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79-675: Design work on a development of the AM-35 with boosted supercharging and an intercooler positioned behind the supercharger began on the factory's initiative in December 1939. A batch of ten prototypes was completed in 1940 and bench-testing began on 5 January 1941. It passed its State acceptance trials the following April and was approved for production. It was tested in a variety of aircraft, but proved to be unreliable and prone to overheating. Factory No. 24 in Moscow built only twenty-nine AM-37s, as

158-415: A knock sensor that monitors if knock is being produced by the fuel being used. In modern computer-controlled engines, the ignition timing will be automatically altered by the engine management system to reduce the knock to an acceptable level. Octanes are a family of hydrocarbons that are typical components of gasoline. They are colorless liquids that boil around 125 °C (260 °F). One member of

237-526: A car’s exhaust note, while a supercharged engine maintains the louder exhaust note of a normally aspirated car. Turbocharged engines are more prone to heat soak of the intake air (since turbocharging can place the hot exhaust components near the intake air system), although this can be overcome through the use of an intercooler . The majority of aircraft engines used during World War II used mechanically driven superchargers because they had some significant manufacturing advantages over turbochargers. However,

316-523: A dynamic compressor are: Common methods of driving a supercharger include: Fuels with a higher octane rating are better able to resist autoignition and detonation . As a result, the amount of boost supplied by the superchargers could be increased, resulting in an increase in engine output. The development of 100-octane aviation fuel, pioneered in the USA in the 1930s, enabled the use of higher boost pressures to be used on high-performance aviation engines and

395-413: A flame wave initiate at the spark plug and then "travel in a fairly uniform manner across the combustion chamber" with the expanding gas mix pushing the piston throughout the entirety of the power stroke. A stable gasoline and air mix will combust when the flame wave reaches the molecules, adding heat at the interface. Knock occurs when a secondary flame wave forms from instability and then travels against

474-460: A higher octane rating are used in higher-compression gasoline engines , which may yield higher power for these engines. The added power in such cases comes from the way the engine is designed to compress the air/fuel mixture, and not directly from the rating of the gasoline. In contrast, fuels with lower octane (but higher cetane numbers ) are ideal for diesel engines because diesel engines (also called compression-ignition engines) do not compress

553-440: A lighter fuel that's less prone to autoignition is a wise "insurance policy". For the same reasons, those lighter fuels which are better solvents are much less likely to cause any "varnish" or other fouling on the "backup" spark plugs. In almost all general aviation piston engines, the fuel mixture is directly controlled by the pilot, via a knob and cable or lever similar to (and next to) the throttle control. Leaning — reducing

632-415: A limiting factor in engine performance. Extreme temperatures can cause pre-ignition or knocking , which reduces performance and can cause engine damage. The risk of pre-ignition/knocking increases with higher ambient air temperatures and higher boost levels. Turbocharged engines use energy from the exhaust gas that would normally be wasted, compared with a supercharger which mechanically draws power from

711-573: A narrow range of load/speed/boost, for which the system must be specifically designed. Positive displacement pumps deliver a nearly fixed volume of air per revolution of the compressor (except for leakage, which typically has a reduced effect at higher engine speeds). The most common type of positive-displacement superchargers is the Roots-type supercharger . Other types include the rotary-screw , sliding vane and scroll-type superchargers. The rating system for positive-displacement superchargers

790-476: A nominal 150-octane rating. Using such fuels, aero engines like the Rolls-Royce Merlin 66 and Daimler-Benz DB 605 DC produced power outputs of up to 2,000 hp (1,500 kW). One disadvantage of forced induction (i.e. supercharging or turbocharging) is that compressing the intake air increases its temperature. For an internal combustion engine, the temperature of the intake air becomes

869-486: A relatively low octane rating; the isomer iso-octane causes less knocking because it is more branched and combusts more smoothly. In general, branched compounds with a higher intermolecular force (e.g., London dispersion force for iso-octane) will have a higher octane rating, because they are harder to ignite. Octane isomers such as n-octane and 2,3,3-trimethylpentane have an octane rating of -20 and 106.1, respectively ( RON measurement). The large differences between

