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True Street – 2017

OSCA True Street Rules – 2017

This class is limited to FWD, RWD, and AWD 4cyl to 10cyl cars and trucks running OEM style automatic or manual transmissions that are Naturally Aspirated, Nitrous Assisted, Turbocharged, Twin Turbocharged, or Supercharged typically using a small drag radial tire (with some exceptions) while maintaining a street type appearance.

 

RACE FORMAT:

  • 1/4 Mile
  • .400 Pro Tree
  • All weights are race weight including driver.

BODY & CHASSIS:

  • Body must be dimensionally stock.
  • Fiberglass/Carbon body panels are limited to hood, rear deck lid, fenders, doors, and bumpers.
  • Cowl hoods may not be taller than 6” from base of hood.
  • Front windshield must be glass.
  • Forward facing scoops are prohibited unless factory installed.
  • Rear wings/spoilers and/or front chin spoilers permitted.
  • Inlets for turbochargers and superchargers must not be exposed to ram air and pass a “line of sight inspection” from the front of the vehicle, i.e. they must be blocked off from a source of air (this includes closing off factory holes/grills).
  • All front ends must be of factory dimensions and cannot be lengthened.
  • Firewall must be in stock location between the lower frame rails and up to the top of the block.
  • OEM front frame rails are required from the firewall to 4” in front of the spindle. Up to a maximum of 50% of them may be modified or fabricated for header clearance. OEM Frame Rails must also be connected to the k-member or lower suspension component by either welding or bolting.
  • OEM Front Strut/Shock Towers must be functional and in stock location with complete factory sheet metal attaching factory frame rail to top of strut tower.
  • Motor plates and solid mounts are permitted.
  • Engine must be in stock location.
  • Fuel Cells permitted.

 

EXHAUST:

  • Mufflers required on all combos, all exhaust must pass through a muffler.
  • Turbos are not considered to be a muffler.
  • Commercially available mufflers permitted. No homemade mufflers permitted.
  • No gutting of mufflers permitted.
  • No insert style mufflers.

INTERIOR:

  • Aftermarket steering columns permitted.
  • Factory type dash accepted.
  • Must have stock appearing door panels.
  • Passenger seats not required.

 

ELECTRICAL:

  • All entries must have operational headlights and taillights.
  • Traction Control devices permitted.
  • Data loggers permitted.

ENGINE:

  • Max 510ci on Naturally Aspirated and Nitrous combinations
  • Max 430ci on Forced Induction combinations
  • Only OEM or Aftermarket “stock bore space” cast blocks are permitted.
  • No Billet cylinder heads/blocks.
  • Only Stock or Aftermarket “Stock Type” Cylinder Heads permitted.
  • No Canted Valve or Hemi Cylinder Heads unless they were OEM on a production engine
  • All Big Blocks must run “Conventional” style Cylinder Heads.

 

INDUCTION:

  • Fabricated Intake Manifolds permitted (see adders below)
  • Intake & Head Porting permitted.
  • All Combos permitted 1x4bbl throttle body, or 1 conventional TB, or 1 Carb.

 

POWER ADDERS:
NITROUS:

  • Single Stage Fogger with up to 2 Nitrous and 2 Fuel Solenoids (1 each per bank) permitted.
  • Single Stage Plate with 1 Nitrous and 1 Fuel Solenoid permitted.
  • In-Line Nitrous Safety Solenoid permitted.
  • Progressive Controllers permitted.
  • Only Commercial Nitrous Plates or Fogger Nozzles permitted.
  • Purge line must clearly exit the hood/cowl or body in a fashion to not allow purged nitrous to enter the engine when racing.
  • Jet sizes may be checked by pin gauge at anytime (0.001” oversize pin must not fit jet orifice)
  • Water/Meth Injection permitted (see adders below)
  • Regulated Air or Vapor pressure type systems (i.e. NANO or similar) permitted.
  • Electrical Thermostat/Pressure controlled bottle heaters permitted.

TURBOCHARGER(S):

  • Must not be modified from manufacturer. Porting prohibited. Housings must be “as cast”.
  • Reducers prohibited.
  • Anti-Surge permitted.
  • Nitrous assisted spooling prohibited.
  • Water/Air Intercoolers prohibited.
  • Air/Air Intercoolers permitted (Nitrous assisted cooling prohibited).
  • Water/meth injection permitted on Non-Intercooled combos only (see adders below)

 

SUPERCHARGER:

  • Must not be modified from manufacturer. Porting prohibited. Housings must be “as cast”.
  • Reducers prohibited.
  • Water/Air Intercoolers only permitted on Roots & Screw Type Supercharger combos (intercooler water must be fed from the engines “water only” coolant system)
  • Air/Air Intercoolers permitted on Centrifugal Supercharger combos.
  • Nitrous assisted intercooling prohibited.
  • Water/meth injection permitted on Non-Intercooled combos only. (see adders below)

 

FUEL:

  • Gasoline and E85 fuels only – Nitro-Methane, Alcohol, prohibited on all combos.

