Reprogrammed ECU (via hardware and/or software) may be used in
the standard housing. Traction control parameters may not be
altered. Altered engine controllers may not alter boost levels in
forced induction engines. Alternate software maps which violate
these restrictions may not be present during competition, regardless
of activation.

15. STREET PREPARED CATEGORY
Cars running in Street Prepared Category must have been series
produced with normal road touring equipment, capable of being
licensed for normal road use in the United States, and normally sold
and delivered through the manufacturer’s retail sales outlets in the
United States. Cars not specifically listed in Stock or Street Prepared
Category classes in Appendix A must have been produced in
quantities of at least 1000 in a 12 month period to be eligible for Street
Prepared Category.
A vehicle may compete in Street Prepared Category if the preparation of
the vehicle has not exceeded the allowable modifications of Stock
Category, except as specified below. However, the distinction between
different years/models used in Stock Category does not apply in Street
Prepared Category. Example: Porsche 911 models that are listed on
the same line are considered the same.
Cars listed as eligible in and prepared to the current national Improved
Touring rules are permitted to compete in their respective Street
Prepared classes. Neither Street Prepared nor Improved Touring cars
are permitted to interchange preparation rules. Improved Touring cars
may use tires which are eligible under current IT rules even if they are
not eligible in Street Prepared.
Cars listed as eligible in and prepared to the current American Sedan
road race rules are permitted to compete in Class B Street Prepared.
Neither Street Prepared nor American Sedan cars are permitted to
interchange preparation rules. American Sedan cars may use tires
which are eligible under current AS rules even if they are not eligible in
Street Prepared.
Cars listed as eligible in and prepared to the current national Touring
category rules are permitted to compete in their respective Street
Prepared classes. Neither Street Prepared nor Touring cars are
permitted to interchange preparation rules. Touring cars may use tires
which are eligible under current Touring rules even if they are not
eligible in Street Prepared.
Cars listed as eligible in and prepared to the current national Street
Touring (ST) class rules are permitted to compete in their respective
Street Prepared classes, with the additional allowance that they may
use any tire which meets the requirements of 15.3 and fits on the STlegal
wheels and within the ST-legal bodywork.
Cars eligible for the current Spec Miata rules are permitted to compete in
class D Street Prepared, with the additional allowance that they may
use any size of any tire which meets the requirements of 15.3 and fits
on the Spec Miata allowed wheels and within the allowed bodywork.
Spec Miata cars in DSP may not intermix use of the Spec Miata and
Street Prepared allowances. The competitor is responsible for being in
possession of the Spec Miata rules and for proving that his/her car
conforms to the rules.
While the rules of the Street Prepared Category have remained
essentially the same, the laws governing various aspects of streetdriven
vehicles have changed over time. The original concept of this
category as made up predominantly of street-driven vehicles has been
rendered inappropriate. The SCCA does not encourage or condone
the breaking of laws governing pollution control systems or the
alteration of street-driven vehicles contrary to state and federal laws
regarding their use. It continues to be the responsibility of the individual
to comply with such state and federal laws.
See Sections 3.8 and 8.3 for documentation requirements.
Specific vehicle classifications are located in Appendix A of these
rules.
15.1 AUTHORIZED MODIFICATIONS
A. All Allowable modifications permitted in Stock Category are allowed.
B. Street Prepared vehicles may only be modified in excess of Stock
Category rules in the following ways. Any modification not specifically
authorized by the Stock Category or Street Prepared rules is
prohibited. No unauthorized modifications are permitted in order to
accommodate authorized modifications (e.g., non-stock hood scoops
or holes necessary for carburetor clearance). Structural modifications,
such as the addition of members known as “jacking rails”, are not
permitted unless specifically authorized herein.
C. Equipment and/or specifications may be exchanged between different
years and models of a vehicle if (a) the item is standard on the
year/model from which it was taken, and (b) the years/ models are
listed on the same line of Appendix A (Street Prepared Classes). The
updated/backdated part or the part to which it is to be attached may
not be altered, modified, machined or otherwise changed to facilitate
the updating/backdating allowance. Standard factory installation
methods, locations, and configurations are allowed. The updating
and/or backdating of engines, transmissions, transaxles, and/or
unibodies must be done as a unit; component parts of these units may
not be interchanged. Cars not listed in the Street Prepared sections of
Appendix A may not be updated/backdated until approved by the SEB
and published in the official SCCA publication.
D. Alternate computer control modules may be used whenever an
equivalent change to the conventional system is allowed. For example,
alternate computer module control of ignition settings or fuel injection is
allowed.
E. Air conditioning systems may be removed in whole or in part. This rule
should not be interpreted to allow modification of the heater system.
