TIRE

Stacked and standing car tires

The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels in order to prevent wear and tear. Today, the vast majority of tires are pneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft.

Tire Pressure Monitoring System

Tire pressure monitoring systems (TPMS) are electronic systems that monitor the tire pressures on individual wheels on a vehicle, and alert the driver when the pressure goes below a warning limit. There are several types of designs to monitor tire pressure. Some actually measure the air pressure, and some make indirect measurements, such as gauging when the relative size of the tire changes due to lower air pressure.

Inflation Pressure

Tires are specified by the vehicle manufacturer with a recommended inflation pressure, which permits safe operation within the specified load rating and vehicle loading. Most tires are stamped with a maximum pressure rating. For passenger vehicles and light trucks, the tires should be inflated to what the vehicle manufacturer recommends, which is usually located on a decal just inside the driver's door or in the vehicle owners handbook. Tires should not generally be inflated to the pressure on the sidewall; this is the maximum pressure, rather than the recommended pressure. High performance and dynamic drivers often increase the tire pressure to near the maximum pressure as printed on the sidewall. This is done to sacrifice comfort for performance and safety. It is definitely very dangerous to allow tire pressure to drop below the recommended placard vehicle pressure, although this is commonly done temporarily when driving on sand to reduce chance of bogging. The reason for this is that it increases the amount of tire wall movement as a result of cornering forces. Should a low pressure tire be forced to perform an evasive maneuver, the tire wall will be more pliable than had it been of a higher pressure, and thus it will "roll" under the wheel. This increases the entire roll movement of the car, and diminishes tire contact area on the negative side of the vector. Thus only half the tire is in contact with the road, and the tire may deform to such an extent that the side wall on the positive vector side becomes in contact with the road. The probability of failing in the emergency maneuver is thus increased.

Further, with low tire pressure—due to the side wall being more pliable—the tire will absorb more of the irregular forces from normal driving, and with this constant bending of the side wall as it absorbs the contours of the road, it heats up the tire wall to possibly dangerous temperatures, as well as degrades the steel wire reinforcement; this often leads to side wall blow-outs. In an extreme case of this phenomenon, the vehicle may drive into a pot-hole, or a hard elevation in the road. Due to the low tire pressure, the side wall at the contact area will temporarily collapse, thereby wedging the tire between the wheel and road, resulting in a tire laceration and blow-out, as well as a damaged wheel. High tire pressures are more inclined to keep its shape during any encounter, and will thus transmit the forces of the road to the suspension, rather than being damaged itself. This allows for an increased reaction speed, and "feel" the driver perceives of the road. Modern tire designs allow for minimal tire contact surface deformity during high pressures, and as a result the traditional wear on the center of the tire due to reasonably high pressures is only known to very old or poorly designed tires.

Feathering occurs on the junction between the tire tread and side wall, as a result of too low tire pressures. This is as a result of the inability of the tire to perform appropriately during cornering forces, leading to aberrant and shearing forces on the feathering area. This is due to the tire moving sideways underneath the wheel as the tire pressures are insufficient to transmit the forces to the wheel and suspension. It may be, that very high tire pressures have only two downsides: The sacrifice in comfort; and the increased chance of obtaining a puncture when driving over sharp objects, such as on a newly scraped gravel road. Many individuals have maintained their tire pressures at the maximum side wall printed value (inflated when cold) for the entire lifetime of the tire, with perfect wear until the end. This may be of negative economic value to the rubber and tire companies, as high tire pressures decrease wear, and minimize side wall blow outs.

Many pressure gauges available at fuel stations have been de-calibrated by manhandling and the effect of time, and it is for this reason that vehicle owners should keep a personal pressure gauge with them to validate the correct tire pressure.

During the early stages of tire engineering, and with current basic tires, the tire contact patch is readily reduced by both over-and-under inflation. Over-inflation may increase the wear on the center contact patch, and under-inflation will cause a concave tread, resulting in less center contact. Most modern tires will wear evenly at very high tire pressures, but will degrade prematurely due to low (or even standard) pressures. An increased tire pressure has many benefits, including decreased rolling resistance. It has been found, that an increased tire pressure almost exclusively results in shorter stopping distances, except in some circumstances that may be attributed to the low sample size. If tire pressure is too low, the tire contact patch is changed more than if it were over-inflated. This decreases rolling resistance, tire flexing, and friction between the road and tire. Under-inflation can lead to tire overheating, premature tread wear, and tread separation in severe cases.

Load Rating

Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating can result in unsafe conditions that can lead to steering instability and even rupture. For a table of load ratings, see tire code.

