Sprint Cup Series - Sprint Cup Cars

Sprint Cup Cars

Sprint Cup Series cars (often called "Cup cars") adhere to a front engine rear-wheel-drive design. A roll cage serves as a space frame chassis and is covered by a 24-gauge sheet metal body. They have a closed cockpit, fenders, a rear spoiler, and an aerodynamic splitter. Fielding a car for one season usually costs $10–20 million. Each team may build their own cars and engines (per NASCAR's specifications) or purchase cars and engines from other teams.

The cars are powered by EFI V8 engines, with cast iron blocks, and a pushrod valvetrain actuating two-valves per cylinder, and limited to 358 cubic inches (about 5.8 liters) displacement. However, modern technology has allowed power outputs near 850 horsepower (630 kW) in unrestricted form while retaining the conventional basic engine design. In fact, before NASCAR instituted the gear rule, Cup engines were capable of operating in excess of 10,000 rpm. A Sprint Cup Engine with the maximum bore of 4.185 inches (106.3 millimeters), and stroke of 3.25 inches (82.55 millimeters) at 9,000 rpm has a mean piston speed of 80.44 fps (24.75 m/s) (roughly that of a Formula One engine). Contemporary Cup engines run 9,800 rpm, 87.59 fps (26.95 m/s), at the road course events, on Pocono Pennsylvania's long front stretch, and at the .526 mile short-track Martinsville Speedway. At the backbone 1.5-2.0-mile tri-oval tracks of NASCAR, the engines produce over 850 hp running 92-9400 rpm for 500 miles, 600 mi for the World 600 Charlotte race.

The front suspension is a double wishbone design, while the rear suspension is a two-link live axle design utilizing trailing arms. Brake rotors must be made of magnetic cast iron or steel and may not exceed 12.72 inches (32.3 centimeters) in diameter. The only aerodynamic components on the vehicles are the front splitter, spoiler, NACA ducts in the windows only, and side skirts. The use of rear diffusers, vortex generators, canards, wheel well vents, hood vents, and undertrays is strictly prohibited. While the cars may reach speeds of about 200 mph (321.8 km/h) on certain tracks, Russ Wicks drove a stock car built to NASCAR's specifications 244.9 mph (394.1 km/h) during a speed record attempt at the Bonneville Salt Flats in October 2007.

Sprint Cup engines carry a Freescale-provided electronic control unit, but traction control and anti-lock brakes are prohibited. Live telemetry is used only for television broadcasts, but the data can be recorded from the ECU to the computer provided the car is in the garage, and not on track.