Turbine engine

Turbine engines produce thrust by increasing the velocity of the air flowing through the engine. A turbine engine consists of an air inlet, compressor, combustion chambers, turbine section, and exhaust. Figure 1: Basic components of a turbine engine. The turbine engine has the following advantages over a reciprocating engine: less vibration, increased aircraft performance, reliability, and ease of operation. Types of turbine engines Turbine engines are classified according to the type of compressors they use. The compressor types fall into three categories—centrifugal flow, axial flow, and centrifugal-axial flow. Compression of inlet air is achieved in a centrifugal flow engine by accelerating air outward perpendicular to the longitudinal axis of the machine. The axial-flow engine compresses air by a series of rotating and stationary airfoils moving the air parallel to the longitudinal axis. The centrifugalaxial flow design uses both kinds of compressors to achieve the desired compression. The path the air takes through the engine and how power is produced determines the type of engine. There are four types of aircraft turbine engines—turbojet, turboprop, turbofan, and turboshaft. Turbojet The turbojet engine contains four sections: compressor, combustion chamber, turbine section, and exhaust. The compressor section passes inlet air at a high rate of speed to the combustion chamber. The combustion chamber contains the fuel inlet and igniter for combustion. The expanding air drives a turbine, which is connected by a shaft to the compressor, sustaining engine operation. The accelerated exhaust gases from the engine provide thrust. This is a basic application of compressing air, igniting the fuel-air mixture, producing power to self-sustain the engine operation, and exhaust for propulsion. Turbojet engines are limited on range and endurance. They are also slow to respond to throttle applications at slow compressor speeds. Turboprop A turboprop engine is a turbine engine that drives a propeller through a reduction gear. The exhaust gases drive a power turbine connected by a shaft that drives the reduction gear assembly. Reduction gearing is necessary in turboprop engines because optimum propeller performance is achieved at much slower speeds than the engine’s operating r.p.m. Turboprop engines are a compromise between turbojet engines and reciprocating powerplants. Turboprop engines are most efficient at speeds between 250 and 400 m.p.h. and altitudes between 18,000 and 30,000 feet. They also perform well at the slow airspeeds required for takeoff and landing, and are fuel efficient. The minimum specific fuel consumption of the turboprop engine is normally available in the altitude range of 25,000 feet to the tropopause. Turbofan Turbofans were developed to combine some of the best features of the turbojet and the turboprop. Turbofan engines are designed to create additional thrust by diverting a secondary airflow around the combustion chamber. The turbofan bypass air generates increased thrust, cools the engine, and aids in exhaust noise suppression. This provides turbojet-type cruise speed and lower fuel consumption. The inlet air that passes through a turbofan engine is usually divided into two separate streams of air. One stream passes through the engine core, while a second stream bypasses the engine core. It is this bypass stream of air that is responsible for the term “bypass engine.” A turbofan’s bypass ratio refers to the ratio of the mass airflow that passes through the fan divided by the mass airflow that passes through the engine core. Turboshaft The fourth common type of jet engine is the turboshaft. It delivers power to a shaft that drives something other than a propeller. The biggest difference between a turbojet and turboshaft engine is that on a turboshaft engine, most of the energy produced by the expanding gases is used to drive a turbine rather than produce thrust. Many helicopters use a turboshaft gas turbine engine. In addition, turboshaft engines are widely used as auxiliary power units on large aircraft. Performance comparison It is possible to compare the performance of a reciprocating powerplant and different types of turbine engines. However, for the comparison to be accurate, thrust horsepower (usable horsepower) for the reciprocating powerplant must be used rather than brake horsepower, and net thrust must be used for the turbine-powered engines. In addition, aircraft design configuration, and size must be approximately the same. BHP Brake horsepower is the horsepower actually delivered to the output shaft. Brake horsepower is the actual usable horsepower. Net Thrust The thrust produced by a turbojet or turbofan engine. THP Thrust horsepower is the horsepower equivalent of the thrust produced by a turbojet or turbofan engine. ESHP Equivalent shaft horsepower, with respect to turboprop engines, is the sum of the shaft horsepower (SHP) delivered to the propeller and the thrust horsepower (THP) produced by the exhaust gases. Figure 2: Engine net thrust versus aircraft speed and drag. Figure 2 shows how four types of engines compare in net thrust as airspeed is increased. This figure is for explanatory purposes only and is not for specific models of engines. The four types of engines are: Reciprocating powerplant. Turbine, propeller combination (turboprop). Turbine engine incorporating a fan (turbofan). Turbojet (pure jet). The comparison is made by plotting the performance curve for each engine, which shows how maximum aircraft speed varies with the type of engine used. Since the graph is only a means of comparison, numerical values for net thrust, aircraft speed, and drag are not included. Comparison of the four powerplants on the basis of net thrust makes certain performance capabilities evident. In the speed range shown to the left of Line A, the reciprocating powerplant outperforms the other three types. The turboprop outperforms the turbofan in the range to the left of Line C. The turbofan engine outperforms the turbojet in the range to the left of Line F. The turbofan engine outperforms the reciprocating powerplant to the right of Line B and the turboprop to the right of Line C. The turbojet outperforms the reciprocating powerplant to the right of Line D, the turboprop to the right of Line E, and the turbofan to the right of Line F. The points where the aircraft drag curve intersects the net thrust curves are the maximum aircraft speeds. The vertical lines from each of the points to the baseline of the graph indicate that the turbojet aircraft can attain a higher maximum speed than aircraft equipped with the other types of engines. Aircraft equipped with the turbofan engine will attain a higher maximum speed than aircraft equipped with a turboprop or reciprocating powerplant. Turbine engine instruments Engine instruments that indicate oil pressure, oil temperature, engine speed, exhaust gas temperature, and fuel flow are common to both turbine and reciprocating engines. However, there are some instruments that are unique to turbine engines. These instruments provide indications of engine pressure ratio, turbine discharge pressure, and torque. In addition, most gas turbine engines have multiple temperature-sensing instruments, called thermocouples, that provide pilots with temperature readings in and around the turbine section. Engine pressure ratio An engine pressure ratio (EPR) gauge is used to indicate the power output of a turbojet/turbofan engine. EPR is the ratio of turbine discharge to compressor inlet pressure. Pressure measurements are recorded by probes installed in the engine inlet and at the exhaust. Once collected, the data is sent to a differential pressure transducer, which is indicated on a cockpit EPR gauge. EPR system design automatically compensates for the effects of airspeed and altitude. However, changes in ambient temperature do require a correction to be applied to EPR indications to provide accurate engine power settings. Exhaust gas temperature A limiting factor in a gas turbine engine is the temperature of the turbine section. The temperature of a turbine section must be monitored closely to prevent overheating the turbine blades and other exhaust section components. One common way of monitoring the temperature of a turbine section is with an exhaust gas temperature (EGT) gauge. EGT is an engine operating limit used to monitor overall engine operating conditions. Variations of EGT systems bear different names based on the location of the temperature sensors. Common turbine temperature sensing gauges include the turbine inlet temperature (TIT) gauge, turbine outlet temperature (TOT) gauge, interstage turbine temperature (ITT) gauge, and turbine gas temperature (TGT) gauge. Torquemeter Turboprop/turboshaft engine power output is measured by the torquemeter. Torque is a twisting force applied to a shaft. The torquemeter measures power applied to the shaft. Turboprop and turboshaft engines are designed to produce torque for driving a propeller. Torquemeters are calibrated in percentage units, foot-pounds, or pounds per square inch. N1 indicator N1 represents the rotational speed of the low pressure compressor and is presented on the indicator as a percentage of design r.p.m. After start the speed of the low pressure compressor is governed by the N1 turbine wheel. The N1 turbine wheel is connected to the low pressure compressor through a concentric shaft. N2 indicator N2 represents the rotational speed of the high pressure compressor and is presented on the indicator as a percentage of design r.p.m. The high pressure compressor is governed by the N2 turbine wheel. The N2 turbine wheel is connected to the high pressure compressor through a concentric shaft. Figure 3: Dual-spool axial-flow compressor. Turbine engine operational considerations Because of the great variety of turbine engines, it is impractical to cover specific operational procedures. However, there are certain operational considerations that are common to all turbine engines. They are engine temperature limits, foreign object damage, hot start, compressor stall, and flameout. Engine temperature limitations The highest temperature in any turbine engine occurs at the turbine inlet. Turbine inlet temperature is therefore usually the limiting factor in turbine engine operation. Thrust variations Turbine engine thrust varies directly with air density. As air density decreases, so does thrust. While both turbine and reciprocating powered engines are affected to some degree by high relative humidity, turbine engines will experience a negligible loss of thrust, while reciprocating engines a significant loss of brake horsepower. Foreign object damage Due to the design and function of a turbine engine’s air inlet, the possibility of ingestion of debris always exists. This causes significant damage, particularly to the compressor and turbine sections. When this occurs, it is called foreign object damage (FOD). Typical FOD consists of small nicks and dents caused by ingestion of small objects from the ramp, taxiway, or runway. However, FOD damage caused by bird strikes or ice ingestion can also occur, and may result in total destruction of an engine. Prevention of FOD is a high priority. Some engine inlets have a tendency to form a vortex between the ground and the inlet during ground operations. A vortex dissipater may be installed on these engines. Other devices, such as screens and/or deflectors, may also be utilized. Preflight procedures include a visual inspection for any sign of FOD. Turbine engine hot/hung start A hot start is when the EGT exceeds the safe limit. Hot starts are caused by too much fuel entering the combustion chamber, or insufficient turbine r.p.m. Any time an engine has a hot start, refer to the AFM, POH, or an appropriate maintenance manual for inspection requirements. If the engine fails to accelerate to the proper speed after ignition or does not accelerate to idle r.p.m., a hung start has occurred. A hung start, may also be called a false start. A hung start may be caused by an insufficient starting power source or fuel control malfunction. Compressor stalls Compressor blades are small airfoils and are subject to the same aerodynamic principles that apply to any airfoil. A compressor blade has an angle of attack. The angle of attack is a result of inlet air velocity and the compressor’s rotational velocity. These two forces combine to form a vector, which defines the airfoil’s actual angle of attack to the approaching inlet air. A compressor stall can be described as an imbalance between the two vector quantities, inlet velocity and compressor rotational speed. Compressor stalls occur when the compressor blades’ angle of attack exceeds the critical angle of attack. At this point, smooth airflow is interrupted and turbulence is created with pressure fluctuations. Compressor stalls cause air flowing in the compressor to slow down and stagnate, sometimes reversing direction. Figure 4: Comparison of normal and distorted airflow into the compressor section. Compressor stalls can be transient and intermittent or steady state and severe. Indications of a transient/intermittent stall are usually an intermittent “bang” as backfire and flow reversal take place. If the stall develops and becomes steady, strong vibration and a loud roar may develop from the continuous flow reversal. Quite often the cockpit gauges will not show a mild or transient stall, but will indicate a developed stall. Typical instrument indications include fluctuations in r.p.m., and an increase in exhaust gas temperature. Most transient stalls are not harmful to the engine and often correct themselves after one or two pulsations. The possibility of engine damage, which may be severe, from a steady state stall is immediate. Recovery must be accomplished quickly by reducing power, decreasing the airplane’s angle of attack and increasing airspeed. Although all gas turbine engines are subject to compressor stalls, most models have systems that inhibit these stalls. One such system uses variable inlet guide vane (VIGV) and variable stator vanes, which direct the incoming air into the rotor blades at an appropriate angle. The main way to prevent air pressure stalls is to operate the airplane within the parameters established by the manufacturer. If a compressor stall does develop, follow the procedures recommended in the AFM or POH. Flameout A flameout is a condition in the operation of a gas turbine engine in which the fire in the engine unintentionally goes out. If the rich limit of the fuel/air ratio is exceeded in the combustion chamber, the flame will blow out. This condition is often referred to as a rich flameout. It generally results from very fast engine acceleration, where an overly rich mixture causes the fuel temperature to drop below the combustion temperature. It also may be caused by insufficient airflow to support combustion. Another, more common flameout occurrence is due to low fuel pressure and low engine speeds, which typically are associated with high-altitude flight. This situation also may occur with the engine throttled back during a descent, which can set up the lean-condition flameout. A weak mixture can easily cause the flame to die out, even with a normal airflow through the engine. Any interruption of the fuel supply also can result in a flameout. This may be due to prolonged unusual attitudes, a malfunctioning fuel control system, turbulence, icing or running out of fuel. Symptoms of a flameout normally are the same as those following an engine failure. If the flameout is due to a transitory condition, such as an imbalance between fuel flow and engine speed, an airstart may be attempted once the condition is corrected. In any case, pilots must follow the applicable emergency procedures outlined in the AFM or POH. Generally, these procedures contain recommendations concerning altitude and airspeed where the airstart is most likely to be successful.

