Proposed Rule Changes for 2023

QUICK LINKS

Use these links to jump directly to specific changes:

• SP3
• Stock
• SPB
• GTB
• 911CUP
• GTD
• GTD-1
• GTC
• Safety (Adopted)
• Stock (Adopted)
• SPB (Adopted)

SP3

     1-Reduce the minimum weight of the 944S 2.5 from 2500 to 2400

This model needs help to be competitive in this class

Stock

    2 – Reduce all minimum weights in Stock Classes G and above by 100 pounds.

Porsche models in these classes are, for the most part, newer cars and are heavier as weight has climbed along with power. It appears that none are dual purpose (street and track) cars, so should be able easily to lose this weight.

    3 – Expand the plastic quarter window allowance for all 911 models.

These are allowed in the air cooled 911s through 1998 as long as a duct is included for driver comfort air. The proposal would allow this for all 911 models, while continuing the requirement that they be used for cabin or helmet air movement, and not for drive train cooling.

    4 – Should this driver comfort allowance be extended to all models?

    5 – Allow two piece rotors but be same dimensions as stock.

The proponent asserts that these cool better.

    6 – Form an SPM (M=mid-engine) class as an option for Boxsters and Caymans not eligible for an existing “spec” class, mainly following Stock rules but generally 150 pounds lighter than Stock.

F-class Boxster racers requested a 150-pound reduction in their class weight, citing, among other things, the stresses the stock weight puts on suspension components, and the relative ease of removing this amount of weight. The Rules Committee suggested we broaden our sights to see if there were more mid-engine cars not eligible for SPB, SPC, or GTB which could compete against each other in a minimally modified spec class, mostly based on F.

This class would contain these models at the weights specified:

00-02 986 Boxster S 3.2L Min. Weight: 2854
03-04 986 Boxster S 3.2L Min. Weight: 2910
00-04 986 Boxster 2.7L Min. Weight: 2582
05 986 Boxster 2.7L Min. Weight: 2811
06-07 987.1 Boxster 2.7L Min. Weight: 2855
08 987.1 Boxster 2.7L Min Weight: 2866
07-08 987.1 Cayman 2.7L Min. Weight: 2866

Which of the following restrictions or allowances from Stock should be required or allowed SPM:

6a – Hankook C51 medium compound Z214, 245/35ZR18 front and 275/35ZR18 rear as the spec tire
6b – Rain tires are free as long as they fit legal rims.
6c – Allow electric/hydraulic power steering.
6d – Allow aftermarket clutch disks and pressure plates of stock equivalent size.
6e – Allow lightened flywheels, aftermarket or other.

SPB

    7 – Allow aftermarket gears of the stock ratios and design (e.g., no straight cut gears).

This addresses the tendency of SPB gears to break off gear tips. Under racing accelerations, the long mainshaft flexes, placing more stress on the tips and less on the roots. This is exacerbated if the car doesn’t have the stock (spring type) clutch disk and stock pressure plate. The aftermarket can provide gears of higher quality steel. As long as the stock ratios and design are used (which can easily be checked), no on track performance advantage should accrue, and more life can be expected from the ever-dwindling supply of gear boxes for this model.

    8 – Allow the 2000-2004 Boxster 2.7 liter in SPB at 2750 pounds minimum weight.

This should allow heavier drivers to enter this class and achieve close to minimum weight. The current 2.5 liter model has a factory horsepower of 201, and this later model is 217. All SPB rules would apply.

GTB

9 – Allow the 996 Carrera Cup wing on the 996 GT3.

“Every car in GTB is able to run a cup style rear wing, the 996, 997, and Caymans are all able to run these wings.  I would like to propose a rule change letting the 996 GT3 to be able to run a cup style wing in GTB class as well.”

10 – Allow the 996 GT3 to lose 100 pounds (3192-3092).

The rationale for both here is that performance of this model in GTB1, which was restricted initially until the performance balance of this model could be evaluated, warrants a reduction in weight, an increase in wing capacity, or both.

 6B-Remove 100 lbs from the 996 GT3 minimum weight in GTB1.

Analysis of lap times at various tracks for the 996 GT3, both when running in J, and this year in GTB1 (at J class specifications and weight), support this reduction.in its GTB1 weight.  The analysis involves an estimation of driver skills.

11 – Add 100 lbs to the 997.2 3.6 (from 3100 to 3200 lbs)

The proponent believes the DFI 997.2 3.6 liter car has an inherent advantage in the balance of performance versus all other GTB1 cars.

12 – GTB1 reduce the weight of the 06-08 987.1 Caymans by 50 pounds.

