Top Fuel is a type of drag racing whose dragsters are the quickest accelerating racing cars in the world and the fastest sanctioned category of drag racing, with the fastest competitors reaching speeds of and finishing the runs in 3.62 seconds. A top fuel dragster accelerates from a standstill to in as little as 0.8 seconds (less than one third the time required by a production Porsche 911 Turbo to reach ) and can exceed in just . This subjects the driver to an average acceleration of about over the duration of the race and with a peak of over . Because of the speeds, this class exclusively races to only a distance, and not the traditional one-fourth of a statute mile, or . The rule was changed in 2008 by the

National Hot Rod Association The National Hot Rod Association (NHRA) is a drag racing governing body, which sets rules in drag racing and hosts events all over the United States and Canada. With over 40,000 drivers in its rosters, the NHRA claims to be the largest motors ...

following the fatal crash of

Funny Car Funny Car is a type of drag racing vehicle and a specific racing class in organized drag racing. Funny cars are characterized by having tilt-up fiberglass or carbon fiber automotive bodies over a custom-fabricated chassis, giving them an appe ...

driver Scott Kalitta during a qualifying session at Old Bridge Township Raceway Park in

Englishtown, New Jersey Englishtown is a borough in Monmouth County, in the U.S. state of New Jersey. The community is nestled within the Raritan Valley region. As of the 2010 United States census, the borough's population was 1,847,FIA at some tracks, and as of 2012 is now the standard Top Fuel distance defined by the FIA. The

International Hot Rod Association The International Hot Rod Association (IHRA) is the second-largest drag racing sanctioning body after the National Hot Rod Association (NHRA). The Carrier Era 1971-1987 The IHRA was formed in November 1970 by businessman Larry Carrier. Through ...

, which at the time sanctioned Top Fuel in Australia, dropped the 1/4 mile distance in September 2017 after Santo Rapisarda, a car owner who often runs NHRA races in the United States, pushed for the change.

Top Fuel racing

2009NHRATopFuelChampTrophyTonySchumacher

Before their run, racers often perform a ''

burnout Burnout or burn-out may refer to: Entertainment * ''Burnout'' (film), a 2017 Moroccan film * ''Burn Out'' (film), a 2017 French film * Burnout (ride), a Funfields amusement ride in Australia * ''Burnout'' (series), a racing game series created by ...

'' in order to clean and heat tires. Additionally, the burnout applies a layer of fresh rubber to the track surface, which greatly improves traction during launch. At maximum throttle and RPM, the exhaust gases escaping from a dragster's open headers produce about of

downforce Downforce is a downwards lift force created by the aerodynamic features of a vehicle. If the vehicle is a car, the purpose of downforce is to allow the car to travel faster by increasing the vertical force on the tires, thus creating more grip ...

. The massive airfoil over and behind the rear wheels produces much more, peaking at around when the car reaches a speed of about . The engine of a Top Fuel dragster generates around 150 dB of sound at full throttle, enough to cause physical pain or even permanent damage. A sound that intense is not just heard, but also felt as pounding vibrations all over one's body, leading many to compare the experience of watching a Top Fuel dragster make a pass to 'feeling as though the entire drag strip is being bombed.' Before a run, race announcers usually advise spectators to cover or plug their ears. Ear plugs and even earmuffs are often handed out to fans at the entrance of a Top Fuel event. Dragsters are limited to a maximum wheelbase of . Currently, the most prolific active driver in Top Fuel is

Tony Schumacher Tony Schumacher may refer to: * Tony Schumacher (drag racer) (born 1969), American drag racer * Tony Schumacher (kayaker) (born 1976), Australian sprint canoeist * Tony Schumacher (German author) (1848–1931), German children books author * Ton ...

