Car Classification

Implementing the 2017 Zone 8 Rules
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About the Zone 8 Car Classification Site


Welcome to the Porsche Club of America (PCA) Zone 8 (Z8) Points Classification System for the Time Trial (TT) and Autocross (AX) series.

Purpose: The purpose of this site is to automate the calculation of points for determining the correct CC class for your Porsche and to provide a public record of that class and the factors that went into determining it. Addtionally, this site may also assist in determining your Street Stock class, but the rules for Street Stock are different enough that it is not always possible. This site cannot help with the spec or 4-door classes. This site may not apply to your car at all if you are not running a CC class.

Please note: In the event of a discrepancy in the class assigned to a car by this site and the class that would be assigned by proper application of the published Z8 Rule Book, the published rules will prevail.

Your honest and constructive feedback is always welcome and appreciated. Help us positively affect the future of the Z8 competition car classification system. Please address any questions, issues or problems to the Zone 8 Rules team at: rulequestions@zone8.org

Philosophy of the Zone 8 Points System

The Pre-2012 Rules System

Prior to 2012, Z8 car classification was based upon placing similar-model cars into the same class, and then progressing them through a hierarchy based upon which modifications have been made to the cars. Over the years a number of factors caused this classification system to be reconsidered.

First of all, there was the problem of determining which of the models were similar and therefore should be classed together. Second, there was the constant proliferation of new Porsche models. Since the classes were model-based, this in resulted in a continual increase in the number of classes. Finally, there were often too few competitors in each class for interesting competition, a problem that was continually exacerbated each time new classes were added.

The Points-Based Classification System

Rather than a model-based system, the new Z8 classification system, as specified in the Z8 Rule Book, is based entirely upon points. Each distinct car model (by specific model and year) has a base point assignment. Each performance-enhancement to a base car adds additional points. For example, changing to a non-stock performance muffler or adjustable shocks, wider tire widths, race tires, and engine displacement increases all add points. A car's base points plus all performance equipment points and tire size points determine its class. Cars with similar point totals compete with each other in a particular class.

In addition to the above "points" classes, we also have the "street" classes. Because of the way the points system works, it is possible that a stock car will end up in the same class as highly modified cars. While this fits the definition of the system, we understand that some drivers of stock cars may prefer otherwise. The purpose of these "street" classes is to provide a place for cars to participate “as delivered.” In general, for these classes any US Spec factory original equipment, whether stock or optional, for that model and year of car is allowed. The vehicle must also be registered for street use. Older vehicles are not represented in these classes because fewer and fewer of them exist in original condition (without modification) as time goes by.

Even with both the “points” and the “street” classes, the number of classes in use dropped by more than half in switching over from the old rules to the current rules.

The Zone 8 Car Classification Website

Recognizing that computing car classes manually is tedious and error-prone, Z8 has provided this web site to make classifying cars as simple and accurate as possible. Moreover, since the site is public, it acts as a peer review mechanism that allows all participants to see what performance equipment their competitors are using. However, this site does not give complete details or explanations on every rule. See http://www.zone8.org/events/rules/current.php for the current rules document.

Determining Base Points

Base points are determined by using power to weight ratios and other known data as a starting point, and may also include subjective adjustments to account for real world performance. It is recognized that a newer car of equal power to weight ratio to an older car is likely to have a performance advantage due to evolutionary changes in chassis, power characteristics and suspension. When assigning base points to new models, these criteria are scrutinized.

Raw Base points

Raw Base points are assigned based on a formula using the car's power to weight ratio, model age and the width of its standard‐equipment wheels. A car's power to weight ratio (PW) is calculated by dividing the PCNA published curb weight (lbs.) of the model (equipped with a manual transmission) by its PCNA published horsepower. The calculated PW ratio is then used to determine the appropriate Raw Base points using the following formula:

(4000 / (Weight/Horsepower)) + (year of model introduction ‐ 2010) + (5 x (width in inches of one front + one rear standard‐equipment wheel ‐ 12 )) = Raw Base points

Explanation: This formula takes the inverse of the PW ratio and multiplies it by 4000 (creating a steepening curve that assigns progressively higher and higher base points for each incremental improvement in PW ratio, then subtracts one point for each year since the model's introduction prior to 2010 (to grant a modest advantange for age and, in future years, a disadvantage for models introduced after 2010), and then adds 5 points for each inch greater than 12 of the car model’s standard‐equipment wheel‐widths (this serves as a rough proxy to capture design and performance advantages as suspension techology & brakes have improved over time, thus further disadvantaging newer cars). Note: Negative points are not given for smaller wheels.

Mid-Engine Adjustment Points

Due to their advantageous handling traits, mid‐engined cars are also assigned 15 adjustment points.

Other Adjustment Points

Other adjustment points may added to or subtracted from each model’s base points as part of the annual rule revision process if deemed appropriate in order to consolidate models, account for the performance potential of specific models or to better balance competition.

Corrections

All facts and figures have been determined and verified to the best of our ability. If you find that any vehicle weights, horsepower figures, displacement figures or standard wheel sizes are incorrect and have Porsche factory documentation supporting your claim, please contact the Zone 8 Rules Team at: rulequestions@zone8.org

A Note about Comparing Cars

Placement in the points classes (CC01-16) is determined by the total of adding together your base points, tire size points and performance equipment points. It is important to note that when you are comparing classes for various car models, comparing base points alone is not fair, sufficient or informative. One must at a minimum include tire size points in the comparison. One should never compare just another’s base points with one’s own total points.