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BoP Lab / Buttonwillow Raceway Park

STL vs FC vs FF pace at Buttonwillow Raceway Park

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

Quickest here: STL 1:54.845 Gavin Wardle, Cal Club 2026 race · FC 1:45.137 Robert Armington, Cal Club 2026 qualifying · FF 1:51.118 Eric Poulsen, Cal Club 2025 race

1:441:461:481:501:521:541:561:588 rule changes between Cal Club 2025 and Cal Club 20268 ▾STL race best at Cal Club 2025: 1:55.682 (Nick Leverone)STL race best at Cal Club 2026: 1:54.845 (Gavin Wardle)STL qualifying best at Cal Club 2025: 1:54.963 (Nick Leverone)STL qualifying best at Cal Club 2026: 1:57.526 (Jared Korth)FC race best at Cal Club 2025: 1:48.522 (Paul MacFarlane)FC race best at Cal Club 2026: 1:45.314 (Robert Armington)FC qualifying best at Cal Club 2025: 1:50.067 (Paul MacFarlane)FC qualifying best at Cal Club 2026: 1:45.137 (Robert Armington)FF race best at Cal Club 2025: 1:51.118 (Eric Poulsen)FF race best at Cal Club 2026: 1:54.741 (Edward Erlandson)FF qualifying best at Cal Club 2025: 1:52.044 (Eric Poulsen)FF qualifying best at Cal Club 2026: 1:53.098 (Edward Erlandson)Cal Club 20252025Cal Club 20262026
STLFCFFsolid race · dashed qualifying · slower is lower
90%92%94%96%98%100%8 rule changes between Cal Club 2025 and Cal Club 20268 ▾STL race best at Cal Club 2025: 100.0% of STL's (Nick Leverone)STL race best at Cal Club 2026: 100.0% of STL's (Gavin Wardle)STL qualifying best at Cal Club 2025: 100.0% of STL's (Nick Leverone)STL qualifying best at Cal Club 2026: 100.0% of STL's (Jared Korth)FC race best at Cal Club 2025: 93.8% of STL's (Paul MacFarlane)FC race best at Cal Club 2026: 91.7% of STL's (Robert Armington)FC qualifying best at Cal Club 2025: 95.7% of STL's (Paul MacFarlane)FC qualifying best at Cal Club 2026: 89.5% of STL's (Robert Armington)FF race best at Cal Club 2025: 96.1% of STL's (Eric Poulsen)FF race best at Cal Club 2026: 99.9% of STL's (Edward Erlandson)FF qualifying best at Cal Club 2025: 97.5% of STL's (Eric Poulsen)FF qualifying best at Cal Club 2026: 96.2% of STL's (Edward Erlandson)Cal Club 20252025Cal Club 20262026
STLFCFFsolid race · dashed qualifying · each class's best lap as a share of STL's at the same event (the reference class, changeable above); 100% is level, higher is quicker
EventSTLFCFF
Qual bestRace bestTrapQual bestRace bestTrapvs STL% of STLQual bestRace bestTrapvs STL% of STL
Cal Club 2026 CALCL262026-02-211:57.526Jared 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%)1:45.137Robert Armington · fastest of 4 · top 4 within 25.0s-4.930s (-4.48%)1:45.314Robert Armington · fastest of 4 · top 4 within 12.9s-3.208s (-2.96%)147.5Bill Wallschlaeger+33.0 mph (+28.9%)-9.531squal -12.389s91.7%qual 89.5%1:53.098Edward Erlandson · fastest of 2+1.054s (+0.94%)1:54.741Edward Erlandson · fastest of 2+3.623s (+3.26%)133.7Edward Erlandson+19.0 mph (+16.5%)-0.104squal -4.428s99.9%qual 96.2%
8 rule changes (STL: 3, FC: 2, FF: 3)3 weight · 2 tyres & wheels · 3 wording · FC USF2000 Tube Frame may use Hewland LD200 4-speed H-pattern as alternative to Hewland JL-200 5-speed sequential. · FC F2000 Metrik ZF2 minimum weight reduced to 1220 lbs. · FF clarifies alternative tire eligibility for cars homologated 1989 or earlier with rocker arm or outboard suspension on all four corners. · STL minimum weights increase across all classes, 1300 cc gains 195 lbs to 1950, up to 1850 cc at 2500. · STL/STU Lotus weight reduced: Evora GT4 to 2700 lbs, Elise Cup R to 2250 lbs, Elise/Exige SC to 2450-2550 lbs. · FF adds rocker arm and outboard suspension cars optional bias ply and VFF tires; removes front-as-rear rule, adds mixing restrictions. · STL Mazda MX5 Challenge minimum weight now references GCR 9.1.7.1 instead of 2500 lbs; spec components removed, only alternative tires allowed. · FF allows older cars with rocker arm or outboard suspension to use bias ply slicks or VFF tires instead of radials.showhide
