BoP Lab / Classes / STU
STU vs P2 vs SM vs FV pace at every track
Lap times across years say as much about the weather as the class. % of STU is each class's best lap as a share of STU's on the same day, so the conditions drop out: 100% is level, less is quicker, and a move in it is the class getting faster or slower against the field.
Closest to the field: STU 100.0% of STU Eric Heinrich, Daytona International Speedway Runoffs 2015 race · P2 84.3% of STU Jeff Shafer, Indianapolis Motor Speedway Runoffs 2017 qualifying · SM 91.3% of STU Travis Wiley, Virginia International Raceway Runoffs 2022 race · FV 90.6% of STU Andrew Whitston, Virginia International Raceway Runoffs 2022 race
| Event | STU | P2 | SM | FV | ||||||||||||||||
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| Qual best | Race best | Trap | Qual best | Race best | Trap | vs STU | % of STU | Qual best | Race best | Trap | vs STU | % of STU | Qual best | Race best | Trap | vs STU | % of STU | |||
| Road America Runoffs 20262026-09-28 | 2:24.912Richard Astacio · fastest of 17 · top 5 within 2.6s+1.829s (+1.28%) | 2:26.416Richard Astacio · fastest of 16 · top 5 within 1.5s+1.919s (+1.33%) | 145.1Hugh Stewart+0.8 mph (+0.5%) | 2:10.606Greg Gyann · fastest of 11 · top 5 within 5.3s+3.201s (+2.51%) | 2:09.441Mike Reupert · fastest of 11 · top 5 within 4.2s+1.119s (+0.87%) | 155.0Matt Strand+2.4 mph (+1.6%) | -16.975squal -14.306s | 88.4%qual 90.1% | 2:42.173Brett Kowalski · fastest of 34 · top 5 within 0.3s-0.938s (-0.58%) | 2:42.725Francisco Barroso · fastest of 35 · top 5 within 0.2s-1.705s (-1.04%) | 119.6Wyatt Couch+0.3 mph (+0.3%) | +16.309squal +17.261s | 111.1%qual 111.9% | 2:46.536Zachary Whitston · fastest of 37 · top 5 within 1.7s+2.435s (+1.48%) | 2:45.272Brian Farnham · fastest of 34 · top 5 within 1.3s-1.464s (-0.88%) | 117.4Rick Shields+0.2 mph (+0.1%) | +18.856squal +21.624s | 112.9%qual 114.9% | ||
17 rule changes (STU: 15, SM: 2)4 cars added · 3 weight · 2 induction · 2 tyres & wheels · 5 wording · 1 other · GT3U wheel and tyre options clarified: 15x7 with 225 section at +275 lbs; 15x9 with 245 section at +275 lbs plus 1.5%; 16–18x9 with 245 section at +275 lbs plus 3.0%. · SM/SMX Mazda rear toe link part number revised from 0000-04-5361426 to 0000-04-5361. · STU cars at or under 2,825 lbs minimum weight limited to 8-inch wheels; over 2,825 lbs limited to 9-inch wheels. · STU GT3U minimum weight increases from GT3 race weight plus 225 to plus 275 pounds; 2.0L unrestricted engines add 75 lbs. · STU adds BMW M50B20TU engine, 1991 cc, minimum weight per chart, must meet all STU engine regulations. · STL, STU weight calculation procedure clarified: positive percentages added first, negative subtracted second, then fixed weights applied. · STU Honda K20C1 Turbo I4 turbo restrictor increases from 35mm to 36mm TIR. · STU GT86 Cup car must meet 2022 Toyota GR Cup rules, tires maximum 245 section width. · SM/SMX part number 0000-10-6900 replaced with 0000-06-5016-KT in GCR 9.1.7.C.1.j.1.c. · STU Mazda Renesis Street Port added to Table B with 2450 lbs minimum weight and 70mm throttle body options. · STU eliminates 33 and 34 mm inlet restrictor options, removing minimum weights of 2380 and 2525 lbs. · STU Mazda MZR engines may now use Fab 9 Elite NC MX5 Performance Intake manifold as alternative option. · STU Mazda MZR (LF, L3, L5) Turbo added; Goodwin intake removed, Jack Spania Racing 70 mm intake and Fab9 Tuning bottom-mount turbo kit approved. · STU 36mm restrictor revised to 2830 cc, 37mm to 2980 cc. · STU removes 275 tire option and 2% weight adder for cars over 3150 lbs; maximum section width now 245. · STU Honda K20 and K24 engines lose 2% weight penalty; minimum weight now per chart only. · STU Honda K24 engine swap weight increases by 2 percent, effective November 1, 2025.show
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| Road America Runoffs 20252025-09-29 | 2:23.083Peter Cunningham · fastest of 16 · top 5 within 2.6s-3.144s (-2.15%) | 2:24.497Chip Herr · fastest of 15 · top 5 within 3.8s-1.327s (-0.91%) | 144.3Chip Herr-1.0 mph (-0.7%) | 2:43.111Bobby Gossett · fastest of 32 · top 5 within 0.3s+2.005s (+1.24%) | 2:44.430Kyle Greenhill · fastest of 28 · top 5 within 0.3s+2.944s (+1.82%) | 119.3Francisco Barroso-0.6 mph (-0.5%) | +19.933squal +20.028s | 113.8%qual 114.0% | 2:44.101Andrew Abbott · fastest of 34 · top 5 within 1.3s+1.458s (+0.90%) | 2:46.736Zachary Whitston · fastest of 29 · top 5 within 0.6s+1.902s (+1.15%) | 117.2Zachary Whitston+0.7 mph (+0.6%) | +22.239squal +21.018s | 115.4%qual 114.7% | |||||||