F. On all forms of suspension, camber/caster adjustment within factory
specifications may be achieved by the use of shims or eccentric
bushings. The intent of this allowance is to permit cars to be restored
to within factory-allowed specification ranges, not to provide an
additional method beyond those permitted in Section 15.8 to obtain
alignment settings beyond the factory specifications.
Refer to Appendix F for past clarifications of these rules.
15.2 BODYWORK
Vehicles may only exceed the allowances of 13.2 as specified herein.
A. Fenders and bumpers may be modified for tire clearance. This
includes the portion of a hood which serves as a fender/wheel well,
where applicable. This does not permit modifications to the chassis or
bodywork inboard of the vertical plane of the hub/wheel mounting face
(at rest, with front wheels straight ahead). Flares may be added
although tires may extend beyond the bodywork. Replacement of
complete hood, flared fenders, or quarter panels is prohibited. Plastic
and rubber wheel well splash shields may be modified for tire
clearance and for installation of fender flares as allowed herein.
B. Factory rub strips, emblems, and mud flaps may be removed
C. Transverse members known as strut bars and suspension braces
may be added, removed, modified, or substituted. They must be bolted
on. Strut bars must be attached to the strut/shock tower. Lower
suspension braces much be attached to the lower suspension pickup
point locations on the chassis within 2 inches in any direction of the
actual suspension attachment to the chassis. Except for standard
parts, no connections to other components are permitted. Additional
holes may be drilled for mounting bolts. Interior trim panels may be
modified to allow installation of strut bars. Holes or slots may be no
larger than necessary and may serve no other purpose. This does not
permit any modifications to the frame or unibody beyond the allowed
mounting holes.
D. Subframe mount bushings may be replaced, but must attach in the
factory location(s) without additional modification or changes.
Subframe position may not be changed. The amount of metal in a
replacement bushing may not be increased relative to the amount of
metal found in a standard bushing for the particular application. Solid
metal bushings are specifically prohibited.
E. Longitudinal (fore-aft) subframe connectors (“SFCs”) are permitted
with the following restrictions:
1. They must only connect previously unconnected boxed frame rails
on unibody vehicles.
2. Each SFC must attach at no more than three points on the unibody
(e.g. front, rear, and one point in between such as a seat mount
brace or rocker box brace).
3. SFCs must be bolted or welded, but welding must be to the OE
subframe stampings, not to the floor pan in between.
4. No cutting of OE subframes or floorpan stampings is permitted.
Drilling is permitted for mounting bolts only.
5. No cross-car/lateral/triangulated connections directly between the
driver’s side and passenger’s side SFCs are permitted. Connections
to OE components such as tunnel braces or closure panels via bolts
are allowed and count as the third point of attachment. No alteration
to the OE components is permitted.
6. SFCs may not be used to attach other components (including but
not limited to torque arm front mounts or driveshaft loops) and may
serve no other purpose.
F. The driver and front passenger seats may be replaced, with the
following restrictions: Seats must be securely mounted per 3.3.3.B.2.
The seating surface must be fully upholstered. Any replacement seat
must be a full back, bucket type automobile seat incorporating a
functional headrest. Kart seats, low back dune buggy seats, and other
similar types of seat are expressly prohibited. Cars may have no fewer
than the standard number of seats. The seat tracks are considered
part of the seat and may be substituted. Alternate seat tracks may
serve no other purpose. The standard seat belts may be removed to
facilitate the installation of alternate restraints complying with safety
requirements.
G. Any steering wheel may be used. An alternate wheel which replaces
an airbag-equipped wheel is not required to have an airbag. An
alternate wheel is not required to have a horn button.
H. Airbags may be electrically disabled but not removed.
I. Spoilers/splitters and cosmetic trim pieces are permitted. Side skirts
may not be used. Spoilers/splitters must comply with the following
subsections. The intent of this allowance is to accommodate commonly
available appearance kits, and replicas thereof, which have no
significant aerodynamic function at Solo speeds.
1. A spoiler/splitter may be added to the front of the car below the
bumper. It may not extend rearward beyond the front most part of the
front wheel well openings, and may not block normal grille or other
openings, or obstruct lights. Splitters may not protrude beyond the
bumper. Openings may not be used for the purpose of ducting air to
the radiator or oil cooler, but they may allow air to flow through a
permitted oil cooler provided no ducting is used. The spoiler may not
function as a wing.
2. A spoiler may be added to the rear of the car provided it complies
with either of the following:
a) It is a production rear spoiler which is standard or optional
equipment of a U.S. model of the vehicle, or an exact replica in an
alternate material.
b) It is a non-production rear spoiler which is mounted to the
rearmost portion of the rear hatch, deck, or trunk lid. The spoiler
may extend no more than 10 inches from the original bodywork in
any direction. Alternatively, in a hatchback, the spoiler may be
mounted to the rear hatch lid at or near the top of the hatch; in
such a configuration the spoiler may extend no more than 4 inches
from the original bodywork in any direction. The spoiler may be no
wider than the bodywork, and it shall not protrude beyond the
overall perimeter of the bodywork as viewed from above. The use
of endplates is prohibited. Angle of attack is free. The spoiler may
not function as a wing.