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948-648: A similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 lower than the RON, but there is no direct link between RON and MON. See the table below. In most countries in Europe, and in Australia and New Zealand,

1027-505: A total displacement of 426 cu in (7.0 L)). However, because 6–71 is the engine's designation rather than that of the blower, the actual displacement of the blower is less; for example, a 6–71 blower pumps 339 cu in (5.6 L) per revolution. Other supercharger manufacturers have produced blowers rated up to 16–71. Dynamic compressors rely on accelerating the air to high speed and then exchanging that velocity for pressure by diffusing or slowing it down. Major types of

1106-409: A turbocharger was called a "turbosupercharger" and was considered a type of supercharger. The first supercharged engine was built in 1878, with usage in aircraft engines beginning in the 1910s and usage in car engines beginning in the 1920s. In piston engines used by aircraft, supercharging was often used to compensate for the lower air density at high altitudes. Supercharging is less commonly used in

1185-476: A two-stage inter-cooled supercharger with a more compact layout. Nonetheless, turbochargers were useful in high-altitude bombers and some fighter aircraft due to the increased high altitude performance and range. Turbocharged piston engines are also subject to many of the same operating restrictions as those of gas turbine engines. Turbocharged engines also require frequent inspections of their turbochargers and exhaust systems to search for possible damage caused by

1264-480: Is a measured and/or calculated rating of the fuel's ability to resist autoignition, the higher the octane of the fuel, the harder that fuel is to ignite and the more heat is required to ignite it. The result is that a hotter ignition spark is required for ignition. Creating a hotter spark requires more energy from the ignition system, which in turn increases the parasitic electrical load on the engine. The spark also must begin earlier in order to generate sufficient heat at

1343-493: Is a mixture of many hydrocarbons and often other additives). Octane ratings are not indicators of the energy content of fuels. (See Effects below and Heat of combustion ). They are only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol energy density can be compared with gasoline in heat-of-combustion tables. It

1422-550: Is built for may cause engine knocking and/or pre-ignition . The octane rating of aviation gasoline was extremely important in determining aero engine performance in the aircraft of World War II . The octane rating affected not only the performance of the gasoline, but also its versatility; the higher octane fuel allowed a wider range of lean to rich operating conditions. In spark ignition internal combustion engines , knocking (also knock , detonation , spark knock , pinging , or pinking ) occurs when combustion of some of

1501-425: Is derived from testing the gasoline in ordinary multi-cylinder engines (rather than in a purpose-built test engine), normally at wide open throttle. This type of test was developed in the 1920s and is still reliable today. The original RdON tests were done in cars on the road, but as technology developed the testing was moved to chassis dynamometers with environmental controls to improve consistency. The evaluation of

1580-411: Is possible for a fuel to have a Research Octane Number (RON) more than 100, because iso-octane is not the most knock-resistant substance available today. Racing fuels, avgas , LPG and alcohol fuels such as methanol may have octane ratings of 110 or significantly higher. Typical "octane booster" gasoline additives include MTBE , ETBE , iso-octane and toluene . Lead in the form of tetraethyllead

1659-430: Is that the intake air is warmer than at high altitude. Warmer air reduces the threshold at which engine knocking can occur, especially in supercharged or turbocharged engines. Methods to cool the intake air at ground level include intercoolers/aftercoolers , anti-detonant injection , two-speed superchargers and two-stage superchargers. In supercharged engines which use a carburetor , a partially-open throttle reduces

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1738-435: Is the octane number of the fuel. For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. A rating of 90 does not mean that the gasoline contains just iso-octane and heptane in these proportions, but that it has the same detonation resistance properties (generally, gasoline sold for common use never consists solely of iso-octane and heptane; it

1817-417: Is too large for the engine displacement. For this reason, supercharged engines are common in applications where throttle response is a key concern, such as drag racing and tractor pulling competitions. A disadvantage of supercharging is that the engine must withstand the net power output of the engine plus the power to drive the supercharger. Additionally, turbochargers provide sound-dampening properties to

