RULES - NATIONAL COMPETITION RULES - MAX CATEGORY

MAX CATEGORY

CLICK HERE FOR TEXT VERSION OF MAX CATEGORY RULES

These are the vehicle classing and preparation rules for the Max Category of SCCA National Time Trials Competition. The intent of Max Category is that these vehicles are examples of "dream" street cars – built or bought.

Competitiveness is not guaranteed, as it is impossible to assure competitiveness without also restricting the imagination and desires – something not done when dreaming.

Once you find where your car may fit within the classing divisions, make sure it fits in Max Category by scrolling down to see what modifications you're allowed to do.

Max Category Classing

Max Category is divided into five classes. Each class is based on a set of allowed displacements or electric motor power along with minimum weights (measured with driver) to avoid ultra-light production cars winning each class.

The basic gist is this: There is a base unmodified naturally aspirated displacement (or kilowatt) limit for each class. If you have factory unmodified single-unit forced induction or you have modified your naturally aspirated engine – you go up one class.  If you have multi-unit forced induction or have added or modified existing forced induction, you go up two classes.

In addition, if you’re under the weight limit of the class, then you would need to go up classes until you find your spot and no car may be less than 95% of curb weight with driver or less than 1,100 lbs. – whichever is higher – and still compete in Max Category.

Max Category Classing

1. Max 1 eligible vehicles include production vehicles and eligible kit cars not weighing less than 2,500 lbs. or 95% of curb weight (with driver), whichever is greater, powered by the following OE engine displacement or KW-rated motor(s):

A. Naturally aspirated 4-cycle engines greater than 6.4L OE measured displacement.

B. Naturally aspirated rotary or 2-cycle engines greater than 2.0L OE measured displacement.

C. Modified or Unmodified single-unit forced-induction engines greater than 4.5L OE measured displacement.

D. Multi-unit forced-induction engine configurations greater than 2.9L (4-cycle) or 1.75L (Rotary/2-Cycle) OE measured displacement.

E. Electric vehicles with greater than 400KW OE rated motor(s).

2. Max 1 eligible vehicles include the following underweight vehicles from classes below:

A. Vehicles within Max 2 eligible limits weighing less than 2,800 lbs. but not less than 2,400 lbs. or 95% of curb weight (whichever is greater).

B. Vehicles within Max 3 eligible limits weighing less than 2,300 lbs. but not less than 2,000 lbs. or 95% of curb weight (whichever is greater).

C. Vehicles within Max 4 eligible limits weighing less than 2,000 lbs. but not less than 1,600 lbs. or 95% of curb weight (whichever is greater).

D. Vehicles within Max 5 eligible limits weighing less than 1,300 lbs. but not less than 1,100 lbs. or 95% of curb weight (whichever is greater).

3. Max 1 eligible vehicles include the following low-production vehicles (less than 1,000 examples):

A. Vehicles which meet power, displacement and configurations for the classes below, not weighing less than 1,100 lbs. or  95% of curb weight (with driver) whichever is greater.

1. Max 2 eligible vehicles include production vehicles of more than 1,000 examples and eligible kit cars not weighing less than 2,800 lbs. or 95% of curb weight (with driver), whichever is greater, powered by the following OE engine displacement or KW-rated motor(s):

A. Unmodified naturally aspirated 4-cycle engines of up to 6.4L OE measured displacement.

B. Unmodified naturally aspirated rotary or 2-cycle engines of up to 2.0L OE measured displacement.

C. Modified naturally aspirated 4-cycle/rotary engines up to their respective Max 3 listed OE measured naturally aspirated unmodified displacement limit.

D. Unmodified single-unit forced induction 4-cycle/rotary engines within their respective Max 3 listed OE measured naturally aspirated unmodified limit.

E. Modified or unmodified multi-unit forced induction engines or modified/added forced induction within Max 4 listed OE measured naturally aspirated unmodified limit.

F. Electric vehicles with unmodified OE batteries and up to 400 KW OE rated motor(s).

G. Electric vehicles with modified/replaced batteries or modified motor(s) up to Max 3 OE rated motor(s).

2. Max 2 eligible vehicles include the following underweight vehicles from classes below:

A. Vehicles powered by Max 3 eligible engines/motors weighing less than 2,500 lbs. but not less than 2,300 lbs. or 95% of curb weight (with driver) whichever is greater.