Speed Rating

The speed rating denotes the maximum speed at which a tire is designed to be operated. For passenger vehicles these ratings range from 99 mph (159 km/h) to 186 mph (299 km/h). For a table of speed ratings, see tire code.

Replacing a tire on a vehicle with one with a lower speed rating than originally specified by the vehicle manufacturer may render the insurance invalid.

Service rating

Tires (especially in the U.S.) are often given service ratings, mainly used on bus and truck tires. Some ratings are for long haul, and some for stop-start multi-drop type work. Tires designed to run 500 miles (800 km) or more per day carrying heavy loads require special specifications.

Treadwear Rating

The treadwear rating or treadwear grade describes how long the tire manufacturers expects the tire to last. A Course Monitoring Tire (the standard tire that a test tire will be compared to) has a rating of "100". If a manufacturer assigns a treadwear rating of 200 to a new tire, they are indicating that they expect the new tire to have a useful lifespan that is 200% of the life of a Course Monitoring Tire. The "test tires" are all manufacturer-dependent. Brand A's rating of 500 is not necessarily going to give you the same mileage rating as Brand B's tire of the same rating. The testing is non-regulated and can vary greatly. Treadwear ratings are only useful for comparing Brand A's entire lineup against itself. Tread wear, also known as tire wear, is caused by friction between the tire and the road surface. Government legal standards prescribe the minimum allowable tread depth for safe operation.

Rotation

Tires may exhibit irregular wear patterns once installed on a vehicle and partially worn. Furthermore, front-wheel drive vehicles tend to wear the front tires at a greater rate compared to the rears. Tire rotation is the procedure of moving tires to different car positions, such as front-to-rear, in order to even out the wear, thereby extending the life of the tire.

Wheel alignment

When mounted on the vehicle, the wheel and tire may not be perfectly aligned to the direction of travel, and therefore may exhibit irregular wear. If the discrepancy in alignment is large, then the irregular wear will become quite substantial if left uncorrected.

Wheel alignment is the procedure for checking and correcting this condition through adjustment of camber, caster and toe angles. These settings also affect the handling characteristics of the vehicle.

Retread

Tires that are fully worn can be re-manufactured to replace the worn tread. This is known as retreading or recapping, a process of buffing away the worn tread and applying a new tread. Retreading is economical for truck tires because the cost of replacing the tread is less than the price of a new tire. Retreading passenger tires is less economical because the cost of retreading is high compared to the price of new cheap tires, but favorable compared to high-end brands.

Worn tires can be retreaded by two methods, the mold or hot cure method and the pre-cure or cold one. The mold cure method involves the application of raw rubber on the previously buffed and prepared casing, which is later cured in matrices. During the curing period, vulcanization takes place and the raw rubber bonds to the casing, taking the tread shape of the matrix. On the other hand, the pre-cure method involves the application of a ready-made tread band on the buffed and prepared casing, which later is cured in an autoclave so that vulcanization can occur.

During the retreading process, retread technicians must ensure the casing is in the best condition possible, in order to minimize the possibility of a casing failure. Casings with problems such as capped tread, tread separation, unrepairable cuts, corroded belts or sidewall damage, or any run-flat or skidded tires, will be rejected.

In most situations, retread tires can be driven under the same conditions and at the same speeds as new tires with no loss in safety or comfort. The percentage of retread failures should be about the same as for new tire failures, but many drivers, including truckers, are guilty of not maintaining proper air pressure on a regular basis, and, if a tire is abused (overloaded, underinflated, or mismatched to the other tire on a set of duals), then that tire (new or recapped) will fail.

Many commercial trucking companies put retreads only on trailers, using only new tires on their steering and drive wheels. This procedure increases the driver's chance of maintaining control in case of problems with a retreaded tire.

SPARK PLUG

Spark plug with single-ground electrode.

In 1860 Étienne Lenoir used an electric spark plug in his first internal combustion engine and is generally credited with the invention of the spark plug.

Early patents for spark plugs included those by Nikola Tesla (in U.S. Patent 609,250 for an ignition timing system, 1898), Frederick Richard Simms (GB 24859/1898, 1898) and Robert Bosch (GB 26907/1898). But only the invention of the first commercially viable high-voltage spark plug as part of a magneto-based ignition system by Robert Bosch's engineer Gottlob Honold in 1902 made possible the development of the internal combustion engine. Subsequent manufacturing improvements can also be credited to Albert Champion, the Lodge brothers, sons of Sir Oliver Joseph Lodge, who developed and manufactured their father's idea and also Kenelm Lee Guinness, of the Guinness brewing family, who developed the KLG brand.

A spark plug (very rarely in British English: a sparking plug) is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.

