft on CTS-V for durability improvement #30117otherneutralAS CTS-V LS6 and LS2 may now use Driveshaft Shop carbon fiber driveshaft for durability.
AS Adjustment to model years of 5th generation RP Camaro #30348wordingneutralAS Chevrolet Camaro SS V8 6.2L model years extended from 10-13 to 10-15.
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.
STU 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.
STU Brake Component Relocation #29990wordingneutralST cars may relocate ABS actuation hardware and wiring anywhere in engine compartment.
STU Porsche PDK #30081wordingneutralSTU Porsche PDK automatic transmission limited to 8 forward speeds instead of torque converter restriction.
STU Reference Letter #29333 Proposed STU 13B Spec Line Changes #30086inductionfasterSTU Mazda 13B Street Port 2400 removes choke location restriction, allows auto-type 2bbl with dual-Y manifold.
STU Drive Shaft Request #30087wordingneutralSTU driveshaft and half-shaft materials change from OEM-type to steel or aluminum.
AS Request for 2015 -2017 Ford Mustang Spec Line #29514cars addedneutralFord Mustang GT 5.0L 15-17 Restricted Preparation classified in AS with 55mm flat plate restrictor required.
AS Request Trunk lid / Rear Hatch clarification #29591wordingneutralAS underhood bracing on stock hoods, trunks, and rear decks may be modified or removed.
AS Common Weight for CTS-V Tire #29759weightfasterAS Cadillac CTS-V 04-07 with 295 tire drops to 3450 lbs; Camaro SS V8 10-13 275 tire removed; Challenger 08-20 gains 315 tire option at 3600 lbs.
AS Correction to specifications inadvertently deleted #30041weightfasterAS Camaro & Firebird (93-02) and Mustang GT (05-14) specifications restored with 200 lb weight reduction for permitted heads.
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.
STU 13B Rules Adjustment #29333cars addedslowerSTU Mazda 13B Street Port classified at 2400 lbs minimum weight, replacing peripheral and bridge port variants.
AS Request Additional Engine Options for Dodge Challenger Spec Line #29543engineslowerAS Dodge Challenger 08-20 gains 6.1L and 6.4L V8 options; 5.7L weight rises to 3500 lbs on 295 tyres, 3600 on 315 tyres.
AS Rule simplification spec line communization #29824wordingfasterAS Camaro/Firebird (93-02) and Mustang Coupe GT (05-14) consolidated into single specs with 100 lb and 300 lb weight reductions respectively.
STL Request clarification on wing measurement #29640aeroneutralST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch.
STU Request clarification on wing measurement #29640aeroneutralST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch.
STU Request for Advanced Aero Rule Wording Clarification. #29124wordingneutralSTU fender flare rules reworded: up to 2" per corner allowed with 1% weight penalty total.
AS Dodge Challenger AS Spec Line Clarification #28698engineslowerAS Dodge Challenger 5.7L V8 gets iron block requirement, 10.5:1 compression max, intake valve 12.7 mm, exhaust 12.3 mm, intake duration 188°, exhaust duration 205°.
AS Dodge Challenger AS Spec Line Clarification #2 #28699wordingneutralAS Dodge Challenger 08-14 rear spoiler part number changes from 1GL20RXF to 1GL20TZZAB.
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.
STU Minimum Weight Determination #27695wordingneutralSTL and STU clarify weight adjustment calculation order: engine adjustments first, then chassis adjustments.
STU ST Gurney flap Wicker clarification #29012wordingneutralSTL and STU rear wing rules clarify that wicker is a Gurney flap; no performance change.
AS Support for R-Type Specification Tires #27450tyres & wheelsunclearAS class pursues specified list of eligible tires; details of tire changes not provided in letter.
AS Spec Tire Request #27519tyres & wheelsunclearAS class pursuing specified list of eligible tires; details pending further communication.
AS Restrictor Plate Change for RP 2011+ Mustang with Coyote Engine #27675wordingunclearNo restrictor plate change implemented; 2021 AS Mustang Coyote under evaluation.
AS 2005-2009 Restricted Prep 4.6 3V #27908engineunclearAS 2005-2009 Restricted Prep 4.6 3V now permits conversion to 2 valve configuration.
AS Request for 2005-2009 Restricted Prep 4.6 3V Parts #27909wordingunclearAS Ford Mustang Coupe GT 4.6L 3V Restricted Prep now permits Ford Performance camshaft kit P/N-M-6550-3V.