  • FC F2000 MZR Spec Line Clarity/Revision Requested #38927wordingneutralFC USF2000 Tube Frame may use Hewland LD200 4-speed H-pattern as alternative to Hewland JL-200 5-speed sequential.
  • FC Adjust F2000 Metrik ZF2 weight #39612weight -20 lbsfasterFC F2000 Metrik ZF2 minimum weight reduced to 1220 lbs.
  • FF Formula F Alternative Tire Rule Proposed Clarifications #39281wordingneutralFF clarifies alternative tire eligibility for cars homologated 1989 or earlier with rocker arm or outboard suspension on all four corners.
  • 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.
  • 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.
  • FF Page 228, FF tire rule 9.1.1.10.e #38251tyres & wheelsneutralFF adds rocker arm and outboard suspension cars optional bias ply and VFF tires; removes front-as-rear rule, adds mixing restrictions.
  • 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.
  • FF Formula F Proposal to Invite Older Cars Via a Tire Rule Change #37802tyres & wheelsfasterFF allows older cars with rocker arm or outboard suspension to use bias ply slicks or VFF tires instead of radials.
Cal Club 2025 CALCL252025-02-221:54.963Nick Leverone · fastest of 16 · top 5 within 3.3s1:55.682Nick Leverone · fastest of 17 · top 5 within 2.6s110.4Ryan Gutile1:50.067Paul MacFarlane · only car1:48.522Paul MacFarlane · only car114.4Paul MacFarlane-7.160squal -4.896s93.8%qual 95.7%1:52.044Eric Poulsen · only car1:51.118Eric Poulsen · only car114.7Eric Poulsen-4.564squal -2.919s96.1%qual 97.5%
83 earlier rule changes on record, in force before Cal Club 2025 (from 2019)12 induction · 9 weight · 7 cars added · 6 engine · 3 tyres & wheels · 2 aero · 44 wording · STL/STU: 90-05 Mazda Miata alternate front wheel hubs moved from General to specific part approval. · FC tire limit reduced to four dry and four wet for Regional/Major/Super Tour, eight for Runoffs. · FF and FC cars with sequential gearbox must add 10 lbs. to minimum weight, down from 25 lbs. · FF and FC cars with sequential gearbox must add 10 lbs. to minimum weight, down from 25 lbs. · FF Honda Fit allows Fast Forward 0.25mm oversize pistons PN FF800-110 as alternative; piston diameter spec clarified to 2.8835 inches. · FF VTEC activation valve must function; EGR blanking plate rule clarified with Fast Forward part numbers. · FC adds F2000 Metrik ZF2 with Ford Zetec engine and four-piston Brembo calipers as spec-line car. · 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. · F600 Rotax 494, 493, 593 engines now require single expansion chamber and pull starter; electric starter optional. · FF Honda Fit gains Fast Forward FF800-100 oversize piston ring pack option. · 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. · FC tire marking rule clarified: four dry and wet tires for Regionals, eight each for Runoffs; damaged tire replacement procedures revised. · USF2000 Van Diemen with Mazda MZR LF-DE 2.0L added as spec line car in FC; removed from FX. · STL ITA/ITS RX7 and 1985+ ITA/ITS/ITB/ITC vehicles clarified to conform to section 9.1.4.2 tire specifications. · FF Honda Fit engine adds Fast Forward part number alternatives for intake, exhaust, oil system, and scavenge pump components. · FC/FF PE3-8400 ECU monitor firmware version reduced from V3.04.50 to V3.04.35. · STL Spec MX5 clutch, wheels, and tyres specified: ACT 0000-02-5004-G6, 17x8 wheels, Toyo RR and RA1 235-40-17. · FC Ford Zetec Performance Electronics ECU