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98-659: Two-stroke engines often have a higher power-to-weight ratio than a four-stroke engine, since their power stroke occurs twice as often. Two-stroke engines can also have fewer moving parts , and thus be cheaper to manufacture and weigh less. In countries and regions with stringent emissions regulation, two-stroke engines have been phased out in automotive and motorcycle uses. In regions where regulations are less stringent, small displacement two-stroke engines remain popular in mopeds and motorcycles. They are also used in power tools such as chainsaws and leaf blowers . The first commercial two-stroke engine involving cylinder compression

196-568: A Bavarian miniature-vehicle manufacturer, bought the rights to the Trabant name and showed a scale model of a "newTrabi" at the 2007 Frankfurt Motor Show . Plans for production included a limited run, possibly with a BMW engine. A Trabant nT model was unveiled two years later in Frankfurt. The Trabant nT consortium includes Herpa, the German specialized-auto-parts manufacturer IndiKar and

294-415: A power-valve system . The valves are normally in or around the exhaust ports. They work in one of two ways; either they alter the exhaust port by closing off the top part of the port, which alters port timing, such as Rotax R.A.V.E, Yamaha YPVS, Honda RC-Valve, Kawasaki K.I.P.S., Cagiva C.T.S., or Suzuki AETC systems, or by altering the volume of the exhaust, which changes the resonant frequency of

392-421: A rotary valve is that it enables the two-stroke engine's intake timing to be asymmetrical, which is not possible with piston-port type engines. The piston-port type engine's intake timing opens and closes before and after top dead center at the same crank angle, making it symmetrical, whereas the rotary valve allows the opening to begin and close earlier. Rotary valve engines can be tailored to deliver power over

490-402: A state monopoly , a Trabant took about ten years to acquire. East German buyers were placed on a waiting-list of up to thirteen years. The waiting time depended on their proximity to Berlin , the capital. Official state price was 7,450 GDR marks and the demand to production ratio was forty three to one (1989). The free market price for a second-hand one was more than twice the price of

588-613: A 1987 Trabant into a 1973 Chevrolet El Camino . The Trabant was planned to return to production in Uzbekistan as the Olimp during the late 1990s, but only one model was produced. Former Bulgarian Foreign Minister and Atlantic Club of Bulgaria founding president Solomon Passy owned a Trabant which was blessed by Pope John Paul II in 2002 and in which he took NATO Secretaries General Manfred Wörner , George Robertson , and Jaap de Hoop Scheffer for rides. In 2005, Passy donated

686-421: A DKW design that proved reasonably successful employing loop charging. The original SAAB 92 had a two-cylinder engine of comparatively low efficiency. At cruising speed, reflected-wave, exhaust-port blocking occurred at too low a frequency. Using the asymmetrical three-port exhaust manifold employed in the identical DKW engine improved fuel economy. The 750-cc standard engine produced 36 to 42 hp, depending on

784-485: A body made of recycled material; the first was the AWZ P70 Zwickau , produced from 1955 to 1959. The material was durable, and the average lifespan of a Trabant was 28 years. The Trabant's build quality was poor, and it was loud, slow, and poorly designed. The car had four principal variants: The engine for the 500, 600 and the original 601 was a small two-stroke engine with two cylinders, accounting for

882-403: A continuous flow of electrolyte. Flow cells typically have the fuel dissolved in the electrolyte. Power-to-weight ratios for vehicles are usually calculated using curb weight (for cars) or wet weight (for motorcycles), that is, excluding weight of the driver and any cargo. This could be slightly misleading, especially with regard to motorcycles, where the driver might weigh 1/3 to 1/2 as much as

980-447: A crossflow engine) is always best and support is good. In some engines, the small end is offset to reduce thrust in the intended rotational direction and the forward face of the piston has been made thinner and lighter to compensate, but when running backward, this weaker forward face suffers increased mechanical stress it was not designed to resist. This can be avoided by the use of crossheads and also using thrust bearings to isolate

