18.1 MODIFIED PRODUCTION-BASED CARS
A. Eligibility Modified classes D (DM) and E (EM) contain production-based cars which are permitted additional modifications beyond those allowed in Prepared classes CP through FP. Models must meet the requirements of Section 13 (first paragraph), be specifically listed in Appendix A, meet the specifications below, or be otherwise recognized by the SEB.
1. Kit Cars Kit cars, which were originally designed, constructed, and licensable for street use, may participate in DM and EM if they are approved by the SEB. Members desiring approval of a particular kit car should provide the SEB with detailed information regarding the kit model and contact info, if available, for the OE manufacturer. For obsolete kit cars, the member will be expected to provide construction specifications, dimensions, and photographs for the SEB to examine and keep on file. The SCCA® will evaluate each submitted kit model individually and the evaluation will ensure that the specific model:
a. Follows current DM and EM allowances regarding minimum floor pan dimensions (see Section 18.1.C.1). b. Has no unusually advantageous aerodynamic features. c. Has no exceptionally low center of gravity. d. Has no exceptionally high strength-to-weight ratio. e. Has no other unique features that would upset the competitive balance in DM and EM. f. Has independently-verifiable evidence of at least 10 examples which meet the approved specification produced. Extremely limited production sports racer-type efforts are discouraged. Constructed examples of approved kits are subject to the following:
g. They will be allowed all, but no more than, the modifications that production-based cars are permitted, with the exception that minimum width for all kit cars shall be no less than 65" (165.1 cm) as measured at the narrower end of the car at the tire outer sidewalls with a minimum 14 psi of tire pressure. h. They are subject to the same engine and transmission restrictions as production-based cars. i.They must meet the same safety requirements as production-based cars. j. They must compete with full standard bodywork and that body must remain recognizable as that of the approved make and model. For these purposes, the chassis of exoskeleton type cars is considered part of the bodywork. A newly-added model is not eligible for the current year’s Solo® National Championships unless its listing was published no later than the July issue of the official SCCA® publication. The list of currently approved models is as follows:
• Exomotive Exocet • Factory Five Racing 818 (S & R) • Sylvia Sports Cars J15 • DF Goblin • Ultima GTR • Superlight SL-C
2.Clones Clones/replicas of SCCA®-recognized production cars are permitted to compete in DM and EM provided they comply with the following requirements:
a. They are substantially similar to and recognizable as the original manufactured vehicle on which they are based. b. Their specifications do not violate any rule stated herein. c. A clone shall not benefit from kit car manufacturer "running changes" unless those changes have also been submitted and approved.
3. Other Models The Panoz Roadster and Porsche 550 Spyder are eligible for competition in DM and EM.
4. Specifications Weight and displacement specifications are as shown in Appendix A.
B. Bodywork
1. Respecting Section 18.1.F:
Aerodynamic Aids, bodywork may be modified beyond the allowances of Section 17.2; however, the shape of the body must remain recognizable as that of the approved make and model. The body must be made of a fire resistant material. Doors, hoods, trunk lids, sunroofs, hatchbacks, etc. need not function as originally designed. Bumpers, grilles, lights, glass, and trim may be removed. Side mirrors and tail/stop lights are not required.
2. Firewalls and floors shall prevent the passage of flame and debris to the driver compartment. For cars having fluid lines in a non-standard routing over the belly pan, the belly pan shall have drain holes to prevent the accumulation of fluids.
3. The driver must be provided with clear and unobstructed access to the driver’s compartment.
4. Interiors may be gutted. The driver’s seat must be securely mounted. Steering and driver seating must be completely to the left or right of the vehicle longitudinal centerline. The seat must be mounted such that no part of the driver’s body below the waist may cross the longitudinal centerline of the car.
5. Body panels may be altered and air ducting installed to accommodate the installation of the water radiator. If the radiator encroaches into the driver compartment, it must be separated from the driver by a metal bulkhead or enclosing container.