23 rule changes (STU: 18, P2: 1, SM: 4)7 weight · 4 cars added · 3 tyres & wheels · 2 engine · 1 induction · 5 wording · 1 other · STU Lotus Elise SC and Exige SC weight reduced from 2450 to 2250 lbs. · STU-TCR gains GT3 TCR spec lines; 275 tyre option now costs 150 lb adder, up from 100 lb. · Lotus Evora GT4 minimum weight drops to 2700 lbs; Elise Cup R to 2250 lbs; Elise SC and Exige SC to 2450–2550 lbs. · STU 2.8–3.2L N/A engines now permit 245 max tyre width; over 3150 lbs cars may run 275 with 2% weight penalty. · STU Mazda MZR intake manifold now allows Goodwin 61-2510 or Gato Performance 31972. · STU Honda JDM H23a added, 2259 cc, minimum weight per chart, must meet ST engine regulations. · SMX drivers must submit data acquisition files on time or face suspension and $250 fine. · SMX penalty language clarified: level 1 and 3 infractions may carry $1,000 fines, level 2 and 4 may carry $500 fines. · SM tire marking rules clarified: one Hoosier SM 7.5 P205/50/ZR17 set per Super Tour weekend, impound after first dry session, damaged tires may be replaced with used tires only. · STU wheels capped at 18 inches diameter; under 2,850 lbs max 8 inches wide, over 2,850 lbs max 9 inches wide. · STU-GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tyre options clarified with weight adjustments. · STU BMW N54/N55 3.0 classified at chart plus 3% minimum weight; N54 twin turbo not allowed. · STU Mini Cooper S SC pulley diameter reduced to 2.185 inches. · STU Honda K20C1 Turbo I4 exempted from 3% direct injection weight adder. · STU GT3U minimum weight increases 150 pounds to 250 pounds. · STU Audi 1.8T Wagon removed; Porsche 944 1800cc weight to Chart, turbo inlet restrictor deleted. · STU-GT3 reclassified as STU-GT3U, effective 1 January 2026. · STU GT3 TCR may run 275-wide DOT tires with 100 lb weight penalty; A compound prohibited at 275. · P2 2000 cc Pinto engine car minimum weight set to 1335 lbs. · SMX OE instrument cluster must stay unmodified and connected; aftermarket dash allowed if wiring only re-routed; alternate gauges now permitted; foot pedal comfort mods allowed without relocation. · STL STU Mazda Miata alternate front hubs Mazda Motorsports Development Part #0000-04-5HUB-S1 approved. · STU BMW N54/N55 turbo inlet restrictors now required per GCR definition; twin turbo conversion to single turbo clarified. · STU Mini Cooper S SC: 1900 stock pulley spec to 2.565 diameter; 2100 now permits 2.285 diameter pulley.show
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| Road America Runoffs 20242024-10-01 | 2:26.227Thomas Noble · fastest of 18 · top 5 within 2.3s-1.656s (-1.12%) | 2:25.824Thomas Noble · fastest of 17 · top 5 within 2.4s-2.586s (-1.74%) | 145.3Thomas Noble+1.1 mph (+0.8%) | 2:07.405Bart Wolf · fastest of 14 · top 5 within 3.0s-1.109s (-0.86%) | 2:08.322Bart Wolf · fastest of 13 · top 5 within 0.6s-1.471s (-1.13%) | 152.5Lucian Pancea-0.6 mph (-0.4%) | -17.502squal -18.822s | 88.0%qual 87.1% | 2:41.106Ethan Goulart · fastest of 49 · top 5 within 0.5s-1.103s (-0.68%) | 2:41.486Brett Kowalski · fastest of 43 · top 5 within 0.3s-2.262s (-1.38%) | 119.9Alex Bertagnoli-1.4 mph (-1.2%) | +15.662squal +14.879s | 110.7%qual 110.2% | 2:42.643Andrew Whitston · fastest of 27 · top 5 within 2.3s-1.351s (-0.82%) | 2:44.834Andrew Abbott · fastest of 27 · top 5 within 0.9s-0.982s (-0.59%) | 116.5Brian Farnham-0.7 mph (-0.6%) | +19.010squal +16.416s | 113.0%qual 111.2% | ||