model renamed PE-3 to PE3-8400; Monitor firmware updated to V3.04.50. · 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. · FC chassis/frame section reorganized: anti-intrusion panels between main tubes clarified, suspension mounting restrictions strengthened, firewall requirements reworded. · 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. · FC Zetec ECU requirements clarified: Pectel T2 or Performance PE-3 required with specific communications ports and SCCA tune-file/map. · FC composite anti-intrusion panels of non-uniform thickness limited to eight fasteners per side. · FC tire marking rules clarified: competitor responsible for declaring, marking, and logging tires with Tech before qualifying or race. · STL Spec MX-5 removes redundant specification line; no performance change. · 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. · FF block relief permitted only as needed to fit allowed crankshaft. · ST oil coolers and filters now explicitly allowed to be added or substituted; wording clarifies existing permissions. · FC Pinto engine loses 10 lbs to 1190; Pinto aluminum head loses 10 lbs to 1190; Zetec loses 10 lbs to 1210. · 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. · FF class cylinder head may now have optional coolant bleed line fitting to top of head for air release. · FF Honda LC1 ECU by HPD permitted effective 12/1/2020, must use HPD lambda sensor. · ST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch. · FC: Pectel T2 and Performance PE-3 ECU maps clarified; SCCA Club or 2013 Pro map required. · FC Zetec engine minimum weight increases 20 lbs to 1220 lbs. · FF Honda LC1 ECU implementation date changed from 3/1/2020 to pending availability of support materials. · 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. · 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. · STL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor. · FF alternator changes from not required to optional. · 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. · FF allows Honda HPD LC1 low-cost ECU with lambda sensor; E1 ECU no longer supported but existing units permitted if sealed. · FF rain tyres now allow Hoosier W3 Radial in addition to existing Hoosier Wet option. · STL Mazda Spec MX5 Challenge adds approved wheel part numbers 0000-04-5706-GM, 0000-04-5706-SL. · FC Zetec connecting rods now allow Eagle #CRS5483F3D in addition to original Ford. · FC adds Mahle #930169439 piston as alternate option to existing Ford, Sealed Power, and United Engine choices. · Mazda Spec MX-5 Challenge classified in STL with 2000cc displacement and 2500 lbs minimum weight. · STU alternate intake manifolds now allowed case-by-case instead of prohibited. · STL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate. · FC Wiseco piston and Crower connecting rod part numbers updated; minimum weight 976 grams. · STL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld. · 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. · FF Honda Fit permitted to use 0.25mm oversize pistons, cylinder honing increased to 73.315mm maximum. · FF heat shield rule clarified: thermal wrap allowed on manifold exterior if easily removable for inspection. · FF catch tank minimum capacity rules clarified: coolant catch tank now one U.S. pint minimum, oil catch tank one U.S. quart minimum. · FC Wiseco piston and Crower connecting rod assembly minimum weight increases from 555 to 976 grams. · 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
  • 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.
  • FC 9.1.1.10.h. FC Tire Rule #36533tyres & wheelsslowerFC tire limit reduced to four dry and four wet for Regional/Major/Super Tour, eight for Runoffs.