B. Vehicles powered by Max 4 eligible engines/motors weighing less than 2,000 lbs. but not less than 1,800 lbs. or 95% of curb weight (with driver) whichever is greater.

C. Vehicles powered by Max 5 eligible engines/motors weighing less than 1,500 lbs. but not less than 1,300 lbs. or 95% of curb weight (with driver) whichever is greater.

1. Max 3 eligible vehicles include production vehicles of more than 1,000 examples and eligible kit cars not weighing less than 2,500 lbs. or 95% of curb weight (with driver), whichever is greater, powered by the following OE engine displacement or KW-rated motor(s):

A. Unmodified naturally aspirated 4-cycle engines of up to 4.5L OE measured displacement..

B. Unmodified naturally aspirated rotary or 2-cycle engines of up to 2.0L OE measured displacement.

C. Modified naturally aspirated 4-cycle/rotary engines up to their respective Max 4 listed OE measured naturally aspirated unmodified displacement limit.

D. Unmodified single-unit forced induction 4-cycle/rotary engines within their respective Max 4 listed OE measured naturally aspirated unmodified displacement limit.

E. Electric vehicles with unmodified OE batteries and up to 250 KW of OE rated motor(s).

F. Electric vehicles with modified/replaced batteries or modified motor(s) up to Max 5 OE rated motor(s) limit.

2. Max 3 (M3) eligible vehicles include the following underweight vehicles from classes below:

A. Vehicles within Max 4 eligible limits weighing less than 2,200 lbs. but not less than 2,000 lbs. or 95% of curb weight, (with driver) whichever is greater.

B. Vehicles within Max 5 eligible limits weighing less than 1,700 lbs. but not less than 1,500 lbs. or 95% of curb weight, (with driver) whichever is greater.

1. Max 4 eligible vehicles include production vehicles of more than 1,000 examples and eligible kit cars not weighing less than 2,200 lbs. or 95% of curb weight (with driver), whichever is greater, powered by the following OE engine displacement or KW-rated motor(s):

A. Unmodified naturally aspirated 4-cycle engines of up to 2.9L OE measured displacement.

B. Unmodified naturally aspirated rotary or 2-cycle engines of up to 1.5L OE measured displacement.

C. Modified naturally aspirated 4-cycle/rotary engines up to their respective Max 5  listed OE measured naturally aspirated unmodified displacement limit.

D. Unmodified single-unit forced induction 4-cycle/rotary engines within their respective Max 5  listed OE measured naturally aspirated unmodified displacement limit.

E. Electric vehicles with unmodified OE batteries and up to 175 KW of OE rated motor(s).

F. Electric vehicles with modified/replaced batteries or modified motor(s) up to Max 5 OE rated motor(s) limit.

2. Max 4 eligible vehicles include the following underweight vehicles from classes below:

A. Vehicles within Max 5 eligible limits weighing less than 1,900 lbs. but not less than 1,700 lbs. or 95% of curb weight, (with driver) whichever is greater. 

1. Max 5 eligible vehicles include production vehicles of more than 1,000 examples and eligible kit cars not weighing less than 1,900 lbs. or 95% of curb weight (with driver), whichever is greater, powered by the following OE engine displacement or KW-rated motor(s):

A. Unmodified naturally aspirated 4-cycle engines of up to 1.9L OE measured displacement. .

B. Unmodified naturally aspirated rotary or 2-cycle engines of up to 1.25L OE measured displacement.

C. Electric vehicles with unmodified OE batteries and up to 100KW of OE rated motor(s).

.

The following kit cars are eligible for Max Category:

1. Shelby Cobra Models

2. Shelby Daytona Coupe Models

3. Corvette 1963 Grand Sport Models

4. Ariel Atom

5. Exocet

6. Noble M400/M12 and Rossion Q1

7. Brunton Auto  - Stalker

8. Factory Five 818/818C

2. Engine Modification Definitions
The following criteria is how "modified" or "unmodified" engines are defined for Max Category classing criteria.