6. Hoods may be altered to allow for induction system changes without restriction. Such alterations shall serve no other purpose.
C. Body and Frame a. Vertical features above the bottom floor pan plane do not have to satisfy original minimum size or shape. Note that the original width and length of the floor pan still have to meet the original dimensions. Drivetrain tunnels and seat mounting platforms may be made smaller than standard. A flat floor pan is legal. b. Floor pan material, thickness, and method of attachment are open. c. Rear passenger doors, if present, may be replaced with non-functional panels. Front and rear doors and door openings may be al tered to accommodate compliant wheelbase changes. d. All other cars, whose factory wheelbase are less than 93" (236.2 cm) may still change their wheelbase, but it must be done without violating the floor pan length as determined by both front and rear factory bulkhead locations.
3. Materials a. Except as specifically authorized, ferrous metal (containing iron) must be used for all primary load-bearing structures of the car. The primary load bearing structure is the main tub or chassis and its connections to the suspension. No aluminum cages or roll bars are allowed. Any ferrous or aluminum alloy is permitted for suspension arms, location links, and uprights/spindles. Beryllium and beryllium alloys are not allowed anywhere on the car. b. The exceptions to the above are parts of the donor production cars that were originally non-metal. In all cases, replacement of these parts or addition of more load bearing structure must be by metal. c. Except as specifically authorized, lightweight substitute materials such as carbon fiber are permitted only so long as they are clearly not load bearing in the primary structure or the suspension. For example, outer body panels in the central tub region must be attached in a flexible manner such as with Dzus® fasteners if nonstandard material composition or non-standard material thicknesses are to be used.
D. Drivetrain
1. Engines must be derived from production automobiles available in the US or elsewhere. Complete race engines derived from production automobile block designs such as the Pontiac® Super Duty 4 and the Cosworth® 16-valve series are allowed. Motorcycle, UTV, ATV, side-by-side, snowmobile, marine, or any other initially nonautomobile design is not allowed even if it was also made available in an automobile. Non-automobile engines are prohibited. 4-stroke automobile motors shall not be converted to 2-stroke.
2. Engine and/or drivetrain changes are permitted within the following limitations:
a. Original front-engine design must remain a front-engine design (i.e., no part of the engine block or cylinder head may extend rearward of the midpoint of the wheelbase). b. Original rear- or mid-engine designs may be interchanged with each other, but no part of the engine block or cylinder head may extend forward of the midpoint of the wheelbase.
3. Non-automobile CVTs are prohibited. Automobile-based CVTs are only allowed with their matching factory engine.
4. Internal and external components of the engine, transmission, and rear differential are unrestricted. Any shifting mechanism or pattern is permitted. Driveshafts may be made of any material deemed safe. Supercharging and turbocharging are permitted without restriction but shall require the displacement specifics of Section 18.0.B.3.
5. Supercharging and turbocharging are permitted for all engines subject to the displacement factor of 18.B. In DM, such induction systems must have a restrictor on the inlet side of the turbo/supercharger. All inducted air must pass through this restrictor which must be constructed of metallic material. The minimum orifice (choke) of the restrictor shall be no greater than 33 mm (1.3"). The restrictor passage may be shaped fore and aft of the choke region. The restrictor choke region must be made of one piece without moving parts. Inlet restrictor must be mounted within 18" of turbo inlet. Tubing between the restrictor and turbo/supercharger inlet must be rigid and made from non expanding parts. The tubing inside diameter may not exceed 3" at any point. Flexible couplers may be used for connections.
E. Minimum Weights Minimum weights for cars in DM and EM and all adjustments to these weights are shown in Appendix A.
F. Aerodynamic Aids
1. These classes are restricted downforce classes. No aerodynamic tunnels, or sealing skirts may be added. No bargeboards, ramps, or other aerodynamic devices are allowed except as specified herein or as part of an SCCA®-approved GT-1 bodywork package for the specific make and model.