J. Roll bars must comply with Section 13.2.H in Stock category. Roll
cages must comply with the following:
1. The roll cage need not be removable. It shall be bolted or welded to
the car.
2. The cage shall attach to the car at no more than 8 points, consisting
of the basic cage with 6 attachment points, and 2 additional optional
braces.
3. The forward part of the cage shall be mounted to the floor of the
vehicle. If used, the 2 optional braces referred to in (2) shall be
mounted, one on either side, from the forward section of the cage to
the firewall or front fender wells. No braces shall pass through the
front firewall.
Installation of roll cages in Street Prepared cars must follow the
same standards for interior modifications to accommodate the
cage installation as those which are applicable to Showroom Stock
or Touring cars in Club Racing.
K. The use of a fuel cell which complies with GCR requirements is
permitted, provided all of the following additional restrictions are met:
1. The capacity of the cell may differ by no more than 20% from that of
the original tank.
2. The location of the cell may differ from that of the original tank by no
more than six inches in any direction.
3. The car meets all applicable Club Racing Time Trials safety
standards, including those for rollover protection and the installation
of a fire extinguisher.
L. Fuel tank changes are permitted only as allowed under 15.1.C and
15.2.J. No additional tanks or reservoirs may be used.
M. Accelerator, brake, and clutch pedals may utilize substitute covers of
unrestricted origin, shape, and size, provided they meet the following
requirements: covers must be securely attached, provide a non-slip
surface, not interfere with each other’s operation, and must be deemed
safe at Tech Inspection.
N. The OE radio may be removed. The OE sound system components,
except wiring, may be removed. Any visible holes which result from the
removal of such equipment must be covered.
O. Sunroof-equipped cars may be converted to a solid-roof configuration
provided a model without a sunroof is listed on the same line in
Appendix A.
15.3 TIRES
Tires must meet the eligibility requirements for Stock Category with the
following exception: the list of non-eligible tires in Section 13.3.A is
replaced with the following list, which may be altered at any time by the
SEB upon notification of membership.
No tire models are currently listed.
15.4 WHEELS
Vehicles may only exceed the allowances of 13.4 as specified herein.
A. Wheels of any diameter, width, or offset may be used. Aftermarket
wheels may be modified to install OE tire pressure sensors.
B. Wheel spacers are permitted. Wheel studs and knock-off wheel drive
pegs may be changed in length and diameter. Wheel bolts may be
replaced with studs and nuts.
15.5 SHOCK ABSORBERS
Vehicles may only exceed the allowances of 13.5 as specified herein.
A. Shock absorber bump stops may be altered or removed.
B. On cars with lever-type shock absorbers, a tube-type shock absorber
may be added. If the lever-type shock serves no other purpose, it must
be removed. If the lever-type shock serves any other purpose, it must
be retained.
C. Any shock absorbers may be used. Shock absorber mounting
brackets which serve no other purpose may be altered, added or
replaced, provided that the attachment points on the body/
frame/subframe/chassis/suspension member are not altered. The
installation may incorporate an alternate upper spring perch/seat
and/or mounting block (bearing mount). The system of attachment may
be changed. The number of shock absorbers shall be the same as
Stock. No shock absorber may be capable of adjustment while the car
is in motion, unless fitted as original equipment. MacPherson strut
equipped cars may substitute struts, and/or may use any insert. This
does not allow unauthorized changes in suspension geometry or
changes in attachment points (e.g., affecting the position of the lower
ball joint or spindle). It is intended to allow the strut length changes
needed to accommodate permitted modifications which affect ride
height and suspension travel. This allowance differs from Improved
Touring Allowance 9.1.3.D.5.b.1.
15.6 BRAKES
Vehicles may only exceed the allowances of 13.6 as specified herein.
A. Any brake line, single or dual master cylinder, vacuum brake booster,
or brake proportioning valves may be used. This does not allow
multiple separate cylinders, but does allow for any single, dual-circuit
cylinder.
B. “Safety brakers” and units such as the “Brake Guard System” are
permitted.
C. ABS braking systems may be disabled, but not removed; brake
boosters may be removed, modified, substituted, or added.
D. Alternate brake rotors are permitted, subject to the following
restrictions:
1. Rotors must be ferrous metal except for standard parts. Aluminum
rotor hats are allowed. Rotor dimensions (diameter and thickness)
must be equal to or greater than standard parts. Cars originally
equipped with solid (non-vented) rotors may utilize vented rotors.