A. Modified Combustion Engine
The following criteria are used to define “modification” of an internal combustion engine: 

1. Modification or replacement of OE (or OE equivalent) head gasket, head bolts or parts in the valve train, or rotating assembly. (E.g., valve springs, lifters, rockers, camshaft(s), pistons, rods, crankshaft, balance shafts, rotors, etc.) 

2. Modification or machining of the engine block, head or rotor-housing beyond factory shop-manual limits. 

3. As well as #1 and #2 above, modification or replacement of the following OE ((or OE equivalent) parts of a forced-induction engine will be considered modified:

a. Turbocharger, including turbine wheel, turbine housing, compressor, compressor housing, intake manifold and any fastening hardware. 

b. Supercharger, including housing, phasing gear, rotors, intake manifold and any fastening hardware. 

B. Modified Electrical or Hybrid Engine
The following criteria are used to define “modification” of an electrical engine or hybrid drivetrain:

1. Increase in voltage output of electric motors by any means.

2. Change in number, type or discharge rate of OE batteries.



Max Category Authorized Modifications

These are the Authorized Modifications for Max Category vehicles (i.e., what you can do to your car and have it stay in Max Category). Max Category, along with Sport, Tuner and Prepped. are restricted rulesets. If a modification is not specifically authorized in these Rules, it is not allowed. (If it doesn't say you can, you can’t.)

The first section outlines the Max Category philosophy, safety minimums, vehicle eligibility and general modification rules. Following that, the individual sections outline what you can do with each system. (e.g., body, engine, suspension, etc.)

Each set of allowances is broken down into two parts, the first of which are the "Layman's Terms." These are a basic way to describe the intent and allowance. For the rules nerds in our midst, or those who think their modification might be close to OK but not quite sure, there will be a link to the full text rules which fully explains what is allowed. There are some rules we trust don't need any more explanation (we use the word "unrestricted" a lot in this section).

In Max Category, a vehicle may have every modification allowed in Sport and Tuner Categories, plus the modifications listed here.

1. Max Category Overview

Max Category is a place for enthusiasts to maximize the street-worthy car of their dreams with minimal limits on engine, suspension and bodywork. Max Category vehicles must have all road-going equipment such as headlights, tail lights, blinkers and windshields/windscreens, if delivered with such. Other than specifically classed kit-cars which do not have headlights and such, Max Category vehicles must be able to be street driven.

Max Category is a restricted ruleset. If modifications are not specifically authorized in these Rules, it is not allowed. (If it doesn't say you can, you can’t.)

1. Vehicles running in Sport, Tuner and Max Categories must meet Safety Level 1 Standards.

A. Roll bars, cages, racing harnesses and other safety equipment may be added, and must meet manufacturers' guidelines for installation. It is highly recommended that they at least meet the minimum for Safety Level 2 or Safety Level 3 Standards.

B. Nothing in the rules prevents you from adding safety equipment; the minimum amount of modification to install safety equipment is allowed.

C. To facilitate safety, vehicles that have an added roll bar (4-points) may remove carpet, seats and trim (including convertible tops) behind the front seats. Vehicles that have an added roll cage (6-points) may remove carpet, seats and trim (including convertible tops) other than the dash.


2. Fuel cells may be used in cars with the following restrictions and allowances:

A. Any replacement fuel cell should be constructed and installed to racing standards. (E.g., FIA/SFI approval, fuel cell enclosure, bladder, and foam baffling.)  

B. OE lines may be replaced in conjunction with a fuel cell provided they are shielded.

C. Any fuel lines—including gauge and vent lines—that pass into or through the driver/passenger compartment, shall be of steel tube or metal braided hoses or bulkheaded.

D. Drivers of cars with modified or replaced OE fuel lines or tanks must wear a suit, shoes, gloves and underwear as specified in SCCA Time Trials Safety Level 2 Standards.

E. Vehicles with modified or replaced OE fuel lines or tanks must have an on-board fire suppression (fire bottle or system) meeting SCCA Time Trials Safety Level 2 Standards.

