A.
PURPOSE AND INTENT
The
Spec Miata (SM) class is intended to provide the membership with the
opportunity to compete in low cost, production-based cars with
limited modifications, suitable for racing competition.
The
rules are intentionally designed to be more open than the Showroom
Stock class but more restricted than the Improved Touring class.
The
vehicle identification number (VIN) shall correspond with the
model-year automobile classified. VIN plates or stampings shall
remain in place. There must be a minimum of two (2) VIN plates or
stampings that correspond with the model year automobile classified.
B.
CLASSIFIED CARS AND WEIGHTS
Classified cars and weights are listed on the Spec Miata
Specification Table.
Cars
are to be weighed with the driver and required ballast. See GCR
Section 9.3.8.
C.
AUTHORIZED MODIFICATIONS
The
following items represent the only modifications and safety items
permitted and/or required on Spec Miata automobiles other than
safety items as required in Section 9. No permitted
component/modification shall additionally perform a prohibited
function. No updating or backdating of cars, models, specifications,
and/or components thereof shall be permitted except as specifically
authorized in these specifications.
A Shop
Manual for the specific make, model, and year of automobile is
required to be in the possession of each entrant. The manual is
intended to aid Scrutineers in identifying parts and the
configuration of the automobile. Overhaul procedures that in the
slightest way would increase performance are not to be utilized;
e.g., porting, etc. Blueprinting and balancing are inconsistent with
the philosophy of this class and are not permitted.
All
adjustments shall be at the manufacturer s specification and/or
within the manufacturer s specified tolerances except as permitted
within the SMCS.
Stock
replacement parts may be obtained from sources other than the
manufacturer provided they are the exact equivalent of the original
parts. The intent of this rule is to allow the competitor to obtain
replacement parts from standard industry outlets, e.g., auto-parts
distributors, rather than from the manufacturer. It is not intended
to allow parts that do not meet all dimensional and material
specifications of new parts from the manufacturer.
1. Engine
Modifications
a. Induction System
1. All air entering the intake tract
shall pass through the fuel injection air inlet.
2. 1600 cc cars may replace the stock
air box with a cone style air filter assembly. The air filter
element is unrestricted. No ducting or baffling of air to the air
filter is permitted.
3. 1600 cc cars may open and adjust,
but not modify, the OEM airflow meter. For 1600 cars, the position
of the air flow meter may be moved provided it remains attached to
the unmodified factory intake tube.
4. 1800 cc cars must use the stock air
box, but the air filter element is unrestricted.
5. 1800 cc cars shall use an air
restrictor. The throttle restrictor shall be placed between the
throttle body and plenum. All intake air shall pass through the
restrictor plate. Restrictor plates must be the proper size as
listed in the Specification Table, must be from Mazdaspeed
Motorsports Development, and must not be modified.
b. Fluid hoses and
clamps, oil filters, fuel filters, and belts (fan, alternator, etc.)
may be substituted with others of equivalent OEM specifications.
c. Fuel System
1. Unleaded fuel filler trap door and
restrictor plate in filler neck may be removed.
2. Refer to GCR Section 9.3.25 for
permitted fuel specifications and for the required fuel sample
acquisition port.
d.
Ignition/Electrical System
1. Spark plugs and spark plug wires may
be substituted.
2. Ignition timing is unrestricted
within stock adjustment capability.
3. Batteries may be replaced with those
of an alternate manufacturer, provided they are of similar amp-hour
capacity, size, and weight and are fitted in the standard location.
Additional battery hold-down devices may be used, and are strongly
recommended.
e. Exhaust System
1. The factory exhaust system beyond
the OEM front down pipe may be replaced, provided:
a. Said replacement system retains the
original configuration, e.g. single tube design, and the tubing
diameter is a maximum of 2.25 outside diameter.
b. The pipe may end anywhere after the
rear subframe. Forward of the rear subframe, the pipe must follow
the original path of the OEM exhaust system.
c. No expansion chambers. A single
muffler may be added.
d. The system meets all event specific
sound requirements.
e. A cat
replacement tube may be installed. The tube shall not exceed 17.5
in length and have an outside diameter no greater than 2.375 .