2. Cross-drilled and/or slotted brake rotors may be used. Slots/holes
are permitted only in the braking area of the rotor. Rotors featuring a
drum-type parking brake in the hat area of the rotor may not be
drilled or slotted in the parking brake area.
E. Drum brakes may be replaced with disc brakes. Disc brake rotors for
such a conversion must be equal to or greater in diameter than the
inside diameter of the standard brake drum. Changes to backing
plates/mounting brackets/brake lines to accommodate this change are
permitted but may serve no other purpose. Drum-to-disc brake
conversions must be bolted, not welded to the axle/control arm/upright.
F. Air ducts may be fitted to the brakes, provided that no changes are
made in the body/structure for their use. They may serve no other
purpose. Backing plates and dirt shields may be modified or removed.
G. A functional, redundant emergency (parking) brake must be present.
H. Brake calipers may be replaced, provided the number of pistons is
equal to or greater than the original number of pistons. Caliper
mounting brackets may be replaced to accommodate this change, but
may serve no other purpose. Alternate caliper brackets must bolt to the
original caliper bracket mounting location(s).
15.7 ANTI-ROLL (SWAY) BARS
Vehicles may only exceed the allowances of 13.7 as specified herein.
Substitution, addition, or removal of any anti-roll bar(s) is permitted.
Bushing material, method of attachment, and locating points are
unrestricted. This does not authorize removal of a welded-on part of a
subframe to accommodate the installation, or the cutting of holes to
route the bar or links. Non-standard lateral members which connect
between the brackets for the bar, including allowed strut bars per
15.2.C, are permitted.
The bar may serve no other purpose which is not explicitly permitted
elsewhere herein. Components such as anti-roll bars and strut
housings which serve dual purposes by also functioning as suspension
locators may not be modified or substituted in ways which change the
suspension geometry or steering geometry, and may not be installed in
positions (e.g. upside down) other than that of the original
configuration.

15.8 SUSPENSION
Vehicles may only exceed the allowances of 13.8 as specified herein.
A. Ride height may only be altered by suspension adjustments, the use
of spacing blocks, leaf spring shackles, torsion bar levers, or change or
modification of springs or coil spring perches. This does not allow the
use of spacers which alter suspension geometry, such as those
between the hub carrier and lower suspension arm. Springs must be of
the same type as the original (coil, leaf, torsion bar, etc.) and except as
noted herein, must use the original spring attachment points. This
permits multiple springs, as long as they use the original mount
locations. Coil spring perches originally attached to struts or shock
absorber bodies may be changed or altered, and their position may be
adjustable. Spacers are allowed above or below the spring.
B. Suspension bump stops may be altered or removed.
C. Suspension bushings may be replaced with bushings of any materials
(except metal) as long as they fit in the original location. Offset
bushings may be used. In a replacement bushing the amount of metal
relative to the amount of non-metallic material may not be increased.
This does not authorize a change in type of bushing (for example ball
and socket replacing a cylindrical bushing), or use of a bushing with an
angled hole whose direction differs from that of the original bushing. If
the Stock bushing accommodated multi-axis motion via compliance of
the component material(s), the replacement bushing may not be
changed to accommodate such motion via change in bushing type, for
example to a spherical bearing or similar component involving internal
moving parts. Pins or keys may be used to prevent the rotation of
alternate bushings, but may serve no other purpose than that of
retaining the bushing in the desired position. Differential mount
bushings are not considered to be suspension bushings and are not
covered by this allowance.
D. Differential mount bushings may be replaced, but must attach in
the factory location(s) without additional modification or changes.
Differential position may not be changed. The amount of metal in a
replacement bushing may not be increased relative to the amount of
metal found in a standard bushing for the particular application. Solid
metal bushings are specifically prohibited.
E. Steering rack bushings may be replaced, but must attach in the
factory location(s) without additional modification or changes. Steering
rack position may not be changed. The amount of metal in a
replacement bushing may not be increased relative to the amount of
metal found in a standard bushing for the particular application. Solid
metal bushings are specifically prohibited. This does NOT allow
shimming or otherwise relocating the steering rack.
F. The following allowances apply to strut-type suspensions: Adjustable
camber plates may be installed at the top of the strut, and the original
upper mounting holes may be slotted. The drilling of holes in order to
perform the installation is permitted, but the center clearance hole may
not be modified. Any type of bearing or bushing may be used in the
adjustable camber plate attachment to the strut. The installation may
incorporate an alternate upper spring perch/seat and/or mounting block
(bearing mount). Any ride height change resulting from installation of
camber plates is allowed. Caster changes resulting from the use of
camber plates are permitted.