VVT-i, VVTL-i, Dual VVT-i, VVT-iE

VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota, similar in performance to the BMW’s VANOS. The Toyota VVT-i system replaces the Toyota VVT offered starting in 1991 on the 5-valve per cylinder 4A-GE engine. The VVT system is a 2-stage hydraulically controlled cam phasing system. VVT-i, introduced in 1996, varies the timing of the intake valves by adjusting the relationship between the camshaft drive (belt, scissor-gear or chain) and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. Adjustments in the overlap time between the exhaust valve closing and intake valve opening result in improved engine efficiency.[1] Variants of the system, including VVTL-i, Dual VVT-i, VVT-iE, and Valvematic, have followed. There are a couple of ways by which car manufacturer's vary the valve timing. The most well known system is the VTEC which is used on some of the Honda engines. Other systems which some of you might not have heard of are: VarioCam/VarioCam Plus which is used on some of the Porsche engines, MIVEC(Mitsubishi Innovative Valve timing and lift Electronic Control) which is used on the Mitsubishi engines, VVT-i(Variable Valve Timing with Intelligence) and now VVTL-i (Variable Valve Timing and Lift with Intelligence) which is being used on the current Toyota and some Lexus engines, VVL(Variable Valve Lift) which is used on the Nissan engines and also featured in the 350Z is the CVTCS (Continuously Variable Valve Timing System) VANOS(Variable Onckenwellen Steuerung) which is used in the BMW engines and also the Double VANOS system on the new 3 Series and they are many more similar systems used by manufacturers such as Ford, Lamborghini and even Ferrari. What do all these Vs have in common? Well, in case you don't already know (or haven't yet guessed despite the monster hint in the article's title), the V stands for valves or, more specifically, variable valve timing. Before you can appreciate how important valve timing is, you have to understand how it relates to engine operation. Remember that an engine is basically a glorified air pump and, as such, the most effective way to increase horsepower and/or efficiency is to increase an engine's ability to process air. There are a number of ways to do this that range from altering the exhaust system to upgrading the fuel system to installing a less-restrictive air filter. Since an engine's valves play a major role in how air gets in and out of the combustion chamber, it makes sense to focus on them when looking to increase horsepower and efficiency. This is exactly what Honda, Toyota and BMW and quite a number of other manufacturer's have done in recent years. By using advanced systems to alter the opening and closing of engine valves, they have created more powerful and clean burning engines that require less fuel and are relatively small in displacement. Before we take a look at each of these variable valve-timing systems, let's rehash how valve timing normally works. Until recently, a manufacturer used one or more camshafts (plus some pushrods, lifters and rocker arms) to open and close an engine's valves. The camshaft/camshafts was turned by a timing chain that connected to the crankshaft. As engine rpm's rose and fell, the crankshaft and camshaft would turn faster or slower to keep valve timing relatively close to what was needed for engine operation. Unfortunately, the dynamics of airflow through a combustion chamber change radically between 2,000 rpm and 6,000 rpm. Despite the manufacturer's best efforts, there was just no way to maximize valve timing for high and low rpm with a simple crankshaft-driven valve train. Instead, engineers had to develop a "compromise" system that would allow an engine to start and run when pulling out of the driveway but also allow for strong acceleration and highway cruising at 70+ mph. Obviously, they were successful. However, because of the "compromise" nature of standard valve train systems, few engines were ever in their "sweet zone," which resulted in wasted fuel and reduced performance. Variable valve timing has changed all that. By coming up with a way to alter valve timing between high and low rpm's, Honda, Toyota and BMW and many more manufacturer's can now tune valve operation for optimum performance and efficiency throughout the entire rev range. Honda was the first to offer what it called VTEC in its Acura-badged performance models like the Integra GS-R and NSX (it has since worked its way into the Prelude and even the lowly Civic). VTEC stands for Variable Valve Timing and Lift Electronic Control. It basically uses two sets of camshaft profiles-one for low and mid-range rpm and one for high rpm operation. An electronic switch shifts between the two profiles at a specific rpm to increase peak horsepower and improve torque. As a VTEC driver, you can both hear and feel the change when the VTEC "kicks in" at higher rpm levels to improve performance. While this system does not offer continuously variable valve timing, it can make the most of high rpm operation while still providing solid drivability at lower rpm levels. Honda is already working on a three-step VTEC system that will further improve performance and efficiency across the engine rpm range. The camshaft in a pushrod engine is often driven by gears or a short chain. Gear-drives are generally less prone to breakage than belt drives, which are often found in overhead cam engines. Toyota saw the success Honda was having with VTEC (from both a functional and marketing standpoint) but decided to go a different route. Instead of the on/off system that VTEC employs, Toyota decided it wanted a continuously variable system that would maximize valve timing throughout the rpm range. Dubbed VVTi for Variable Valve Timing with intelligence (Is this a dig at Honda, suggesting their system isn't intelligent?), Toyota uses a hydraulic rather than mechanical system to alter the intake cam's phasing. The main difference from VTEC is that VVTi maintains the same cam profile and alters only when the valves open and close in relation to engine speed. Also, this system works only on the intake valve while VTEC has two settings for the intake and the exhaust valves, which makes for a more dramatic gain in peak power than VVTi can claim. Ferrari has a really neat way of doing this. The camshafts on some Ferrari engines are cut with a three-dimensional profile that varies along the length of the cam lobe. At one end of the cam lobe is the least aggressive cam profile, and at the other end is the most aggressive. The shape of the cam smoothly blends these two profiles together. A mechanism can slide the whole camshaft laterally so that the valve engages different parts of the cam. The shaft still spins just like a regular camshaft, but by gradually sliding the camshaft laterally as the engine speed and load increase, the valve timing can be optimized. Several other manufacturers, including Ford, Lamborghini and Porsche have jumped on the cam phasing bandwagon because it is a relatively cheap method of increasing horsepower, torque and efficiency. BMW has also used a cam phasing system, called VANOS (Variable Onckenwellen Steuerung) for several years. Like the other manufacturers, this system only affected the intake cams. But, as of 1999, BMW is offering its Double VANOS system on the new 3 Series. As you might have guessed, Double VANOS manipulates both the intake and exhaust camshafts to provide efficient operation at all rpm's. This helps the new 328i, equipped with a 2.8-liter inline six, develop 193 peak horsepower and 206 pound-feet of torque. More impressive than the peak numbers, however, is the broad range of useable power that goes along with this system. Several engine manufacturers are experimenting with systems that would allow infinite variability in valve timing. For example, imagine that each valve had a solenoid on it that could open and close the valve using computer control rather than relying on a camshaft. With this type of system, you would get maximum engine performance at every RPM. Something to look forward to in the future! To close these series of articles on camshafts, you can see that as the benefits of variable valve timing used on cams become more apparent to both consumers and manufacturers, you can expect to see it on just about every vehicle sold in the world. I suspect that in five years, variable valve timing will be like ABS or side-impact beams: only really cheap cars won't have it.