1896-557: Is usually based on their capacity per revolution . In the case of the Roots blower, the GMC rating pattern is typical. The GMC rating is based on how many two-stroke cylinders - and the size of those cylinders - that it is designed to scavenge , with GMC's model range including 2–71, 3–71, 4–71 and 6–71 blowers. The 6–71 blower, for example, is designed to scavenge six cylinders of 71 cu in (1.2 L) each, resulting in an engine with

1975-663: The 1925 Delage , and the 1926 Bugatti Type 35C . Amongst the most famous supercharged cars is the Bentley 4½ Litre ("Blower Bentley"), which was introduced in 1929. In 1935, the development of screw-type superchargers reached a milestone when Swedish engineer Alf Lysholm patented a design for a rotary-screw compressor with five female and four male rotors. In the 21st century, supercharged production car engines have become less common, as manufacturers have shifted to turbocharging to achieve higher fuel economy and power outputs. For example, Mercedes-Benz's Kompressor engines of

2054-602: The Lockheed Constellation , and the C-124 Globemaster II . In the 1985 and 1986 World Rally Championships, Lancia ran the Delta S4 , which incorporated both a belt-driven supercharger and exhaust-driven turbocharger. The design used a complex series of bypass valves in the induction and exhaust systems as well as an electromagnetic clutch so that, at low engine speeds, a boost was derived from

2133-416: The air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug , but when one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at

2212-528: The gas turbine and a pre-turbine section of the exhaust system. The size of the ducting alone was a serious design consideration. For example, both the F4U Corsair and the P-47 Thunderbolt used the same radial engine , but the large barrel-shaped fuselage of the turbocharged P-47 was needed because of the amount of ducting to and from the turbocharger in the rear of the aircraft. The F4U used

2291-423: The ideal gas law . Higher compression ratios necessarily add parasitic load to the engine, and are only necessary if the engine is being specifically designed to run on high-octane fuel. Aircraft engines run at relatively low speeds and are " undersquare ". They run best on lower-octane, slower-burning fuels that require less heat and a lower compression ratio for optimum vaporization and uniform fuel-air mixing, with

2370-596: The "headline" octane rating prominently displayed on the pump is the RON, but in Canada, the United States, and Mexico, the headline number is the simple mean or average of the RON and the MON, called the Anti-Knock Index ( AKI ), and often written on pumps as (R+M)/2 . AKI is also sometimes called PON (Pump Octane Number). Because of the 8 to 12 octane number difference between RON and MON noted above,

2449-398: The 1.6 litre Mercedes 6/25 hp and 2.6 litre Mercedes 10/40 hp , both of which began production in 1923. They were marketed as Kompressor models, a term which was used for various models until 2012. Supercharged racing cars from around this time included the 1923 Fiat 805-405 , the 1923 Miller 122 the 1924 Alfa Romeo P2 , the 1924 Grand Prix season car from Sunbeam,

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2528-420: The 21st century, as manufacturers have shifted to turbochargers to reduce fuel consumption and increase power outputs. There are two main families of superchargers defined according to the method of gas transfer: positive displacement and dynamic superchargers. Positive displacement superchargers deliver an almost constant level of boost pressure increase at all engine speeds, while dynamic superchargers cause

2607-551: The AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's sensitivity, and is not typically published for those countries that use the Anti-Knock Index labelling system. See the table in the following section for a comparison. Another type of octane rating, called Observed Road Octane Number ( RdON ),

2686-471: The German engines being significantly larger in displacement. Two-stage superchargers were also always two-speed. After the air was compressed in the low-pressure stage , the air flowed through a heat exchanger (" intercooler ") where it was cooled before being compressed again by the high-pressure stage and then possibly also aftercooled in another heat exchanger. While superchargers were highly used in