AS Request for Full Preparation Classification for 2010-2014 Camaro #28030cars addedunclear2010-2014 Camaro reclassified to AS; full preparation classification approved effective 2020-07-01.
AS Cylinder Heads #28696wordingunclearAS class cylinder head replacement options under review; implementation planned for 2021 season.
AS Request for Max Rotor Diameter Change #28748suspension & brakesfasterAS Mustang, Camaro, Firebird, Capri max brake rotor diameter increases from 12.2 to 13.1 inches.
AS Request increase rotor diameter #28797suspension & brakesneutralAS rotor diameter increase approved; see Fastrack letter #28748 for details.
STL Request for Addition to GT3 Approved Turbo List #27576wordingneutralGT3 and STU add Borg-Warner EFR6258 to approved turbocharger list.
STU Request for Alternate Intake Manifold #26514wordingneutralSTU request for alternate intake manifold denied; no rule change issued.
STU Request for Addition to GT3 Approved Turbo List #27576wordingneutralGT3 and STU add Borg-Warner EFR6258 to approved turbocharger list.
STU Request BoP for my Car #29004wordingneutralSTU large displacement turbo engines limited by GCR turbo list; non-turbo trim suggested as more competitive.
STU Sequential Shifters in STU #29031wordingneutralSTU sequential shifters referred to Board of Directors for approval; no change implemented yet.
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.
STU Rotary Help #27833cars addedneutralSTU Mazda 13B Bridge Port and Street Port engines added with 2550 and 2250 lbs minimum weights respectively.
AS weight adjustments for 2020 season #28785weight -50 lbsfasterAS Chevrolet/Pontiac Camaro & Firebird (82-92) loses 50 lbs, to 3500.
STL STL Honda B18 restrictor changes #28794inductionfasterSTL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor.
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.
STU Request to approve Honda S2000 HKS supercharger #27281enginefasterSTU Honda S2000 adds HKS Supercharger kits 12001-AH006 and 12001-AH010 as allowed.
STU Request BoP on the Lotus #27637weight +100 lbsslowerSTU Lotus Elise Cup R and SC models, plus Exige SC, gain 100–200 lbs minimum weight.
STU Turbo Inlet Restrictor On MK5 Volkswagen #27704inductionslowerSTU Volkswagen GTI/GLI MK5 and Jetta Mk4 may install turbo inlet restrictor in OEM turbo inlet housing.
STU Honda K20C1 removal #27732inductionslowerSTU Honda K20C1 Turbo I4 restrictor reduces from 36mm to 35mm.
STU 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.
STU Alternate Engine for Porsche 944 #28259engineunclearSTU Porsche 944 now permits VW/Audi 1.8L and 2.0L turbo engines as alternates.
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.
STU Please Modify the STU Wheel Size Rule for Clarity #27694weightfasterSTU vehicles over 2951 lbs base weight may use 9 inch wide wheels, up from 2950 lbs.
STU Turbo Engine Cars Base Weight #28032wordingneutralSTU turbocharged engines now use base weight instead of minimum weight, with 3% DI increase applied to base weight.
AS Rear Trailing Arms #28007suspension & brakesneutralAS rear trailing arms may be replaced with tubular arms maintaining stock length and axle location purpose only.
AS Weight reduction for cars running iron heads #28010weightfasterAS Ford and GM full-prep cars get 200 lb weight reduction, up from 150 lb.
AS 05-10 Mustang with HR cam classification #28226cars addedneutral05-10 Ford Mustang Coupe GT 4.6L OHC classified AS with 3200 lbs minimum weight, HR cam restricted prep.
AS 10-15 Camaro Full Prep classification #28227cars addedneutralAS 10-15 Chevrolet Camaro Full Prep classified with 3400 lbs base weight, over 313 CID engine 3700 lbs maximum.
STU Request for an electronic throttle body #27342wordingneutralSTU cars with manual OEM throttle bodies may convert to OEM electronic throttle body of same inner diameter.
AS Request to add SMG to 9.1.6.B.1 AS Intent #27140cars addedneutralAS Spec Mustang (SMG) added as Restricted Prep class.
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.
STU Request to correct E&O advanced aerodynamics #27290wordingneutralSTU wing assembly wording corrected: no part higher than roof height.