history of automobile

1770: Nicolas-Joseph Cugnot built a three wheeled steam powered wagon. An example is preserved at the Musee des Arts et Metiers, Paris.
1801: Richard Trevithick built a steam powered coach. (His later 1803 carriage had a road accident.)
1861, UK: Speed limits of 10mph (16km/h) in the country and 5mph (8km/h) in town were imposed on powered vehicles.
1865, UK: Speed limits were lowered to 4mph (country) and 2mph (town) and a man on foot and carrying a red flag had to precede each vehicle by 60 yards, esp. to warn those with horses. (After 1878 the man on foot no longer needed to carry a flag.)
1884: Starley and Sutton invent the Rover Safety Cycle (bicycle); the company later developed into Rover cars.
1885: Karl Benz (1844-1929) built a motorised tricycle driven by an oil-spirit internal combustion engine in 1885. This is widely held to be the first successful motor vehicle.
1885: Gottlieb Daimler (1834-1900) built a motorised bicycle in 1885 and a 4-wheel motor carriage in 1886.
1892 August 26: Rudolf Diesel filed a patent application for 'a method of apparatus for converting heat into work,' US letters patent #542,846, 16 July 1895, and, filed 15 July 1895, 'internal combustion engine' #608,845, 9 August 1898 -- the compression-ignition, "diesel" engine.
1896, UK: Speed limits on light [road-] locomotives were raised from 4mph to 14mph and they no longer needed to be preceded by a man on foot. The first London to Brighton run was held in celebration.
1898: The World Land Speed Record was set at 63.15km/h (39.24mph) by Gaston the Comte de Chasseloup-Laubat driving a Jeantaud electric car [Geo00].
1898: The Renault Voiturette type A.
1898: Latil (France) made front wheel drive units and then 4x4.
1898: Tatra started manufacturing.
1899: Camille Jenatzy and de Chasseloup-Laubat traded the Land Speed Records until Jenatzy raised it to 105.88km/h (65.75mph) driving the electric La Jamais Contente [Geo00]. The car survives at the Compiegne Musee de la Voiture (Automobile Museum).
1899: Fabbrica Italiana Automobili Torino (Fiat) was formed.
1899: August Horch began a car company carrying his own surname in 1899; it evolved into Auto-Union and eventually Audi.
1900: Ferdinand Porsche's La Toujours Contente had battery-power with four electric motors, one at each wheel. (He later patented the Mixte transmission in which a petrol engine drove a dynamo and electric motors drove the wheels. It was too expensive for the day.)
1900: Puch's first car.
1901: Volume imports of cars began into Australia starting with De Dion Boutons.
1902: Leon Serpollet raised the Land Speed Record to 120.8km/h (75.06mph) in the Easter Egg Gardner-Serpollet steam car [Geo00].
1902: Mercedes registered as a trademark. March 1, 1902, the first 40hp Mercedes Simplex ever built was supplied to Emil Jellinek in Nice. It was named after Jellinek's daughter.
1902: Charles Stewart Rolls starts up C.S. Rolls and Co., later Rolls Royce.
1902: Spyker featured a 6-cylinder engine and four wheel drive!
1902: Minerva started making cars.
1903: Ford, Model A.
1904: The Federation International de l'Automobile (FIA) was founded.
1904: Rover 8hp.
1906: Societa Italinana Automobili Darracq (SIAD) founded; it later became Alfa Romeo (about 1921).
1906: Vincenzo Lancia released his first car.
1906: Fred Marriott, driving a Stanley steam car, at Daytona, raised the World Land Speed record to 121.57mph [NT98] over 1km; his speed of 127.66mph over one mile was not recognised internationally. (Also see Aug. 2009.)
1907: Felix and Norman Caldwell of South Australia applied for a patent for four wheel drive with four wheel steering; they went on to build Caldwell Vale 4x4 trucks with Henry Vale.
1907: The Peking to Paris car race was won by an Itala [Bar72].
08
A 1908 Itala.
1908: "General Motors (GM) was formed in the USA in 1908 when William C. (Billy) Durant brought Oldsmobile and Buick together to form General Motors Company. A year later, Cadillac and Oakland (which became Pontiac in 1932) marques joined General Motors." --GM.
1908: Ford Model-T production began.
1908: Harry Dutton and Murray Aunger drove from Adelaide to Darwin in a 25hp Talbot.
1909: Bugatti built his first car.
1911: FWD sold its first 4x4.
1911: First Indianapolis 500 race.
1913: Jeffrey Quad 4x4 truck went into production.
1913: Bamford and Martin Ltd founded; later became Aston Martin.
1914: The Society Anonima Officine Alfieri Maserati, Bologna, was created by the Maserati brothers.
1915: Big Lizzie road train (.au).
1917: First Oshkosh four wheel drive truck.
1919: Bentley founded.
1921: DKW - scooters first.
1922: Citroen half-tracks crossed the Sahara, leaving from Touggourt in Algeria.
1922: Baby Austin 7.
1922: Swallow Sidecar Company founded; later became Jaguar cars in 1945.
1923, May 26-27: First 24 hour race at Le Mans, won by Andre Lagache and Rene Leonard in a Chenard & Walcker at 92.06 km/h.
1924: Ernest Eldridge (GB), driving the Fiat special Mephistopheles (below) fitted with a 21.7-litre Fiat airship engine, set a Land Speed Record of 234.98km/h (146.01mph).
M at speed, more recently
1924: The first MG car was built - on a modified Morris Oxford chassis.
1924, December 28: Citroen half-tracks left to traverse Africa.
1925: Chrysler founded.
1927: Henry Segrave driving the "1000hp" Sunbeam raised the World Land Speed Record to over 200mph --FIA.
1927: Model-T production ended; 15 million Model Ts had been built from 1908 to 1927.
1927-1928: Francis Birtles drove a Bean car from England to Melbourne taking 10 months.
1928: Malcolm Campbell, driving Bluebird with a 950hp Napier engine, raised the World Land Speed Record to 206.96mph.
1929: AEC started to build AWD trucks in conjunction with FWD (UK).
1929: Henry Segrave driving the Golden Arrow raised the World Land Speed Record to 231.36mph (327.34km/h) -- FIA.
1929: First Monaco Grand Prix was won by Williams in a Bugatti -- FIA.
1931: Bentley taken over by Rolls Royce.
1931-1932: Citroen-Haardt expedition, using Citroen half-tracks, followed part of Marco-Polo's route from Beirut to Beijing.
1932: Audi became part of Auto-Union, with DKW, Horch and Wanderer.
1932: Miller 4x4 racing cars at Indianapolis.
1934: AEC road train (one of three built) was brought to Australia. It consisted of an 8×8 prime-mover and two 8-wheel self-tracking trailers.
1934: Dodge started building 4WD trucks (-George Miles).
1934: Prototype PX-33 four wheel drive car built for the Japanese government; the car did not go into production (Mitsubishi). Thanks to Balazs Toth.
1935: Malcolm Campbell in Bluebird raised to raised the World Land Speed Record to 301.129mph (484.620km/h) -- FIA.
1936: Toyota's first production car, the AA.
1937: Svenska Aeroplan Aktiebolaget, aircraft factory founded, later became Saab.
1937: ‘Gesellschaft zur Vorbereitung des deutschen Volkswagens mbH’, Company for the Development of the German People's Car (VW), was registered [Hop71].
1938: GAZ 61 - Russian 4x4.
1940: The Jeep specifications were issued. 1940-1941: Bantam built 2700 light 4x4s, early "Jeeps".
1941-1945: Ford and Willys-Overland built 700,000 General Purpose vehicles for WWII. GP became Jeep.
1946, October 10: Unimog introduced (- H. J. Feil); also see 1951.
1948: Series-1 Land-Rover released.
1948: Porsche's first car had a 1086cc 30kW VW engine.
1948: Jaguar XK120 launched.
1948: Holden 48-215.
1948: Ford released the 1st of the F-Series vehicles.
1950: The Ford GPA, or amphibious Jeep, Half Safe was "driven" across the Atlantic ocean by Ben and Elinore Carlin. This is true!
1950: VW Transporter lays down the foundations of the hippy era.
1950: The first round of the inaugural FIA Formula One (F1) World Championship was held at Silverstone on 13 May; the seven-race season included Monaco, Switzerland, Belgium, France, Italy and the Indianapolis 500. "Nino" Farina, driving an Alfa Romeo 158, won the first race, and the championship.
1951: First Toyota Landcruiser was built under the BJ Jeep name. The LandCruiser name came in 1954.
1951: Daimler Benz ("Mercedes") took over Unimog; also see 1948.
1952: Suzuki's first motorcycle.
1952 March 12: Launch of the racing sports car version of the Mercedes Benz 300SL (of the gullwing doors).
1953: The first Redex Reliability Trial was held. Competitors had two weeks to cover 11,000km taking them around Australia. Ken Tubman and John Marshall won in a Peugeot 203.
1954-1956: The amphibious Jeep La Tortuga "drove" from Alaska to Tierra del Fuego.
1955-1956: London to Singapore Overland (except for the Channel!) in 2×Land-Rovers.
1955: Suzuki's first car.
1955: The wonderful Goggomobil.
1955 December 5: The 8 mile Preston by Pass (part of the M6) opened -- the UK's first stretch of motorway. The first stretch of the M1 opened on 2 November 1959 -- AA.
1958: First Toyota LandCruisers imported into Australia.
1959: BMC Mini went on sale.
1959: Haflinger by Steyr-Daimler-Puch.
1960: A Jeep and a Land-Rover traversed the Darien Gap.
1960: Ford Falcon XK.
1960: The first British traffic wardens took up duty in September.
1961: Jaguar E-type unveiled at the Geneva Motor Show.
1961: Stirling Moss drove a Ferguson Project 99 (P99) with the Ferguson 4WD system to victory in the Oulton Park Gold-Cup race.
1964, 17 July: Donald Campbell in Bluebird (4WD) raised the World Land Speed Record to 403mph at Lake Eyre, Australia.
1964: Porsche 911, it went on to become a classic.
1964: Mini Moke went on sale.
1965: VW bought Audi.
1965: Craig Breedlove in the jet car Spirit of America set a World Land Speed Record of 600.601mph (966.574km/h) -- FIA.
1966: The Jensen FF road car had Formula Ferguson 4WD and Dunlop Maxaret anti-lock brakes (ABS).
1967, January 4: Donald Campbell (1921-1967) was killed while attempting to raise the world water speed record to over 300mph on Coniston Water, uk.
1969: Ferrari joined the Fiat group.
1969, 20 July: The lunar module, Eagle, from Apollo 11 landed on the moon carrying Neil Armstrong and Buzz Aldrin.
1970: Range Rover released - luxury full-time 4WD.
1971: Lunar rover "car" on the moon in the Apollo 15 mission.
1971: Ford Falcon XY ute 4WD (.au).
1971-1972: British Trans-Americas Range Rover expedition. The Darien Gap was the most difficult section.
1974: Subaru Leone 4x4 car.
1978 August: The .au Gvmt introduced import parity pricing for local oil and petrol reached au$0.21/litre [the Age p.5 1/1/2009] -- $0.95 per (imperial) gallon.
petrol au$0.21/l
1979: AMC produced the Eagle 4x4 car.
1981: The specifications for the High Mobility Multipurpose Wheeled Vehicle (HMMWV) was issued; later known as the Humvee or Hummer.
1981: Audi revolutionized rallying with the Quattro 4WD rally car.
1981: Porsche showed the Porsche 911 AWD concept car at the Frankfurt Motor Show.
1983: Land-Rover 110, coil-sprung, full-time 4WD.
1983: Richard Noble, driving the jet car Thrust2, raised the World Land Speed Record to 1019.47km/h (633.468mph), Black Rock Desert, 4/10/83 [NT98].
1984: A Porsche 911 AWD won the Paris Dakar rally.
1986: Porsche 959 AWDs finished 1, 2 and 6 in the Paris Dakar rally.
1992: McLaren F1 rewrote the super-car rule book.
1993: Maserati was bought by Fiat from de Tomaso.
1994: BMW bought Rover Group from BAe.
1996: Lotus was taken over by Proton.
1996: The new Jeep Wrangler got coil springs.
1997: Thrust SSC, driven by Andy Green, broke the sound barrier and raised the World Land Speed Record to 1227.985kph (763.035mph), Mach 1.0175 under the prevailing conditions [NT98].
1998: Bentley bought by VW. Is nothing sacred? BMW pulled a swifty and bought the Rolls Royce name.
1998: Bugatti name bought by VW.
1998: Chrysler and Mercedes-Benz merged to form DaimlerChrysler (splitting up again in 2007).
1999: Volvo cars sold to Ford.
2000: Ford bought LandRover, and Phoenix took over MG - Rover from BMW.
2001: BMW put the retro. new Mini on sale in Europe (.au in 2002).
2001 July: Rolls-Royce and Bentley Motor Cars announced details of the last Rolls-Royce Silver Seraph model to commemorate 97 years of Rolls-Royce cars; production ends with 2001. VW continued to build Bentleys but future Rolls Royces were to be built at BMW's new factory.
2002: Rolls-Royce became pure BMW, and Bentley pure Volkswagen.
2008: Crude oil rose as high as us$147/barrel in July before falling to the us$30s at year's end as the global financial crisis bit.
ULP au$1.00 to $1.70/l
2008: Needing cash, Ford sold Jaguar and LandRover to Tata of India.
2009, January 29: The Skycar, a "buggy" fitted with a parafoil wing, flew the Straits of Gibraltar en route from Paris to Tombouctou (Timbuktu).
2009: General Motors (GM) and Chrysler passed into bankruptcy and were restructured, the latter forming an alliance with Fiat. VW and Porsche began a merger.
2009, August 25 & 26: The British Steam Car raised the Land Speed Record for a steam powered car to 139.843mph and 148.308mph over the measured mile and kilometer respectively. (See 1906.)
2010, August 24: The Venturi Buckeye Bullet 2.5 streamliner (Ohio State Univ., Venturi Automobile), driven by Roger Schroer, set a Land Speed Record for a battery powered electric vehicle of 495.526 km/h (307.905mph) for 1km, 495.140 km/h (307.666mph) for 1 mile -- FIA (A.8.3).