2765-623: The Spitfire and Hurricane planes powered by the Rolls-Royce Merlin engine were equipped largely with single-stage and single-speed superchargers. In 1942, two-speed two-stage supercharging with aftercooling was applied to the Rolls Royce Merlin 61 aero engine. The improved performance allowed the aircraft they powered to maintain a crucial advantage over the German aircraft they opposed throughout World War II, despite

2844-436: The United States patented the design for an air mover for use in blast furnaces and other industrial applications. This air mover and Birmingham's ventilation compressor both used designs similar to that of the later Roots-type superchargers . In March of 1878, German engineer Heinrich Krigar obtained the first patent for a screw-type compressor. The design was a two-lobe rotor assembly with identically-shaped rotors, however

2923-403: The air density at 30,000 ft (9,100 m) is 1 ⁄ 3 of that at sea level, resulting in 1 ⁄ 3 as much fuel being able to be burnt in a naturally aspirated engine, therefore the power output would be greatly reduced. A supercharger/turbocharger can be thought of either as artificially increasing the density of the air by compressing it or as forcing more air than normal into

3002-456: The air pressure within the carburetor. In cold conditions, this low pressure air can cause ice to form at the throttle plate. Significant quantities of ice can cause engine failure, even with the engine operating at full rated power. Octane rating An octane rating , or octane number , is a standard measure of a fuel 's ability to withstand compression in an internal combustion engine without causing engine knocking . The higher

3081-403: The available air) or "lean of peak" (less fuel, leaving some oxygen in the exhaust) as either will keep the fuel-air mixture from detonating prematurely. Because of the high cost of unleaded, high-octane avgas , and possible increased range before refueling, some general aviation pilots attempt to save money by tuning their fuel-air mixtures and ignition timing to run "lean of peak". Additionally,

3160-649: The benefit to the operational range was given a much higher priority to American aircraft because of a less predictable requirement on the operational range and having to travel far from their home bases. Consequently, turbochargers were mainly employed in American aircraft engines such as the Allison V-1710 and the Pratt & Whitney R-2800 , which were comparably heavier when turbocharged, and required additional ducting of expensive high-temperature metal alloys in

3239-433: The boost pressure to rise exponentially with engine speed (above a certain threshold). Another family of supercharger, albeit rarely used, is the pressure wave supercharger . Roots blowers (a positive displacement design) tend to be only 40–50% efficient at high boost levels, compared with 70-85% for dynamic superchargers. Lysholm-style blowers (a rotary-screw design) can be nearly as efficient as dynamic superchargers over

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3318-410: The cylinder every time the piston moves down on the intake stroke. Since a supercharger is usually designed to produce a given amount of boost at high altitudes (where the air density is lower), the supercharger is often oversized for low altitude. To prevent excessive boost levels, it is important to monitor the intake manifold pressure at low altitude. As the aircraft climbs and the air density drops,

3397-421: The decreased air density at higher altitudes (such as Colorado) and temperatures (as in summer) requires leaning (reduction in amount of fuel per volume or mass of air) for the peak EGT and power (crucial for takeoff). The selection of octane ratings available at filling stations can vary greatly between countries. Due to its name, the chemical "octane" is often misunderstood as the only substance that determines

3476-482: The definition of octane rating. The following table lists octane ratings for various other fuels. Higher octane ratings correlate to higher activation energies : the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition, self-ignition, pre-ignition, detonation, or knocking. Because octane

3555-503: The design did not reach production. Also in 1878, Scottish engineer Dugald Clerk designed the first supercharger which was used with an engine. This supercharger was used with a two-stroke gas engine. Gottlieb Daimler received a German patent for supercharging an internal combustion engine in 1885. Louis Renault patented a centrifugal supercharger in France in 1902. The world's first series-produced cars with superchargers were

3634-597: The direct measurements required for research or motor octane numbers. An octane index can be of great service in the blending of gasoline. Motor gasoline, as marketed, is usually a blend of several types of refinery grades that are derived from different processes such as straight-run gasoline, reformate, cracked gasoline etc. These different grades are blended in amounts that will meet final product specifications. Most refiners produce and market more than one grade of motor gasoline, differing principally in their anti-knock quality. Being able to make sufficiently accurate estimates of