Spark plugs have an insulated central electrode which is connected by a heavily insulated wire to an ignition coilmagneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder. or

Reciprocating internal combustion engines can be divided into spark-ignition engines, which require spark plugs to initiate combustion, and compression-ignition engines (diesel engines), which compress the air and then inject diesel fuel into the heated compressed air mixture where it autoignites.

Spark plugs may also be used in other applications such as furnaces where a combustible mixture should be ignited. In this case, they are sometimes referred to as flame igniters.

Components of a typical, four stroke cycle, DOHC piston engine.

(E) Exhaust camshaft, (I) Intake camshaft,

(S) Spark plug, (V) Valves, (P) Piston,

 (R) Connecting rod, (C) Crankshaft,

(W) Water jacket for coolant flow.

Operation

The plug is connected to the high voltage generated by an ignition coil or magneto. As the electrons flow from the coil, a voltage difference develops between the central electrode and side electrode. No current can flow because the fuel and air in the gap is an insulator, but as the voltage rises further, it begins to change the structure of the gases between the electrodes. Once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The ionized gas becomes a conductor and allows electrons to flow across the gap. Spark plugs usually require voltage of 12,000–25,000 volts or more to 'fire' properly, although it can go up to 45,000 volts. They supply higher current during the discharge process resulting in a hotter and longer-duration spark.
As the current of electrons surges across the gap, it raises the temperature of the spark channel to 60,000 K. The intense heat in the spark channel causes the ionized gas to expand very quickly, like a small explosion. This is the "click" heard when observing a spark, similar to lightning and thunder.
The heat and pressure force the gases to react with each other, and at the end of the spark event there should be a small ball of fire in the spark gap as the gases burn on their own. The size of this fireball or kernel depends on the exact composition of the mixture between the electrodes and the level of combustion chamber turbulence at the time of the spark. A small kernel will make the engine run as though the ignition timing was retarded, and a large one as though the timing was advanced.

Parts of the Plug

Diagram of single-ground spark plug.

• Terminal : The top of the spark plug contains a terminal to connect to the ignition system.
• Insulator : Its major function is to provide mechanical support for the central electrode, while insulating  the high voltage.
• Ribs : to improve the electrical insulation and prevent electrical energy from leaking along the insulator surface from the terminal to the metal case.
• Insulator Tip : must resist high temperatures while retaining electrical insulation.
• Seals :  the seals ensure there is no leakage from the combustion chamber.
• Metal Case :  serves to remove heat from the insulator and pass it on to the cylinder head, and acts as the ground for the sparks passing through the central electrode to the side electrode.
• Central Electrode : The central electrode is usually the one designed to eject the electrons (the cathode) because it is the hottest (normally) part of the plug.
• Side Elektrode : Some designs have provided a copper core to this electrode, so as to increase heat conduction.

SPLIT-SINGLE

Post WWII arrangement,

carburettor to the front under the exhaust (neither visible).

Transfer port visible at back.

One connecting rod 'piggy-backed' on another.

 The split-single (Doppelkolbenmotor to its German and Austrian manufacturers), is a variant on the two-stroke engine with two cylinders sharing a single combustion chamber.

There have been "single" (ie twin-bore) and "twin" (ie four bore) models and several important internal developments, the last of them being obvious externally too, with the carburettor (uniquely amongst motorcycles) moving to the front of the engine under the exhaust.

The split-single system sends the intake fuel-air mixture up one bore to the combustion chamber, sweeping the exhaust gases down the other bore and out of the exposed exhaust port. The split-single two-stroke thus delivers better economy than the common forms of two-stroke and runs better at small throttle openings, at the cost of a heavier engine.

In the 60 year history of this arrangement there were two important variants, earlier versions have a single, Y-shaped or V-shaped connecting rod and these look much like a regular single cylinder two-stroke engine with a single exhaust, a single carburettor in the usual place behind the cylinders and a single sparkplug. Racing versions of this design can be mistaken for a regular twin-cylinder, since they had two exhausts or two carburettors but these are actually connected to a single bore in an engine with a single combustion chamber. Some models, including those in mass-production, used two spark-plugs igniting one combustion chamber.

After World War II, more sophisticated internal mechanisms improved mechanical reliability and led to the carburettor being placed in front of the barrel, tucked under and to the side of the exhaust. This is the arrangement seen in the United States and marketed by Sears as the Twingle.