F. Participants are cautioned that this is not an allowance to maximize fuel delivery by installing higher-performance parts than authorized by category rules. (E.g., installing an upgraded fuel pump if it's not otherwise allowed.)

Max Category is open to production cars and eligible kit cars using almost any automobile drivetrain and is meant to fit between the current Tuner and Unlimited Categories.

All of the general modification rules of Sport and Tuner Categories are allowed in Max.

Max Category vehicles may only be driven, stopped and steered through the wheels and tires. When the word “unrestricted” is used in these rules, it is under the assumption that the modifications and controls are within this parameter.

Max Category vehicles are likely to be street-driven cars, and 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.

2. Max Category Chassis, Interior and Bodywork

You need to keep the stock chassis or unibody. We don't want you creating a tube frame and putting stock bodywork on it.

The frame or unibody (from shock tower to shock tower or “ladder” frame) is sacrosanct. These must stay intact unless otherwise allowed in these Rules.

1. Body, frame and sheet metal (such as transmission tunnel) may be altered to the minimum extent required to allow engine swaps, transmission swaps and suspension modifications.

2. Subframes may be replaced or modified.

3. Vehicle perimeter and wheelbase must be full-scale to original model. Incidental wheelbase and overall dimension changes resulting from the allowed replacement of suspension components or modification of suspension design are allowed. This is not an allowance to shorten or lengthen the chassis/body (e.g., change the scale from the original).

You can customize your interior so you can replace (but not remove) the carpet, seats, trim and maybe even paneling. We're not going to argue too hard if you do things like remove package trays and such, but we don't want bare interiors. Bare metal interiors are race cars. Unless you can show us a REALLY compelling reason it's done that way on your street car, we're going to consider bare metal/stripped interiors an Unlimited Category car. (It better look like the Hughes H-1 Racer in there.) "Because I like battleship grey paint" isn't a compelling reason.

Of course, if you add roll bars, you can remove all that stuff from the front seats back, and if you put a cage in, you can remove everything but the dash.

1. Cosmetic interior components like panels, carpet and seats may be replaced (but not removed), as long as fire walls are retained and fumes are not vented into the cockpit. Panels may be added to insulate the driver from venting and exhaust. The driver’s normal seated position may not be relocated, unless it is a right-side drive conversion to match existing production cars.

2. Fuel tank/cell may be modified or replaced and must be separated from the driver/passengers as originally manufactured or by a metal panel/bulkhead if the OE structure is modified. If the fuel tank is moved from the OE location, it should be a motorsports-style fuel cell constructed of a housing, bladder and foam. Fuel must not vent into the driver/passenger compartment directly or indirectly.

3. As with Sport/Tuner Categories, there is a “safety loophole.” If you add a roll bar meeting Safety Level 2 Standards, you can remove carpet and trim (convertible tops included) from behind the driver and passenger seats and even replace an airbag-equipped steering wheel. If you install a full cage meeting Safety Level 3 Standards, you can remove all the trim and carpet other than the dash.

You can replace or modify body panels, but the overall dimensions and wheelbase need to stay full-scale or changed only minimally by other allowed modifications. You can replace or modify subframes in order to do other allowed modifications. You can do fancy stuff like add fasteners to attach bodywork, and you can remove fenders and running boards from pre-war cars. No matter what you do, no part of the car other than the wheels and tires can be less than 3 inches from the ground. 

1. No portion of the vehicle or bodywork (other than exhaust/exhaust hangers) may be less than 3 inches from the ground.

2. Body panels may be modified or replaced in the original standard locations. Frame or Unibody may only be modified the minimal amount to account for allowed modifications. Subframes may be replaced or modified.

3. Body panels may be attached with removable fasteners (e.g., Dzus®).

4. “Side Skirts” sometimes referred to as “barge boards” may be added with the following restrictions:

A. No portion of the side skirts/barge boards may be less than 3 inches from the ground.

B. Horizontal portions of a side-skirt/barge-board may not extend more than 3-inches from OE bodywork when viewed from above.

C. They may not extend further than 12” inboard from the outer limits of OE bodywork.

5. Fenders and running boards may be removed from vehicles with a production year prior to 1946, as long as the removal of those parts does not expose the interior of the car or engine compartment.