The allowance of an improved intake for this model was intended to keep it competitive in class, but it seemed unfair to those who would not want this modification not to add some offsetting weight. This model, which formed the bulk of the original GTB class, has been at a competitive disadvantage in recent years. When this model was allowed the option of running the GT3 intake, 50 pounds was added to the minimum weight for those choosing this option.

13 – Add the 981 GT4 Club Sport to GTB3 at 3100 lbs.

14 – Allow aftermarket carbon fiber doors, with or without a window frame, in GTB Caymans.

GTB has long allowed cars in these classes to use 996/997 Carrera Cup bodywork parts as long as they could bolt on without modification. Cup doors, which come with an integrated plastic window, can’t bolt up to a Cayman due to differing roof lines. Subsequently the GTB rules allowed aftermarket bolt-on replica body parts, which come without a window, or with a plastic nominal window surround. Has the allowance of aftermarket parts made this distinction obsolete?

15-Create a GTB2 class for GTB1 eligible Caymans only, with an unrestricted allowance for a larger throttle body and plenum

A substantial number of Cayman drivers in B1 favor a Cayman only class. GTB was created for 911 Koni Challenge lightly modified 996s, but, with the serendipitous advent of the Napelton Interseries for the then new Cayman model, the Caymans were included almost as an afterthought. Caymans have come to dominate the car counts, and many of those drivers believe the class would be stronger without the 911s. Excluding 911 models from GTB1 is simply unfair to the owners of those cars. Allowing Caymans to move to the currently vacant GTB2, with an extra power modification, will create this separation for those who want it Other GTB1 Cayman models may opt to stay in GTB1. This also would give Cayman racers in series which allow these intake modifications (e.g. IGT) a suitable class to run in PCA.

911CUP

17-THE FOLLOWING PROPOSALS ARE DESIGNED GENERALLY TO MAKE THE STOCK CLASS RULES WHICH GOVERN MUCH OF THE STOCK BASED 911CUP VARIANT CLOSER TO THOSE APPLICABLE TO SP911

The major differences between the current 911Cup rules (basically just 150 pounds less weight, with everything otherwise what Stock allows) and the SP911 rules (which are a stand-alone full set of rules) in terms of performance are as follows:

• • SP911 headers are restricted in primary tube size. This was intended to increase engine life by keeping power down, and because it was easy to measure and check.
  • SP911 rims are restricted to 16″ in diameter. The 15″ rims are the functional equivalent of a 7:31 ring and pinion.
  • SP911 shocks are restricted to 2-way adjustment, and custom shock housing is not allowed.
  • SP911 brakes are free. Balance bars have been allowed.
  • SP911 weights are lower.
  • SP911 intakes allow improved breathing, and this amounts to about 10 (or more) horsepower despite the exhaust header restriction.

It is not proposed to alter the SP911 rules. The following proposals are based generally on SP911 rules, and are 911Cup (stock rule based version) allowances for the class. Except for 17g, 17h, and 17i, they are proposed not as performance enhancements, but to reduce cost and improve longevity.

17a – Chassis reinforcement is free, subject to a requirement that no more than two tubes may penetrate the front firewall, and no more than two tubes may penetrate the rear firewall. 

This change would allow, in addition to more reinforcing tubing in the front and rear of the car, plating, gusseting, and seam welding. It would not allow replacement of chassis members with tubing (i.e., no tube or semi-tube frame cars), nor would it allow removal of stock sheet metal parts not otherwise allowed to be removed or altered.

17b -Stock bodywork parts which are bolted on may be replaced with aftermarket replica parts, which may be of alternate materials. Rear fenders may be replaced with such parts so long as a steel perimeter remains. 

This is a cost containment measure, as steel replacement parts grow in cost and decline in availability as used parts. Cars must still make weight, and weights are based on what can be achieved with steel parts.

17c – Any Porsche caliper and rotor may be used. Single master cylinders are free and need not be boosted. Brake balance adjusters are free as long as they are not cockpit adjustable. Balance bars and ABS systems are not allowed.

17d – Tub sheet metal interior to the body skin in the trunk forward of the firewall may be cut out, altered, and ducted for oil and brake cooling air flow, but may not exit out the bumper cover, hood, cowl, or fender or through the fire wall (i.e, may only exit downward or into the front wheel wells).

17e – Removal of front headlights and metal headlight buckets is allowed, and plastic headlight covers are not required.

17f – SP911 glazing and rear spoiler and wing rules (SP911 1.C. and 1.D apply), but only the windshield needs to be polycarbonate (Lexan).