For modern vehicle taxation purposes the split-single suffers no penalty and offers no advantage, as only the swept volume is considered, not the number of cylinders or spark plugs. This remains true even if the two pistons are not the same size and have different strokes (mechanically possible, if rarely used). This simple calculation was not always the case (see Tax horsepower, as used in the UK and some European countries in the 1920s and 1930s).
Lubrication weaknesses of the early "side-by-side" versions with the carburettor in the "normal" place behind the cylinder, were substantially the same as with all other two-strokes running on the same "petro-oil" mixture. However, they were greatly eased in the later ones, since the cool, lubricated mixture is delivered straight onto the hot (exhaust side) of the hotter, exhaust piston from the carburettor at the front of the engine under the exhaust.
Lubrication weaknesses of the early "side-by-side" versions with the carburettor in the "normal" place behind the cylinder, were substantially the same as with all other two-strokes running on the same "petro-oil" mixture. However, they were greatly eased in the later ones, since the cool, lubricated mixture is delivered straight onto the hot (exhaust side) of the hotter, exhaust piston from the carburettor at the front of the engine under the exhaust.

TWO-STROKE ENGINE

A two-stroke engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft (an up stroke and a down stroke of the piston, compared to twice that number for a four-stroke engine). This is accomplished by using the end of the combustion stroke and the beginning of the compression stroke to perform simultaneously the intake and exhaust (or scavenging) functions. In this way, two-stroke engines often provide high specific power, at least in a narrow range of rotational speeds. The functions of some or all of the valves required by a four-stroke engine are usually served in a two-stroke engine by ports that are opened and closed by the motion of the piston(s), greatly reducing the number of moving parts. Gasoline (spark ignition) versions are particularly useful in lightweight (portable) applications, such as chainsaws, and the concept is also used in diesel compression ignition engines in large and weight insensitive applications, such as ships and locomotives.

Invention of the two-stroke cycle is attributed to Scottish engineer Dugald Clerk, who in 1881 patented his design, his engine having a separate charging cylinder. The crankcase-scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day.

The two-stroke engine was very popular throughout the 20th century in motorcycles and small-engined devices, such as chainsaws and outboard motors, and was also used in some cars, a few tractors and many ships. Part of their appeal was their simple design (and resulting low cost) and often high power-to-weight ratio. Many designs use total-loss lubrication, with the oil being burned in the combustion chamber, causing "blue smoke" and other types of exhaust pollution. This is a major reason for two-stroke engines being replaced by four-stroke engines in many applications.

Two-stroke engines continue to be commonly used in high-power, handheld applications such as string trimmers and chainsaws. The light overall weight, and light-weight spinning parts give important operational and even safety advantages. For example, only a two-stroke engine that uses a gasoline-oil mixture can power a chainsaw operating in any position.

These engines are still used for small, portable, or specialized machine applications such as outboard motors, high-performance, small-capacity motorcycles, mopeds, underbones, scooters, tuk-tuks, snowmobiles, karts, ultralights, model airplanes (and other model vehicles) and lawnmowers. The two-stroke cycle is used in many diesel engines, most notably large industrial and marine engines, as well as some trucks and heavy machinery.

A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab and German manufacturers DKW and Auto-Union. The Japanese manufacturer Suzuki did the same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, but Eastern Bloc countries continued until around 1991, with the Trabant and Wartburg in East Germany. Lotus of Norfolk, UK, has a prototype direct-injection two-stroke engine intended for alcohol fuels called the Omnivore which it is demonstrating in a version of the Exige.

two-stroke engine

 

The intake pathway is opened and closed by a rotating member. A familiar type sometimes seen on small motorcycles is a slotted disk attached to the crankshaft which covers and uncovers an opening in the end of the crankcase, allowing charge to enter during one portion of the cycle.
Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members with suitable cutouts arranged to rotate one within the other - the inlet pipe having passage to the crankcase only when the two cutouts coincide. The crankshaft itself may form one of the members, as in most glow plug model engines. In another embodiment, the crank disc is arranged to be a close-clearance fit in the crankcase, and is provided with a cutout which lines up with an inlet passage in the crankcase wall at the appropriate time, as in the Vespa motor scooter.
The advantage of a rotary valve is it enables the two-stroke engine's intake timing to be asymmetrical, which is not possible with piston port type engines. The piston port type engine's intake timing opens and closes before and after top dead center at the same crank angle, making it symmetrical, whereas the rotary valve allows the opening to begin earlier and close earlier.
Rotary valve engines can be tailored to deliver power over a wider speed range or higher power over a narrower speed range than either piston port or reed valve engine. Where a portion of the rotary valve is a portion of the crankcase itself, it is particularly important that no wear is allowed to take place.