In Max Category, you can add wings, spoilers, splitters, air damns, diffusers and cosmetic canards, but we do limit you some with restrictions like wing sizes and heights and such. Chances are most people will make it, but if you have an SCCA Street Modified car with aero surfaces at the limit of the rules, you're going to end up in Unlimited Category.

Wings, wing endplates, spoilers, canards and splitters may be added, removed, or modified with the following restrictions.

1. Non-OE wings have the following restrictions:

A. May not be added in addition to an OE wing.

B. Only one wing may be added.

C. May only be attached behind the centerline of the rear axle and may not attach to suspension components.

D. The number of wing elements is limited to two (2).

E. Wings designed to be adjustable while the car is in motion must be locked in a single position.

F. Wings, and any component thereof, may not extend beyond the OE vehicle width as defined by the outermost portion of the OE bodywork Including mirrors, door handles, rub strips and trim.

G. No portion of the wing or its components (including end plates and mounts) may be more than 6 inches (15.24 cm) forward of the rear axle, more than 6 inches (15.24 cm) beyond the rearmost portion of the bodywork, and have the following restrictions on height:

1. On sedans/coupes/trucks the wing may not be more than 10 inches (25.4 cm) above the roofline of the vehicle. For convertibles/roadsters with no roof and targas with no rear window, the windshield frame, or windshield of any material shall be considered the top of the roofline.

2. On hatchbacks/wagons/Sport Utility Vehicles, the wing may not be more than 14 inches (35.56 cm) above the roofline of the vehicle.

H. Reinforcements to the wing mounting area may be used but may serve no other purpose.

I. Spoilers and rear wings are mutually exclusive such that a builder may use one or the other, but not both.

2. A spoiler may be added to the rear of the car provided it complies with the following:

A. It is a production rear spoiler which is standard or optional equipment of a US 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 (254 mm) 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 (101.6 mm) from the original bodywork in any direction. The spoiler shall not protrude beyond the perimeter of the original bodywork as viewed from above. The use of endplates is prohibited. Angle of attack is free. The spoiler may not function as a wing.

C. Spoilers and rear wings are mutually exclusive such that a builder may use one or the other, but not both

3. Canards are allowed with the following restrictions.

A. Canards may extend a maximum of 4 inches (10.16 cm) forward of front bodywork/fascia as viewed from above.

B. No portion of the canard may extend past the widest part of the front bodywork/fascia as viewed from above.

C. Canard area will be measured in the same manner as wings. Canard area may not exceed 1.2 square feet (1114.8 cm²).

D. Canards may have endplates. The endplates may not connect to a splitter.

E. Canards may not be within 3 inches of the splitter.

4. A front spoiler/air dam/splitter is permitted, with the following restrictions.

A. Splitter blade shall be installed parallel to the ground (within ±3° fore and aft) and may extend a maximum of 5 inches (12.7 cm) from the front bodywork/fascia as viewed from above.

B. No part of the front spoiler/air dam shall be lower than 3 inches from the ground.

C. Splitters may not extend rearward past the vertical centerline of the front wheels.

D. Openings in the front spoiler/air dam are permitted for the purposes of ducting air to the brakes, cooler, and radiator.

E. OE (factory) front spoiler/splitters are permitted, and if mounted in the stock location, have no height restrictions.

5. Diffusers are allowed with the following restrictions:

A. May not extend forward past the vertical centerline of the rear wheels.

B. May not extend more than 6” from the rear bodywork, as viewed from above.

C. No part of the diffuser shall be lower than 3 inches from the ground.

D. OE (factory) front diffusers are permitted, and if mounted in the stock location, have no height restrictions.

3. Max Category Wheels, Tires and Brakes

Any wheels are allowed. Non-metallic wheels must be certified/approved from an appropriate, recognized standards organization (e.g., FIA, SFI, SAE, TUV, etc.).

(We trust you don't need layman's terms for that rule.)

Max Category cars must be on street tires with at least 200 treadwear and meet all the eligibility requirements of Sport and Tuner Categories, but there are no width limits.