3713-780: The early 2000s (such as the C 230 Kompressor straight-four, C 32 AMG V6, and CL 55 AMG V8 engines) were replaced around 2010 by turbocharged engines in models such as the C 250 and CL 65 AMG models. However, there are exceptions, such as the Audi 3.0 TFSI supercharged V6 (introduced in 2009) and the Jaguar AJ-V8 supercharged V8 (upgraded to the Gen III version in 2009). In the 1930s, two-speed drives were developed for superchargers for aero engines providing more flexible aircraft operation. The arrangement also entailed more complexity of manufacturing and maintenance. The gears connected

3792-507: The engine. Lighter and "thinner" fuel also has a lower specific heat , so the practice of running an engine "rich" to use excess fuel to aid in cooling requires richer and richer mixtures as octane increases. Higher-octane, lower-energy-dense "thinner" fuels often contain alcohol compounds incompatible with the stock fuel system components, which also makes them hygroscopic . They also evaporate away much more easily than heavier, lower-octane fuel which leads to more accumulated contaminants in

3871-412: The engine. Therefore turbocharged engines usually produce more power and better fuel economy than supercharged engines. However, turbochargers can suffer from turbo lag (especially at lower RPM), where the exhaust gas flow is initially insufficient to spin the turbocharger and achieve the desired boost level, thus leading to a delay in the throttle response . This is often a result of a turbo charge which

3950-401: The evaluation of the anti-knock quality of gasoline. Such substitute methods include FTIR, near infrared on-line analyzers, and others. Deriving an equation that can be used to calculate ratings accurately enough would also serve the same purpose, with added advantages. The term Octane Index is often used to refer to the use of an equation to determine a theoretical rating, in contradistinction to

4029-768: The extreme heat and pressure of the turbochargers. Such damage was a prominent problem in the early models of the American Boeing B-29 Superfortress high-altitude bombers used in the Pacific Theater of Operations during 1944–45. Turbocharged piston engines continued to be used in a large number of postwar airplanes, such as the B-50 Superfortress , the KC-97 Stratofreighter , the Boeing 377 Stratocruiser ,

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4108-406: The fuel system. It is typically the hydrochloric acids that form due to that water and the compounds in the fuel that have the most detrimental effects on the engine fuel system components, as such acids corrode many metals used in gasoline fuel systems. During the compression stroke of an internal combustion engine, the temperature of the air-fuel mix rises as it is compressed, in accordance with

4187-439: The fuel, but rather compress only air, and then inject fuel into the air that was heated by compression. Gasoline engines rely on ignition of compressed air and fuel mixture, which is ignited only near the end of the compression stroke by electric spark plugs . Therefore, being able to compress the air/fuel mixture without causing detonation is important mainly for gasoline engines. Using gasoline with lower octane than an engine

4266-449: The ignition spark coming as late as possible in order to extend the production of cylinder pressure and torque as far down the power stroke as possible. The main reason for using high-octane fuel in air-cooled engines is that it is more easily vaporized in a cold carburetor and engine and absorbs less intake air heat which greatly reduces the tendency for carburetor icing to occur. With their reduced densities and weight per volume of fuel,

4345-406: The intake gas, forcing more air into the engine in order to produce more power for a given displacement . The current categorization is that a supercharger is a form of forced induction that is mechanically powered (usually by a belt from the engine's crankshaft ), as opposed to a turbocharger , which is powered by the kinetic energy of the exhaust gases. However, up until the mid-20th century,

4424-446: The lifespan of engines. In 1927, Graham Edgar devised the method of using iso-octane and n-heptane as reference chemicals, in order to rate the knock resistance of a fuel with respect to this isomer of octane, thus the name "octane rating". By definition, the isomers iso-octane and n-heptane have an octane rating of 100 and 0, respectively. Because of its more volatile nature, n-heptane ignites and knocks readily, which gives it