1078-406: A cutoff voltage are typically specified for a battery by its manufacturer. The output voltage falls to the cutoff voltage when the battery becomes "discharged". The nominal output voltage is always less than the open-circuit voltage produced when the battery is "charged". The temperature of a battery can affect the power it can deliver, where lower temperatures reduce power. Total energy delivered from

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1176-496: A cyclist's power-to-weight output decreases with fatigue, it is normally discussed with relation to the length of time that he or she maintains that power. A professional cyclist can produce over 20 W/kg (0.012 hp/lb) as a five-second maximum. Trabant Trabant ( German: [tʁaˈbant] ) is a series of small cars produced from 1957 until 1991 by former East German car manufacturer VEB Sachsenring Automobilwerke Zwickau . Four models were made:

1274-467: A fluid, or storage in a pressure vessel . A variety of effects can be harnessed to produce thermoelectricity , thermionic emission , pyroelectricity and piezoelectricity . Electrical resistance and ferromagnetism of materials can be harnessed to generate thermoacoustic energy from an electric current. All electrochemical cell batteries deliver a changing voltage as their chemistry changes from "charged" to "discharged". A nominal output voltage and

1372-563: A higher discharge current – and therefore higher power-to-weight ratio – but only with a lower energy capacity. Power-to-weight ratio for batteries is therefore less meaningful without reference to corresponding energy-to-weight ratio and cell temperature. This relationship is known as Peukert's law . Capacitors store electric charge onto two electrodes separated by an electric field semi-insulating ( dielectric ) medium. Electrostatic capacitors feature planar electrodes onto which electric charge accumulates. Electrolytic capacitors use

1470-406: A liquid electrolyte as one of the electrodes and the electric double layer effect upon the surface of the dielectric-electrolyte boundary to increase the amount of charge stored per unit volume. Electric double-layer capacitors extend both electrodes with a nanoporous material such as activated carbon to significantly increase the surface area upon which electric charge can accumulate, reducing

1568-507: A mass of 380 kg (840 lb), giving it a power-to-weight ratio of 0.65 kW/kg (0.40 hp/lb). Examples of high power-to-weight ratios can often be found in turbines. This is because of their ability to operate at very high speeds. For example, the Space Shuttle 's main engines used turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen ) into

1666-527: A mix of gasoline and oil directly under the bonnet/hood. In contrast, the West German Volkswagen Beetle received a number of updates (including improvements in efficiency) over a similar period. VEB Sachsenring Automobilwerke Zwickau had its origins in the former Auto Union / DKW business which had operated out of the site prior to the war, and the company's first products were essentially copies of pre-war DKW designs. Following

1764-530: A new one, and the average worker had to wait ten to thirteen years on a waiting list, or, if available, pay more than double for a second hand model. The Trabant had a steel frame, with the roof, boot lid, bonnet, wings and doors made of duroplast , a hard plastic made from recycled cotton waste from the Soviet Union and phenol resins from the East German dye industry. It was the second car with

1862-469: A patent in 1880 in Germany. The first truly practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott , who started producing twin-cylinder water-cooled motorcycles in 1908. Two-stroke gasoline engines with electrical spark ignition are particularly useful in lightweight or portable applications such as chainsaws and motorcycles. However, when weight and size are not an issue,

1960-647: A period of time is equal to the difference in its total energy over that period of time, so the rate at which work is done is equal to the rate of change of the kinetic energy (in the absence of potential energy changes). The work done from time t to time t + Δ t along the path C is defined as the line integral ∫ C F ⋅ d x = ∫ t t + Δ t F ⋅ v ( t ) d t {\displaystyle \int _{C}\mathbf {F} \cdot d\mathbf {x} =\int _{t}^{t+\Delta t}\mathbf {F} \cdot \mathbf {v} (t)dt} , so

2058-410: A premixed gas-oil mixture at the pump. Because the Trabant had no fuel pump , its fuel tank was above the motor so fuel could reach the carburettor by gravity; this increased the risk of fire in front-end accidents. Earlier models had no fuel gauge, and a dipstick was inserted into the tank to determine how much fuel remained. Known for its dull colour scheme and cramped, uncomfortable ride, the Trabant