Tires must meet the following requirements to be eligible for use in Max Category. No tire model will be eligible for Time Trials competition until it meets all requirements of this Section. Tire models not meeting the requirements by April 30 are not eligible for Time Trials competition until after the Time Trials National Championships of the year.

1. Original Equipment (OE) Tires
OE DOT-Approved Tires may be run providing the following conditions are met:

A. The tire size and model is as delivered from the factory on that model and trim level car. (E.g., The 100UTQG GoodYear Eagle F1 Supercar 305/30ZR19 (Front) and 325/30ZR19 (Rear) on the 2018 Chevrolet Camaro ZL1 1LE.)

B. The car is not prepped beyond Sport Category rules. (The car does not have to be classed in Sport Category, but its modification may not be beyond those rules.)

C. The tire must not appear on the following exclusion list, which may be altered at any time by the Time Trials Board (TTB) upon notification of membership.

There are no tires currently listed.

2. Aftermarket/Non-OE Tires

A. Specification

1. Minimum UTQG Treadwear Grade of 200.

2. Minimum molded tread depth of 7/32 inch as specified by the manufacturer.

3. Listed in a current year or prior two years of the “Tire Guide®” and/or the “Tread Design Guide®” (www.tireguides.com).

4. US Department of Transportation (DOT) approval.

5. Tires must be designed for highway use on passenger cars.

B. Eligibility Requirements:
The following are prerequisites before a tire can be used in competition at Time Trials Events.

1. Tire availability: Tires are considered available when competitors can take possession through retail channels. Pre-orders are not considered available.

2. Tires must be equally available to all competitors. Tires that are in short supply do not specifically violate this Section. Extensive shortages may result in the tire being placed on the exclusion list until supply is replenished. Tire variations differing from standard specification, delivered only on a limited basis, or only to selected competitors may not be used.

3. Tire models must have tires available in at least four (4) rim diameters and in at least six (6) sizes which meet these requirements.

4. Material Change: Tires which previously met the eligibility requirements that undergo a significant compound change, tread pattern change, or other significant redesign reset the requirement for eligibility described in this Section.

5. A tire model which was previously allowed by these rules continues to be eligible for competition until specifically disallowed.

6. Reintroduction: Models that were once discontinued will be considered a new model once reintroduced and must meet all the requirements of this Section.

7. The tire must not appear on the following exclusion list, which may be altered at any time by the Time Trials Board (TTB) upon notification of membership.

Kumho V720 ACR (less than minimum molded tread depth)

3. Tire Use

A. Scored Sessions
Unless a “wet session” is declared by event officials, vehicles must run on the same set of tires for all scored competition rounds, and the tires should be marked with a stamp on grid of the first competition. Tires may also be replaced at the discretion of the Technical Chief in cases safety issues such as damage or excessive wear. (Entrants are warned that damage caused by deliberate abusive handling or deliberate shaving should not be given a replacement allowance.)

B. Unscored Sessions
Vehicles are required to practice on tires which are legal for scored sessions in their class, but do not have to be the same set.


4. Other

A. Tires may be shaved evenly and parallel to the axis of rotation, but may not otherwise be siped, grooved or modified.

B. Tires must have a minimum tread depth of 2/32nds at two (2) points 180 degrees apart.

C. No recap and/or retread tires may be used.

D. Excluded tires: Tires may be excluded for, but not limited to, low volume production, extensive availability limitations and specialty design.

Components, lines, hoses and method of attachment are unrestricted.

4. Max Category Steering and Suspension

Your imagination can run wild here, from replacing a steering box on a vintage car to creating fully customized steering systems.

Components, lines, hoses and method of attachment are unrestricted.

Suspension components can be changed,meaning you can customize suspension, mounting points and parts. 

Components and method of attachment are unrestricted.

5. Max Category - Electrical

Other than electric or hybrid cars, electrical system components and wiring are unrestricted.

Note: We want to include electric cars, but we do not want to make electric cars class-killers. We're looking at how to write smart rulesets for common modifications to electric and hybrid vehicles as they become more common. If you really understand these systems, we want to hear from you about reasonable and controllable allowances for them.

6. Category - Engine and Drivetrain

Other than electric and hybrid cars, the engine control, ECU and electronics are unrestricted.