 

TRANSMISSION:

  • Any OEM style automatic or OEM manual transmission is permitted.
  • Clutch assisted/clutch-less manual transmissions permitted.
  • Manual transmissions must utilize SFI approved bell housing.
  • Electronic/Air Shifters permitted.

 

REAR SUSPENSION:

  • Stock Style Suspension permitted
  • Leaf Spring suspension permitted (see weight breaks below)
  • Ladder Bar and 4-Link style suspensions permitted (see weight adders below)
  • Stock type IRS or Upper/Lower Control Arm type permitted.
  • Aftermarket replacement control arms are permitted.
  • Coil over shocks are permitted.
  • Anti-roll permitted.
  • Wheelie bars are prohibited.

 

FRONT SUSPENSION:

  • Factory type front suspension only.
  • If vehicle came with upper and lower control arms it must retain them.
  • Aftermarket replacement control arms are permitted.
  • Coil over shocks are permitted.
  • Aftermarket K-Members/Commercially available sub-Frames permitted.

TIRES:

         Level 1

  • 235/60/15 – M/T ET Street Radial 3752R
  • 275/60/15 – M/T ET Street Radial 3754R
  • 255/50/16 – M/T ET Street Radial 3793R
  • 275/40/17 – M/T ET Street Radial 3743R
  • 295/45/17 – M/T ET Street Radial II 3745R
  • 315/30/18 – M/T ET Street Radial II 3784R
  • 305/35/19 – M/T ET Street Radial II 3723R
  • 305/35/20 – M/T ET Street Radial II 3727R
  • 275/50/15 – M/T ET Street S/S 3451
  • 275/60/15 – M/T ET Street S/S 3453
  • 255/50/16 – M/T ET Street S/S 3460
  • 275/40/17 – M/T ET Street S/S 3470
  • 285/40/18 – M/T ET Street S/S 3481
  • 305/35/19 – M/T ET Street S/S 3491
  • 275/40/20 – M/T ET Street S/S 3401

Level 2

  • 5R15 – M/T ET Street – 3753
  • 275x50x15 – M/T ET Street R 3552
  • 5-16 – M/T ET Street 3793
  • 5-15 – Hoosier Quicktime Pro #17421
  • 5-15 – M/T ET Street 3755 (Discontinued)
  • 5-16 – M/T ET Street 3796 (Discontinued)
  • 5-17 – M/T ET Street 3743 (Discontinued)
  • 5-15 – M/T ET Street 3754 (Discontinued)
  • 5-15 – Hoosier Quicktime Pro #17601
  • 5-16 – Hoosier Quicktime Pro #17603
  • 5-15 – M/T ET Street SS 3554
  • 5R17 – M/T ET Street R 3572
  • 5R18 – M/T ET Street R 3580
  • 5×15 – M/T ET Drag 3052

Level 3

  • 275/60/15 M/T ET Street Radial Pro 3754X
  • 5×15 M/T ET Drag 3054/3054ST
  • 5×15 M/T ET Drag 3055/3055S/3055C

 

Weight Adders:

  • Level 2 Tire +50lbs (NA Combos excluded)
  • Level 3 Tire +100lbs (NA Combos excluded)
  • Fabricated Intake Manifold +50lbs
  • Water or Meth Injection +50lbs
  • Ladder Bar Rear Suspension +25lbs
  • 4-Link Rear Suspension +50lbs

 

Weight Breaks:

  • No Intercooler or Meth/Water -50#
  • Leaf Spring Rear Suspension -50#

 

N/A WEIGHTS:

1900# (add 7# per ci over 290ci up to 409ci)

2750# (add 4# per ci over 410ci up to 510ci)

 

NITROUS WEIGHTS:

NITROUS LEVEL 1

1925# (add 6# per ci over 220ci up to 249ci)

2075# (add 6# per ci over 250ci up to 309ci)

2450# (add 5# per ci over 310ci up to 409ci)

2975# (add 3.5# per ci over 410ci up to 510ci)

Max Jet Sizes:

  • 082(x1 jet)
  • 055(x2 jets)
  • 039(x4 jets)
  • 031(x6 jets)
  • 027(x8 jets)
  • 025(x10 jets)

 