AS Request Ride Height Clarification #26598wordingneutralAS class minimum ride height clarified to 5 inches measured at rocker panel, excluding seams and cladding.
STL Request clarification for manifold and throttle in STU #27004inductionfasterSTU alternate intake manifolds now allowed case-by-case instead of prohibited.
STU Remove -2mm penalty from SR20DET Nissan #26982enginefasterSTU Nissan SR20DET removes -2mm penalty in Table B.
STU Request clarification for manifold and throttle in STU #27004inductionfasterSTU alternate intake manifolds now allowed case-by-case instead of prohibited.
AS Request to Revert to 2017 Weights #25885weightfasterAS Ford Mustang (79-93) 313 CID and under loses 100 lbs to 3150; over 313 CID loses 100 lbs to 3450.
STL Request Restrictor Plate correction #26779inductionfasterSTL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate.
STU Request to clarify afterrmarket side skirts exhaust exit #26814wordingneutralSTU aftermarket side skirts must meet 3-inch ride height, no openings except jacks or side exhaust, no wider than fascias, not higher than door bottom, no chassis reinforcement.
STU Wheel Flare wording #26872wordingneutralSTU fender flare wording clarified: each fender may be flared up to 2" for tire clearance with 1% weight penalty.
STL Request Ride Height Clarification #26597wordingneutralSTL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld.
STU Request Ride Height Clarification #26597wordingneutralSTL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld.
STU Request to Use Japanese Mazda 13b Intake Manifold #25790inductionfasterSTU Mazda 13B Bridge Port may use ELITE ROTARY SHOP FD V2.0 intake manifold instead of stock.
STU Request Alternate Intake for Mazda MZR In a Rear Wheel Drive App. #26352inductionunclearSTU Mazda MZR LF/L3/L5 may use Goodwin Part #61-2510 intake manifold with stock or Acura throttle body.
STU E&O Suspension #26424wordingneutralSTU suspension rules clarified: alternate components from same manufacturer moved from section E to section D.
STU Revisit B20 VTEC #26530enginefasterSTU Honda/Acura B20 classified at 1973 cc, now permits VTEC B16 or B18 cylinder head and intake manifold.
STU Move Flared Fenders to STU Advanced Aero #26564aeroneutralSTU flared fenders up to 2" with 1% weight penalty moved from base to Advanced Aero rules.
STU TCA Civic SI E&O #26606tyres & wheelsslowerTCA Honda Civic Si (2017-) must run 37mm TIR maximum as of June 1, 2019.
STU S54 Spec line #26620wordingneutralSTU BMW S54B32 OEM reclassified from E46 designation, 3246 cc, 3300 lbs minimum weight.
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.
STU Request to Class Assignment for 2017 Civic #24287cars addedneutralHonda Civic Si 2017- classified STU at 1500cc, 2800 lbs minimum with OEM engine and bodywork.
STU Request to run E46 3246cc in STU #25126cars addedneutralSTU BMW E46 S54 OEM 3246cc added at 3300 lbs minimum weight, no Super Touring allowances.
STU Engine Classification for Rotary #25564wordingunclearSTU Mazda 13B and 13B Bridge Port may use RE or REW housings and intake with turbo removed.
STU K24/K20 Head Swap Clarification/Amendment #25899wordingneutralSTU Honda K24 may use intake part #s 17100-RRB-A00 or 17100-PRB-A10.
STU Request to Classify 12a Bridge Ported Rotary Engine #25985cars addedneutralSTU Mazda 12A Bridge Port engine classified at 2550 lbs minimum weight with specified carburetor induction options.
STU World Challenge Car Eligibility #26387wordingunclearSTU World Challenge car weight calculation method removed; new basis unclear from text provided.
STU Request a phone call for discussion regarding weight #26398inductionfasterSTU AWD cars no longer required to reduce restrictor 1 mm from table.
STU Advanced Aero E&O #26413aeroneutralSTU rear wing maximum cord length set to 12 inches, end plates to 72.0 square inches each.
AS SMG Mustang eligibility in American sedan #26224cars addedneutralAS Spec Mustang (SMG) newly classified with 107.1 wheelbase, 3.73 gears, 355mm front brakes, 300mm rear.
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.
STU Request to Equalize Direct Injected Turbo Cars #24890cars addedneutralSTU Honda K20C1 Turbo I4 1996cc added at 3025 lbs minimum weight with 36mm TIR.
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.