The Two-stroke cycle
1=TDC
2=BDC
 A: intake/scavenging 
 B: Exhaust 
 C: Compression 
 D: Expansion(power) 

 This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel/air mixture strikes the cylinder head, then follows the curvature of the combustion chamber, and then is deflected downward. This not only prevents the fuel/air mixture from traveling directly out the exhaust port, but also creates a swirling turbulence which improves combustion efficiency, power and economy. Usually, a piston deflector is not required, so this approach has a distinct advantage over the cross-flow scheme (above). Often referred to as "Schnuerle" (or "Schnürl") loop scavenging after the German inventor of an early form in the mid 1920s, it became widely adopted in that country during the 1930s and spread further afield after World War II. Loop scavenging is the most common type of fuel/air mixture transfer used on modern two-stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop-scavenged two-stroke engines. This operational feature was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ and Walter Kaaden. Loop scavenging, disc valves and expansion chambers worked in a highly coordinated way to significantly increase the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha and Kawasaki. Suzuki and Yamaha enjoyed success in grand Prix motorcycle racing in the 1960s due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was the piston could be made nearly flat or slightly dome shaped, which allowed the piston to be appreciably lighter and stronger, and consequently to tolerate higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes and compression losses.
SAAB built 750 and 850 cc 3-cylinder engines based on a DKW design that proved reasonably successful employing loop charging. The original SAAB 92 had a two-cylinder engine of comparatively low efficiency. At cruising speed, reflected wave exhaust port blocking occurred at too low a frequency. Using the asymmetric three-port exhaust manifold employed in the identical DKW engine improved fuel economy. The 750 cc standard engine produced 36 to 42 hp, depending on the model year. The Monte Carlo Rally variant, 750 cc (with a filled crankshaft for higher base compression), generated 65 hp. An 850 cc version was available in the 1966 SAAB Sport (a standard trim model in comparison to the deluxe trim of the Monte Carlo). Base compression comprises a portion of the overall compression ratio of a two-stroke engine.

SIX-STROKE ENGINE

The six-stroke engine is a type of internal combustion engine based on the four-stroke engine, but with additional complexity intended to make it more efficient and reduce emissions. Two different types of six-stroke engine have been developed since the 1990s:

In the first approach, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke. The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air. The currently notable designs in this class are the Crower six-stroke engine, invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India.

The second approach to the six-stroke engine uses a second opposed piston in each cylinder that moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. Functionally, the second piston replaces the valve mechanism of a conventional engine but also increases the compression ratio. The currently notable designs in this class include two designs developed independently: the Beare Head engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.

The M4+2 engine working cycle animation

The term "Six Stroke" was coined by the inventor of the Beare Head, Malcolm Beare. The technology combines a four stroke engine bottom end with an opposed piston in the cylinder head working at half the cyclical rate of the bottom piston. Functionally, the second piston replaces the valve mechanism of a conventional engine. first use of "sixstroke" 1994.

The M4+2 engines have much in common with the Beare Head engines, combining two opposed pistons in the same cylinder. One piston working at half the cyclical rate of the other. But while the main function of the second piston in a Beare Head engine is to replace the valve mechanism of a conventional four stroke engine, the M4+2 take the principle one step further.

The working principle of the engine is explained in the Two- and four-stroke engines article.

FOUR-STROKE ENGINE

Four-stroke cycle used in gasoline/petrol engines.

A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.

There are two common types of engines, which are closely related to each other but have major differences in their design and behavior. The earliest of these to be developed is the Otto cycle engine which was developed in 1876 by Nikolaus August Otto in Cologne, Germany. This engine is most often referred to as a petrol engine or gasoline engine, after the fuel that powers it. The second type of four-cycle engine is the Diesel engine developed in 1893 by Rudolph Diesel, also of Germany. Diesel created his engine to maximize efficiency which was lacking in the Otto engine. There are several major differences between the Otto cycle engine and the four cycle diesel engine. The diesel engine is made in both a two-cycle and a four-cycle version. Ironically Otto's company Deutz AG produces primarily diesel engines in the modern era.

The Otto cycle is named after the 1876 engine of Nikolaus A. Otto, who built a successful four-cycle engine which was based on the work of Jean Joseph Etienne Lenoir^. It was the third engine type that Otto developed. It used a sliding flame gateway for ignition of its fuel which was a mixture of illuminating gas and air. After 1884 Otto also developed the magneto allowing the use of an electrical spark for ignition, which had been unreliable on the Lenoir engine.

Today, the internal combustion engine (ICE) is used in motorcycles, automobiles, boats, trucks, aircraft, ships, heavy duty machinery, and in its original intended use as stationary power both for kinetic and electrical power generation. Diesel engines are found in virtually all heavy duty applications such as trucks, ships, locomotives, power generation, and stationary power. Many of these diesel engine are two cycle with power ratings up to 105,000 hp (78,000 kW).