Note: We want to include electric cars, but we do not want to make electric cars class-killers. We're looking at how to write smart rulesets for common modifications to electric and hybrid vehicles as they become more common. If you really understand these systems, we want to hear from you about reasonable and controllable allowances for them.

Intakes are unrestricted. Forced induction may be added.

Cooling systems for engine, transmissions and differentials are unrestricted.

You can swap engines as long as the engine goes in the same end of the car, and stays transverse/longitudinal as the OE car came with. The engine you swap in also needs to come from a production automobile.

What you do to your engine will affect your class - modified naturally aspirated engines go up one class, unmodified single-unit forced-induction engines go up one class, and any multi-unit or modified forced induction goes up two classes.

For example, if you swap in a "stock" naturally-aspirated engine into your car you go into the class with "unmodified" limits. If that engine comes with a single-unit forced induction or you build that naturally-aspirated engine, you go up one class. If you modify or add forced induction or it comes with twin-turbos, then it goes up two classes.  

1. Allowed Engine Modifications
Components (internal and external) may be modified or replaced, other than the following restrictions:

A. Engines must be derived from production automobiles. Motorcycle, snowmobile, marine or other engines of non-automobile design are not permitted.

B. The engine orientation and the general engine bay location must not be changed from OE. (E.g., Vehicles with transverse engines may only install an engine in a transverse orientation, vehicles with longitudinal engines may only install an engine in a longitudinal orientation, front-engine stays front-engine, rear/mid-engine stays rear/mid-engine.)

2. Engine Modification Definitions
The following criteria is how "modified" or "unmodified" engines are defined for Max Category classing criteria.

A. Modified Combustion Engine
The following criteria are used to define “modification” of an internal combustion engine: 

1. Modification or replacement of OE (or OE equivalent) head gasket, head bolts or parts in the valve train, or rotating assembly. (E.g., valve springs, lifters, rockers, camshaft(s), pistons, rods, crankshaft, balance shafts, rotors, etc.) 

2. Modification or machining of the engine block, head or rotor-housing beyond factory shop-manual limits. 

3. As well as #1 and #2 above, modification or replacement of the following OE ((or OE equivalent) parts of a forced-induction engine will be considered modified:

a. Turbocharger, including turbine wheel, turbine housing, compressor, compressor housing, intake manifold and any fastening hardware. 

b. Supercharger, including housing, phasing gear, rotors, intake manifold and any fastening hardware. 

B. Modified Electrical or Hybrid Engine
The following criteria are used to define “modification” of an electrical engine or hybrid drivetrain:

1. Increase in voltage output of electric motors by any means.

2. Change in number, type or discharge rate of OE batteries.



The transmission, differentials and transfer cases may be changed, provided they are production-vehicle units (no race-specific applications). The internals of those cases may be modified or replaced, as long as it is not a dogbox or sequential conversion. The reverse gear must also always work.

Exhaust is unrestricted other than it must exit from under the vehicle. It may exit through the bodywork.

7. Max Category - Fuel

Max Category vehicles must meet Sport and Tuner Category fuel rules, but the use of E85 is not restricted.

1. Fuel System

Max Category vehicles fueling system components including injectors, lines and tanks are unrestricted provided they meet all safety rules. 

2. Allowed Fuel

1. Max Category vehicles will use fuel which is “Federally approved for use on public highways.” This does not allow racing-type fuels which are available at service station pumps.The use of E85 is not restricted.

2. Propane or Compressed Natural Gas (CNG) fuel may be used in any category provided that the following conditions are met:

A. The tank must be located in a safe location on the car and be firmly and securely mounted. This does not permit the cutting of vehicle sheet metal (e.g., the trunk floor) for tank installation.

B. The tank must conform to Federal and local container standards and have an emergency relief/cut-off control.

C. For use of propane or CNG as a fuel, no changes to the induction system of the engine may be made with the exception of the necessary fuel lines to the carburetor or fuel injection. There may also be no other engine parts changed.

D. The entire system must meet local ordinances covering the use and transmission of compressed gas.

E. Propane or CNG may not be used in combination with another fuel.