15 rule changes (STU: 4, P2: 5, SM: 4, FV: 2)2 aero · 2 engine · 1 induction · 8 wording · 2 other · FV ferrous rotor must not be cross-drilled; pad cleaning grooves limit unchanged at three per side. · SMX Spec MX-5 camera requirement: non-functioning recorder now will instead of may warrant penalty or disqualification. · SM and SMX must run latest AIM Data Logger Spec MX-5 ECU Protocol, effective 2024-09-01. · SMX Mazda MX-5 OE versus OEM definitions clarified in GCR section 9.1.7.1; wording change only. · SM and SMX now allow an alternate shifter bushing at the bottom of the shift lever. · STU RWD turbo cars no longer required to reduce inlet restrictor by 1 mm from table minimum. · P2 Spec Line E engine notes clarify oil system, ECU, and exhaust remain unrestricted; wording only. · P2 FIA Group CN notes clarify V de V European Proto Endurance Challenge bodywork, rear diffuser, wing, wheels, assisted shifting allowed; regulations link provided. · STU Mini Cooper S SC gains alternate LEAP OMICRON hood scoop part LEP-OMICRON3 as permitted option. · STU BMW S54 B32 OEM dry sump oiling system now permitted. · STL and STU now permit electric power steering pumps, OEM electric-assisted steering, or column-mounted electric steering assist systems. · P2 AMAC and related cars: clarified B.1 modified engine range to 2008 and older stock engines only, with 38mm restrictor and 1025 lbs minimum weight. · P2 Suzuki GSX-R1000 engine: 2007–2008 crankcase 11300-21860 may be replaced with 2016–2019 GSX-S1000 part 11301-04840. · FV front wheel bearings wording clarified; specification unchanged. · P2 Table 1 engine date ranges clarified: Stock Engine replaced with specific marques Suzuki, Yamaha, Honda, BMW for 2009-newer and 2008-older rows.show
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| Virginia International Raceway Runoffs 20232023-09-23 | 2:00.389Johan Schwartz · fastest of 13 · top 5 within 2.3s-0.226s (-0.19%) | 2:02.302Mark Liller · fastest of 14 · top 5 within 1.6s-30.055s (-19.73%) | 144.0Mark Liller+0.1 mph (+0.1%) | 1:48.590Greg Gyann · fastest of 12 · top 5 within 1.7s+1.024s (+0.95%) | 1:48.829Lucian Pancea · fastest of 11 · top 5 within 0.9s-27.005s (-19.88%) | 150.9Lucian Pancea-0.2 mph (-0.2%) | -13.473squal -11.799s | 89.0%qual 90.2% | 2:14.986Danny Steyn · fastest of 52 · top 5 within 0.1s+0.322s (+0.24%) | 2:16.229Julian DaCosta · fastest of 46 · top 5 within 0.3s-2.878s (-2.07%) | 120.3Jim Drago+1.1 mph (+0.9%) | +13.927squal +14.597s | 111.4%qual 112.1% | 2:15.639Andrew Whitston · fastest of 27 · top 5 within 1.4s+0.523s (+0.39%) | 2:16.611Andrew Abbott · fastest of 23 · top 5 within 1.6s-1.482s (-1.07%) | 115.6Brian Farnham-0.2 mph (-0.2%) | +14.309squal +15.250s | 111.7%qual 112.7% | ||
12 rule changes (STU: 3, P2: 8, SM: 1)3 engine · 2 cars added · 2 weight · 5 wording · STU adds 2022 Toyota GR Cup and GR86 Cup, both 2387cc, 2700 lbs, 18-inch wheels, 245/620R18 slicks. · P2 minimum side body height must equal front axle centerline height, viewed from side. · P2 closed cockpit single seat cars now prohibited unless Table 1 spec line permits. · P2 engine table spec line B.1 redundant effective date language removed and table updated. · P2 motorcycle restrictor reduced 35mm to 34mm for 2011+ Kawasaki; minimum weights increased to 1100 lbs for 2009+ engines; cockpit length corrected to 23.622 inches. · STU Mazda BP5A now classified at 1839 cc displacement, 2510 lbs minimum weight, alternate intake manifold permitted. · STU minimum weights adjusted: 2450 cc to 2595 lbs, 2600 cc to 2710 lbs. · Sebeco NP01-EVO and Elan NP01 added to P2 with Mazda 2.0L MZR, no restrictor required, 1600 lb minimum weight. · P2 Radical SR3/SR4, Cup, Club Sport, Pro-Sport, PR6: assisted shifting clarified from A-assisted to Aassisted; Cup engine restrictor changed from Unrestricted to Not required. · P2 chassis now allows composite materials partially installed; anti-intrusion panels attachment simplified; Stohr and converted models clarified. · SM Mazda MX-5 Miata 01-05 minimum weight rises to 2450 lbs, or 2465 with alternate bore.show
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| Virginia International Raceway Runoffs 20222022-09-24 | 2:00.615Johan Schwartz · fastest of 21 · top 5 within 2.6s+0.667s (+0.56%) | 2:32.357Mark Liller · fastest of 19 · top 5 within 4.3s+31.874s (+26.46%) | 143.9Johan Schwartz+0.1 mph (+0.1%) | 1:47.566Tim Day Jr · fastest of 12 · top 5 within 3.0s-1.545s (-1.42%) | 2:15.834Greg Gyann · fastest of 12 · top 5 within 10.1s+25.576s (+23.20%) | 151.1Robert Iversen+1.8 mph (+1.2%) | -16.523squal -13.049s | 89.2%qual 89.2% | 2:14.664Danny Steyn · fastest of 60 · top 5 within 0.2s+0.112s (+0.08%) | 2:19.107Travis Wiley · fastest of 58 · top 5 within 0.9s+2.648s (+1.94%) | 119.2Jonathan Neudorf-0.6 mph (-0.5%) | -13.250squal +14.049s | 91.3%qual 111.6% | 2:15.116Brian Farnham · fastest of 29 · top 5 within 1.1s-0.596s (-0.44%) | 2:18.093Andrew Whitston · fastest of 28 · top 5 within 1.2s-0.196s (-0.14%) | 115.8Jonathan Weisheit+1.1 mph (+0.9%) | -14.264squal +14.501s | 90.6%qual 112.0% | ||