, and the most successful crew chief is Alan Johnson, who was the crew chief for six of Schumacher's championships, the back-to-back titles won by driver Gary Scelzi and was the crew chief for his brother Blaine for his entire professional career. The first female driver in the Top Fuel category is also the most associated female in the drag racing world,

Shirley Muldowney Shirley Muldowney (born June 19, 1940), also known professionally as "Cha Cha" and the "First Lady of Drag Racing", is an American auto racer. She was the first woman to receive a license from the National Hot Rod Association (NHRA) to drive a ...

, who won three championships during her career.

Fuel

Since 2015,

NHRA The National Hot Rod Association (NHRA) is a drag racing governing body, which sets rules in drag racing and hosts events all over the United States and Canada. With over 40,000 drivers in its rosters, the NHRA claims to be the largest motorspo ...

regulations limit the composition of the fuel to a maximum of 90%

nitromethane Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as i ...

; the remainder is largely methanol. However, this mixture is not mandatory, and less nitromethane may be used if desired. While nitromethane has a much lower

energy density In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or . Often only the ''useful'' or ex ...

() than either gasoline () or methanol (), an engine burning nitromethane can produce up to 2.4 times as much power as an engine burning gasoline. This is made possible by the fact that, in addition to fuel, an engine needs oxygen in order to generate force: of air (21% oxygen) is required to burn of gasoline, compared to only of air for one kilogram of nitromethane, which, unlike gasoline, already has oxygen in its molecular composition. For a given amount of air consumed, this means that an engine can burn 7.6 times more nitromethane than gasoline. Nitromethane also has a high latent

heat of vaporization The enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy ( enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. ...

, meaning that it will absorb substantial engine heat as it vaporizes, providing an invaluable cooling mechanism. The laminar

flame speed The flame speed is the measured rate of expansion of the flame front in a combustion reaction. Whereas ''flame velocity'' is generally used for a fuel, a related term is explosive velocity, which is the same relationship measured for an explosive. ...

and combustion temperature are higher than gasoline at and respectively. Power output can be increased by using very rich air-fuel mixtures. This also helps prevent pre-ignition, which is often a problem when using nitromethane. Due to the relatively slow burn rate of nitromethane, very rich fuel mixtures are often not fully ignited and some remaining nitromethane can escape from the exhaust pipe and ignite on contact with atmospheric oxygen, burning with a characteristic yellow

flame A flame (from Latin '' flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density the ...

. Additionally, after sufficient fuel has been combusted to consume all available oxygen, nitromethane can combust in the absence of atmospheric oxygen, producing

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

, which can often be seen burning from the exhaust pipes at night as a bright white flame. In a typical run the engine can consume between and of fuel during warmup, burnout, staging, and the quarter-mile run.

Top fuel engines

Rules

Like many other motor sport formulas originating in the United States,

-sanctioned drag racing favors heavy restrictions on engine configuration, sometimes to the detriment of technological development. In some cases, teams are required to use technologies that may be decades old, resulting in cars that may seem substantially less advanced than the average family car. However, while some basic facets of engine configuration are heavily restricted, other technologies, such as

fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...

, clutch operation, ignition, and car materials and design, are under constant development. NHRA competition rules limit the

engine displacement Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as a loose indicator of t ...

to . A bore with a stroke are customary dimensions. Larger bores have been shown to weaken the cylinder block.

Compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stat ...

is about 6.5:1, as is common on engines with overdriven Roots-type

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced indu ...

Engine

The engine used to power a Top Fuel drag racing car is based on a second generation Chrysler RB Hemi, but is built exclusively of specialized parts, it retains the basic configuration with two valves per cylinder activated by

pushrod A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) ...

s from a centrally-placed camshaft. The engine has hemispherical combustion chambers, a 58-degree in. to ex. valve stem angle; bore pitch. The

block Block or blocked may refer to: Arts, entertainment and media Broadcasting * Block programming, the result of a programming strategy in broadcasting * W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...

is machined from a piece of

forged Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which ...