References
[Bar72] L. Barzini, Peking to Paris, Alcove Press, 1972, edited and reprinted from the 1907 original.
[Geo00] N. Georgano (ed), The Beaulieu Encyclopedia of the Automobile (2 vols.), The Stationary Office, London, 2000.
[Hop71] K. B. Hopfinger, The Volkswagen Story, G.T.Foulis & co., 1971.
[NT98] R. Noble & D. Tremayne, THRUST Through the Sound Barrier, Partridge 1998.
See motoring books.

Diesel Injection Pump

First thing's first: Pull the valve cover. I find that unscrewing the three 10 mm bolts that hold in the cruise control actuator and moving it over allows for easy replacement of the valve cover, for what it's worth. Then remove the fan blad and shroud from the bay by means of the four 10mm nuts that hold the fan in place. This will give you enough "swinging" room for turning the engine over by hand. Use a 27mm socket (a 1-1/8" works, also) on a small extension, 1/2" drive for turning the crank over by hand, and never go backwards. OK, this is all familiar from the valve adjustment routine.

To pull the pump, remove all lines attached. There is one fuel line banjo bolt on the block-side of the pump, one fuel line banjo bolt on the fender-side, and oil-feed line on the fender-side, and the fuel suply that goes to the priming pump and then from the pump to the main filter. I usually leave the two that run from the filter attached to the pump, and just removing them from the filter block. Remove the oil-feed from the pump, and this will allow easy access to the first nut you will remove. It is a 13mm, and there are three of them. The bottom is the easiest, I think. Just lay barely under the front of the car, reach your hand up there with a gear wrench, and feel for it. It's easy. To get to the top one, I use a 13mm deep-wall on a 6-inch extension on a U-joint on a 3/8" drive socket wrench. It's not to tough. And the middle one (blocked earlier by the oil-feed) can only be had by an open-ended wrench.

The final attachment is held in the back. It is a royal PITA to get to, and I have made a mock-up replacement. You will almost HAVE to use a gear wrench for it (it makes life a LOT easier). Once that is off, go under the car, and remove the support bracket that mounts to the block at the rear of the pump (held on by two 13mm bolts). Once all of this stuff is disconnected, you can remove the pump with the filter housing in place by sliding it straight back and upwards at the same time. I have heard it is sometimes necessary to remove the rack dampener pin, but I have never had to do so, and I have done this job probably around 11 or 12 times.

Once the pump is out, you will need to put your new one in. Crank the engine over many times by hand to get everything "settled". I doubt this does anything at all, but it's a mental thing for me (OK, so I'm crazy ;-). Look on the cam shaft near the front of the engine where it slides through the first bearing mount. You will see a tick mark. Turn the engine over until the stationary tick mark and the mobile tick mark are lined up. Your harmonic balancer should read at 0* TDC. Crank the engine around again, passing TDC once (that will be the exhaust stroke), and stop at 24* BEFORE TDC the second time. The tick mark on the cam should be just shy of reaching the TDC marker.

With the engine at this time setting, you will shoot the pump in. Take a 3/4" wrench for socket wrench, and as you look upon the nut on the front of the injection pump, turn it clockwise, making several resolutions. Then crank it, and again, only clockwise, until the spot with a missing tooth lines up with the dash mark that is set about 15* behind 12:00. It is easy for it to move out of time, so you must be gentle with the reinstallation.