36 rule changes (STU: 21, P2: 10, SM: 1, FV: 4)7 weight · 6 engine · 3 cars added · 2 aero · 2 tyres & wheels · 15 wording · 1 other · STU Mazda 13B Turbo added as Chart Limited displacement, streetport only, alternative turbos only. · STU OEM louver vents no longer count against vent allowance or 200 square inch limit. · STU non-4-valve engines gain 9% base engine weight reduction allowance; 2400cc minimum weight drops 1 lb to 2595. · STU normally-aspirated engines 2976cc–3200cc with single throttle body lose 10% base engine weight reduction allowance. · ST removes redundant language about engine balance shaft removal and alternate pulley installation. · P2 chassis construction clarified: full composite allowed; partial composite must roll without composite parts installed. · P2 classification wording cleaned up in GCR section 9.1.8.C and GCR contents. · STU cars that qualified for 9 inch wheels in 2021 may continue running them through 2022 only. · STU splitter definition clarified: must attach to lowest point of front, have no vertical deviations. · P2 Oldsmobile cam rules correct spelling from 'after market' to 'aftermarket' in two sections. · SM Majors must run authorized Penske shock and mount; Regional competitors not required until further evaluation. · STU BMW E36 M3 (95-99) S52B32 minimum weight cut to 3110 lbs from 3200, displacement to 3152 cc. · STU BMW S50B32 Euro maximum displacement 3201 cc, minimum weight 3300 lbs, permits 0.040 overbore and 0.5 compression increase. · ST engine swap origin rule narrowed: North America changed to United States only for case-by-case approval. · STU Honda CRX 84-91 and Civic Del Sol 93-97 both ineligible for front-wheel-drive weight reductions. · STU wheel width rule clarified: under 2950 lbs uses max 8.0 inches, 2950 lbs and over uses max 9.0 inches. · STU single-throttle body cars get lower minimum weights: 2450cc to 2596 lbs, 2500cc to 2635 lbs, 2550cc to 2675 lbs. · FV connecting rod options expanded to include BrianCrower part BC6417 and Newland Group part 4M113077. · FV connecting rods minimum weight 425.0 grams, center-to-center length 130 +0.10/-0.25 mm; Crower, BrianCrower, Newland Group parts allowed if meeting specs. · P2 adds Beasley B2 at 1350 lbs with Mazda 12A, 40.5mm venturi, and up to 16.5in wing chord. · P2 wings: terminology change from 'cord' to 'chord', and 'only' removed from Bobsy and Jondal notes. · P2 Converted F5 cars renamed F500, must retain F500 suspension, minimum width 55 inches. · STU single throttle body weight reduction removed; minimum weights revised down to 2990 lbs at 3000cc from 3300 lbs. · STU Audi A4 1.8T minimum weight fixed to 3050 lbs, K04 turbo removed, VF30 with 35mm restrictor required; Porsche 944 1800 weight fixed to 3050 lbs, VW/Audi 1.8L engine removed, 35mm inlet restrictor required. · STL and STU Improved Touring vehicles must now conform to section 9.1.4 Tires & Wheels. · P2 motorcycle engines gain 5cc to 1505cc max, two-stroke gains 5cc to 1205cc max, automotive engines add 50 lbs minimum weight to 1350 lbs. · STU engines may delete balance shafts and plug openings; alternate pulleys or gears allowed only for timing belt or chain operation. · STU hood vents now allow louvers within 200 square inches. · FV Crower connecting rods SP93280B and BC6417 allowed as direct replacement, must meet OEM minimum weight. · P2 Control Area definition clarified: rectangular zone from rear edge of front tires to front edge of rear tires, full car width. · STU adds Honda K23 with 2354 cc displacement and chart minimum weight, K24 block allowed with K23 internals and head. · STU Honda K23 relaxes internal engine requirement, now needs only K23 crankshaft. · STL/STU intake manifold and cylinder head porting clarified as free; intake and exhaust porting wording removed. · FV allows Crower SP93280B and Brian Crower Racing Rods connecting rods as direct replacements, matching OEM minimum weight. · P2 specification line B.1 engine table entry amended; details of change not provided in excerpt. · P2 Control Area definition clarified: rear tire edge and front tire edge bounds, car's lower surface width, floor extensions and aerodynamic attachments included, vertical structures prohibited.show