aluminum. It has press-fitted, ductile iron liners. There are no water passages in the block, which adds considerable strength and stiffness. The engine is cooled by the incoming air/fuel mixture and the lubricating oil. Like the original Hemi, the racing cylinder block has a deep skirt for strength. There are five main bearing caps, which are fastened with aircraft-standard-rated steel studs, with additional reinforcing main studs and side bolts (" cross-bolting"). There are three approved suppliers of these custom blocks; Keith Black, Brad Anderson, and Alan Johnson. The

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinder (engine), cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas ...

s are machined from aluminum

billets A billet is a living-quarters to which a soldier is assigned to sleep. Historically, a billet was a private dwelling that was required to accept the soldier. Soldiers are generally billeted in barracks or garrisons when not on combat duty, alt ...

. As such, they, too, lack water jackets and rely entirely on the incoming air/fuel mixture and lubricating oil for their cooling. The original Chrysler design of two large valves per cylinder is used. The intake valve is made from solid

titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...

and the exhaust from solid Nimonic 80A or similar. Seats are of

ductile iron Ductile iron, also known as ductile cast iron, nodular cast iron, spheroidal graphite iron, spheroidal graphite cast iron and SG iron, is a type of graphite-rich cast iron discovered in 1943 by Keith Millis. While most varieties of cast iron ar ...

Beryllium-copper Beryllium copper (BeCu), also known as copper beryllium (CuBe), beryllium bronze, and spring copper, is a copper alloy with 0.5–3% beryllium but can contain other elements as well. Beryllium copper combines high strength with non-magnetic and ...

has been tried but its use is limited due to its toxicity. Valve sizes are around for the intake and for the exhaust. In the ports there are integral tubes for the push rods. The heads are sealed to the block by copper gaskets and stainless steel

o-ring An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...

s. Securing the heads to the block is done with aircraft-rated steel studs and stud nuts. The camshaft is billet steel, made from 8620 carbon or S7 through-hardened tool steel or similar. It runs in five oil pressure lubricated bearing shells and is driven by gears in the front of the engine. Mechanical roller lifters ( cam followers) ride atop the cam lobes and drive the steel push rods up into the steel

rocker arm In the context of an internal combustion engine, a rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake/exhaust valve. Rocker arms in automobiles are typically made from stamped steel, ...

s that actuate the valves. The rockers are of roller tip type on the intake and exhaust sides. Like the cam follower rollers, the steel tip roller rotates on a steel roller bearing and the steel rocker arms rotate on a pair of through-hardened tool steel shafts within bronze bushings. Intake and exhaust rockers are billet. The dual valve springs are of coaxial type and made out of titanium. Valve retainers are also made of titanium, as are the rocker covers. Billet steel crankshafts are used; they all have a cross plane a.k.a. 90 degree configuration and run in five conventional bearing shells. 180 degree crankshafts have been tried. Due to ease of laying out an exhaust system with even pulsation, the 180 degree crankshaft can offer increased power in engines with interacting exhaust. However this does not concern Top Fuel engines with separate exhaust pipes for each cylinder. A 180 degree crankshaft is about lighter than 90 degree crankshaft, but they create a lot of vibration. Such is the strength of a top fuel crankshaft that in one incident, the entire engine block was split open and blown off the car during an engine failure, and the crank, with all eight connecting rods and pistons, was left still bolted to the clutch.

Piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas- ...

s are made of forged aluminum. They have three rings and aluminum buttons retain the steel wrist pin. The piston is anodized and

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chem ...

coated to prevent

galling Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is cau ...

during the high thrust load operation encountered. The top ring is an L-shaped section "Dykes" ring that provides a good seal during combustion but a second ring must be used to prevent excessive oil from entering the combustion chamber during intake strokes as the Dykes-style ring offers less than optimal reverse gas/oil sealing. The third ring is an oil scraper ring whose function is to scrape the majority of the oil film off of the cylinder wall as the piston descends, to prevent oil being exposed to combustion heat and contaminating the upcoming round of fuel/air. This "oil scraping" also provides a key heat removal step for the cylinder walls and piston skirts, the oil film is renewed as the piston moves upward after BDC. The

connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksha ...

s are of forged aluminum and do provide some shock damping, which is why aluminum is used in place of titanium, because titanium connecting rods transmit too much of the combustion impulse to the big-end rod bearings, endangering the bearings and thus the crankshaft and block. Each con rod has two bolts, shell bearings for the big end while the pin runs directly in the rod.