Slide the collar that came off out of the engine with the pump over the sprocket on the pump. There is no special way to do this... just slide it on without turning anything. Piece of cake. Then, gently lower the pump into the engine, frontside going down first at an angle, and let it slide into place. Tighten it down at a random position with the nuts (NOT the rear bolt) and connect the feed lines. Pump the hand-priming pump to hell, and vent off your fuel filter so that there is NO more air in the system. Crank the engine over by hand, and see if fuel comes out of the feed lines. If it does, great. If not, reconnect your fuel injection lines, and pull the socket wrench of the engine. Then, disconnect your glow plug relay, go in your car, and hit the starter a few times to build some pressure in the lines without starting the engine. Go remove the line #1 injection line, and soak up the diesel in the port with the corner of a shop rag, being careful not to leave lint or anything behind. Then crank the engine over by hand, monitoring that first port. When you just BARELY start to see fuel well up in it, stop. Look at your degree marker. If it is at 24* BTDC, then your perfect, though I hear running at 26* can offer a little more low-end power. To advance, loosen the three nuts, and tilt the pump AWAY from the block with a cheater bar of some sort. Two people help this to be done a little more easily, as one can hold the cheater bar in place while the other tightens the pump. The lines will act as a memory-spring that can be a pain to deal with. If you want, remove all the lines (which is what I prefer).

car sound systems

Many people just spend too much and in some cases go into debt. What can make this particular situation worse is that people go into debt for a system they realize they do not even like. First, figure out how much money there is available to spend. Then decide how much of the car audio system needs to be replaced. At this point plan a budget - how much can you afford to spend? Therefore you can locate system components in your price range. Deciding what is most important in the car audio system and plan to spend more on the important items. Going over budget is the first and most common mistake car audio system buyers make.Another thing to consider is how much of the car is going to need to be modified for your potential choices. For example, some speaker installation will require many modifications to be made to the car. Modifications will need to be made by a professional and therefore you will have to budget into the total cost of the car audio system parts as well as labor. Another car audio systems mistake is that the owner of the car does not think about the future. How long are you going to keep the car for? Will you sell the car with the new audio system or will you remove it before sale? Remember audio systems never increase the value of a car enough to balancewhat was spent on the audio system in the first place. Also, if you plan on remove the system before you sell the car that could be problematic. Having a radio and an audio system are high priorities when people are searching for a new car to buy.

When and for what do you use the car for? If the car sees a lot of use as well as wear and tear, then buying higher quality components like the car speakers is a great idea. Understandably, if you are spending more time in your car then at home you want to make sure it is as comfortable and entertaining as possible. However, if the car is only used for weekly shopping, low end parts are more appropriate.Another car audio system mistake people make is choosing a system, which is not appropriate for the type of music they listen too. This is probably the most important factor, which should influence the choice of the right car audio system. If the music that you enjoy is strong, bass beats then a high-end
power amplifier is needed. In addition, subwoofers would also be a good choice. However, if your music choice is at the opposite end of the music range then you will need a different audio system setup. For example, if you listen to classical music or trendy pop music, you will need to get a car audio that has a strong speaker system that offer even play of the sound spectrum.

EFI Systems

EZ-EFI Self Tuning Electronic Fuel Injection

For years racers have known that FAST fuel injection systems are an excellent choice for their high revving, nitrous oxide, supercharger and turbocharger equipped rides. The FAST classic and XFI systems have also found their way onto many street machines. Though these systems served their users well, the Engineering team at FAST saw that many didn't have a need for the advanced functionality of the XFI systems, nor did they want to undergo a more lengthy install which may require them to replace their intake manifold and ignition systems.

Many prospective user's reasons for making the switch to EFI are the result of a desire to get the throttle response, mileage and power benefits that result from the ability to maintain the precise air to fuel ratios an electronic fuel injection system is able to deliver. In addition to delivering the aforementioned benefits, the FAST EZ-EFI systems also put an end to changing jets every time the weather and/or altitude changes.

While competing systems employ 20 year old OEM technology ECU's, awkward, costly and fragile mass air sensors, and narrow band O2 sensors (great for mileage, but not helpful for tuning for power), the FAST EZ-EFI offers dyno proven performance that may only be obtained from a wideband O2 equipped, speed density EFI system. Only the EZ-EFI system is worthy to wear the FAST brand name. In addition to its technical advantages, all FAST efi products are backed by the resources of the COMP performance group. If you were ever to have a question about, or problem with an EZ EFI product you can be assured that you will receive the service and support you need.

The EZ-EFI features an all new, patent-pending, self tuning control strategy. Simply hook it up, answer the basic setup Wizard questions on the included hand-held display and watch the system tune itself as you drive. Countless research and development hours were spent on a number of prototype test vehicles to develop a high-quality system truly worthy of the FAST brand.

Capable of supporting engines making up to 550 horsepower, the FAST EZ-EFI Self Tuning Fuel Injection System is a complete system which includes an ECU, wide-band oxygen sensor, wiring harness, fuel injectors, optional fuel pump kit and other assorted components, including an innovative 4150 flange Throttle Body. This Throttle Body delivers a total package approach for any 4150 (Holley square bore) type intake manifold. All necessary components are provided with the EZ-EFI kit, including appropriate fuel injectors and fuel rails. In addition, the EZ-EFI system works with original carb-style throttle linkage and is ready to accept all OEM sensors.

Installation of an EZ-EFI system can be completed easily in an afternoon and doesn’t require any EFI experience or expertise.

automotive electrical

Automotive electrical component's technology has shown tremendous improvement is the recent past. In every vehicle hundreds of pieces of components are attached for its proper functioning including electrical components. These electrical systems are the most important component of your car which makes it run. The resource to charge these auto electrical components is the battery. If your vehicle is not powered by a good quality battery it will not function properly.


In an electrical power system there is a web of wires and fuses which have the main function of delivering the current and the power to various electrical components. The quality of these electrical components decides for your safety. So, be very careful while choosing your auto component manufacturers. However, there are many auto component companies which provide quality electrical component but the one who ensures quality and durability is the right one.


Pricol is an auto parts supplier based in India who strive for excellence in all their services through socially and environmentally acceptable means. We market our products in the most responsible manner and try to make our customers, suppliers, employees and shareholders feel proud of this association. We make best utilization of all our resources to maximize our quality standards and face the market competition with full grace and dignity.


Are you looking for automotive electrical components? Need reliable assistance then Pricol is your destination. But before that, get familiar with the various electrical components available in the market. Some of the major electrical components which are designed by top-notch manufacturers including us are:

* Battery: Every car's electrical system is totally dependent on the battery. This is considered as the primary source of electrical energy when you start or turn off your vehicle's engine. With this battery all the components get the supply of electrical power including the ignition system and the starter.
* Alternator: This auto electrical component is used to provide power to the vehicle's accessories, such as the vehicle lights, radio system. This device converts the gasoline engine power to the electrical energy which is then utilized for running the electrical components in the vehicle. In addition to this, alternator recharges the battery in case of emergency when the battery loses some of its strength needed for powering the car.
* Starter: This automotive electrical component starts the engine once you turn on the ignition switch. It is placed at the back of the engine or sometimes at the front of the transmission system. One of the major components in the starter is the starter switch which controls the flow of electricity from the battery to the starter.
* Lights: For the safety of the driver, lights are the major components. If you don't have a proper lighting system in your vehicle you life is always at risk especially in the foggy nights. Lights are available in variety of types including taillights, headlights, fog lights and various other exterior lights situated at different places like at the front, sides and rear of the vehicle. The moment the driver activates a light's switch, an electrical signal starts travelling from the car's battery to its lights. This way the lights starts turning on and off.

For any further information on this auto electrical components contact Pricol.com. We are a trusted name in the industry, you can rely on us!

Automatic transmission models

Some of the best known automatic transmission families include:

* General Motors — Powerglide, "Turbo-Hydramatic" TH350, TH400 and 700R4, 4L60-E, 4L80-E, Holden Trimatic
* Ford: Cruise-O-Matic, C4, C6, AOD/AODE, E4OD, ATX, AXOD/AX4S/AX4N
* Chrysler: TorqueFlite 727 and 904, A500, A518, 45RFE, 545RFE
* BorgWarner (later Aisin AW)
* ZF Friedrichshafen automatic transmissions
* Allison Transmission
* Voith Turbo
* Aisin AW; Aisin AW is a Japanese automotive parts supplier, known for its automatic transmissions and navigation systems
* Honda
* Nissan/Jatco
* Volkswagen Group - 01M
* Drivetrain Systems International (DSI) - M93, M97 and M74 4-speeds, M78 and M79 6-speeds

Automatic transmission families are usually based on Ravigneaux, Lepelletier [disambiguation needed], or Simpson planetary gearsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission (AMT).

Many of the above AMTs exist in modified states, which were created by racing enthusiasts and their mechanics by systematically re-engineering the transmission to achieve higher levels of performance. These are known as "performance transmissions". An example of a manufacturer of high performance transmissions of General Motors and Ford transmissions is PerformaBuilt.
Continuously variable transmissions
Main article: Continuously variable transmission

A fundamentally different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly and steplessly alter its gear ratio by varying the diameter of a pair of belt or chain-linked pulleys, wheels or cones. Some continuously variable transmissions use a hydrostatic drive — consisting of a variable displacement pump and a hydraulic motor — to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.

A slightly different approach to CVT is the concept of toroidal CVT or infinitely variable transmission (IVT). These concepts provide zero and reverse gear ratios.

Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an electronically-controlled CVT (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a differential using an electric motor-generator.
Manually controlled automatic transmissions

Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:

Throttle kickdown
Most automatic transmissions include some means of forcing a downshift into the lowest possible gear ratio if the throttle pedal is fully depressed. In many older designs, kickdown is accomplished by mechanically actuating a valve inside the transmission. Most modern designs use a solenoid-operated valve that is triggered by a switch on the throttle linkage or by the engine control unit (ECM) in response to an abrupt increase in engine power.
Mode selection
Allows the driver to choose between preset shifting programs. For example, Economy mode saves fuel by upshifting at lower engine speeds, while Sport mode (aka "Power" or "Performance") delays shifting for maximum acceleration. The modes also change how the computer responds to throttle input.
Low gear ranges
Conventionally, automatic transmissions have selector positions that allow the driver to limit the maximum ratio that the transmission may engage. On older transmissions, this was accomplished by a mechanical lockout in the transmission valve body preventing an upshift until the lockout was disengaged; on computer-controlled transmissions, the same effect is accomplished by firmware. The transmission can still upshift and downshift automatically between the remaining ratios: for example, in the 3 range, a transmission could shift from first to second to third, but not into fourth or higher ratios. Some transmissions will still upshift automatically into the higher ratio if the engine reaches its maximum permissible speed in the selected range[citation needed].
Manual controls
Some transmissions have a mode in which the driver has full control of ratio changes (either by moving the selector, or through the use of buttons or paddles), completely overriding the automated function of the hydraulic controller. Such control is particularly useful in cornering, to avoid unwanted upshifts or downshifts that could compromise the vehicle's balance or traction. "Manumatic" shifters, first popularized by Porsche in the 1990s under the trade name Tiptronic, have become a popular option on sports cars and other performance vehicles. With the near-universal prevalence of electronically controlled transmissions, they are comparatively simple and inexpensive, requiring only software changes, and the provision of the actual manual controls for the driver. The amount of true manual control provided is highly variable: some systems will override the driver's selections under certain conditions, generally in the interest of preventing engine damage. Since these gearboxes also have a throttle kickdown switch, it is impossible to fully exploit the engine power at low to medium engine speeds[dubious – discuss][citation needed].
Second gear takeoff
Some automatics, particularly those fitted to larger capacity or high torque engines, either when "2" is manually selected, or by engaging a winter mode, will start off in second gear instead of first, and then not shift into a higher gear until returned to "D." Also note that as with most American automatic transmissions, selecting "2" using the selection lever will not tell the transmission to be in only 2nd gear; rather, it will simply limit the transmission to 2nd gear after prolonging the duration of 1st gear through higher speeds than normal operation. The 2000-2002 Lincoln LS V8 (the five-speed automatic without manumatic capabilities, as opposed to the optional sport package w/ manu-matic 5-speed) started in 2nd gear during most starts both in winter and other seasons by selecting the "D5" transmission selection notch in the shiftgate (for fuel savings), whereas "D4" would always start in 1st gear. This is done to reduce torque multiplication when proceeding forward from a standstill in conditions where traction was limited--on snow- or ice-covered roads, for example.

Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine RPM against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.
See also

* Semi-automatic transmission
* AMC and Jeep transmissions
* Hydraulics
* Dual clutch transmission
* Multimode manual transmission

Hydraulic automatic transmissions

The predominant form of automatic transmission is hydraulically operated; using a fluid coupling or torque converter, and a set of planetary gearsets to provide a range of gear ratios.
Parts and operation

A hydraulic automatic transmission consists of the following parts:

* Torque converter: A type of fluid coupling, hydraulically connecting the engine to the transmission. It takes the place of a mechanical clutch, allowing the transmission to stay in gear and the engine to remain running while the vehicle is stationary, without stalling. A torque converter differs from a fluid coupling, in that it provides a variable amount of torque multiplication at low engine speeds, increasing breakaway acceleration. This is accomplished with a third member in the coupling assembly known as the stator, and by altering the shapes of the vanes inside the coupling in such a way as to curve the fluid's path into the stator. The stator captures the kinetic energy of the transmission fluid, in effect using the leftover force of it to enhance torque multiplication.
* Pump, not to be confused with the impeller inside the torque converter, is typically a gear pump mounted between the torque converter and the planetary gearset. It draws transmission fluid from a sump and pressurizes it, which is needed for transmission components to operate. The input for the pump is connected to the torque converter housing, which in turn is bolted to the engine's flywheel, so the pump provides pressure whenever the engine is running and there is enough transmission fluid.[2]
* Planetary gearset: A compound epicyclic planetary gearset, whose bands and clutches are actuated by hydraulic servos controlled by the valve body, providing two or more gear ratios.
* Clutches and bands: to effect gear changes, one of two types of clutches or bands are used to hold a particular member of the planetary gearset motionless, while allowing another member to rotate, thereby transmitting torque and producing gear reductions or overdrive ratios. These clutches are actuated by the valve body (see below), their sequence controlled by the transmission's internal programming. Principally, a type of device known as a sprag or roller clutch is used for routine upshifts/downshifts. Operating much as a ratchet, it transmits torque only in one direction, free-wheeling or "overrunning" in the other. The advantage of this type of clutch is that it eliminates the sensitivity of timing a simultaneous clutch release/apply on two planetaries, simply "taking up" the drivetrain load when actuated, and releasing automatically when the next gear's sprag clutch assumes the torque transfer. The bands come into play for manually selected gears, such as low range or reverse, and operate on the planetary drum's circumference. Bands are not applied when drive/overdrive range is selected, the torque being transmitted by the sprag clutches instead. Bands are used for braking; the GM Turbo-Hydramatics incorporated this.[citation needed].
* Valve body: hydraulic control center that receives pressurized fluid from the main pump operated by the fluid coupling/torque converter. The pressure coming from this pump is regulated and used to run a network of spring-loaded valves, check balls and servo pistons. The valves use the pump pressure and the pressure from a centrifugal governor on the output side (as well as hydraulic signals from the range selector valves and the throttle valve or modulator) to control which ratio is selected on the gearset; as the vehicle and engine change speed, the difference between the pressures changes, causing different sets of valves to open and close. The hydraulic pressure controlled by these valves drives the various clutch and brake band actuators, thereby controlling the operation of the planetary gearset to select the optimum gear ratio for the current operating conditions. However, in many modern automatic transmissions, the valves are controlled by electro-mechanical servos which are controlled by the electronic engine control unit (ECU) or a separate transmission control unit (TCU). (See History and improvements below.)
* Hydraulic & lubricating oil: called automatic transmission fluid (ATF), this component of the transmission provides lubrication, corrosion prevention, and a hydraulic medium to convey mechanical power (for the operation of the transmission). Primarily made from refined petroleum, and processed to provide properties that promote smooth power transmission and increase service life, the ATF is one of the few parts of the automatic transmission that needs routine service as the vehicle ages.

The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissions much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.
[edit] Energy efficiency

Hydraulic automatic transmissions are almost always less energy efficient than manual transmissions due mainly to viscous and pumping losses; both in the torque converter and the hydraulic actuators. A relatively small amount of energy is required to pressurize the hydraulic control system, which uses fluid pressure to determine the correct shifting patterns and operate the various automatic clutch mechanisms.

Manual transmissions use a mechanical clutch to transmit torque, rather than a torque converter, thus avoiding the primary source of loss in an automatic transmission. Manual transmissions also avoid the power requirement of the hydraulic control system, by relying on the human muscle power of the vehicle operator to disengage the clutch and actuate the gear levers, and the mental power of the operator to make appropriate gear ratio selections. Thus the manual transmission requires very little engine power to function, with the main power consumption due to drag from the gear train being immersed in the lubricating oil of the gearbox.

The energy efficiency of automatic transmission has increased with the introduction of the torque converter lock-up clutch, which practically eliminates fluid losses when engaged. Modern automatic transmission also minimize energy usage and complexity, by minimizing the amount of shifting logic that is done hydraulically. Typically, control of the transmission has been transferred to computerized control systems which do not use fluid pressure for shift logic or actuation of clutching mechanisms.

The on road acceleration of an automatic transmission can occasionally exceed that of an otherwise identical vehicle equipped with a manual transmission in turbocharged diesel applications. Turbo-boost is normally lost between gear changes in a manual whereas in an automatic the accelerator pedal can remain fully depressed. This however is still largely dependent upon the number and optimal spacing of gear ratios for each unit, and whether or not the elimination of spooldown/accelerator lift off represent a significant enough gain to counter the slightly higher power consumption of the automatic transmission itself.
[edit] History and improvements

Modern automatic transmissions can trace their origins to an early "horseless carriage" gearbox that was developed in 1904 by the Sturtevant brothers of Boston, Massachusetts. This unit had two forward speeds, the ratio change being brought about by flyweights that were driven by the engine. At higher engine speeds, high gear was engaged. As the vehicle slowed down and engine RPM decreased, the gearbox would shift back to low. Unfortunately, the metallurgy of the time wasn't up to the task, and owing to the abruptness of the gear change, the transmission would often fail without warning.

The next significant phase in the automatic transmission's development occurred in 1908 with the introduction of Henry Ford's remarkable Model T. The Model T, in addition to being cheap and reliable by the standards of the day, featured a simple, two speed plus reverse planetary transmission whose operation was manually controlled by the driver using pedals. The pedals actuated the transmission's friction elements (bands and clutches) to select the desired gear. In some respects, this type of transmission was less demanding of the driver's skills than the contemporary, unsynchronized manual transmission, but still required that the driver know when to make a shift, as well as how to get the car off to a smooth start.

In 1934, both REO and General Motors developed semi-automatic transmissions that were less difficult to operate than a fully manual unit. These designs, however, continued to use a clutch to engage the engine with the transmission. The General Motors unit, dubbed the "Automatic Safety Transmission," was notable in that it employed a power-shifting planetary gearbox that was hydraulically controlled and was sensitive to road speed, anticipating future development.

Parallel to the development in the 1930s of an automatically-shifting gearbox was Chrysler's work on adapting the fluid coupling to automotive use. Invented early in the 20th century, the fluid coupling was the answer to the question of how to avoid stalling the engine when the vehicle was stopped with the transmission in gear. Chrysler itself never used the fluid coupling with any of its automatic transmissions, but did use it in conjunction with a hybrid manual transmission called "Fluid Drive" (the similar Hy-Drive used a torque converter). These developments in automatic gearbox and fluid coupling technology eventually culminated in the introduction in 1939 of the General Motors Hydra-Matic, the world's first mass-produced automatic transmission.

