Drag Racing Glossary:
Saturday, 16 December 2000 08:00


Breakout: Used only in handicap racing, the term breakout refers to a contestant running quicker than he or she "dialed" his or her vehicle (predicted how quick it would run). Unless his or her opponent commits a more serious infringement (e.g., red-lights, crosses the centerline, or fails a post-race inspection), the driver who breaks out loses. If both drivers break out, the one who runs closest to his or her dial is the winner.

Burnout: Spinning the rear tires in water to heat and clean them prior to a run for better traction. A burnout precedes every run.

Christmas Tree: The Tree, as it often is called, is the noticeable electronic starting device between lanes on the starting line. It displays a calibrated-light countdown for each driver.

Deep Staged: A driver is deep staged when, after staging, he or she rolls a few inches farther, which causes the prestage light to go out. In that position, the driver is closer to the finish line but dangerously close to a foul start.

Dial-Under: Dialing under allows drivers in Super Stock and Stock, which are handicap categories, to select an elapsed time quicker than the national index. As with a dial-in, a driver selects a dial-under, or e.t., that he or she thinks the car will run based on qualifying
performance. The breakout rule is in effect.

Diaper: A blanket made from ballistic and absorbent, often Kevlar, that surrounds the oil pan and serves as a containment device during engine explosions. Required on Top Fuel dragsters, Funny Cars, Alcohol Dragsters, and Alcohol Funny Cars.

Displacement: In an engine, displacement is the total volume of air-to-fuel mixture that an engine theoretically is capable of drawing into all cylinders during one operating cycle.

Elapsed Time: An elapsed time, or e.t., is the time it takes a vehicle to travel from the starting line to the finish line.

Eliminations: After qualifying, vehicles race two at a time, resulting in one winner and one loser. Winners continue to race in tournament-style competition until one remains.

Foul Start: A foul start is indicated by a red-light on the Christmas Tree when a car has left the starting line before receiving the green light, or starting signal.

Fuel Injection: A fuel-delivery system that replaces conventional carburetion. Fuel injection delivers fuel under pressure directly into the combustion chamber or indirectly through the airflow chamber.

Full Tree: Used in Competition, Super Stock, and Stock, for which a handicap starting system is used to equalize competition. The three amber bulbs on the Christmas Tree flash consecutively five-tenths of a second apart, followed five-tenths later by the green starting light. a perfect reaction time on a full Tree is .500.

Guard Beam: A light beam-to-photcell connection located 16 inches past the staged beam that is used to prevent a competitor from gaining an unfair starting-line advantage by blocking the stage beam with a low-installed object such as an oil pan or header collector pipe. If the guard beam is activated while the staged beam is still blocked, the red foul light is triggered on the Christmas Tree and the offender is automatically disqualified.

Headers: Fine-tuned exhaust system that routes exhaust from the engine. Replaces
conventional exhaust manifolds.

Hemi: A hemi engine has a hemispherically shaped cylinder-head combustion chamber, like a ball cut in half.

Holeshot: Reacting quicker to the Christmas Tree starting lights to win a race against a quicker opponent.

Hydraulic: When a cylinder fills with too much fuel, thus prohibiting compression by the cylinder and causing a mechanical malfunction, usually an explosive one.

Index: The expected performance for vehicles in a given class as assigned by NHRA. It allows various classes of cars in the same category to race against each other competitively.

Interval Timers: Part of a secondary timing system that records elapsed times, primarily for the racers' benefit, at 60, 330, 660, and 1,000 feet.

Methanol: Pure methyl alcohol produced by synthesis for use in Alcohol Dragsters and Alcohol Funny Cars.

Nitromethane: Produced specifically as a fuel for drag racing. It is the result of a chemical reaction between nitric acid and propane.

Pre-staged: When a driver is approximately seven inches behind the starting line and the small yellow light atop his of her side of the Christmas Tree is glowing.

Pro Tree: Used in Top Fuel, Funny Car, Pro Stock, Pro Stock Bike, Alcohol Dragster, Alcohol Funny Car, Super Comp, Super Gas, and Super Street, which feature heads-up competition. All three large amber lights on the Christmas Tree flash simultaneously, followed four-tenths of a second later by the green starting light. A perfect reaction time on a Pro Tree is .400.

Reaction Time: The time it takes a driver to react to the green starting light on the Christmas Tree, measured in thousandths of a second. The reaction-time counter begins when the last amber light flashes on the Tree and stops when the vehicle clears the stage beam.

Rpm: Revolutions per minute, or rpm, is a measure of engine speed as determined by crankshaft spin.

Sixty-foot Time: The time it takes a vehicle to cover the first 60 feet of the racetrack. It is the most accurate measure of the launch from the starting line, which in most cases determines how quick the rest of the run will be.

Slider Clutch: A multi-disc clutch designed to slip until a predetermined rpm is reached. Decreases shock load to the drive wheels.

Speed Trap: The final 66 feet to the finish line, known as the speed trap, where speed is recorded.

Staged: A driver is staged when the front wheels of the car are right on the starting line and the small yellow light below the prestaged light on his or her side of the Christmas Tree is glowing. Once a driver is staged, the calibrated countdown (see Christmas Tree) may begin at any time.

Supercharger: The supercharger, or blower, is a crank-driven air-to-fuel mixture compressor. It increases atmospheric pressure in the engine, resulting in added horsepower.

Wedge: An engine with a wedge combustion chamber, a combustion chamber resembling a wedge in shape. Need not have parallel intake and exhaust valve stems.

Weight Transfer: Weight transfer is critical to traction. Vehicles are set up to provide a desired weight transfer to rear wheels. When the vehicle accelerates, the front wheels lift and the weight shifts to the rear wheels, which makes them less likely to spin.

Wheelie Bars: Used to prevent excessive front-wheel lift. In FWD cars, they limit the weight transfer to the rear wheels.