CRS press liason and CRS2 competitor Erik Christiansen has put together an article explaining the CRS classes for 2013, including the new Open Light class:

The California Rally Series is an overlay championship consisting of events in the southwest sanctioned by a variety of sanctioning bodies. Since different sanctioning bodies have differing class structures, the California Rally Series has our own five classes that are scored at every CRS event in order to create a meaningful regional championship. Below is a summary of the classes; please see the rulebook for complete details.

The Performance Stock class has been popular among CRS competitors since it was introduced almost twenty years ago with the goal of creating an economical “driver’s class.” This class is for two-wheel drive, normally aspirated four cylinder cars with limited modifications allowed. In an effort to control costs, P-Stock cars are also limited to vehicles with a Blue Book value of less than $4,000. Competitors are allowed certain modifications to the suspension, engine and drivetrain of the vehicle, however items such as the stock intake and exhaust manifolds, and brake systems retained. This creates a rule set that is easily enforced through visual inspection, but prevents competitors from building high-horsepower machines. Updated or backdated components within the same model body style are allowed, but not across different generations.

Two-wheel drive competitors looking for less restrictive rules fall into either CRS-2 or CRS-5. CRS-2 is consistently one of the most populated classes on almost every rally entry list. It consists of low-displacement cars such as VW Golfs and Honda Civics. Other than engine displacement, there are no restrictions on modifications, so brakes can be upgraded, suspension components modified and aftermarket exhaust headers are allowed (to name a few common modifications).

CRS-5 takes this open concept even further by removing the displacement limit, and is popular among high-horsepower two-wheel drive vehicles. This class usually has V-8 trucks and muscle cars, and high-horsepower turbo cars like the Dodge Neon SRT-4. CRS-5 competitors are typically in the hunt for an overall podium or even a win at many events.

New for 2013 is the CRS Open Lite class (which replaced the production based CRS-GT class). This class is geared for normally aspirated four-wheel drive cars, such as the iconic Subaru Impreza 2.5RS. These vehicles are growing in popularity and CRS Open Lite gives competitors a chance to race against each other without the expenses associated with a high-horsepower turbo engine.

Finally, the pinnacle of the CRS class structure is Open 4wd. This class has it all: four wheel drive, turbos and no limit on modifications. Typical Open 4wd cars include Subaru WRX STIs and Mitsubishi Lancer Evolutions. These are the cars you typically find at the top of th leaderboard, setting stage record times at most events.

As a reminder, the California Rally Series is not a sanctioning body. The CRS classes described above are for the purpose of creating a meaningful regional championship. Each event on the CRS schedule will have a sanctioning body that has certain safety rules and regulations.

Please consult the appropriate rulebook (e.g. NASA Rallysport or Rally America) for safety requirements.

Hope to see you on the stages soon!