2. Original exhaust system heat shields
may be removed.
f. Clutch System
and Flywheel:
All cars
shall use either the stock OEM pressure plate appropriate model year
or the ACT pressure plate (Mazdaspeed p/n: 0000-0205401-SS (1.6L
cars) or 0000-0205404-AC (1.8L cars)). The unmodified pressure plate
shall be bolted directly to the appropriate stock, unmodified
flywheel. The 94 model year may utilize the flywheel from the 95-05
model years. Any clutch disk may be used.
g. Lubricants
may be substituted with any lubricant. Oil additives are
unrestricted.
h. The engine block
and/or cylinder head may be
decked/milled to achieve the factory specified compression ratio for
the correct model year as listed on the specification table.
i. Camshafts
shall comply with
the Official Camshaft Data as supplied by the SCCA Tech Department.
j. Cast iron cylinder liners
(sleeves) may be
installed to restore damaged or worn cylinder bores to the original
dimension.
2. Cooling System
a. Any radiator may be used, provided
it is mounted in the original location, maintains the same plane as
the original core and requires no body or structure modifications to
install. Any openings created by fittng an alternate radiator shall
be blocked to prevent air from entering the engine compartment. The
stock cooling fan(s) must be maintained.
At least one
functional stock OEM cooling fan must be mounted in one of the stock
locations.
b. Thermostats may be modified,
removed, or replaced.
c. All cars may install the Upper
Radiator Seal, p/n NA75-50-OK7A
d. A radiator screen of one-fourth
(1/4) inch minimum mesh may be added in front of the radiator and
contained within the bodywork.
e. The factory air conditioning systems
may be removed. Items that serve a dual purpose, such as the
alternator/air conditioning compressor bracket, may not be
substituted.
f. Engine coolant fluid, coolant/heater
hoses and clamps may be substituted. Heater core may be bypassed. It
may not be modified or removed. Heater water control valve(s) may be
added or substituted.
3.
Transmission/Final Drive
a. Transmission and final drive ratios
must remain stock for the year of car. 1999-up cars shall only use
the 5 speed transmission and the 4.3 differential ratio. All cars
may use the stock unmodified OEM open differential or one of the
approved alternates listed below.
b. 1990 to 1993 Miatas may use the
stock, unmodified viscous limited slip differential or the
MAZDASPEED Motorsports Development limited slip differential, part
number #QN10-64-A00 (previously TOY1-27-200 & 0000-02- 5501).
c. 1994 and newer cars may use the
stock Torsen limited slip differential.
d. The 90-93 Miatas
may convert to the 99-05 differential housing and the 4.3
differential gear ratio from the 99-05 model years. This conversion
includes the driveshaft and half-shafts. The original 90-93 model
rear suspension uprights must be retained.
4. Chassis
Suspension modifications are limited to
the addition of the MAZDASPEED Motorsports Development Spec Miata
kit and those modifications detailed in this area.
a. MAZDASPEED Motorsports Development
Spec Miata kit
1990-93 1.6 DOHC K-SPEC-M5-SUSP
1994-97 1.8 DOHC K-SPEC-M5-SUS8
1999-up 1.8 DOHC K-SPEC-M5-SUS9
The
following is a breakdown of components supplied within these kits.
All parts numbers are MAZDASPEED Motorsports Development parts
numbers. No substitution of parts is allowed. The kits must be used
in their entirety.
1. Shocks
Front Bilstein 0000-04-5225-BL
Rear Bilstein 0000-04-5226-BL
2. Springs
Front Eibach ERS 700 lbs/6
0000-04-9700-06
Rear Eibach ERS 325 lbs/7
0000-04-9325-07
3. Coil-Over kit
Front/Rear 0000-04-5402AW
4. Anti-Roll Bars
K-SPEC-M5-SUSP
Eibach kit - front / rear bars
0000-04-5302-EB
Front 24mm Adjustable
Rear 15mm Adjustable
K-SPEC-M5-SUS8
Eibach kit - front / rear bars
0000-04-5303-EB
Front 27mm non-Adjustable
Rear 15mm Adjustable
K-SPEC-M5-SUSP9
Eibach kit front / rear bars
000-04-5304-EB
Front
27mm
non-Adjustable
Rear
15mm
Adjustable
b. All cars shall use unmodified
Mazdaspeed bump stop (Part # 0000-04-5993AW).