Available as an option on 1940 Oldsmobiles and later Cadillacs, the Hydra-Matic combined a fluid coupling with three hydraulically-controlled planetary gearsets to produce four forward speeds plus reverse. The transmission was sensitive to engine throttle position and road speed, producing fully automatic up- and down-shifting that varied according to operating conditions.

The Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley, Hudson, Kaiser, Nash, and Rolls-Royce. It also found use during World War II in some military vehicles. From 1950-1954, Lincoln cars were also available with the Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to the Hydra-Matic, but of a different design.

Interestingly, the original Hydra-Matic incorporated two features which are widely emulated in today's transmissions. The Hydra-Matic's ratio spread through the four gears produced excellent "step-off" and acceleration in first, good spacing of intermediate gears, and the effect of an overdrive in fourth, by virtue of the low numerical rear axle ratio used in the vehicles of the time. In addition, in third and fourth gear, the fluid coupling only handled a portion of the engine's torque, resulting in a high degree of efficiency. In this respect, the transmission's behavior was similar to modern units incorporating a lock-up torque converter.

In 1956, GM introduced the "Jetaway" Hydra-Matic, which was different in design than the older model. Addressing the issue of shift quality, which was an ongoing problem with the original Hydra-Matic, the new transmission utilized two fluid couplings, the primary one that linked the transmission to the engine, and a secondary one that replaced the clutch assembly that controlled the forward gearset in the original. The result was much smoother shifting, especially from first to second gear, but with a loss in efficiency and an increase in complexity. Another innovation for this new style Hydra-Matic was the appearance of a Park position on the selector. The original Hydra-Matic, which continued in production until the mid-1960s, still used the Reverse position for parking pawl engagement.

The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Packard's Ultramatic in mid-1949 and Chevrolet's Powerglide for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the converter for additional torque multiplication. In the early 1950s, BorgWarner developed a series of three-speed torque converter automatics for American Motors, Ford Motor Company, Studebaker, and several other manufacturers in the US and other countries. Chrysler was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953, and the three-speed TorqueFlite in 1956. The latter was the first to utilize the Simpson compound planetary gearset.

General Motors produced multiple-turbine torque converters from 1954 to 1961. These included the Twin-Turbine Dynaflow and the triple-turbine Turboglide transmissions. The shifting took place in the torque converter, rather than through pressure valves and changes in planetary gear connections. Each turbine was connected to the drive shaft through a different gear train. These phased from one ratio to another according to demand, rather than shifting. The Turboglide actually had two speed ratios in reverse, with one of the turbines rotating backwards.

By the late 1960s, most of the fluid-coupling four-speed and two-speed transmissions had disappeared in favor of three-speed units with torque converters. Also around this time, whale oil was removed from automatic transmission fluid[3]. By the early 1980s, these were being supplemented and eventually replaced by overdrive-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter pump and turbine together to eliminate slip at cruising speed) to improve fuel economy.

As computerised engine control units (ECUs) became more capable, much of the logic built into the transmission's valve body was offloaded to the ECU. (Some manufacturers use a separate computer dedicated to the transmission, but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.

ZF Friedrichshafen and BMW were responsible for introducing the first six-speed (the ZF 6HP26 in the 2002 BMW E65 7-Series). Mercedes-Benz's 7G-Tronic was the first seven-speed in 2003, with Toyota introducing an eight-speed in 2007 on the Lexus LS 460. Derived from the 7G-Tronic, Mercedes-Benz unveiled a semi-automatic transmission with the torque converter replaced with a wet multi clutch called the AMG SPEEDSHIFT MCT[4].

automatic gearbox

An automatic gearbox is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually. Most automatic transmissions have a defined set of gear ranges, often with a parking pawl feature that locks the output shaft of the transmission.

Similar but larger devices are also used for heavy-duty commercial and industrial vehicles and equipment. Some machines with limited speed ranges or fixed engine speeds, such as some forklifts and lawn mowers, only use a torque converter to provide a variable gearing of the engine to the wheels.

Besides automatics, there are also other types of automated transmissions such as continuous variable transmissions (CVTs) and semi-automatic transmissions, that free the driver from having to shift gears manually, by using the transmission's computer to change gear, if for example the driver were redlining the engine. Despite superficial similarity to other automated transmissions, automatic transmissions differ significantly in internal operation and driver's feel from semi-automatics and CVTs. An automatic uses a torque converter instead of clutch to manage the connection between the transmission gearing and the engine. In contrast, a CVT uses a belt or other torque transmission schema to allow an "infinite" number of gear ratios instead of a fixed number of gear ratios. A semi-automatic retains a clutch like a manual transmission, but controls the clutch through electrohydraulic means.

A conventional manual transmission is frequently the base equipment in a car, with the option being an automated transmission such as a conventional automatic, semi-automatic, or CVT. The ability to shift gears manually, often via paddle shifters, can also be found on certain automated transmissions (manumatics such as Tiptronic), semi-automatics (BMW SMG), and continuous variable transmissions (CVTs) (such as Lineartronic).



Automatic transmission modes

Conventionally, in order to select the transmission operating mode, the driver moves a selection lever located either on the steering column or on the floor (as with a manual on the floor, except that most automatic selectors on the floor don't move in the same type of pattern as a manual lever; most automatic levers only move vertically). In order to select modes, or to manually select specific gear ratios, the driver must push a button in (called the shift lock button) or pull the handle (only on column mounted shifters) out. Some vehicles position selector buttons for each mode on the cockpit instead, freeing up space on the central console. Vehicles conforming to US Government standards must have the modes ordered P-R-N-D-L (left to right, top to bottom, or clockwise). Prior to this, quadrant-selected automatic transmissions often used a P-N-D-L-R layout, or similar. Such a pattern led to a number of deaths and injuries owing to unintentional gear selection, as well as the danger of having a selector (when worn) jump into Reverse from Low gear during engine braking maneuvers.

Automatic transmissions have various modes depending on the model and make of the transmission. Some of the common modes include

Park (P)
This selection mechanically locks the output shaft of transmission, restricting the vehicle from moving in any direction. A parking pawl prevents the transmission from rotating, and therefore the vehicle from moving, although the vehicle's non-driven roadwheels may still rotate freely. For this reason, it is recommended to use the hand brake (or parking brake) because this actually locks (in most cases) the rear wheels and prevents them from moving. This also increases the life of the transmission and the park pin mechanism, because parking on an incline with the transmission in park without the parking brake engaged will cause undue stress on the parking pin. An efficiently-adjusted hand brake should also prevent the car from moving if a worn selector accidentally drops into reverse gear during early morning fast-idle engine warm-ups[citation needed]. It should be noted that locking the transmission output shaft does not positively lock the driving wheels. If one driving wheel slips while the transmission is in park, the other will roll freely as the slipping wheel rotates in the opposite direction. Only a (properly adjusted) parking brake can be relied upon to positively lock both of the parking-braked wheels. (This is not the case with certain 1950's Chrysler products that carried their parking brake on the transmission tailshaft, a defect compounded by the provision of a bumper jack). It is typical of front-wheel-drive vehicles for the parking brake to be on the rear (non-driving) wheels, so use of both the parking brake and the transmission park lock provides the greatest security against unintended movement on slopes. Unfortunately, the rear of most front-wheel-drive vehicles has only about half the weight on the rear wheel as is on the front wheels, greatly reducing the security provided by the parking brake as compared to either rear-wheel-drive vehicles with parking brake on the rear wheels (which generally have near half of the total vehicle weight on the rear wheels, except for empty pickup and open-bed trucks) or to front-wheel-drive vehicles with the parking brake on the front wheels, which generally have about two-thirds of the vehicle's weight (unloaded) on the front wheels.

A car should be allowed to come to a complete stop before setting the transmission into park to prevent damage. Usually, Park (P) is one of only two selections in which the car's engine can be started, the other being Neutral (N). In many modern cars and trucks, the driver must have the foot brake applied before the transmission can be taken out of park. The Park position is omitted on buses/coaches with automatic transmission (on which a parking pawl is not practical), which must be placed in neutral with the parking brakes set. Advice is given in some owner's manuals [example: 1997 Oldsmobile Cutlass Supreme owner's manual] that if the vehicle is parked on a steep slope using the park lock only, it may not be possible to release the park lock (move the selector lever out of "P"). Another vehicle may be required to push the stuck vehicle uphill slightly to remove the loading on the park lock pawl.

Most automobiles require P or N to be set on the selector lever before the internal combustion engine can be started. This is typically achieved via a normally open inhibitor switch, which is wired in series with the starter motor engagement circuit, and is only closed when P or N is selected, thus completing the circuit (when the key is turned to the start position)

Reverse (R)
This engages reverse gear within the transmission, giving the ability for the vehicle to drive backwards. In order for the driver to select reverse in modern transmissions, they must come to a complete stop, push the shift lock button in (or pull the shift lever forward in the case of a column shifter) and select reverse. Not coming to a complete stop can cause severe damage to the transmission[citation needed]. Many modern automatic transmissions have a safety mechanism in place, which does to some extent prevent (but does not completely avoid) inadvertently putting the car in reverse when the vehicle is moving forwards. This mechanism usually consists of a solenoid-controlled physical barrier on either side of the Reverse position, which is electronically engaged by a switch on the brake pedal. Therefore, the brake pedal needs to be depressed in order to allow the selection of reverse. Some electronic transmissions prevent or delay engagement of reverse gear altogether while the car is moving.

Some shifters with a shift button allow the driver to freely move the shifter from R to N or D, or simply moving the shifter to N or D without actually depressing the button. However, the driver cannot put back the shifter to R without depressing the shift button to prevent accidental shifting, especially at high speeds, which could damage the transmission.