Superchargers

The

must be a 14-71 type

Roots blower The Roots-type blower is a positive displacement lobe pump which operates by pumping a fluid with a pair of meshing lobes resembling a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake si ...

. It has twisted lobes and is driven by a toothed belt. The supercharger is slightly offset to the rear to provide an even distribution of air. Absolute manifold pressure is usually , but up to is possible. The manifold is fitted with a burst plate. Air is fed to the compressor from

throttle A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ...

butterflies with a maximum area of . At maximum pressure, it takes approximately to drive the supercharger. These superchargers are in fact derivatives of General Motors scavenging-air blowers for their

two-stroke diesel engine A two-stroke diesel engine is an internal combustion engine that uses compression ignition, with a two-stroke combustion cycle. It was invented by Hugo Güldner in 1899.Mau (1984) p.7 In compression ignition, air is first compressed and heat ...

s, which were adapted for automotive use in the early days of the sport. The model name of these superchargers delineates their size – the once commonly used 6-71 and 4-71 blowers were designed for General Motors diesels having six cylinders of each, and four cylinders of each, respectively. Thus, the currently used 14-71 design can be seen to be a huge increase in power delivery over the early designs, purpose-built for the GM Detroit Diesel truck powerplants. Mandatory safety rules require a secured Kevlar-style blanket over the supercharger assembly as "blower explosions" are not uncommon, from the volatile air/fuel mixture coming from the

fuel injector Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...

s being drawn directly through them. The absence of a protective blanket exposes the driver, team and spectators to shrapnel in the event that nearly any irregularity in the induction of the air/fuel mixture, the conversion of combustion into rotating crankshaft movements, or in the exhausting of spent gasses is encountered. Note that Detroit Diesel did not produce a 14–71.

Oil and fuel systems

The oil system has a

wet sump Within piston engines, a wet sump is part of a lubrication system whereby the crankcase sump is used as an integral oil reservoir. An alternative system is the dry sump, whereby oil is pumped from a shallow sump into an external reservoir.Wet sump ...

which contains of SAE 70 mineral or synthetic racing oil. The pan is made of titanium or aluminum. Titanium can be used to prevent oil spills in the event of a blown rod. Teams are fined and points are lost if oil is spilled on the track surface, so all teams make provision for absorbent blankets/diapers below the engine. Oil pump pressure is somewhere around during the run, at start up, but actual figures differ between teams. Fuel is injected by a constant flow injection system. There is an engine driven mechanical fuel pump and about 42 fuel nozzles. The pump can flow per minute at 7500 rpm and fuel pressure. In general 10 injectors are placed in the injector hat above the supercharger, 16 in the intake manifold and two per cylinder in the cylinder head. Usually a race is started with a leaner mixture, then as the clutch begins to tighten as the engine speed builds, the air/fuel mixture is enriched. As the increased engine speed builds up pump pressure, the mixture is made leaner to maintain a predetermined ratio that is based on many factors, especially race track surface friction. The

stoichiometry Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equ ...

of both methanol and

is considerably greater than that of racing gasoline, as they have oxygen atoms attached to their carbon chains and gasoline does not. This means that a "fueler" engine will provide power over a very broad range from very lean to very rich mixtures. Thus, to attain maximum performance, before each race, by varying the level of fuel supplied to the engine, the mechanical crew may select power outputs barely below the limits of tire traction. Power outputs which create tire slippage will "smoke the tires" and as a result the race is often lost.