The four cycles refer to intake, compression, combustion (power), and exhaust cycles that occur during two crankshaft rotations per power cycle of the four cycle engines. The cycle begins at Top Dead Centre (TDC), when the piston is farthest away from the axis of the crankshaft. A cycle refers to the full travel of the piston from Top Dead Centre (TDC) to Bottom Dead Centre (BDC). (See Dead centre.)

1. INTAKE stroke: on the intake or induction stroke of the piston , the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air, or just air in a diesel engine, is forced by atmospheric (or greater) pressure into the cylinder through the intake port. The intake valve(s) then close. The volume of air/fuel mixture that is drawn into the cylinder, relative to the volume of the cylinder is called, the volumetric efficiency of the engine.
2. COMPRESSION stroke: with both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the air, or fuel-air mixture into the combustion chamber of the cylinder head.
3. POWER stroke: this is the start of the second revolution of the engine. While the piston is close to Top Dead Center, the compressed air–fuel mixture in a gasoline engine is ignited, usually by a spark plug, or fuel is injected into the diesel engine, which ignites due to the heat generated in the air during the compression stroke. The resulting massive pressure from the combustion of the compressed fuel-air mixture forces the piston back down toward bottom dead centre.
4. EXHAUST stroke: during the exhaust stroke, the piston once again returns to top dead center while the exhaust valve is open. This action evacuates the burnt products of combustion from the cylinder by expelling the spent fuel-air mixture out through the exhaust valve(s).

MOTOCROSS, SUPERCROSS AND SUPERMOTO

Start of a Motocross race

Motocross (or MX) is the direct equivalent of road racing, but off road, a number of bikes racing on a closed circuit. Motocross circuits are constructed on a variety of non-tarmac surfaces such as dirt, sand, mud, grass, etc., and tend to incorporate elevation changes either natural or artificial. Advances in motorcycle technology, especially suspension, have led to the predominance of circuits with added "jumps" on which bikes can get airborne. Motocross has another noticeable difference from road racing, in that starts are done en masse, with the riders alongside each other. Up to 40 riders race into the first corner, and sometimes there is a separate award for the first rider through (see holeshot). The winner is the first rider across the finish line, generally after a given amount of time or laps or a combination.

Motocross has a plethora of classes based upon machine displacement (ranging from 50cc 2-stroke youth machines up to 250cc 2-stroke and 450cc 4-stroke), age of competitor, ability of competitor, sidecars, quads/ATVs, and machine age (classic for pre 1965/67, Twinshock for bikes with two shock absorbers, etc).

Supercross riders from the 2006 series in Anaheim

Supercross (or SX) is simply indoor motocross. Supercross is more technical and rhythm like to riders. Typically situated in a variety of stadiums and open or closed arenas, it is notable for its numerous jumps. In North America, this has been turned into an extremely popular spectator sport, filling large baseball stadiums, leading to Motocross being now termed the "outdoors". However, in Europe it is less popular, as the predominate focus there is on Motocross.

A Supermoto rider on a tarmac section

Supermoto is a racing category that is a crossover between road-racing and motocross. The motorcycles are mainly motocross types with road-racing tyres. The racetrack is a mixture of road and dirt courses (in different proportions) and can take place either on closed circuits or in temporary venues (such as urban locations).

The riding style on the tarmac section is noticeably different from other forms of tarmac-based racing, with a different line in corners, sliding of the back wheel around the corner, and using the leg straight out to corner (as opposed to the noticeable touching of the bent knee to the tarmac of road racers).

SIDECAR AND TRUE ROAD RACING

Sidecar racing

Sidecar racing is a category of sidecar motorcycle racing. Older sidecar road racers generally resembled solo motorcycles with a platform attached, modern racing sidecars are purpose built low and long vehicles. Sidecarcross resembles MX motorcycles with a high platform attached. In sidecar racing a rider and a passenger work together to make the machine perform.

Sidecar racing has many sub-categories including: – Sidecarcross (sidecar motocross) – Sidecar trials – F1/F2 road racing

Road Racing on temporarily closed public roads

True road racing is run on tracks built from closed public and/or park roads and sometimes extra pieces of purpose built track. In the past true road racing was very commonplace but today few races have survived and even fewer have been added. Only one truly international championship exists at present by the name of "International Road Racing Championship" (IRRC). Most races are held within Europe. Ireland is probably the country with the most true road racing circuits still in use. The Isle of Man probably has the most tracks per inhabitant or surface area. Other countries where true road races are held are the Netherlands, Belgium, Germany, Great Britain (though due to law only outside England or in parks), the Czech Republic, New Zealand and Macau.