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2156-406: A quarter-century. Also unchanged was its production method, which was extremely labour-intensive. Production started from 34,000 p.a. in 1964, reached 100,000 p.a. in 1973, to a high of 150,000 in 1989. The Trabant 1.1 was a 601 with a better-performing 1.05-liter (64 cu in), 45 PS (33 kW) VW Polo engine. With a slightly modified look (including a floor-mounted gearshift), it

2254-448: A scavenging function. The units run in pairs, with the lower half of one piston charging an adjacent combustion chamber. The upper section of the piston still relies on total-loss lubrication, but the other engine parts are sump lubricated with cleanliness and reliability benefits. The mass of the piston is only about 20% more than a loop-scavenged engine's piston because skirt thicknesses can be less. Many modern two-stroke engines employ

2352-658: A similar system. Traditional flywheel magnetos (using contact-breaker points, but no external coil) worked equally well in reverse because the cam controlling the points is symmetrical, breaking contact before top dead center equally well whether running forward or backward. Reed-valve engines run backward just as well as piston-controlled porting, though rotary valve engines have asymmetrical inlet timing and do not run very well. Serious disadvantages exist for running many engines backward under load for any length of time, and some of these reasons are general, applying equally to both two-stroke and four-stroke engines. This disadvantage

2450-463: A single charge cycle is affected by both the battery temperature and the power it delivers. If the temperature lowers or the power demand increases, the total energy delivered at the point of "discharge" is also reduced. Battery discharge profiles are often described in terms of a factor of battery capacity . For example, a battery with a nominal capacity quoted in ampere-hours (Ah) at a C/10 rated discharge current (derived in amperes) may safely provide

2548-401: A speed | v ( t ) | {\displaystyle |\mathbf {v} (t)|\;} and angle ϕ {\displaystyle \phi \;} with respect to the centre and radial of a gravitational field by an onboard powerplant , then the associated kinetic energy is where: The work–energy principle states that the work done to the object over

2646-667: A train. As the coefficient of friction between steel wheels and rails seldom exceeds 0.25 in most cases, improving a locomotive's power-to-weight ratio is often counterproductive. However, the choice of power transmission system, such as variable-frequency drive versus direct-current drive , may support a higher power-to-weight ratio by better managing propulsion power. Most vehicles are designed to meet passenger comfort and cargo carrying requirements. Vehicle designs trade off power-to-weight ratio to increase comfort, cargo space, fuel economy , emissions control , energy security and endurance. Reduced drag and lower rolling resistance in

2744-518: A turbocharger. Crankcase-compression two-stroke engines, such as common small gasoline-powered engines, are lubricated by a petroil mixture in a total-loss system . Oil is mixed in with their petrol fuel beforehand, in a fuel-to-oil ratio of around 32:1. This oil then forms emissions, either by being burned in the engine or as droplets in the exhaust, historically resulting in more exhaust emissions, particularly hydrocarbons, than four-stroke engines of comparable power output. The combined opening time of

2842-522: A vehicle design can facilitate increased cargo space without increase in the (zero cargo) power-to-weight ratio. This increases the role flexibility of the vehicle. Energy security considerations can trade off power (typically decreased) and weight (typically increased), and therefore power-to-weight ratio, for fuel flexibility or drive-train hybridisation . Some utility and practical vehicle variants such as hot hatches and sports-utility vehicles reconfigure power (typically increased) and weight to provide

2940-474: A water-cooled, three-cylinder, 1,000  cc (61  cu in ), two-stroke DKW engine. The original Trabant, introduced in 1958, was the P 50 . Trabant's base model, it shared a large number of interchangeable parts with the latest 1.1s. The 500 cc, 17 PS (13 kW) P50 evolved into a 20 PS (15 kW) version with a fully synchronized gearbox in 1960, and received a 23 PS (17 kW), 600 cc (37 cu in) engine in 1962 as

3038-400: A wider speed range or higher power over a narrower speed range than either a piston-port or reed-valve engine. Where a portion of the rotary valve is a portion of the crankcase itself, of particular importance, no wear should be allowed to take place. In a cross-flow engine, the transfer and exhaust ports are on opposite sides of the cylinder, and a deflector on the top of the piston directs

