SCCA A Street Prepared Boxster Setup

General Notes

The SCCA Street Prepared Category rules include all the modifications allowed in Stock Category, plus those listed below. There are several reasons why I don't recommend competing with a standard Boxster in ASP:

1. The other cars in ASP may have significant advantages over the Boxster, such as lighter weight and more power. And the new Boxster S is everything the standard Boxster is, but with a bigger engine! (Seems unfair, eh? But that's life in the fast lane! They can't very well have a class for every car out there.)
2. Your Boxster, if prepared to the limit of the rules, will likely become unsuitable for street driving, contrary to the original intent of the category. Most SP competitors transport their cars to the autocrosses on trailers, and only drive them at the autocrosses.

If none of this deters you, and you still want to try ASP, read on.

Allowed Modifications

As with the Stock rules, the SP rules change slightly every year, but the basics have been unchanged for many years. Visit the SFR SCCA website's Solo II Street Prepared Rules page for details.

Below is a summary of the changes you can make to your Boxster, in addition to the Stock changes, and still remain legal in SP.

• The distinction between different years/models used in Stock Category does not apply in Street Prepared Category. So you can interchange parts from any year and model of Boxster that you want... within certain limits:

1. The item is standard (or optional) on the year/model from which it was taken.
2. The years/models are listed on the same line of Appendix A in the rules (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. The updating and/or backdating of engines, transmissions or transaxles must be done as a unit; component parts of these units may not be interchanged.

• 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.
• Air conditioning systems may be removed in whole or in part.
• Fenders and bumpers may be modified for tire clearance.
• Strut bars are permitted with all types of suspension. Strut bars may be mounted only transversely across the car from upper right to upper left suspension mounting point and from lower right to lower left suspension mounting point.
• Any fully padded and upholstered front seat may be used.
• Any steering wheel may be used.
• Spoilers and cosmetic trim pieces are permitted. Side skirts may not be used.
• Fuel cells may be used to replace the standard fuel tank.
• Accelerator, brake, and clutch pedals may utilize substitute covers of unrestricted origin, shape, and size.
• Wheels of any diameter, width, or offset may be used, and wheel spacers may be added.
• Air ducts may be fitted to the brakes, provided that they extend in a forward direction only, and that no changes are made in the body/structure for their use.
• Any anti-sway bar is permitted. Bushing material, method of attachment, and locating points are unrestricted.
• Ride height may be altered by suspension adjustments or change or modification of springs or coil spring perches. Coil spring perches originally attached to struts or shock absorber bodies may be changed or altered, and their position may be adjustable.
• 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.
• Adjustable camber plates may be installed at the top of struts, and the original upper mounting holes may be slotted. The center clearance hole may not be modified.
• Any ignition setting adjustment or system may be used.
• Relocation of the battery is permitted but not into the passenger compartment.
• 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.
• Carburetors, fuel injection, intercoolers and intake manifolds are unrestricted.
• Air cleaner may be changed or removed, velocity stacks may be added.
• Emission control devices may be modified or removed.
• Exhaust manifolds and muffler systems are free, except that they must be quiet and terminate behind the driver.
• Any clutch, flywheel or torque converter that uses the standard attachment to the crankshaft may be used.
• 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.

That is quite a long list, and few of these mods are minor or unimportant. You may see why I wrote earlier that SP preparation usually results in a car unsuited for street driving. But if that's OK with you, then who am I to dissuade you? If you built a Boxster to these rules, it would certainly be an awesome and unique car!

How to Make These Modifications

Most of them are discussed in detail elsewhere on this site. Here are the Stock allowances:

Tires

Wheel Alignments

Mufflers

Air Filters

Wheels

Here are the additional SP allowances:

Wheels

Springs, Struts and Sway Bars

Camber Plates

Computers

Intakes

Headers

Limited Slip Differentials

But most importantly, don't forget that the driver is the ultimate factor! Sign up for a school if you can, or buy a copy of one of the high-performance driving books listed in my storefront.

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