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| Indianapolis Motor Speedway Runoffs 20212021-09-25 | 1:47.078Joe Moser · fastest of 30 · top 5 within 2.0s-1.843s (-1.69%) | 1:47.441Joe Moser · fastest of 28 · top 5 within 1.8s-1.946s (-1.78%) | 146.9Kip VanSteenburg | 1:33.235Tim Day Jr · fastest of 16 · top 5 within 3.3s+1.409s (+1.53%) | 1:35.322Tim Day Jr · fastest of 10 · top 5 within 4.8s+2.841s (+3.07%) | 150.3Robert Iversen | -12.119squal -13.843s | 88.7%qual 87.1% | 1:57.695Brian Henderson · fastest of 90 · top 5 within 0.5s-0.611s (-0.52%) | 1:58.837Brian Henderson · fastest of 88 · top 5 within 0.3s-0.263s (-0.22%) | 119.8Kyle Greenhill | +11.396squal +10.617s | 110.6%qual 109.9% | 1:57.479Andrew Whitston · fastest of 48 · top 5 within 0.8s+1.720s (+1.49%) | 1:57.234Alex Scaler · fastest of 47 · top 5 within 1.0s+1.311s (+1.13%) | 124.0Mark Edwards | +9.793squal +10.401s | 109.1%qual 109.7% | ||
21 rule changes (STU: 12, P2: 8, SM: 1)3 cars added · 3 engine · 1 aero · 1 suspension & brakes · 1 weight · 11 wording · 1 other · P2 CN Honda K20A-FD2 engine rebuild clarified: balancing, porting, polishing prohibited; valve jobs and honing must follow factory procedures. · P2 Converted F5 cars must retain F5 suspension and meet P2 non-spec requirements except minimum width is 55 inches. · P2 minimum body width clarified: cannot extend inward beyond vertical plane through tire centerlines. · STU fender flare wording clarified: flare of exterior contour may not change wheel opening size, location or shape from side view. · STU Mazda 12A Bridgeport weight reduced from 2550 lbs to 2350 lbs. · P2 tonneau covers now allowed to meet minimum dimensions; cockpit equipment attachment wording clarified. · P2 removes effective date 01/01/2021 from six car spec lines in Table 1. · P2 engine specs B.1, B.2, B.3 limited to maximum 4 valves per cylinder. · STU fender flare rules clarified: maximum 2 inches total, must cover tire contact patch from above, cannot alter body configuration or wheel opening geometry. · SM adds procedure for CRB-approved obsolete parts and BOP testing in sanctioned events with point forfeiture. · STU Honda S2000 now allows F20/F22 K24 crankshaft with chart weight for achieved displacement. · ST oil coolers and filters now explicitly listed as addable or substitutable parts in vents and breathers section. · P2 adds new spec line for 2-cycle 3-cylinder engine up to 820cc with 10 front, 14–15 rear wheel width. · ST 90-05 Mazda Miata allowed alternate front wheel hub Mazda Motorsports Development Part #0000-04-5HUB-S1. · ST cars may now relocate ABS actuation hardware and wiring anywhere in the engine compartment. · STU Porsche PDK automatic transmission limited to 8 forward speeds; sequential DCT systems require 3.5% minimum weight increase. · STU Mazda 13B Street Port 2400 removes choke location rule, allows auto-type 2bbl with any dual-Y manifold. · STU driveshaft and half-shafts now explicitly permitted in steel or aluminum, removing OEM material requirement. · STU Mazda 13B Spec and Bridge Port removed; Street Port added at 2400 lbs minimum weight. · P2 motorcycle-engine cars: 2009+ stock 37mm restrictor, 2008- stock 35mm, modified 1075 lbs. Honda K20A 50mm restrictor. Various spec cars: restrictors increased or decreased 0.5–3mm. · ST aero devices and reference areas must include end plates, exclude fasteners under 1/2" protrusion.show
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| Road America Runoffs 20202020-10-02 | 2:27.883David Fiorelli · fastest of 14 · top 5 within 4.1s | 2:28.410Anthony Geraci · fastest of 14 · top 5 within 3.1s | 144.2David Fiorelli | 2:08.514Robert Iversen · fastest of 12 · top 5 within 3.0s | 2:09.793Robert Iversen · fastest of 12 · top 5 within 3.9s | 153.1Robert Iversen | -18.617squal -19.369s | 87.5%qual 86.9% | 2:42.209Kyle Greenhill · fastest of 77 · top 5 within 0.5s | 2:43.748Preston Pardus · fastest of 75 · top 5 within 1.0s | 121.3Kyle Greenhill | +15.338squal +14.326s | 110.3%qual 109.7% | 2:43.994Hunter Phelps-Barron · fastest of 28 · top 5 within 0.6s | 2:45.816Alex Scaler · fastest of 24 · top 5 within 1.5s | 117.1Hunter Phelps-Barron | +17.406squal +16.111s | 111.7%qual 110.9% | ||