1999-up cars shall use the bump stops
from the Mazdaspeed kit (p/n 0000-04-5993-AW) in conjunction with
the 1999-up stock upper mount assembly consisting of the upper mount
(p/n: NC10-28-340C), the upper mount bushing (p/n: NC10-28-775) and
the upper mount washer (p/n: NC10-28-774). All other OEM upper
mounting hardware shall be discarded.
c. Subframe braces may be updated to
stock 1997 configuration utilizing the MAZDASPEED Motorsports
Development Spec Miata kit.
d. Anti-roll bar links may be replaced
and may be adjustable, but the attachment points must remain stock.
The control arms and specified anti-roll bar may not be modified.
One end of the sway bar(s) may be disconnected as a suspension
tuning aid. The bar must remain in place and be solidly attached to
the suspension on one end.
e. Suspension alignments (camber,
caster, toe) are unrestricted within the limits of the unmodified
factory adjustments. Minimum ride height is unrestricted.
f. No relocation or reinforcement of
any suspension component or mounting points is permitted.
g. Hardware items (nuts & bolts) may be
replaced by similar items performing the same fastening function(s).
h. Manual or power steering racks may
be used. Power steering racks may be converted to manual by removing
all power steering components.
i. Towing eyes per GCR Section 9.3.46
are required. Stock towing eyes may be modified, replaced, or
removed but may serve no other purpose.
j. Hubcaps and wheel trim shall be
removed.
k. All chassis/structural/electrical
repairs, if performed, shall be in concurrence with factory
procedures, specifications, and dimensions. Unless specifically
authorized by the manufacturer for repair or allowed by these rules,
no reinforcement, i.e., seam welding, material addition, etc., is
permitted.
l. The front shock tower
connector/brace is not permitted on the 1999 and newer cars.
5. Brakes
a. Backing plates and dirt shields may
be ventilated or removed.
b. Brake lines may be replaced with
steel lines or Teflon lined metal braided hose.
c. Cars with antilock braking systems
must have the system disabled as specified in GCR 9.3.11.
d. Parking brake mechanisms, and
actuating components may be removed.
e. Brake pads and brake fluid are
unrestricted
f. 2001 and newer cars must use the
255mm(F) and 252mm(R) brakes. The larger brakes 269.5mm(F) and
267.9mm(R) are not permitted.
6. Wheels/Tires
Any wheel/tire may be used within the
following limitations:
a. Required rim diameter is fifteen
(15) inches. Maximum rim width is seven (7) inches. Minimum weight
of wheel shall be 13 lbs without spacers.
b. Other than the stock 15 Mazda steel
wheel, all wheels must be one-piece metal castings (not multi-piece
wheels, bolted, riveted or welded together).
c. Tires:
1. National Competition
All cars shall use the Toyo Proxes RA-1
(205/50R15)
2. Regional Competition
Any DOT approved tire is permitted.
Racing, recapped, or regrooved tires are not allowed. Tire size is
unrestricted. The only modifications allowed to tires are having
treads shaved or trued. Individual regions may require spec
tires for regional races. Supplemental regulations for specific
events should be checked.
d. Track may be changed to accommodate
larger tires, provided that there is safe tire/fender/chassis
clearance under all conditions of steer, bump, and rebound.
Aftermarket wheel studs, lug nuts, and wheel spacers are permitted.
e. Tire tread (that portion of the tire
that contacts the ground under static conditions) shall not protrude
beyond the fender opening when viewed from the top perpendicular to
the ground. To determine compliance, the vehicle should be rolled
through a powdered substance, as raced with driver, in order to
indicate the tire tread contact patch under static conditions.
7. Body/Structure
a. Fenders and wheel openings shall
remain unmodified. It is permitted to roll under or flatten any
interior lip on the wheel opening for tire clearance. Non metallic
inner fender liners may be removed.
b. Body repair shall be performed using
every reasonable effort to maintain stock body contours, lips, etc.