G. Camber bolts may be installed, providing these parts use the original,
unmodified mounting points. Caster changes resulting from the use of
camber bolts are permitted.
H. Camber kits, also known as camber compensators, may be installed.
These kits consist of either adjustable length arms or arm mounts that
provide a lateral adjustment to the effective length of a control arm.
Alignment outside the factory specifications is allowed. The following
restrictions apply:
1. On double/unequal arm (e.g. wishbone, multi-link) suspensions, only
the upper arms OR lower arms may be modified or replaced, but not
both. Non-integral longitudinal arms that primarily control fore/aft
wheel movement (e.g. trailing arm(s) or link(s) of a multi-link
suspension) may not be replaced, changed, or modified.
2. On arm-and-strut (MacPherson/Chapman) suspensions, the lower
arms may be modified/replaced OR other methods of camber
adjustment as allowed by paragraphs 15.8.C, F, or G may be used,
but not both.
3. On swing or trailing arm suspensions, the main arms may not be
modified or replaced, but lateral locating links/arms may be modified
or replaced.
4. The replacement arms or mounts must attach to the original
standard mounting points. All bushings must meet the requirements
of 15.8.C. Intermediate mounting points (e.g. shock/spring mounts)
may not be moved or relocated on the arm, except as incidental to
the camber adjustment. The knuckle/bearing housing/spindle
assembly cannot be modified or replaced.
Note: Many modern suspension designs known by other names
actually function as double A-arm designs. These include the rear
suspensions on 88+ Honda Civic/Integra, Neon, E36 BMW, and
most ‘multi-link’ and are covered by 15.8.H.1.
I. Solid axle suspension allowances:
1. Addition or replacement of suspension stabilizers (linkage
connecting the axle housing or De Dion to the chassis, which
controls lateral suspension location) is permitted.
2. Traction bars or torque arms may be added or replaced.
3. A panhard rod may be added or replaced.
4. The upper arm(s) may be removed, replaced, or modified, and the
upper pickup points on the rear axle housing may be relocated.
5. The lower arms may not be altered, except as permitted under
15.8.C, or relocated.
Methods of attachment and attachment points are unrestricted, but
may serve no other purpose (e.g. chassis stiffening). This does not
authorize removal of a welded-on part of a subframe or bodywork to
accommodate the installation.
J. On strut-equipped cars, the strut’s lower integral mounting bracket, for
attachment to the upright or spindle, is unrestricted provided it attaches
to the stock location. Any resulting change to the position of the strut
centerline is allowed. Such brackets shall serve no other purpose. This
does not allow for changes to the integral steering arm on cars that
have the steering arm integrated with the strut body.
K. Changes in alignment parameters which result directly from the use of
allowed components are permitted. For example, the dimensional
changes resulting from the use of a cylindrical offset bushing which
meets the restrictions of 15.8.C are allowed, including those resulting
from a change in the pivoting action to (a) about the mounting bolt, or
(b) about the bushing itself. Eccentric bolts are permitted for
suspension adjustment only if they are as specified by the factory, per
the last paragraph of 13.8.
15.9 ELECTRICAL SYSTEM
Except for those with electric and hybrid powertrains, vehicles may only
exceed the allowances of 13.9 as specified herein.
A. Any ignition setting, adjustment, or system may be used, subject to
the requirements of 15.10.D. This does not prohibit the use of ‘twostep’
rev limiters used when the car is stationary.
B. The make, model number, and size of the battery may be changed but
not its voltage.
C. Relocation of the battery or batteries is permitted but not into the
passenger compartment. If the battery is relocated and the original
battery tray can be removed by simply unbolting it, the tray may be
removed, or relocated with the battery. Holes may be drilled for
mounting or passage of cables. Longer cables may be substituted to
permit relocation. The number of battery or batteries may not be
changed from stock. The area behind the rearmost seat is not
considered to be within the passenger compartment. The area under
the rearmost seat is considered to be within the passenger
compartment.
D. Any starter, generator, or alternator may be used in the original
position. An alternator or generator must have an electrical output
(including amperage) equal to or greater than the original equipment
unit. Any generator or alternator pulley and belt of the same type as
standard may be used (see 15.10.Y).
E. Wiring harnesses may not be removed in whole or in part. Wiring
connectors for emissions control devices are considered part of the
harness, not part of the emissions control system, and may not be
removed.
15.10 ENGINE AND DRIVE TRAIN
Except for those with electric and hybrid powertrains, vehicles may only
exceed the allowances of 13.10 as specified herein.