2. The hood, tub, roof, rear fenders, and rear deck are not permitted to be reshaped to achieve downforce. The front of the car may be reshaped to accommodate the construction of spoilers, air dams, and splitters, and may be widened to rear body width as specified in Section 18.1.E.3.c below. Ramps joining the front fender flares to the splitter/spoiler/airdam assembly which are included as part of a SCCA®-approved GT-1 front bodywork package are allowed.
3. Front Aero a. The standard OE or a non-standard front spoiler or air dam may be used. A non-standard front spoiler is not permitted to protrude forward beyond the overall outline of the car as viewed from above or aft of the forward most part of the front fender opening and shall not be mounted more than 4.0" (101.6 mm) above the horizontal centerline of the front wheel hubs. b. The spoiler may cover the normal grille opening at the front of the car. Cooling duct openings are permitted. If the front radiator is removed or relocated, no aerodynamic use of the unobstructed front radiator pathway may be made. The front spoiler may be attached to the original bodywork or it may replace the bodywork it would otherwise cover. c. The front spoiler may not be wider than either the front or rear bodywork, measured as the maximum distance between the outside edges of the wheel well openings or fender flares at axle height. The total fore-to-aft curvature or deviation of the rear spoiler, measured at the trailing edge, shall not exceed 10.0" (254.0 mm) as viewed from above. The front spoiler must be connected to bodywork above the spoiler across its full width. New bodywork may be added to close the gaps between the fenders, nose, and spoiler/splitter/airdam assembly on cars with open or irregular front bodywork such as the Ford® Model T, MG® TD, Morgan®, and Lotus® 7. When these or similar vehicles use a full-width front spoiler, the car’s spoiler/airdam is required to be vertical (between 80-100°) for the lower 8.0" (20.3 cm) of its extent. The change in top view outline caused by these bodywork changes is allowed. d. Front splitters are allowed but must be installed parallel to the ground within ±1.0" (±25.4 mm) fore to aft. The splitter trailing edge must be fully sealed to the front bodywork/fender flair/spoiler and the splitter may not get wider as it extends forward. From each point on its trailing edge the splitter can extend no more than
8.0" (15.2 cm) directly forward of the top-view outline of the car. The splitter must be a single plane with the top and bottom surfaces parallel, with an overall height of 1.0" (24.5 mm) or less. The leading edge of the splitter may be rounded (the radius area may extend backwards no more than the splitter thickness). The bottom of the splitter may attach to the belly pan but is not required to do so. Splitter endplate mounting location may be at the outside lateral end or inboard of the outside lateral end of the splitter. Additional mounting plates or strakes may be added inboard of the endplates but these must be no larger than the endplates. e. A front splitter and its associated features shall not function as a diffuser. f. An OE splitter which does not conform to these requirements may be used unmodified on the original make and model. g. Canards are allowed and may extend a maximum of 6" (15.24 cm) forward of front bodywork/fascia as viewed from above. No portion of the canard may extend past the widest part of the front bodywork/ fascia as viewed from above. Canard area will be measured in the same manner as wings using Section 12, Definitions. Canard area may not exceed 1.2 sq. ft. (1114.8 cm²). The canards may have endplates. The endplates may connect the splitter and the canard. The splitter and canard endplate total surface area is limited to 100 sq. in. (645.2 cm2) for each side.