  • FC Change FF/FC Weight with Sequential Gearbox #36651weightfasterFF and FC cars with sequential gearbox must add 10 lbs. to minimum weight, down from 25 lbs.
  • FF Change FF/FC Weight with Sequential Gearbox #36651weightfasterFF and FC cars with sequential gearbox must add 10 lbs. to minimum weight, down from 25 lbs.
  • FF Alternative Oversize Honda Fit Pistons #37064wordingneutralFF Honda Fit allows Fast Forward 0.25mm oversize pistons PN FF800-110 as alternative; piston diameter spec clarified to 2.8835 inches.
  • FF Update to FF EGR Blanking Plate Rule #36633wordingneutralFF VTEC activation valve must function; EGR blanking plate rule clarified with Fast Forward part numbers.
  • FC Four Pot Calipers #35481cars addedneutralFC adds F2000 Metrik ZF2 with Ford Zetec engine and four-piston Brembo calipers as spec-line car.
  • 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.
  • FC Please correct omitted punctuation #34890engineneutralF600 Rotax 494, 493, 593 engines now require single expansion chamber and pull starter; electric starter optional.
  • FF Honda Fit Oversize Piston Rings #35305wordingneutralFF Honda Fit gains Fast Forward FF800-100 oversize piston ring pack option.
  • 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.
  • FC Review FC Runoffs Tire Marking Rule #34274wordingneutralFC tire marking rule clarified: four dry and wet tires for Regionals, eight each for Runoffs; damaged tire replacement procedures revised.
  • FC USF2000 Van Diemen with Mazda MZR LF-DE 2.0L in FC #34329cars addedneutralUSF2000 Van Diemen with Mazda MZR LF-DE 2.0L added as spec line car in FC; removed from FX.
  • 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.
  • FF Add Fast Forward Part Numbers for Honda Fit Engine #33752wordingneutralFF Honda Fit engine adds Fast Forward part number alternatives for intake, exhaust, oil system, and scavenge pump components.
  • FC E&O 9.1.1.B.16.j #33634wordingunclearFC/FF PE3-8400 ECU monitor firmware version reduced from V3.04.50 to V3.04.35.
  • 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.
  • FC Add Specification to Performance Electronics ECU for Ford Zetec #32761wordingneutralFC Ford Zetec Performance Electronics ECU model renamed PE-3 to PE3-8400; Monitor firmware updated to V3.04.50.
  • 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.
  • FC Clean up Chassis/Frame section #31867wordingneutralFC chassis/frame section reorganized: anti-intrusion panels between main tubes clarified, suspension mounting restrictions strengthened, firewall requirements reworded.
  • 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.
  • FC Clarify Zetec ECU requirements #31554wordingneutralFC Zetec ECU requirements clarified: Pectel T2 or Performance PE-3 required with specific communications ports and SCCA tune-file/map.
  • FC Clarify composite anti-intrusion panel language #31426wordingneutralFC composite anti-intrusion panels of non-uniform thickness limited to eight fasteners per side.
  • FC Clarify tire marking requirements #31455wordingneutralFC tire marking rules clarified: competitor responsible for declaring, marking, and logging tires with Tech before qualifying or race.
  • STL Request to clean up Spec MX-5 Redundancy #31069wordingneutralSTL Spec MX-5 removes redundant specification line; no performance change.
  • STL VW Engine Request #30625engineslowerSTL Volkswagen 2.0L TFSI 1984cc classified with turbocharger removal required, meeting all other STL specs.
  • STL Solstice Ride Height #30183wordingneutralSTL Pontiac Solstice/Saturn Sky allowed 4" ride height.
  • 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.
  • FF Kent crankshaft clarification #30426wordingneutralFF block relief permitted only as needed to fit allowed crankshaft.
  • 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.