 

SUPER SPORT AND ENDURANCE RACING

Supersport racing

Supersport racing is another category of motorcycle road racing that employs modified production motorcycles. To be eligible for Supersport racing, a motorcycle must have a four-stroke engine of between 400 and 600 cc for four-cylinder machines, and between 600 and 750 cc for twins, and must satisfy the FIM homologation requirements. Supersport regulations are much tighter than Superbikes. Supersport machines must remain largely as standard, while engine tuning is possible but tightly regulated.

 

 

Endurance racing

 

 

 

 

 

Endurance racing is a category of motorcycle road racing which is meant to test the durability of equipment and endurance of the riders. Teams of multiple riders attempt to cover a large distance in a single event. Riders are given the ability to change during the race. Endurance races can be run either to cover a set distance in laps as quickly as possible, or to cover as much distance as possible over a preset amount of time.

 

GRAND PRIX AND SUPERBIKE

MotoGP racing

Grand Prix motorcycle racing refers to the premier category of motorcycle road racing. It is divided into three distinct classes:

• 125 cc — Engines in this class are two-stroke. This class is also restricted by rider age, with an upper limit of 25 for newly signed riders and wild card entries and an absolute upper limit of 28 for all riders.
• Moto2 — Introduced by Dorna Sports, the commercial rights holder of the competition, in 2010 as a 600 cc four-stroke class. Prior to that season, the intermediate class was 250 cc with two-stroke engines. Moto2 races in the 2010 season will allow both engine types; from 2011 on, only the four-stroke Moto2 machines will be allowed in this class.
• MotoGP — 800 cc four-stroke.

Grand prix motorcycles are prototype machines not based on any production motorcycle.

Superbike racing

Superbike racing is a category of motorcycle road racing that employs modified production motorcycles. Superbike racing motorcycles must have four stroke engines of between 800 cc and 1200 cc for twins, and between 750 cc and 1000 cc for four cylinder machines. The motorcycles must maintain the same profile as their roadgoing counterparts. The overall appearance, seen from the front, rear and sides, must correspond to that of the bike homologated for use on public roads.

TARGA RACING AND KART RACING

A Toyota MR2, driven by Adam Spence in the 2006 Targa Tasmania prologue stage.

Targa is a tarmac-based road rally which is run all around the world. This began with the Targa Florio. There are many races including Targa Tasmania held on the Australian island state of Tasmania run annually since 1992. The event takes its name from the Targa Florio, a former motoring event held on the island of Sicily. The competition concept is drawn directly from the best features of the Mille Miglia, the Coupe des Alpes and the Tour de Corse. Other events around the world include the Targa Newfoundland based in Canada, Targa West based in Western Australia, Targa New Zealand and other smaller events.

A sprint kart race in Atwater California hosted by the International Karting Federation.

Although often seen as the entry point for serious racers into the sport, kart racing, or karting, can be an economical way for amateurs to try racing and is also a fully fledged international sport in its own right. A large proportion of professional racing drivers began in karts, often from a very young age, such as Michael Schumacher and Fernando Alonso. Several former motorcycle champions have also taken up the sport, notably Wayne Rainey, who was paralysed in a racing accident and now races a hand-controlled kart. As one of the cheapest ways to go racing, karting is seeing its popularity grow worldwide.

Despite their diminutive size, karting's most powerful class, superkart, can have a power-to-weight ratio of 440 hp/tonne.

RALLYING

Rallying at international and most national championship levels involves two classes of homologated road legal production based car; Group N Production cars and more modified Group A cars. Cars compete on (closed) public roads or off-road areas run on a point-to-point format where participants and their co-drivers "rally" to a set of points, leaving in regular intervals from start points. A rally is typically conducted over a number of "special stages" of any terrain, which entrants are often allowed to scout beforehand at reduced speeds compiling detailed shorthand descriptions of the track or road as they go. These detailed descriptions are known as "pace notes." During the actual rally, the co-driver reads the pace notes aloud (using an in-helmet intercom system) to the driver, enabling them to complete each stage as quickly as possible. Competition is based on lowest total elapsed time over the course of an event's special stages, including penalties.

Jari-Matti Latvala driving the Ford Focus RS WRC 09 in 2010 Rally Finland.

The top series is the World Rally Championship (WRC), but there also regional championships and many countries have their own national championships. Some famous rallies include the Monte Carlo Rally, Rally Argentina, Rally Finland and Rally GB. Another famous event (actually best described as a "rally raid") is the Paris-Dakar Rally. There are also many smaller, club level, categories of rallies which are popular with amateurs, making up the "grass roots" of motor sports. Cars at this level may not comply fully with the requirements of group A or group N homologation. Rallying is the most widely used motor sport around the world as it can race on any circuit type. As well as the WRC other major rally events include the British Rally Championship, Intercontinental Rally Challenge, African Rally Championship, Asia-Pacific Rally Championship and endurance rally events like the Dakar Rally.