4503-657: The lower of the two. One is referred to as the "aviation lean" rating, which for ratings up to 100 is the same as the MON of the fuel. The second is the "aviation rich" rating and corresponds to the octane rating of a test engine under forced induction operation common in high-performance and military piston aircraft. This utilizes a supercharger , and uses a significantly richer fuel/air ratio for improved detonation resistance. The most common currently used fuel, 100LL , has an aviation lean rating of 100 octane, and an aviation rich rating of 130. The RON/MON values of n- heptane and iso-octane are exactly 0 and 100, respectively, by

4582-444: The mid-1900s and during WWII , they have largely fallen out of use in modern piston-driven aircraft . This can largely be attributed to the higher temperature and lighter alloys that make turbochargers more efficient than superchargers, as well as the lower maintenance due to less moving parts. Due to the reduced air density at higher altitudes, supercharging and turbocharging have often been used in aircraft engines. For example,

4661-445: The mixture from its maximum amount — must be done with knowledge, as some combinations of fuel mixture and throttle position (that produce the highest ) can cause detonation and/or pre-ignition , in the worst case destroying the engine within seconds. Pilots are taught in primary training to avoid settings that produce the highest exhaust gas temperatures, and run the engine either "rich of peak EGT " (more fuel than can be burned with

4740-570: The new engine was designated, in 1941 before the German advance forced the factory to evacuate in October. Mikulin had been unable to resolve the issues with the AM-37 in the meantime and production was not resumed. Data from Kotelnikov, Russian Piston Aero Engines Related development Related lists Supercharger In an internal combustion engine , a supercharger compresses

4819-479: The octane family, 2,2,4-Trimethylpentane (iso-octane), is used as a reference standard to benchmark the tendency of gasoline or LPG fuels to resist self-ignition. The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and normal heptane that would have the same anti-knocking capability as the fuel under test. The percentage, by volume, of 2,2,4-trimethylpentane in that mixture

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4898-401: The octane number by either of the two laboratory methods requires a special engine built to match the tests' rigid standards, and the procedure can be both expensive and time-consuming. The standard engine required for the test may not always be available, especially in out-of-the-way places or in small or mobile laboratories. These and other considerations led to the search for a rapid method for

4977-427: The octane number, the more compression the fuel can withstand before detonating. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates the resistance to detonating under pressure without a spark. Whether or not a higher octane fuel improves or impairs an engine's performance depends on the design of the engine. In broad terms, fuels with

5056-493: The octane rating (or octane number) of a fuel. This is an inaccurate description. In reality, the octane rating is defined as a number describing the stability and ability of a fuel to prevent an engine from unwanted combustions that occur spontaneously in the other regions within a cylinder (i.e., delocalized explosions from the spark plug). This phenomenon of combustion is more commonly known as engine knocking or self-ignition, which causes damage to pistons over time and reduces

5135-414: The octane rating of gasoline is not directly related to the power output of an engine. Using gasoline of a higher octane than an engine is designed for cannot increase its power output. Octane became well known in American popular culture in the 1960s, when gasoline companies boasted of "high octane" levels in their gasoline advertisements. The compound adjective "high-octane", meaning powerful or dynamic,

5214-404: The octane rating that will result from blending different refinery products is essential, something for which the calculated octane index is specially suited. Aviation gasolines used in piston aircraft engines common in general aviation have a slightly different method of measuring the octane of the fuel. Similar to an AKI, it has two different ratings, although it is usually referred to only by

5293-418: The octane ratings for the isomers show that the compound octane itself is clearly not the only factor that determines octane ratings, especially for commercial fuels consist of a wide variety of compounds. "Octane" is colloquially used in the expression "high-octane". The term is used to describe a powerful action because of the association with the concept of "octane rating". This is a misleading term, because

5372-580: The optimum moment for the four-stroke cycle . In a simple explanation, the forward moving wave of combustion that burns the hydrocarbon + oxygen mixture inside the cylinder like a wave that a surfer would wish to surf upon is violently disrupted by a secondary wave that has started elsewhere. The shock wave of these two separate waves creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential (incremental heating plus power loss) to completely destructive (detonation while one of