  • FC Request for FC Weight Change #30171weightfasterFC Pinto engine loses 10 lbs to 1190; Pinto aluminum head loses 10 lbs to 1190; Zetec loses 10 lbs to 1210.
  • 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.
  • FF Allow Optional Coolant Bleed Line to Correct a Known Problem #29673wordingneutralFF class cylinder head may now have optional coolant bleed line fitting to top of head for air release.
  • FF Clarification regarding Honda LC1 ECU implementation date #29684wordingneutralFF Honda LC1 ECU by HPD permitted effective 12/1/2020, must use HPD lambda sensor.
  • STL Request clarification on wing measurement #29640aeroneutralST aero devices and reference areas now include end plates but exclude fasteners protruding over 1/2 inch.
  • FC Urgent: SCCA PE3 map unsuitable #29475wordingneutralFC: Pectel T2 and Performance PE-3 ECU maps clarified; SCCA Club or 2013 Pro map required.
  • FC Request for weight adjustments to equalize FC competition. #28888weightslowerFC Zetec engine minimum weight increases 20 lbs to 1220 lbs.
  • FF Clarification regarding Honda LC1 ECU implementation #29135wordingneutralFF Honda LC1 ECU implementation date changed from 3/1/2020 to pending availability of support materials.
  • 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.
  • 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.
  • STL STL Honda B18 restrictor changes #28794inductionfasterSTL Honda B18 restrictor reduced from 54mm to 53mm flat plate; B18C1 added with 54mm restrictor.
  • FF E&O FF Kent Engine alternator language #28204wordingneutralFF alternator changes from not required to optional.
  • 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.
  • FF Honda Racing HPD low cost ECU proposal #27563engineneutralFF allows Honda HPD LC1 low-cost ECU with lambda sensor; E1 ECU no longer supported but existing units permitted if sealed.
  • FF Update rain tire designation #28443tyres & wheelsneutralFF rain tyres now allow Hoosier W3 Radial in addition to existing Hoosier Wet option.
  • 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.
  • FC Request for Better Zetec Connecting Rods #27710wordingneutralFC Zetec connecting rods now allow Eagle #CRS5483F3D in addition to original Ford.
  • FC Add Alternate Piston #27795wordingneutralFC adds Mahle #930169439 piston as alternate option to existing Ford, Sealed Power, and United Engine choices.
  • 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.
  • STL Request clarification for manifold and throttle in STU #27004inductionfasterSTU alternate intake manifolds now allowed case-by-case instead of prohibited.
  • STL Request Restrictor Plate correction #26779inductionfasterSTL Acura/Honda B18 except C engine restrictor increases from 53mm to 54mm flat plate.
  • FC E&O Wiseco piston and Crower connecting rod #26659wordingneutralFC Wiseco piston and Crower connecting rod part numbers updated; minimum weight 976 grams.
  • STL Request Ride Height Clarification #26597wordingneutralSTL and STU ride height measurement clarified: without driver, at rocker panel lowest point, excluding pinch weld.
  • STL Request to Allow VW 1.8L Engine #25614cars addedneutralSTL adds VW 1.8L R4 20VT 1781cc, 1 minimum weight, turbo removed permitted.
  • 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.
  • FF Request for Oversize Honda Fit Pistons #25810enginefasterFF Honda Fit permitted to use 0.25mm oversize pistons, cylinder honing increased to 73.315mm maximum.
  • FF Heat Shield - Fit Intake #26102wordingneutralFF heat shield rule clarified: thermal wrap allowed on manifold exterior if easily removable for inspection.
  • FF Request catch cans/tanks clarification #26158wordingneutralFF catch tank minimum capacity rules clarified: coolant catch tank now one U.S. pint minimum, oil catch tank one U.S. quart minimum.
  • FC Correct Wiseco piston and connecting rod #25809weightslowerFC Wiseco piston and Crower connecting rod assembly minimum weight increases from 555 to 976 grams.
  • 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 STL" is the class's best as a share of STL'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 STL'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.