31 rule changes (STU: 17, P2: 6, SM: 2, FV: 6)5 engine · 5 tyres & wheels · 4 cars added · 2 weight · 1 aero · 1 induction · 1 suspension & brakes · 9 wording · 3 other · SM allows aftermarket radiators in original location with stock OEM cooling fan, and permits 1990-1997 cars to install upper radiator seal NA75-50-OK7A. · P2 rear wing rules clarified: standard wing 6×12 inches, end plates 14-inch square; alternate 1-meter formula wing 110cm wide, 9×18 inches, end plates 14×18 inches. · STU fender flare rule reworded: now per-corner up to 2" total, 1% weight penalty applies to entire modification. · SM rear brake caliper may use single bracket under upper retaining bolt head to prevent pin failure. · STL and STU clarify weight adjustment calculation order: engine adjustments first, then chassis percentage additions, subtractions, and fixed pounds. · STL STU rear wing Gurney flap terminology clarified from wicker to Gurney flap in mounting and chord rules. · FV now permits 4 bolt wheels in addition to existing specifications. · FV now allows 4-bolt pattern wheels in addition to existing specifications. · STU request for alternate intake manifold denied; no change to rules. · GT3 and STU add Borg-Warner EFR6258 turbocharger to approved turbo lists. · STU large displacement turbo engines limited by GCR turbo list; no BoP change granted. · STU sequential shifters referred to Board of Directors for approval; no rule change effective. · Elan NP01 added to P2 Table 1 as Spec Line car with 2000cc displacement and 42mm restrictor. · STU Mazda 13B Bridge Port and Street Port added with 2550 lbs and 2250 lbs minimum weight respectively. · P2 Enterprises Sports Racer now permits 55mm flat plate intake restrictor Part # WM303013 as alternative to SIR. · P2 Enterprise Sports Racer 2.3L engine must use SIR or Flat Plate restrictor meeting peak horsepower, sized in whole or 0.5mm increments. · STU Honda S2000 gains HKS Supercharger kits 12001-AH006 and 12001-AH010 as allowed options. · STU Lotus Elise Cup R and SC Exige SC gain 100 lbs minimum weight to 2300, 2500. · STU Volkswagen GTI/GLI MK5 and Jetta Mk4 may now install turbo inlet restrictor in OEM housing, per TIR spec. · STU Honda K20C1 Turbo I4 restrictor reduces from 36mm to 35mm. · STU GM Ecotech LNF now permitted without turbo, 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 to original. · FV rain tyre changes to Hoosier #44266 22.5 x 5.0 x 15 WET or W3. · P2 electronic throttle control wording clarified: ETC permitted if stock ECU throttle pedal activates original throttle shaft mechanism. · STU vehicles over 2951 lbs base weight may use 9 inch wide wheels, changed from 2950 lbs. · STU turbocharged engines now use base weight instead of minimum weight; DFI cars add 3% to base weight. · FV allows non-spec Hoosier tyres at Regional races only; Majors, Super Tour, and Runoffs require spec tyres from 1/1/2020. · Formula Vee now allows 22.5 x 5.5 x 15 rear tires on front axle; rain tire mandated as Hoosier #44266 22.5 x 5.0 x 15 from 1/1/2020. · P2 adds BMW to permitted motorcycle-based engines alongside Kawasaki, Suzuki, Yamaha, Honda. · FV wheels may now be 15-inch 4.5J steel VW with same 5-bolt pattern as standard 4J, within track limits. · STU allows OEM electronic throttle bodies, manual conversion, cam changes, and manual-to-electronic conversion with same inner diameter.show
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| Virginia International Raceway Runoffs 20192019-10-05 | 1:59.948Kevin Boehm · fastest of 25 · top 5 within 3.5s | 2:00.483Kevin Boehm · fastest of 25 · top 5 within 2.5s | 143.8Kevin Boehm | 1:49.111Robert Iversen · fastest of 14 · top 5 within 0.8s | 1:50.258Greg Gyann · fastest of 13 · top 5 within 0.4s | 149.4Robert Iversen | -10.225squal -10.837s | 91.5%qual 91.0% | 2:14.552Todd Buras · fastest of 60 · top 5 within 0.2s | 2:16.459Elivan Goulart · fastest of 56 · top 5 within 0.4s | 119.8Jim Drago | +15.976squal +14.604s | 113.3%qual 112.2% | 2:15.712Andrew Whitston · fastest of 26 · top 5 within 1.5s | 2:18.289Zachary Whitston · fastest of 19 · top 5 within 0.4s | 114.8Roger Siebenaler | +17.806squal +15.764s | 114.8%qual 113.1% | ||