Neutral/No gear (N)
This disengages all gear trains within the transmission, effectively disconnecting the transmission from the driven roadwheels, so the vehicle is able to move freely under its own weight and gain momentum without the motive force from the engine (engine braking). This is the only other selection in which the vehicle's engine can be started.

Drive (D)
This position allows the transmission to engage the full range of available forward gear trains, and therefore allows the vehicle to move forward and accelerate through its range of gears. The number of gear ratios a transmission has depends on the model, but they initially ranged from three (predominant before the 1990s), to four and five speeds (losing popularity to six-speed autos, though still favored by Chrysler and Honda/Acura)[citation needed]. Six-speed automatic transmissions are now probably the most common offering Toyota Camry V6 models, the Chevrolet Malibu LTZ, Corvette, GM trucks, Pontiac G8, Ford Falcon BF 2005-2007 and Falcon FG 2008 - current in Australia with 6 speed ZF, and most newer model Ford/Lincoln/Mercury vehicles). However, seven-speed autos are becoming available (found in Mercedes 7G gearbox), as are eight-speed autos in the newer models of Lexus and BMW cars.

Overdrive (D, OD, or a boxed [D])
This mode is used in some transmissions to allow early computer-controlled transmissions to engage the Automatic Overdrive. In these transmissions, Drive (D) locks the Automatic Overdrive off, but is identical otherwise. OD (Overdrive) in these cars is engaged under steady speeds or low acceleration at approximately 35–45 mph (56–72 km/h). Under hard acceleration or below 35–45 mph (56–72 km/h), the transmission will automatically downshift. Vehicles with this option should be driven in this mode unless circumstances require a lower gear.

Third (3)
This mode limits the transmission to the first three gear ratios, or sometimes locks the transmission in third gear. This can be used to climb or going down hill. Some vehicles will automatically shift up out of third gear in this mode if a certain RPM range is reached in order to prevent engine damage. This gear is also recommended while towing a caravan.

Second (2 or S)
This mode limits the transmission to the first two gear ratios, or locks the transmission in second gear on Ford, Kia, and Honda models. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time. Some vehicles will automatically shift up out of second gear in this mode if a certain RPM range is reached in order to prevent engine damage.

Although traditionally considered second gear, there are other names used. Chrysler models with a three-speed automatic since the late 1980s have called this gear 3 while using the traditional names for Drive and Low.

First (1 or L [Low])
This mode locks the transmission in first gear only. In older vehicles, it will not change to any other gear range. Some vehicles will automatically shift up out of first gear in this mode if a certain RPM range is reached in order to prevent engine damage. This, like second, can be used during the winter season, or for towing.

As well as the above modes there are also other modes, dependent on the manufacturer and model. Some examples include:

D5
In Hondas and Acuras equipped with five-speed automatic transmissions, this mode is used commonly for highway use (as stated in the manual), and uses all five forward gears.
D4
This mode is also found in Honda and Acura four- or five-speed automatics, and only uses the first four gear ratios. According to the manual, it is used for stop-and-go traffic, such as city driving.
D3 or 3
This mode is found in Honda, Acura, Volkswagen and Pontiac four-speed automatics and only uses the first three gear ratios. According to the manual, it is used for stop-and-go traffic, such as city driving.
S or Sport
This is commonly described as Sport mode. It operates in an identical manner as "D" mode, except that the upshifts change much higher up the engine's rev range. This has the effect on maximising all the available engine output, and therefore enhances the performance of the vehicle, particularly during acceleration. This mode will also downchange much higher up the rev range compared to "D" mode, maximising the effects of engine braking. This mode will have a detrimental effect on fuel economy. Hyundai has a Norm/Power switch next to the gearshift for this purpose on the Tiburon.

Some early GMs equipped with Tourqueflite transmsissons used (S) to indicate Second gear, being the same as the 2 position on a Chrysler, shifting between only first and second gears. This would have been recommended for use on steep grades, or slippery roads like dirt, or ice, and limited to speeds under 40 mph. (L) was used in some early GMs to indicate (L)ow gear, being the same as the 2 position on a Chrysler, locking the transmission into first gear. This would have been recommended for use on steep grades, or slippery roads like dirt, or ice, and limited to speeds under 15 mph.

+ −, and M
This is for the Manual mode selection of gears in certain automatics, such as Porsche's Tiptronic. The M feature can also be found in Chrysler and General Motors products such as the Dodge Magnum and Pontiac G6, as well as Toyota's Camry, Corolla, Fortuner, Previa and Innova. Mitsubishi and some Audi models (TT), meanwhile do not have the M, and instead have the + and -, which is separated from the rest of the shift modes; the same is true for some Peugeot products like Peugeot 206. Meanwhile, the driver can shift up and down at will by toggling the (console mounted) shift lever like a semi-automatic transmission. This mode may be engaged either through a selector/position or by actually changing the gears (e.g., tipping the gear-down paddles mounted near the driver's fingers on the steering wheel).
Winter (W)
In some Mercedes-Benz, BMW and General Motors Europe models, a winter mode can be engaged so that second gear is selected instead of first when pulling away from stationary, to reduce the likelihood of loss of traction due to wheelspin on snow or ice. On GM cars, this was D2 in the 1950s, and is Second Gear Start after 1990. On Ford, Kia, and Honda automatics, this feature can be accessed by moving the gear selector to 2 to start, then taking your foot off the accelerator while selecting D once the car is moving.
Brake (B)
A mode selectable on some Toyota models. In non-hybrid cars, this mode lets the engine do compression braking, also known as engine braking, typically when encountering a steep downhill. Instead of engaging the brakes, the engine in a non-hybrid car switches to a lower gear and slows down the spinning tires. The engine holds the car back, instead of the brakes slowing it down. GM called this "HR" ("hill retarder") and "GR" ("grade retarder") in the 1950s. For hybrid cars, this mode converts the electric motor into a generator for the battery. It is not the same as downshifting in a non-hybrid car, but it has the same effect in slowing the car without using the brakes.

Hybrid Synergy Drive system

Toyota uses its sophisticated Hybrid Synergy Drive system to power today’s Prius, a follow-on to the first-generation Toyota Hybrid System. Both automakers are now offering their second generation hybrid vehicles. In 2003, Honda introduced the five-passenger Honda Civic Hybrid, which offers a more powerful adaptation of the IMA system. A completely redesigned and more powerful Prius appeared as a 2004 model.

Both the Toyota and Honda hybrids are parallel configurations, with wheels driven by both their internal combustion engine and electric motor. In detail, however, they work quite differently.
Enginecrosssefront
The Honda IMA system’s electric motor/generator supplies additional power to the gasoline engine when needed for acceleration or when driving demands are greater, such as when climbing grades, thus the designation “motor assist.” The Honda gasoline engine always provides propulsion.



Things are reversed with Toyota’s Hybrid Synergy Drive, which finds the Prius starting out on battery electric power. The gasoline engine seamlessly starts up to provide additional power during acceleration, at higher speeds, or when driving up grades. This ability to run at times on battery power alone is an important distinction to some folks, since this means Toyota’s hybrids are actually zero emission vehicles during the time they’re electrically driven. Honda’s hybrids cannot do this.

The Prius uses a four-cylinder, 1.5-liter Atkinson cycle engine. The four-stroke Atkinson cycle, invented by James Atkinson in 1882, is different than the Otto cycle engine we’re used to driving in very distinct ways. Compared to the Otto cycle, where the intake valve is closed near bottom-dead-center, the Atkinson cycle does not close the intake valve at BDC, but leaves it open as the piston rises on the compression stroke. What this means is that some of the air/fuel charge is pushed back out and into the intake manifold and is used in other cylinders. This reduces the volume of the air/fuel mixture that’s compressed and combusted without severely restricting the throttle opening. Restricting throttle opening results in large pumping losses and greatly reduced efficiency. This method of reducing power output without incurring large pumping losses makes the Prius engine much more efficient than a conventional Otto cycle engine under most operating conditions. Effectively, the use of the Atkinson cycle allows the Prius engine to operate quite efficiently at relatively low power levels while still having sufficient power for climbing hills at freeway speeds.

The Prius uses the same basic 1.5 liter engine as the Toyota Echo, where the engine is rated at 108 horsepower at 6000 rpm. The Atkinson cycle allows the engine to be downsized to 76 horsepower at 4600 rpm while still being as efficient, or perhaps more so, than the Echo variant. Also, adding a supercharger to the Atkinson cycle results in the Miller cycle like that used in the Mazda Millenia.

Variable intake valve timing (VVT-I) reduces cylinder pressure to eliminate knocking, important because the engine has a 13:1 compression ratio. A high compression ratio, while good for performance and efficiency, can lead to pre-ignition (knocking), which can damage an engine if unchecked. The aluminum, dual overhead camshaft (DOHC) 16-valve engine produces 76 horsepower at 5000 rpm and 82 lbs-ft of torque at 4200 rpm. Because the engine speed is limited, it can use smaller and lighter components for improved fuel economy. The engine earns an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) rating, is a Super Ultra Low Emission Vehicle (SULEV), and has an EPA rating of 60 mpg city/51 mpg highway, for a combined estimated 55 mpg fuel economy rating.

Toyota’s HSD also takes special measures to address cold start emissions. Since combustion is not as efficient when an engine is cold and a catalytic converter must reach operating temperature before it can treat exhaust gases, cold starts result in greater emissions levels. The HSD system stores hot coolant in a three-liter vacuum bottle and dumps this into the engine during a cold start to help remedy this.