Purpose:
The purpose of the Time Trials Production (TT) classes is to provide a formulaic method for classifying cars for Club and Time Trials competition. These classes are intended for, but not limited to, vehicles that are normally classed in the Street Prepared, Street Touring, and Street Modified Solo classes.
It is assumed that cars competing in the Time Trials Production classes are prepared beyond the Showroom Stock classes, but not to the specifications of the Club Racing classes defined in the GCR. It is also assumed that Time Trials classed cars will have similarly prepared suspension and brakes, making considerations for such modifications unnecessary for classification purposes. Finally, it is understood that these classifications are new and based on limited data and experience, and will therefore be inappropriate in some cases. In such cases, the event officials are given the authority to make changes with regards to an individual’s car classification in the interest of balanced competition. Any changes to an individual’s car classification will be documented by the event officials with the reasons for the change and sent to the Time Trials Divisional Program Manager and the SCCA Time Trials Administrative Council for review.
Cars Eligible:
Commonly available production automobiles intended for street use, modified for Club Trials or Time Trials competition (original frame or unibody), and on DOT approved tires (street or R-compound). It is recommended that cars eligible for Showroom Stock participate in their stock class. Likewise cars prepared for SCCA Club Racing should participate in their GCR defined class. However, all production based cars are eligible for Time Trials Production classification.
Classification:
Cars will be classed by their equivalent engine displacement (liters) and shall compete in their applicable Time Trials Production class listed below. A vehicle’s equivalent displacement is determined by the current (factory or modified) displacement multiplied by 1 + the sum of the appropriate modifiers (listed below), and rounded to the nearest 0.1 liter to determine the final classification. Please note that more than one modifier can apply to one car, but each modifier can be applied only once.
| Time Trials Production Classes | ||
| Class | Minimum Displacement (liters) | Maximum Displacement (liters) |
| TT-1 | 8.0 | Unlimited |
| TT-2 | 5.7 | 7.9 |
| TT-3 | 4.8 | 5.6 |
| TT-4 | 4.0 | 4.7 |
| TT-5 | 3.2 | 3.9 |
| TT-6 | 0.0 | 3.1 |
Weight Modifier Calculations:
For use with the weight modifiers, the car must be weighed in race trim, with driver. Cars will have their weight signed off in their log book by an SCCA tech inspector, in order to prevent having to reweigh the vehicle at every event. It is the driver’s responsibility to maintain the weight of the vehicle at the signed off weight (+/- 10 lbs), or have the vehicle reweighed and signed off if the weight is changed. If scales aren’t available at an event for classification use, the factory specified curb weight of the vehicle without the driver will be used for classification. As an alternative, a certified public scales weighing of the car and designated driver will be accepted until weighing at an event is available. The certified public scales weight certificate shall remain with the log book until event scales are available and the race trim weight is signed off by an SCCA tech inspector.
| Displacement Modifier Chart | ||
| Modifier | Name | Notes |
| -0.25 | Diesel | Applied to any vehicle that runs on diesel fuel. |
| 2.00 | Rotary | Applied to any vehicle powered by a rotary motor. |
| 0.80 | Forced Induction | Applied to any turbocharged or supercharged vehicle. |
| 0.40 | Altered Boost | Applied to any vehicle running non-factory levels of boost (via boost controllers, wastegate modification, ECU reprogramming, other electronic engine management, blow off/pop off valve changes, pulleys, and/or porting/polishing of forced induction components). “Non-factory” boost is defined not only as peak boost changes, but boost curve changes as well. This includes normally aspirated cars that have added forced induction. Changes in boost levels as a result of modification to systems not directly related to boost control (i.e. changes to exhaust systems, intercoolers/after coolers, intake, etc.) are permitted without requiring the application of this multiplier. |
| 0.25 | Multi-valve | Applied to any vehicle with three or more valves per cylinder. |
| 0.25 | Multi-cam | Applied to any vehicle with two or more camshafts. |
| 0.50 | Variable Valve Timing | Applied to any vehicle with variable valve timing (including but not limited to Honda VTEC, Toyota VVTi, Subaru AVCS, BMW Vanos, etc.) |
| Variable | Lightweight | Applied to any vehicle weighing (with driver) or with a factory specified curb weight (without driver) less than 2700 lbs. Modifier is 0.001 for every pound less than 2700. |
| Variable | Heavyweight | Applied to any vehicle weighing (with driver) or with a factory specified curb weight (without driver) greater than 3200 lbs. Modifier is -0.001 for every pound over 3200. |