4. Rear spoilers a. If a rear spoiler is used, it shall be mounted to the rear hatch, deck, or trunk lid, and mount no further forward than the base of the rear window. The spoiler extension for the entire spoiler is set by one measurement at the lateral midpoint of the car. At that point, the spoiler may not extend more than 10.0" (25.4 cm) from the attachment point out to the outer or free edge. This sets the maximum height above ground at all other locations on the spoiler. The result may be a flat topped rather than contoured spoiler. Alternatively, the spoiler may be mounted at the rear of the roof, or to the rear hatch lid at or near the top of the hatch; in such a configuration the spoiler may extend no more than 7.5" (19.1 cm) from the original bodywork, measured as described above. The spoiler angle of attack is free. The rear spoiler is measured from leading, attached edge to trailing or outermost, free edge. Its measurement is independent of its angle of attack. b. The spoiler may not be wider than the rear bodywork, measured as the maximum distance between the outside edges of the wheel well openings or fender flares at axle height. The total fore-to-aft curvature or deviation of the rear spoiler, measured at the trailing edge, shall not exceed 10.0" (25.4 cm) as viewed from above. c. Aerodynamic aids permitted in Section 18.1.F shall not function as wings. Therefore, the spoiler may not overhang the bodywork such that air passes both over and underneath it. If the rear spoiler overhangs the side of the car, the lower edge of the spoiler shall be supported by bodywork that will prevent air from passing underneath the spoiler. This may be accomplished by extending the spoiler to join the bodywork or wheel opening/fender flare beneath the overhang.
5. Diffusers are allowed at the rear of the car only; no part of the rear diffuser shall cross the wheelbase centerline into the front half of the vehicle. The diffuser may protrude rearward beyond the top view outline of the car. The diffuser shall have no more than 25.0" (63.5 cm) front to back of expanding chamber; this 25.0" expansion chamber length is inclusive of all parts/components/body forward and rearward of the diffuser. A diffuser is defined as an expanding chamber between the vehicle and the ground for the purpose of accelerating air ahead of it to develop low pressure. Vanes or strakes are allowed inside the diffuser; sideplates and strakes may extend below the diffuser surface as long they do not attain a definite seal with the ground on level ground. Closed undersides or belly pans (lower surface) are permitted. The entire length of the underbody may be closed off to permit proper airflow to a rear diffuser or to smooth the underside of the car. The belly pan shall be flat within 1.0" (25.4 mm) total deviation. No tunnels or other underbody aerodynamic features are permitted. Chassis rake is free. Additionally, no side skirt or body side, etc., may extend more than 1.0 cm (0.394") below this lower surface anywhere on the car to the rear of the front axle unless specifically permitted by these rules.
6. If a factory production car or kit car was supplied with tunnels they may remain but they must be blocked in a safe manner to prevent them from functioning to provide downforce. For example, foam or sheet metal may be firmly attached in tunnels to ruin their shape or to stop airflow.
7. Vanes, strakes, and/or endplates (elements) are permitted on front and rear spoilers. A minimum distance of 6.0" (152.4 mm) must separate adjacent elements. These do not have to be square or rectangular; the side profile shape is open. For each element, the total area may be no more than:
• 56 sq. in. (362.9 cm²) for a roof spoiler; • 100 sq. in. (645.16 cm²) for a trunk spoiler; • 100 sq. in. (645.16 cm²) for a front splitter.
8. Wings may be added, removed, or modified. Non-OE wings may only be attached to the chassis or body behind the centerline of the rear axle. The total combined surface area of all wings shall not exceed 8 sq. ft. (0.7432 m2) as calculated per Section 18.0.C., Definitions. The number of wing elements is limited to 2. Wings designed to be adjustable while the car is in motion must be locked in a single position. Spoilers under 17.2.P and rear wings are mutually exclusive such that a builder may use one or the other, but not both. Wing endplate surface area is limited to 200 sq. in. (1290.3 cm2) each and the number of endplates is limited to a maximum of 2. No part of the wing may extend past the widest part of the car.
G.Brakes The use of any type brakes, pads, and components are permitted (disc or drum). The location of brake components (inboard vs. outboard) may be changed from original. The original "emergency" or hand brake may be removed.
H. Tolerances A tolerance of ±½" (±12.7 mm) shall be used when measuring floor pan dimensions from the car’s original specifications.
I. Other
1. At least 50% the width of each tire must be covered by the fenders, for no less than 75% of the length of the tire, when viewed from the top of the fender perpendicular to the ground. No sharp edges are permitted.
2. Suspension systems and wheels are free.
3. The use of a windscreen is not required.
4. Roll bar requirements for cars competing in DM and EM are as specified in Section 3.3.2.