17g – Allow the 3.0-liter models to run carburetors, with the limitations being:

• that the carbs not be larger than 46s
• they must use a venturi which limits maximum horsepower to 225 RWHP, and average horsepower of 220 RWHP, measured (as in SP911) at 500 RPM above HPMax and 500 RPM and 1,000 RPM below HPMax, on a standard DynoJet machine
• A dyno sheet conforming to the SP911 requirements at the end of the SP911 engine rules in the rule book is required. The dyno sheet must include the numerical data table from which the curves are generated in order to calculate the average horsepower. After sufficient testing has occurred, a maximum venturi size may be added to the rule.

17h – The horsepower limits and dyno sheet requirements in 17g apply to the stock based 3.2-liter models as well

17i – Reset the stock based version of the 911Cup car weights to 2440 pounds.

GTD

18 – What GTA class should modified Cayman factory race cars run in?

These are factory race cars, and should fit within the GTA classes. As factory race cars, GTA is a better place for modified cars (including those running other than the class required tires) to run than are the traditional GT classes.

GTD-1

19 – Allow aftermarket GTD-1 headers which bolt onto the factory stock tailpipes.

19a – Should these be with or without catalytic converters?

The headers on one side of these factory race cars crack and fail. Replacements are expensive, are on their third iteration, and must be replaced in pairs. One solution is to allow replacement with headers available in the aftermarket. All promise improvement over stock (street models), and the headers without cats have longer primaries and hence flow better. Headers with cats (as are the factory headers) would keep the power levels closer to original, but the heat of the cats can damage nearby electrical components.

20 – The latest Cayman Club Sport factory race car is the RS/CS. What GTC class is appropriate for these factory race cars? What GTA class is appropriate for these cars if modified?

GTC

21 – Allow GTC6 and 7 to run aftermarket adjustable shocks.

Per the request: “The stock shocks are unreliable – they frequently leak and are expensive to rebuild or replace”

22 – Allow GTC6 and 7 to use stock dimension aftermarket wheels.

“For supply chain concerns and for cost reasons, I would like to propose that the GTC6 and 7 rules be changed to be similar to the other GTC rules in the regard of the wheels that can be used.  The wheels offered by PMNA have been in and out of stock regularly, only available in Germany.  In fact, they currently are not available in the states at I write this.”

Add GTC 6 and 7 to this wording:

GTC4 and GTC5 wheels must be 3-piece wheels of the same width, diameter, offsets, and be of the same metal as the original factory wheels.

23 – Allow aftermarket/alternate drive axles and CVs for all GTC models.

PMNA replacement axles for th2022ese models are expensive, and often of uncertain availability, especially as the models age. The outer CVs on these cars are not meant to be rebuilt, even for something as simple as a ripped boot. A shop has shown that, with some grinding, the boots can be removed and the CVs disassembled or replaced, along with new boots. While doing this, the CV grooves (new or old CVs) can be slightly enlarged with a cylindrical abrasive, so the balls move freely. This greatly reduces the heat in the CVs, allowing high pressure grease to function adequately, and not overheat and damage boots, extending the life of an expensive component.

24 – Allow GTC4 to raise the wing like the GTC3.

The proponent cites the allowance for this given to the 996 Cups, which was premised on the stock Cup wing position obstructing the rear view, and says the C4s have the same sight line issue.

The following proposals are adopted effective immediately, without need for further comment:

Safety

     1-Triangular FIA or SFI approved window nets mounted according to the manufacturer’s specifications and in accordance with FIA regulations for sedan race cars are acceptable as the required window net, and do not require arm restraints

As before, nets adequate for head protection but inadequate for hand/arm protection will be allowed with arm restraints. Porsche factory race cars come with triangular style nets, and arm restraints are not required in professional race series where these nets are used.

Stock

     2 – 928s may install a dry sump system

The shallow sump does not allow effective baffling, which causes oil to overwhelm the breather and put oil on the track, and causes the oil pump to ingest foam, reducing oil pressure and bearing life. This allowance will not give the 928s a competitive advantage.

     3 – Aftermarket fuse boxes/holders are allowed

This is something not specifically mentioned in the stock rules, but which many have done in older cars.

     4 – Windshield washer components may be removed

SPB

     5 – The horn may be removed

This is included because of the strict “if no rule says you can, you can’t” basis of this and other classes. This rule also applies to the Stock class.

SPB racers should also note that the safety rules applicable to all cars allow a dry break refueling port with certain requirements and limitations, and this is, by its nature, applicable to SPBs as well as all other models.