A. Engines must retain standard type lubricating system, but may have
any oil pan (Accusump-type systems allowed), oil pump and pickup, oil
coolers, oil or fuel filters. Fuel filters must be of automotive type and
may serve no other purpose; a substituted fuel filter may not be used
as a reservoir. Substituted fuel filters may not exceed one quart total
capacity. A permitted oil cooler may be positioned in an opening in an
allowed spoiler, provided no unauthorized modifications are made in
order to perform the installation.
B. Heat shields may be added.
C. Induction allowances are as follows:
1. Carburetors, fuel injection, and intake manifolds are unrestricted,
subject to 15.10.D. Alternate throttle linkage and connections to
facilitate installation of allowed induction systems are permitted, but
may serve no other purpose. If an induction system item is allowed
to be removed and its original mounting bracket can be removed by
simply unbolting it, the bracket may be removed as well.
2. Except for standard parts as defined in these rules, the external use
while on course of liquids, ice, dry ice, refrigeration systems,
vaporized compressed gases, etc. to reduce the temperature of the
intake air charge is prohibited. Wrapping of intakes with liquidsoaked
fabric is not permitted.
3. As utilized only on engines originally equipped with forced induction,
induction charge heat exchangers (known as “intercoolers” or
“charge air coolers (CACs)”) are unrestricted in size and
configuration. Air-to-air CACs and radiators for air-to-liquid CACs
must be cooled only by the atmosphere, except for standard parts.
Body panels, fascias, or structural members may not be cut or
altered to facilitate CAC installation.
4. Turbochargers and/or superchargers (“forced induction”) may not be
added, changed, or modified (this does not allow ceramic coating of
turbochargers). On vehicles originally equipped with forced induction:
a) No hardware changes or alterations to turbocharger(s) or
supercharger(s), in size or number, are permitted. Turbochargers
or superchargers may be updated/backdated only in conjunction
with the accompanying complete engine unit.
b) No changes are allowed to waste gate(s) size, number, or
location. No changes are allowed to variable-geometry turbine
(VGT) hardware.
c) No changes are allowed to supercharger drive system pulleys.
Belt tensioners may be added/changed to reduce belt slip.
d) No changes are permitted to blow-off/pop-off valves.
e) Compressor bypass valves (CBVs) are considered part of the air
intake system and may be added, replaced, or updated/backdated
independently of the other components of a forced induction
system.
f) Boost regulation systems, either electronic or mechanical, and
electronic fuel cuts referencing boost pressure may be altered or
modified except as prohibited herein. Boost pressure changes
resulting from authorized changes are permitted.
D. Traction and/or stability control systems, as defined in 12.11, must be
standard parts at standard settings, or electronically disabled.
E. Air cleaner(s) may be changed or removed, velocity stacks may be
added.
F. Emission control devices may be modified or removed. This permits
the oil filler cap to be modified or substituted, but does not allow valve
covers or cam covers to be altered to install a breather or for any other
purpose.
G. Intake water injection systems are allowed.
H. Fuel lines and pumps are unrestricted except as specified herein, as
long as they do not pose a safety hazard. Fuel lines may be no larger
than 1/2" i.d. and may only connect to the original fuel tank or allowed
fuel cell. They may be no longer than necessary for reasonable and
safe installation, and may serve no other purpose. A single fuel feed
line may be used. A single fuel return line may be used, and a fitting for
connecting it may be added at or near the top of the fuel tank. This
does not authorize “cool-cans”.
I. Exhaust manifolds and muffler systems are free, except that they must
be quiet and terminate behind the driver. Exhaust heat shields may be
removed. Rear- and mid-engine cars without exhaust headers/manifold
systems may use any exhaust system that meets the requirements of
3.5. This permits the removal of “heater boxes” in order to install
headers on such cars.
J. Engine mounts may be replaced, but must attach in the factory
location(s) without additional modification or changes. Engine position
may not be changed. Hydraulic shock type rear engine locators, or
bobble struts, may be replaced by manufacturer’s performance part or
aftermarket replacement part. This part must retain factory dimensions
and attachment points, including factory design. (Example: If factory
locator/bobble strut is gas or hydraulic piston type, replacement part
must be gas or hydraulic piston type.) If one or more non-OE engine
mounts are used, 15.10.K does not apply and a torque suppression
device may not be used.
K. One bolt-on torque suppression device may be used. A torque
suppression device attaches from the engine to the body, frame, or
subframe in one location, and controls engine movement at that
location along a single axis only. It may serve no other purpose.
Examples of permitted devices:
1) a chain
2) a rod with spherical bearings at each end.
Examples of devices not permitted:
1) any link which confines movement along more than one axis.
2) an engine mounting plate, or one or more plates rigidly bolted
between the engine and the frame. Holes may be drilled to mount a
torque suppression device. The installation may not include the
welding of any plate(s) to the bodywork or to the motor mount(s), nor
may it include multiple non-parallel links.