41 rule changes (STU: 22, P2: 9, SM: 4, FV: 6)8 engine · 6 cars added · 4 induction · 3 aero · 2 weight · 1 suspension & brakes · 1 tyres & wheels · 13 wording · 3 other · FV exhaust exit opening repositioned: minimum one inch, maximum four inches behind rear body. · P2 Honda K20A-FD2 non-composite chassis intake restrictor note clarified; restrictor implementation date removed. · FV allows fifteen-inch steel wheels at 4J or 4.5J width, standard VW sedan or within track dimensions. · P2 motorcycle engines: Stock restrictor to 35mm, Modified to 34mm; weights up to 1025 and 1125 lbs respectively. B.5 restrictor to 33mm, weight to 1185 lbs. · STU wing assembly wording corrected: no part may be higher than roof height. · P2 cars limited to power application on maximum two wheels. · STU Nissan SR20DET removes -2mm penalty from Table B. · STU allows alternate intake manifolds on case-by-case basis; stock throttle device and manifold otherwise required. · P2 Enterprise minimum weight increased to 1375 lbs.; peak horsepower of sealed ESR engine reduced per CRB specification. · FV exhaust outlet opening max distance from body rear increased from 3 to 4 inches. · STU aftermarket side skirts now allowed if they meet 3-inch ride height, lack ducts except jacks or exhaust, don't exceed fascia width, stay below door bottom, and don't reinforce chassis. · STU wheel flare wording clarified: each fender may be flared to 2" with 1% weight penalty, maintaining OEM profile. · FV front track maximum 52.500 inches; rear track 49.125–50.750 inches; spacers now allowed. · STL and STU ride height measurement clarified: lowest rocker panel point without driver, excluding pinch weld. · FV disc brake assembly minimum weight clarified to 16.5 lbs total; caliper minimum weight requirement of 1.65 lbs removed. · STU Mazda 13B Bridge Port now permits ELITE ROTARY SHOP FD V2.0 intake manifold; stock throttle body requirement removed. · STU Mazda MZR gains alternate Goodwin intake manifold option with stock or Acura throttle body. · STU alternate suspension components rule moved from section E to section D. · STU Honda/Acura B20 now permits B16 or B18 VTEC cylinder head and matching intake manifold. · STU flared fenders up to 2" with 1% weight penalty moved from base to Advanced Aero. · STU Honda Civic Si TCA 2017- requires 37mm TIR throttle as of June 1, 2019. · STU BMW S54B32 OEM classified separately from E46, displacement 3246 cc, minimum weight 3300 lbs, OEM engine mandatory. · P2 stock and modified engines get smaller restrictors (35.0mm, 34.0mm, 33.0mm) and heavier minimums (1025, 1125, 1185 lbs). · P2 Line A.1 restrictor reduced from 40mm to 38mm. · SM fuel pump and filter now permitted as Mazda or OEM equivalent part. · Honda Civic Si 2017- added to STU with 1500cc displacement, 2800 lbs minimum weight, OEM engine and bodywork, specific HPD parts allowed. · STU BMW E46 S54 OEM 3246cc added at 3300 lbs minimum; no Super Touring allowances, OEM intake and cams, 1mm overbore, compression +0.5 permitted. · STU Mazda 13B and 13B Bridge Port may use 13B RE or REW housings and intake with turbo removed. · STU Honda K24 may use intake part numbers 17100-RRB-A00 or 17100-PRB-A10. · STU Mazda 12A Bridge Port added, minimum weight 2550 lbs, Nikki or Auto-type carburettor with specified modifications. · STU World Challenge car weight rule deleted; no replacement specified. · STU AWD/RWD cars no longer must reduce restrictor 1 mm from table. · STU rear wing maximum 12" cord, 72 sq in end plates each, roof height max, body width limit. · FV intake manifold horizontal tube measurement location clarified; removed specific distance ranges from rule text. · SM allows factory Mazda ECU and injector harnesses (P/N 0000-10-020E-99, 0000-10-080D-99) on 1999–2000 model year cars, unmodified. · SM electrical rules reorganized and clarified; alternator now externally regulated only by OEM ECU or master kill switch; harness repair by splicing permitted. · SM tire tread protrusion language removed from GCR 9.1.7.C.5. · P2 Spec Line cars now allow 1345cc Hayabusa stock engines at 1050 lb minimum with 30mm restrictor. · P2 Group CN Honda K20A-FD2 55mm intake restrictor implementation delayed from 1 January to 3 March 2019. · P2 Honda K20A-FD2 Group CN must use stock intake manifold, 64mm throttle, 55mm restrictor at 1500 lbs minimum. · STU adds Honda K20C1 Turbo I4, 1996 cc, 3025 lbs minimum weight, 36mm TIR required.show