NITROUS LEVEL 2

2175# (add 6# per ci over 220ci up to 249ci)

2350# (add 6# per ci over 250ci up to 309ci)

2700# (add 5# per ci over 310ci up to 409ci)

3200# (add 4# per ci over 410ci up to 510ci)

Max Jet Sizes:

  • 099(x1 jet)
  • 065(x2 jets)
  • 046(x4 jets)
  • 038(x6 jets)
  • 032(x8 jets)
  • 029(x10 jets)

 

NITROUS LEVEL 3

2475# (add 6# per ci over 220ci up to 249ci)

2650# (add 6# per ci over 250ci up to 309ci)

3000# (add 5# per ci over 310ci up to 409ci)

3500# (add 4# per ci over 410ci up to 510ci)

Max Jet Sizes:

  • 110(x1 jet)
  • 075(x2 jets)
  • 053(x4 jets)
  • 043(x6 jets)
  • 037(x8 jets)
  • 033(x10 jets)

 

NITROUS LEVEL 4

2825# (add 6# per ci over 220ci up to 249ci)

3000# (add 6# per ci over 250ci up to 309ci)

3350# (add 5# per ci over 310ci up to 409ci)

3850# (add 4# per ci over 410ci up to 510ci)

 

Max Jet Sizes:

  • 150(x1 jet)
  • 087(x2 jets)
  • 061(x4 jets)
  • 050(x6 jets)
  • 043(x8 jets)
  • 039(x10 jets)

 

SUPERCHARGER WEIGHTS:

Supercharger Level 1

  • Base weight: 2075#
  • Procharger C-1 (add 3.4# per ci over 220ci)
  • Procharger C-1R (add 2.9# per ci over 230ci)
  • Procharger C-2 (add 3.2# per ci over 170ci)
  • Procharger P600B (add 3.3# per ci over 135ci)
  • Vortech V-1 S (add 2.8# per ci over 190ci)
  • Vortech V-1 SC (add 3.1# per ci over 210ci)
  • Vortech V-2 S (add 4.2# per ci over 165ci)
  • Vortech V-2 SC (add 3.0# per ci over 200ci)
  • Vortech V-1 SCi (add 3.3# per ci over 175ci)
  • Vortech V-2 SCi (add 3.4# per ci over 190ci)
  • Vortech V-1 Si (add 3.1# per ci over 130ci)
  • Vortech V-2 E (add 3.5# per ci over 165ci)
  • Base weight: 2175#
  • Procharger P-1SC (add 3.0# per ci over 150ci)
  • Procharger P-1SC-1 (add 2.6# per ci over 130ci)
  • Procharger P-1SC-2 (add 3.0# per ci over 150ci)
  • Vortech V-2 Si (add 2.6# per ci over 175ci)
  • Vortech V-3 Si (add 2.5# per ci over 190ci)
  • Base weight: 2400#
  • Procharger D1 (add 2.8# per ci over 135ci)
  • Procharger D1-SC (add 3.0# per ci over 145ci)
  • Procharger F-1 (add 3.1# per ci over 120ci)
  • Vortech V-1 Ti (add 3.1# per ci over 155ci)
  • Vortech V-7 JT (add 3.2# per ci over 160ci)
  • Base weight: 2600#
  • Procharger F-1D (add 2.7# per ci over 140ci)

 

Supercharger Level 2

  • Base weight: 2800#
  • Procharger F-1A (add 2.4# per ci over 140ci)
  • Procharger F-1A-91 (add 2.4# per ci over 140ci)
  • Procharger F-1A-94, F-1C (add 2.7# per ci over 140ci)
  • Procharger F-1C-94 (add 2.8# per ci over 140ci)
  • Vortech V-7 YSi (add 2.8# per ci over 160ci)
  • Vortech V-4 J (add 2.9# per ci over 170ci)
  • Vortech V-27 YSi (add 3.0# per ci over 165ci)
  • Base weight: 2975#
  • Procharger F-1C-10.5 (add 2.8# per ci over 145ci)
  • Procharger F-1R (add 2.8# per ci over 150ci)
  • Procharger D1R (add 3.1# per ci over 170ci)
  • Vortech V-4 X (add 3.3# per ci over 180ci)

 

Supercharger Level 3

  • Base weight: 3150#
  • Vortech V-24 X (add 3.1# per ci over 190ci)
  • Base weight: 3300#
  • Vortech V-4 XX (add 3.2# per ci over 200ci)
  • Vortech V-4 Z (add 4.3# per ci over 190ci)

 

Supercharger Level 4

  • Base weight: 3650#
  • Procharger F-1X (add 3.7# per ci over 225ci)
  • Vortech V-24 Z (add 2.6# per ci over 210ci)