If a torque suppression device is used, 15.10.J does not apply and
replacement engine mounts may not be used.
L. Engine cooling radiators may be replaced with alternate parts subject
to the following restrictions:
1. Radiator core dimensions (width, height, thickness) must be no
smaller than the standard part.
2. Radiator must mount to OE radiator mounts.
3. Fluid capacity and dry weight of the radiator must be no less than
that of the standard part. Installation of an alternate radiator may
serve no other purpose (e.g. to allow a cold air intake passage).
M. The engine fan and fan shroud (unless it serves another purpose,
e.g., as an alternator/generator mount) may be removed, modified or
replaced. Electrically driven fans are allowed. Flex fans are not
allowed.
N. Transmission mounts may be replaced, but must attach in the factory
location(s) without additional modification or changes. Transmission
position may not be changed. The amount of metal in a replacement
mount may not be increased relative to the amount of metal found in a
standard mount for the particular application. Solid metal mounts are
specifically prohibited.
O. On two-cycle engines, the ports must be of standard heights, size and
configuration; crankcase volume and reed plates must not be altered.
P. Any metal clutch assembly, metal flywheel or metal torque converter
that uses the standard attachment to the crankshaft may be used.
Non-metallic friction surfaces (e.g. clutch disks) are permitted. Dowel
pins may be added. Any hydraulic clutch line may be used. Minor
repositioning of the clutch slave cylinder is allowed to accommodate
the alternate clutch, but the unit may not be relocated and the
repositioning may serve no other purpose. This allowance does not
permit the substitution of slave cylinders or the use of non-original
methods of clutch actuation (e.g. pull type versus push type).
Q. Any mechanical shift linkage may be used.
R. Limited slip differentials are permitted. This permits locked
differentials, either by design, welding, or mechanical means.
Differential cases, internal differential parts, and axle stubs may be
machined as required for clearance and installation to the extent that
material may only be removed, not added, and the exterior of the case
may not be altered in any way. This machining may serve no other
purpose. Any other modifications or substitutions to accommodate the
installation of the limited slip differential must meet the requirements of
15.1.B and 15.1.C.
S. Cylinders may be rebored to no more than 0.0472 in. over standard
bore and the appropriate standard oversize piston may be substituted.
This overbore dimension is an absolute limit; no additional tolerance is
permitted to accommodate wear. Cast or forged, non-stock pistons of
the same dimensions and configuration as original equipment pistons
may be used. Additionally the replacement pistons must be of the
same weight or greater as the original equipment pistons.
Replacement pistons must match OE piston configuration exactly
including quench area. The allowance for the use of aftermarket
forgings vs. OE castings does not permit alternate piston dome
designs. This allowance does not permit alternative ring configurations.
T. Rotating and reciprocating parts may be balanced but not lightened.
U. Intake and exhaust ports and manifold openings may be matched
provided no change is made more than one inch from the port/manifold
interface. Material may be removed to facilitate port matching, but no
material may be added.
V. Any transmission oil cooler may be used.
W. The engine cylinder head(s) may be milled only to that amount
specified in the manufacturer’s workshop manual. If no amount is
specified then a maximum of 0.010 in. may be milled.
X. Axle/halfshaft and driveshaft retention/location devices may be
installed for safety reasons to control the motion of attached shafts
upon the failure of a coupling or universal joint. They may serve no
other purpose. This allowance does not include “C-clip eliminators.”
Y. Any crankshaft damper or pulley may be used. SFI-rated dampers are
recommended. Supercharged cars may not change the effective
diameter of any pulley which drives the supercharger.
Z. Any accessory pulleys and belts of the same type (e.g. V-belt,
serpentine) as standard may be used. This allowance applies to
accessory pulleys only (e.g., alternator, water pump, power steering
pump, and crankshaft drive pulleys). Supercharged cars are excluded
from this allowance. Alternate pulley materials may be used. Idler
pulleys may be used for belt routing in place of items which the rules
specifically allow to be removed, such as smog pumps and air
conditioning compressors. They may serve no other purpose.
AA. Camshafts and related parts must remain standard except that
alternate cam drive pulleys or gears may be used to adjust cam timing
if no variable cam and/or valve timing system exists as standard. Type
of cam drive (chain, belt, gear) must remain as standard. Alternate
parts of the same general type (e.g. roller chain in place of “silent”
chain) may be substituted. Mating parts (block, heads, covers,
retainers, etc.) may not be altered. Vehicles equipped with a variable
cam and/or valve timing system as standard may use alternate
computer calibration to adjust cam and/or valve timing but may not
change or substitute cam drive components (hardware).
BB. Upper engine shields made of plastic material, the purpose of which
is to hide mechanical components in the engine compartment, may be
removed if they have a solely aesthetic and/or acoustic function.