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| Sonoma Raceway Runoffs 20182018-10-10 | 1:19.234Franklin Church · fastest of 10 · top 5 within 21.5s | 1:46.514Kevin Boehm · fastest of 9 · top 5 within 7.4s | 103.0Franklin Church | 1:28.784Tim Day Jr · fastest of 17 · top 5 within 5.0s | 1:32.071Chuck Bona · fastest of 18 · top 5 within 0.9s | 144.4Tim Day Jr | -14.443squal +9.550s | 86.4%qual 112.1% | 1:54.355Ken Sutherland · fastest of 48 · top 5 within 0.7s | 1:55.278Michael Carter · fastest of 48 · top 5 within 0.3s | 102.2Danny Steyn | +8.764squal +35.121s | 108.2%qual 144.3% | 1:52.637Skip Streets · fastest of 29 · top 5 within 1.6s | 1:53.639Alex Scaler · fastest of 28 · top 5 within 0.4s | 106.3Skip Streets | +7.125squal +33.403s | 106.7%qual 142.2% | ||
| No rule changes on record between these events | ||||||||||||||||||||
| Indianapolis Motor Speedway Runoffs 20172017-09-25 | 1:48.921Rob Huffmaster · fastest of 34 · top 5 within 2.0s | 1:49.387Rob Huffmaster · fastest of 31 · top 5 within 2.4s | 1:31.826Jeff Shafer · fastest of 26 · top 5 within 4.9s | 1:32.481Jeff Shafer · fastest of 24 · top 5 within 3.8s | -16.906squal -17.095s | 84.5%qual 84.3% | 1:58.306Chris Haldeman · fastest of 86 · top 5 within 0.5s | 1:59.100Michael Gagliardo · fastest of 83 · top 5 within 0.6s | +9.713squal +9.385s | 108.9%qual 108.6% | 1:55.759Michael Varacins · fastest of 39 · top 5 within 1.0s | 1:55.923Michael Varacins · fastest of 32 · top 5 within 1.3s | +6.536squal +6.838s | 106.0%qual 106.3% | ||||||
| No rule changes on record between these events | ||||||||||||||||||||
| Mid-Ohio Sports Car Course Runoffs 20162016-09-19 | 1:32.738Joe Moser · fastest of 16 · top 5 within 2.5s | 1:34.597Cameron Maugeri · fastest of 16 · top 5 within 0.8s | 1:20.188Jeff Shafer · fastest of 18 · top 5 within 4.0s | 1:20.904Jeff Shafer · fastest of 16 · top 5 within 2.2s | -13.693squal -12.550s | 85.5%qual 86.5% | 1:40.514Justin Hille · fastest of 45 · top 5 within 0.3s | 1:40.764Michael Carter · fastest of 44 · top 5 within 0.3s | +6.167squal +7.776s | 106.5%qual 108.4% | 1:37.942Alex Scaler · fastest of 41 · top 5 within 0.3s | 1:38.066Flinn Lazier · fastest of 38 · top 5 within 0.7s | +3.469squal +5.204s | 103.7%qual 105.6% | ||||||
| No rule changes on record between these events | ||||||||||||||||||||
| Daytona International Speedway Runoffs 20152015-09-21 | 2:05.494Eric Heinrich · fastest of 18 · top 5 within 4.6s | 2:06.756Eric Heinrich · fastest of 17 · top 5 within 3.5s | 1:51.825Chris Farrell · fastest of 17 · top 5 within 3.6s | 1:52.355Jeff Shafer · fastest of 17 · top 5 within 2.8s | -14.401squal -13.669s | 88.6%qual 89.1% | 2:18.661Andrew Carbonell · fastest of 62 · top 5 within 0.6s | 2:24.067Todd Lamb · fastest of 59 · top 5 within 0.8s | +17.311squal +13.167s | 113.7%qual 110.5% | 2:21.167Roger Siebenaler · fastest of 31 · top 5 within 0.8s | 2:21.142Andrew Whitston · fastest of 30 · top 5 within 1.1s | +14.386squal +15.673s | 111.3%qual 112.5% | ||||||
By track
| Track | Events | Typical % of STU | Best | Latest |
|---|---|---|---|---|
| Road America | 4 | 100.0% | 100.0%Runoffs 2020 | 100.0%Runoffs 2026 |
| Virginia International Raceway | 3 | 100.0% | 100.0%Runoffs 2019 | 100.0%Runoffs 2023 |
| Indianapolis Motor Speedway | 2 | 100.0% | 100.0%Runoffs 2017 | 100.0%Runoffs 2021 |
| Daytona International Speedway | 1 | 100.0% | 100.0%Runoffs 2015 | 100.0%Runoffs 2015 |
| Mid-Ohio Sports Car Course | 1 | 100.0% | 100.0%Runoffs 2016 | 100.0%Runoffs 2016 |
| Sonoma Raceway | 1 | 100.0% | 100.0%Runoffs 2018 | 100.0%Runoffs 2018 |
About this data
Every event the class ran, at any track, oldest to newest on the chart and newest first in the table. Each point is the class's best lap as a share of STU's best on the same day: the weather and the day cancel out, so one figure compares across years where lap times cannot; a class that suits one track more than another still reads differently there. It still moves when the yardstick's own balance changes or its field thins, and an event the yardstick did not run has no point. A best from fewer than three cars is greyed. The rule changes that took effect between two events are folded between their rows.