 

Limited/Underdriven Supercharger Levels 1-4

*******Contact OSCA for more information

 

TURBO WEIGHTS:
Turbo Level 1

1825# (add 1.8# per ci over 120ci)

  • Precision 62mm PT6266
  • Garrett 64.7mm GT4088
  • On3 Performance 67mm
  • Turbonetics 69mm GT-K 750
  • Precision 60mm GEN2 PT6062
  • Garrett 62.5mm/62.3mm GTX3582R/GTW3684R
  • BorgWarner 50-57mm S200SX

 

2050# (add 1.7# per ci over 120ci)

  • Precision 62mm GEN2 PT6266
  • Precision 64mm GEN2 PT6466
  • Turbonetics 72mm GT-K 850
  • Garrett 67.8mm GT4094R
  • Garrett 65mm GTX4088R
  • Garrett 70.3mm GT4294/GT4294R
  • GT45 68.7mm
  • On3 Performance 70mm
  • BorgWarner 60-65mm S300SX3

 

Turbo Level 2

2275# (add 1.7# per ci over 120ci)

  • Precision 67mm PT6766
  • Precision 71mm PT7175
  • Garrett 70.3mm GTX4294R/GTX4594R
  • Garrett 74.7mm GT4202/GT4202R
  • GT45 76mm
  • T76 76.71mm
  • T88 63mm
  • On3 Performance 76mm GT45
  • On3 Performance 76mm
  • On3 Performance 78mm
  • Turbonetics 76mm Hurricane 7668 “Vanessa” – 11534-BB
  • BorgWarner 66-69mm S300SX3

 

Turbo Level 3

2750# (add 2.3# per ci over 140ci)

  • Turbonetics 75mm GT-K 1050
  • Turbonetics TN Series 76mm TN 1100
  • Precision 72mm PT7275
  • Precision 80mm PT80
  • Precision 68mm GEN2 PT6870
  • Garrett 79.8mm GT4508R
  • Garrett 75.8mm GTX4202R
  • Garrett 79.8mm GT4708/GT4708R/GT4780R
  • Garrett 67.5mm GT3794R
  • On3 Performance 88mm
  • GT45 80mm
  • BorgWarner 67-75mm S400SX4

 

Turbo Level 4

2975# (add 2.5# per ci over 150ci)

  • Precision 76mm PT7675
  • Garrett 79.8mm GTX4508R
  • BorgWarner 76-82mm S400SX4
  • Mitsubishi TD08 84.7mm

 

TWIN TURBO WEIGHTS:

Twin Turbo Level 1a

2410# (add 2.7# per ci over 220ci)

  • Twin Garrett 53mm GT3071R
  • Twin T67 67mm GT67
  • Twin T3/T4 Hybrid 58mm
  • Twin On3 Performance 61mm
  • Twin Turbonetics 53.56mm TN400
  • Twin Comp 53mm CT3-5356

 

Twin Turbo Level 1b

2870# (add 3.1# per ci over 220ci)

  • Twin Garrett 53mm GT3076R
  • Twin Precision 55mm PTB003-5531

 

Twin Turbo Level 2a

3250# (add 3.7# per ci over 220ci)

  • Turbonetics 61mm GT-K 600
  • Turbonetics 64mm GT-K 700
  • Precision 58mm PT5858
  • Precision 62mm TA6262/TA6266/PT6262
  • Garrett 58mm GTX3076R/GTX3576R
  • Garrett 58.3mm GTW3476R
  • Garrett 61.4mm GT3582R
  • Garrett 63.5mm GT3788R/GT4088R
  • BorgWarner EFR 7670 57.2mm
  • BorgWarner 50-57mm S200SX
  • T70 56.2mm
  • GT30 53mm GT3071R Stage III
  • GT30 57mm GT3082R Stage III
  • GT30 61.4mm GT3582R Stage III
  • GT35 55mm

 

Twin Turbo Level 2b

3575# (add 4# per ci over 220ci)

  • Precision 60mm GEN2 PT6062
  • Precision 62mm PT6266
  • Garrett 62.5mm/62.3mm GTX3582R/GTW3684R
  • Garrett 64.7mm GT4088
  • On3 Performance 67mm
  • Turbonetics 69mm GT-K 750
  • BorgWarner 60-65mm S300SX3

 

**OSCA will be closely watching the data from this class, and if required, will make immediate changes to the rules in order to work towards parity.

**If you have a combination not currently listed in the rules, but feel your car should fit into the class, please contact us with specific details and we will see if we can work you in. 

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