5451-544: The other obvious benefit is that an aircraft with any given volume of fuel in the tanks is automatically lighter. And since many airplanes are flown only occasionally and may sit unused for weeks or months, the lighter fuels tend to evaporate away and leave behind fewer deposits such as "varnish" (gasoline components, particularly alkenes and oxygenates slowly polymerize into solids). Aircraft also typically have dual "redundant" ignition systems which are nearly impossible to tune and time to produce identical ignition timing, so using

5530-453: The path of the primary flame wave, thus depriving the power stroke of its uniformity and causing issues including power loss and heat buildup. The other rarely-discussed reality with high-octane fuels associated with "high performance" is that as octane increases, the specific gravity and energy content of the fuel per unit of weight are reduced. The net result is that to make a given amount of power , more high-octane fuel must be burned in

5609-415: The proper time for precise ignition. As octane, ignition spark energy, and the need for precise timing increase, the engine becomes more difficult to "tune" and keep "in tune". The resulting sub-optimal spark energy and timing can cause major engine problems, from a simple "miss" to uncontrolled detonation and catastrophic engine failure. Mechanically within the cylinder, stability can be visualized as having

5688-399: The results with those for mixtures of iso-octane and n-heptane. The compression ratio is varied during the test to challenge the fuel's antiknocking tendency, as an increase in the compression ratio will increase the chances of knocking. Another type of octane rating, called Motor Octane Number ( MON ), is determined at 900 rpm engine speed instead of the 600 rpm for RON. MON testing uses

5767-452: The supercharger to the engine using a system of hydraulic clutches, which were initially manually engaged or disengaged by the pilot with a control in the cockpit. At low altitudes, the low-speed gear would be used, to prevent excessive boost levels. At higher altitudes, the supercharger could be switched to a higher gear to compensate for the reduced intake air density. In the Battle of Britain

5846-500: The supercharger. In the middle of the rev range, a boost was derived from both systems, while at the highest revs the system disconnected the drive from the supercharger and isolated the associated ducting. This was done in an attempt to exploit the advantages of each of the charging systems while removing the disadvantages. In turn, this approach brought greater complexity and affected the car's reliability in WRC events, as well as increasing

5925-457: The throttle can be progressively opened to obtain the maximum safe power level for a given altitude. The altitude at which the throttle reaches full open and the engine is still producing full rated power is known as the critical altitude . Above the critical altitude, engine power output will reduce as the supercharger can no longer fully compensate for the decreasing air density. Another issue encountered at low altitudes (such as at ground level)

6004-459: The valves is still open). Knocking should not be confused with pre-ignition —they are two separate events with pre-ignition occurring before the combustion event. However, pre-ignition is highly correlated with knock because knock will cause rapid heat increase within the cylinder eventually leading to destructive pre-detonation. Most engine management systems commonly found in automobiles today, typically electronic fuel injection (EFI), have

6083-546: The weight of engine ancillaries in the finished design. Twincharged engines have occasionally been used in production cars, such as the 2005-2013 Volkswagen 1.4 litre and the 2017-present Volvo B4204T43/B4204T48 2.0 litre four-cylinder engines. In 1849, G. Jones of Birmingham, England began manufacturing a lobe pump compressor to provide ventilation for coal mines. In 1860, the Roots Blower Company (founded by brothers Philander and Francis Marion Roots) in

6162-486: Was once a common additive, but concerns about its toxicity have led to its use for fuels for road vehicles being progressively phased out worldwide beginning in the 1970s. The most common type of octane rating worldwide is the Research Octane Number ( RON ). RON is determined by running the fuel in a test engine at 600 rpm with a variable compression ratio under controlled conditions, and comparing

6241-567: Was used to vastly increase the power output for several speed record airplanes. Military use of high-octane fuels began in early 1940 when 100-octane fuel was delivered to the British Royal Air Force fighting in World War II. The German Luftwaffe also had supplies of a similar fuel. Increasing the octane rating became a major focus of aero engine development for the remainder of the war, with later fuels having up to

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