Street Prepared Class D
Acura
Integra (1990-93)
Integra (+ Type R) (1994-01)
RSX (all)
Alfa Romeo
1600 Coupes & Spiders (all)
1750 & 2000 Coupes & Spiders (all)
GTV V6 (all)
Milano
Audi
A4 (1.8T, FWD & quattro) (1995-01)
A4 (1.8T, FWD & quattro) (2002-10)
Coupe & Quattro Coupe
BMW
325 & 328 (E30 chassis)
323, 325, & 328 (E36 chassis)
328 & 330 (E46 chassis, non-M3)
3 Series (16v, NOC)
Bavaria
Chevrolet, Pontiac, Buick, Oldsmobile, & Geo
Cobalt SS (n/a) (2005-07)
Cobalt SS Supercharged (2005-07)
Cobalt SS Turbo (2008-10)
HHR SS Turbo
J Body (4-cyl Turbo, Quad 4 DOHC, & V6)
L Body (Quad 4 & V6)
N Body (4-cyl Turbo, Quad 4, & V6)
Spectrum Turbo (1985-89)
Storm GSi (1985-89)
X Body (V6)
Chrysler, Plymouth, & Dodge
Acclaim (V6 & Turbo)
Charger GLH-S
Conquest & Starion (non-turbo)
Daytona Turbo
Daytona (V6)
GLH-S & GLH Turbo
Laser Turbo (NOC) & K-car Turbo
Shadow (4-cyl Turbo & V6)
Shelby Charger Turbo
Spirit (4-cyl Turbo & V6)
SRT-4
Sundance Turbo
Dodge & Mitsubishi
Colt Turbo & Mirage Turbo (1984-88)
Colt Turbo & Mirage Turbo (1989-92)
Eagle
Summit Turbo (16v) (1989-90)
Fiat & Bertone
X1/9
Ford & Mercury
Capri (4-cyl & 6-cyl) (1971-77)
Capri (1991-95)
Contour SVT
Cougar (1999-2002)
Focus SVT
Fusion & Milan (6-cyl) (2006-10)
Probe (Turbo & V6)
Honda
Civic Si (1999-2000)
Civic Si (2002-05)
Civic Si (2006-10)
Del Sol (DOHC)
Prelude 4WS
Prelude (1983-2001) (NOC)
Hyundai
Tiburon
Isuzu
I-Mark LS (16v & Turbo, FWD) (1985-89)
I-Mark RS (16v & Turbo, FWD)
Impulse RS Turbo (AWD) (1990-93)
Impulse Turbo & RS (RWD) (1983-89)
Impulse XS (16v non-turbo) (1990-93)
Impulse (16v & Turbo)
Stylus XS & RS (16v) (1990-93)
Lexus
IS300
Maserati
BiTurbo
Mazda
323 GT & GTX (AWD)
6 (6-cyl)
Mazdaspeed 3
Mazdaspeed Protege
MX-6 (Turbo & V6)
Spec Miata (See 15.0 for preparation allowance requirements)
Mercedes
190 (1984-93) (all)
C230
Merkur
XR4Ti
MINI
Cooper S (+ JCW & JCW GP)
Mitsubishi
Cordia Turbo
Eclipse (2000-10)
Galant (all)
Tredia Turbo
Nissan & Datsun
200SX SE-R
200SX Turbo
200SX (V6)
240SX
Maxima
Pulsar (16v)
Pulsar NX Turbo
Sentra (2.0L) (1995-99)
Sentra (2.0L) (2000-01)
Pontiac & Toyota
Corolla XRS (2005-06), Matrix XRS (2003-06), & Vibe GT (2003-06)
Matrix & Vibe (AWD) (2003-08)
Porsche
914 (4-cyl)
924 (Audi engine)
Renault
Fuego Turbo
R5 Turbo
Saab
99, 99 EMS, & 99 Turbo
900 & 900 Turbo (1979-93)
900 & 900 Turbo (1994-98)
Saturn
Ion (all) & NOC
Subaru
Impreza 2.5
Legacy & Outback (6-cyl, all) (1998-2004)
Legacy & Outback (6-cyl, all) (2005-10)
Toyota
Camry V6
Celica (2000-05)
Celica All-Trac (all)
Corolla FX16
Supra (1982-86)
Volkswagen
Corrado (all)
Golf & Jetta (VR6)
Golf, Jetta, & New Beetle (1.8T, Mk4 chassis) (1999-2005)
New Beetle Turbo
Passat VR6
R32
Volvo
240 Series Turbo (all)
C30 (2006-09)
6-cyl (n/a) & 4-cyl (mechanically forced-induction) 2WD sedans under
3.0L not otherwise classified.
(See Section 15.1.C for update/backdate limitations.)