NHRA - National Hot Rod Association

NHRA Glossary

Drag racing terms


Air Box

Used primarily on Pro Stock Motorcycles, it settles "negative air" around carburetors the way a hood scoop does on a car.

Air Foil

The same as a wing — a stabilizer, generally used to create downforce, which increases stability and tire-to-track adherence at high speeds.


When a driver lets off the throttle to regain traction or to avoid or stop tire shake.

Bang the blower

An explosion inside the supercharger caused by a flame from the combustion process accidentally re-entering the supercharger, where fuel and air are present. Generally caused by a stuck or broken intake valve that normally would be closed during the combustion sequence.


Used only in handicap racing. Refers to a vehicle running quicker than the racer has ­predicted, or “dialed.” The racer who breaks out loses unless his or her opponent breaks out by more or commits a more serious foul, such as leaving too soon (see “Foul Start”) or crossing the centerline.


The bottom spot in the field, usually the No. 16 qualifying position. Also called the “bubble.”


When a racer is moved from a higher ­qualifying position to a lower one after another ­competitor improves.

Burned piston

When a cylinder runs lean (too much air in the air-to-fuel mixture) and excessive heat burns or melts the piston.


Spinning the rear tires in water before a run to heat and clean them and put rubber on the track for better traction.

Christmas Tree

Also called the Tree, the ­electronic starting device between the lanes on the starting line.


Short for parachute, this device helps slow the car at the end of a run.

Clutch Can

The bell-shaped housing, or bellhousing, used to encase the clutch and flywheel.

Clutch Lockup

The progression of clutch-disc engagement controlled by an air-timer management system.

Deep Stage

To roll a few inches farther into the stage beam, indicated by the pre-stage lights on the Christmas Tree turning off. In that position, a racer is closer to the finish line and also closer to a foul start (red-light).


Used in Super Stock and Stock, when a driver selects, or dials, an elapsed time quicker than the national index. Drivers select a dial-under, or e.t., that they think their car will run based on ­previous performance.


An absorbent blanket made from ballistic material, often Kevlar, that surrounds the oil pan to contain oil and parts in case of an engine explosion; required for Top Fuel, Funny Car, Top Alcohol Dragster, and Top Alcohol Funny Car.


Another word for dragster.


Did not qualify.

Dropped cylinder

When a cylinder runs too rich (too much fuel in the air/fuel mixture) and prevents the spark plug(s) from firing.

Dropped Cylinder

When a spark plug fails to ignite, ­substantially decreasing total power ­output by the engine. A dropped cylinder is often ­distinguishable by raw fuel spewing from an exhaust header.

Elapsed Time (e.t.)

The time it takes a vehicle to travel from the starting line to the finish line.


The portion of an event that ­determines a race winner, usually Sunday. Vehicles are raced two at a time, resulting in one winner and one loser. Winners continue to race in a tournament-style ­competition until only one remains.


Another word for a Funny Car.

Foul Start

Also known as a red-light. When a vehicle leaves the starting line before the green light, ­indicated by the red light on the Tree. When a foul start occurs in eliminations, the racer is eliminated from further competition at the event (unless his or her opponent commits a worse infraction). A red-light in qualifying has no impact on the racer’s attempt; his or her time still counts toward qualifying for the event.

Full Tree

Used in Comp, Super Stock, Stock, Top ­Dragster, and Top Sportsman for which a ­handicap starting system equalizes competition. The three amber lights flash consecutively five-tenths of a second apart, followed five-tenths later by the green light.


Path of traction laid down by other ­vehicles that have gone down the racetrack; for example, “in the groove.”


The head start given to the slower car in a race featuring two vehicles of varying performance potentials. Used in Comp, Super Stock, Stock, Top Dragster, and Top Sportsman.



A fine-tuned exhaust system that routes exhaust from the engine; replaces conventional exhaust manifolds


A Hemi engine has a hemispherical shaped cylinder-head combustion chamber, like a ball cut in half


Tire; for example, “He was smokin’ the hides.”

Holeshot Win

When a racer with an e.t. slower than that of his or her opponent wins an ­eliminations round because he or she had a ­better reaction time, or left the starting line first.


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


An e.t. assigned by NHRA as a predictor of performance for vehicles in that class. Indexes allow various classes of cars in the same ­eliminator to race competitively.

Interval Timers

Elapsed time clocks at 60, 330, 660, and 1,000 feet that record the e.t. from the starting line to those intervals.


When a car gets out of the groove; for example, “He got loose at about 60 feet.”

Loud Pedal

Gas pedal or throttle.


Pure methyl alcohol produced by ­synthesis; used in some Top Alcohol Dragsters and all Top Alcohol Funny Cars.


Known as “nitro,” CH3NO2 is the result of a chemical reaction between nitric acid and propane. Primary fuel for Top Fuel dragsters, Funny Cars, and injected nitro ­dragsters in Top Alcohol Dragster.


When a race car deposits oil from the engine onto the racing surface, causing a delay.

On the Trailer

Where a race car is put after ­losing or not qualifying; for example, “He was on the trailer after round one.”


When a racer is approximately 7 inches behind the starting line and the top half of the circle of small blue lights atop his or her side of the Christmas Tree is illuminated.

Pro Tree

Used in Top Fuel, Funny Car, Pro Stock, Pro Stock Motorcycle, Top Alcohol Dragster, Top Alcohol Funny Car, Super Comp, Super Gas, Super Street, and Pro Mod, all of which feature ­heads-up (no handicap) competition. The three large amber lights flash simultaneously, followed four-tenths of a second later by the green light.


Another name for a dragster.

Reaction Time

The time it takes for a vehicle’s front tires to clear the staging beam after the green light comes on; measured in fractions of a second. A perfect reaction time is .000.


See “Foul Start.”

Safety Safari®

A team of men and women responsible for transporting equipment from race to race, preparing and maintaining the racing surface, and providing support in an emergency. The NHRA Safety Safari is presented by AAA.

Sand Trap

Located beyond the shutdown area; used to help stop errant race cars.



Shutdown Area

Area past the finish line where race vehicles come to a stop and racers are picked up by their crews.

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 and is the interval most critical to a quick e.t.


Racing tire that does not have tread.

Slider clutch

A multi-disc clutch designed to slip until a predetermined rpm is reached; decreases shock load to the drive wheels.

Smoked the Tires

When a car loses traction; also “blew the tires off” or “hazed the tires.”

Speed Trap

The final 66 feet to the finish line where speed is calculated.


When the front wheel or wheels of the vehicle are on the starting line. Once the racer is staged, the calibrated countdown of the amber lights leading to the green starting light may begin anytime.


Slang term for the finish line.


A crank-driven air/fuel-mixture compressor, also called a blower. It increases atmospheric pressure in the engine to produce more horsepower.

The Wally®

Official NHRA trophy.

Time Slip

Given to the racer or crew after a run, it lists the reaction time, interval times, elapsed time, and speed.

Tire Shake

A severe vibration that usually occurs at the beginning of the run and is the result of losing traction.


A racer whose reaction time is ­significantly slower than an opponent’s is said to have been Treed.


An exhaust-driven intake air compressor (see supercharger).

Wally Parks

NHRA founder (1913-2007), for whom The Wally is named.


An engine with a combustion chamber resembling a wedge in shape

Weight transfer

Critical to traction. Vehicles are set up to provide a desired weight transfer to the rear wheels. Upon acceleration, the front wheels lift and the weight shifts to the rear wheels, which makes them less likely to spin.

Wheelie bar(s)

Used to prevent excessive front-wheel lift.