STOCK CAR RACING

Practice for the Daytona 500.

In North America, stock car racing is the most popular form of auto racing. Primarily raced on oval tracks, stock cars vaguely resemble production cars, but are in fact purpose-built racing machines which are built to tight specifications also called Silhouette racing cars.

The largest stock car racing governing body is NASCAR (National Association for Stock Car Auto Racing). NASCAR's premier series is the Sprint Cup Series, its most famous races being the Daytona 500, the Southern 500, the Coca-Cola 600, and the Brickyard 400. NASCAR also runs several feeder series, including the Nationwide Series, and Camping World Truck Series (a pickup truck racing series). The series conduct races across the entire continental United States. The NASCAR Canadian Tire Series conducts races across Canada and the NASCAR Corona Series conducts races across Mexico.

NASCAR also governs several smaller regional series, such as the Whelen Modified Tour. Modified cars are best described as open-wheel cars. Modified cars have no parts related to the "stock" vehicle for which they are named after. A number of Modified cars display a "manufacturers" logo and "vehicle name", yet use components produced by another automobile manufacturer.

A World of Outlaws late model stock car on a dirt track.

There are also other stock car governing bodies, such as Automobile Racing Club of America and United Speed Alliance Racing.

In the UK, British Stock car racing is also referred to as "Short Circuit Racing". This takes place on shale or tarmac tracks – usually around 1/4 mile in length. The governing bodies for the sport are the Oval Racing Council (ORC) and BriSCA. Both bodies are made up of individual stadium promoters. There are around 35 tracks in the UK and upwards of 7000 active drivers. The sport is split into three basic "divisions" – distinguished by the rules regarding car-contact during racing. The most famous championship is the BriSCA F1 Stock Cars. Full contact formulas include Bangers, Bombers and Rookie Bangers – and racing features Demolitions Derbies, Figure of Eight racing and Oval Racing

Semi Contact Formulas include BriSCA F1, F2 and Superstox – where bumpers are used tactically.

Non-contact formulas include National Hot Rods, Stock Rods and Lightning Rods.

UK Stock car racing started in the 1950s and grew rapidly through the 60s and 70s.

SPORTS CAR RACING

In sports car racing, production derived versions of sports cars also known as grand tourers (GTs), and purpose built sports prototype cars compete within their respective classes on closed circuits. The main global championship series for GT car racing is the FIA GT1 World Championship. There is also the FIA GT3 European Championship as well as the less powerful GT4 European Cup. Previously, an intermediate FIA GT2 European Championship existed, but the FIA dropped it to cut costs. Other major GT championships include the Japanese Super GT championship and the International GT open for GT2 and GT3 cars. There are also national GT championships using mainly GT3 and GT4 cars featuring professional and amateur drivers alike.

The Audi R8 was one of the most successful sports prototypes ever made, seen here at Road Atlanta.

Sports prototypes, unlike GT cars, do not rely on road legal cars as a base. They are closed wheel and often closed cockpit purpose built race cars intended mainly for endurance racing. They have much lower weight and more down force compared to GT cars making them much faster. They are raced in the 24 hours of Le Mans and in the (European) Le Mans series, Asian Le Mans Series and the American Le Mans Series. These cars are referred to as LMP (Le Mans prototype) cars with LMP1 being run mainly by manufacturers and the slightly less powerful LMP2 cars run by privateer teams. All three Le Mans Series run GT cars in addition to Le Mans Prototypes; these cars have different restrictions than the FIA GT cars.

These races are often conducted over long distances, at least 1,000 km (621 mi), and cars are driven by teams of two or more drivers, switching every few hours. Due to the performance difference between production-based sports cars and purpose-built sports prototypes, one race usually involves several racing classes each fighting for their own championship. Another prototype and GT racing championship exists in the United States, which began in 2000, the Grand-Am, sanctions its own endurance series the Rolex Sports Car Series which consists of slower and lower cost race cars compared to LMP and FIA GT cars.

Famous sports car races include the 24 Hours of Le Mans, the Rolex 24 at Daytona, 24 Hours of Spa-Franchorchamps, the 12 Hours of Sebring, and the 1,000-mile (1,600 km) Petit Le Mans at Road Atlanta. There is also the 24 Hours of the Nürburgring on the infamous Nordschleife track and the Dubai 24 Hour which is aimed at GT3 and below cars with a mixture of professional and pro-am drivers.