Any body repair modification having as its purpose increased
clearance is prohibited.
c. The R package Miata chin spoiler
is allowed on 1990-1997 cars provided it is mounted in the OEM
location. 1999-up cars may use the OEM chin spoiler for these cars
(99-00
p/n: NC10-V4-900F
or 01-05 p/n: NO67-V4-900G).
d. Windshield Clips/Rear Window Straps
per GCR Section 9.3.53. are permitted and recommended.
e. Convertible tops and attaching
hardware shall be completely removed. Cars may compete with the
Mazda factory detachable hard top in place (latches shall be
replaced with positive fasteners), but it is not mandatory. When no
top is used, driver shall wear arm restraints, and the cage will
meet the helmet clearance rule.
f. Body side moldings, rocker panel
moldings, and wheel opening trim pieces may be removed.
g. The plastic trim on the hood may be
removed.
h. Hood and trunk clips are permitted.
Stock hood and trunk latches may be disabled or removed.
i. Ducting may be added to provide
fresh air to the driver compartment. This ducting shall be located
in the driver and/or passenger vent window area by means of a
transparent/alternate vent window material and duct with no
modifications to the bodywork.
To improve driver
exit through the window area, the driver vent window and verticle
vent window support may be removed as a pair. If removed, ducting
may be in the passenger side vent window only.
j. Radio antennas may be removed.
Antennas for two-way radios may be added.
8. Driver/Passenger
Compartment - Trunk
a. The driver s seat shall be replaced
with a one-piece bucket-type race seat. All seat mountings shall be
reinforced. Factory seat tracks/brackets may be modified,
reinforced, and/or removed to facilitate replacement mountings
provided they perform no other function. The passenger seat must be
removed.
b. Any steering wheel, except wood
rimmed types, and its required mounting modifications may be used.
Any shift knob may be used.
c. Gauges and instruments may be added,
replaced, or removed. They may be installed in the original
instrument(s) location using a mounting plate(s), or any other
location using a secure method of attachment. Other than
modifications make to mount instruments and provide for roll cage
installation, the remainder of the dash board or panel shall
remain intact.
d. Any interior or exterior mirrors may
be used.
e. Carpets, center consoles, cargo
bins, seat belts, floor mat, radio system, headliners, dome lights,
grab handles, sun visors and their insulating and attaching
materials may be removed. Other than to provide for the installation
of required safety equipment or other authorized modifications, no
other driver/passenger compartment alterations or gutting are
permitted.
The door window glass, window operating
mechanism, and inside door latch/lock operating mechanism may be
removed and the inner door structural panel may be modified, but not
removed. The stock side impact beam and the outside door latch/lock
operating mechanism shall not be removed or modified. This gutting
of the door shall only be made if roll cage incorporates
NASCAR-style side protection extending into the door.
f. Two way radios may be used.
g. Spare wheels and tires, jacks and
tools shall be removed from the cargo/trunk area. Spare tire covers
and trunk mats and/or trunk carpeting shall be removed.
h. Modifications may be made to the
foot pedals to improve the comfort and accessibility to the driver.
Dead pedal/foot rest and heel stop may be added.
i. If ballast is required to meet the
required weight it shall be added as follows:
1. All ballast shall be securely
mounted on the passenger floor.
2. Each segment of ballast shall be
fastened with a minimum of two (2) one-half (1/2) inch bolts and
positive lock nuts of SAE Grade 5 or better and shall utilize large
diameter, load distributing washers.
3. Holes may be drilled in the
passenger floorpan for the purposes of mounting the ballast and the
floorpan may be reinforced for that purpose only.
j. All cars shall run with both front
door windows fully open (down).
9. Safety
a. Roll cages shall meet all
requirements of GCR Section 9.4.2, for Showroom Stock cage
configuration, tubing size, and material. Regardless of car weight,
all Spec Miata autos may be constructed to the requirements for a
<2200-pound car.
b. Steering lock mechanisms shall be
removed. See GCR Section 9.3.41.
c. An electrical master ( kill )
switch is required. See GCR Section 9.3.33.
d. Installation of a fire extinguisher
or fire system is required. See GCR 9.3.22.
e. Glass headlights shall be taped.
Rear brake lights may be taped with transparent tape. Turn signals,
front parking lights, backup lamps, and side marker lights may be
taped.
f. Air bag systems shall be disarmed
and may be removed.
g. In any automobile where allowed
removal of seat belts, upholstery, etc., creates an opening between
the driver/passenger compartment and an exposed gas tank, or part
thereof, including the filler tube, a metal bulkhead which
completely fills such opening shall be installed. See GCR 9.3.26