Ignition and timing

The air/fuel mixture is ignited by two

spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...

s per cylinder. These plugs are fired by two 44-

ampere The ampere (, ; symbol: A), often Clipping (morphology), shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One amp ...

magnetos A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator ...

. Normal

ignition timing In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need f ...

is 58-65 degrees

BTDC In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC). ...

(This is dramatically greater

spark advance Spark commonly refers to: * Spark (fire), a small glowing particle or ember * Electric spark, a form of electrical discharge Spark may also refer to: Places * Spark Point, a rocky point in the South Shetland Islands People * Spark (surname) * ...

than in a petrol engine as "nitro" and alcohol burn far slower). Directly after launch the timing is typically decreased by about 25 degrees for a short time as this gives the tires time to reach their correct shape. The ignition system limits the engine speed to 8400 rpm. The ignition system provides initial 60,000 volts and 1.2 amperes. The long duration spark (up to 26 degrees) provides energy of . The plugs are placed in such a way that they are cooled by the incoming charge. The ignition system is not allowed to respond to real time information (no computer-based spark lead adjustments), so instead a timer-based retard system is used.

Exhaust

The engine is fitted with eight individual open exhaust pipes, in diameter and long. These are made of steel and fitted with

thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of th ...

s for measuring of the

exhaust gas temperature Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...

. They are called "zoomies" and exhaust gases are directed upward and backwards. Exhaust temperature is about at idle and by the end of a run. During a nighttime event, the slow-burning nitromethane can be seen to extend flames many feet out from the exhaust pipes. The engine is warmed up for about 80 seconds. After the warm up the

valve cover Rocker covers are covers that are bolted on over rocker arms in an internal combustion engine. They are called valve covers in the United States, Canada, and in situations where Rocker Arms are not present, such as some Overhead Cam, and most Du ...

s are taken off, oil is changed and the car is refueled. The run including tire warming is about 100 seconds which results in a "lap" of about three minutes. After each lap, the entire engine is disassembled and examined, and worn or damaged components are replaced.

Performance

Measuring the power output of a top fuel engine directly is not always feasible. Certain models use a torque sensor incorporated as part of the RacePak data system.

Dynamometer A dynamometer or "dyno" for short, is a device for simultaneously measuring the torque and rotational speed ( RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by t ...

s that can measure the output of a Top Fuel engine exist; however, the main limitation is that a Top Fuel engine cannot be run at its maximum power output for more than 10 seconds without overheating or possibly destroying itself explosively. Making such high power levels from such relatively limited displacement is a result of using very high boost levels and running at extremely high RPMs; both of these stress the internal components to a high degree, meaning that the peak power can only safely be achieved for brief periods of time, and even then only by intentionally sacrificing components. The engine power output can also be calculated based upon the car's weight and its performance. The calculated

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may ...

output of these engines is most likely somewhere between , which is about twice as powerful as the engines installed on some modern

diesel locomotive A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving whe ...

s, with a

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of t ...

output of approximately and a brake mean effective pressure of . In late 2015, tests using sensors developed by AVL Racing showed peak power of over . For the purposes of comparison, a 2009 SSC Ultimate Aero TT, which at the time was among the world's most powerful production automobiles, produces of power and of torque. From start to finish the engine will turn 240 revolutions. Including start up, burnout, staging and the race, the engine must survive just 500 revolutions before being rebuilt.

Engine weight

*Block with liners *Heads each *Crankshaft *Complete engine

Mandatory safety equipment

Much of organized drag-racing is sanctioned by the National Hot Rod Association. Since 1955, the association has held regional and national events (typically organized as single elimination tournaments, with the winner of each two car race advancing) and has set rules for safety, with the more powerful cars requiring ever more safety equipment. Typical safety equipment for contemporary top fuel dragsters: full face helmets with fitted HANS devices; multi-point, quick release safety restraint harn