Two-stroke engine - Misplaced Pages Continue

3136-408: Is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's power output being divided by the weight (or mass ) of the vehicle, to give a metric that

3234-413: Is accepted in most cases where cost, weight, and size are major considerations. The problem comes about because in "forward" running, the major thrust face of the piston is on the back face of the cylinder, which in a two-stroke particularly, is the coolest and best-lubricated part. The forward face of the piston in a trunk engine is less well-suited to be the major thrust face, since it covers and uncovers

3332-402: Is an important vehicle characteristic that affects the acceleration of sports vehicles. Propeller aircraft depend on high power-to-weight ratios to generate sufficient thrust to achieve sustained flight, and then for speed. Jet aircraft produce thrust directly . Power-to-weight ratio is important in cycling, since it determines acceleration and the speed during hill climbs . Since

3430-568: Is an object of ridicule for many Germans and is regarded as symbolic of the fall of the Eastern Bloc . Known as a "spark plug with a roof" because of its small size, the car did gain public affection. Its design remained essentially unchanged from its introduction in the late 1950s, and the last model was introduced in 1990. The 1980s model had no tachometer , no indicator for either the headlights or turn signals, no fuel gauge, no rear seat belts, no external fuel door, and drivers had to pour

3528-419: Is attributed to Scottish engineer Dugald Clerk , who patented his design in 1881. However, unlike most later two-stroke engines, his had a separate charging cylinder. The crankcase -scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day . On 31 December 1879, German inventor Karl Benz produced a two-stroke gas engine, for which he received

3626-596: Is being phased out. Honda , for instance, ceased selling two-stroke off-road motorcycles in the United States in 2007, after abandoning road-going models considerably earlier. Due to their high power-to-weight ratio and ability to be used in any orientation, two-stroke engines are common in handheld outdoor power tools including leaf blowers , chainsaws , and string trimmers . Two-stroke diesel engines are found mostly in large industrial and marine applications, as well as some trucks and heavy machinery. Although

3724-574: Is common in on-road, off-road, and stationary two-stroke engines ( Detroit Diesel ), certain small marine two-stroke engines ( Gray Marine Motor Company , which adapted the Detroit Diesel Series 71 for marine use ), certain railroad two-stroke diesel locomotives ( Electro-Motive Diesel ) and large marine two-stroke main propulsion engines ( Wärtsilä ). Ported types are represented by the opposed piston design in which two pistons are in each cylinder, working in opposite directions such as

3822-417: Is conversely usually lower. Fuel cells and flow cells , although perhaps using similar chemistry to batteries, do not contain the energy storage medium or fuel . With a continuous flow of fuel and oxidant, available fuel cells and flow cells continue to convert the energy storage medium into electric energy and waste products. Fuel cells distinctly contain a fixed electrolyte whereas flow cells also require

3920-500: Is equal to thrust per unit mass multiplied by the velocity of any vehicle. The power-to-weight ratio (specific power) is defined as the power generated by the engine(s) divided by the mass. In this context, the term "weight" can be considered a misnomer, as it colloquially refers to mass. In a zero-gravity (weightless) environment, the power-to-weight ratio would not be considered infinite. A typical turbocharged V8 diesel engine might have an engine power of 250 kW (340 hp) and

4018-420: Is independent of the vehicle's size. Power-to-weight is often quoted by manufacturers at the peak value, but the actual value may vary in use and variations will affect performance. The inverse of power-to-weight, weight-to-power ratio (power loading) is a calculation commonly applied to aircraft, cars, and vehicles in general, to enable the comparison of one vehicle's performance to another. Power-to-weight ratio

Two-stroke engine - Misplaced Pages Continue

4116-499: Is only delivered if the powerplant is in motion, and is transmitted to cause the body to be in motion. It is typically assumed here that mechanical transmission allows the powerplant to operate at peak output power. This assumption allows engine tuning to trade power band width and engine mass for transmission complexity and mass. Electric motors do not suffer from this tradeoff, instead trading their high torque for traction at low speed. The power advantage or power-to-weight ratio

4214-432: Is that the two-stroke's crankcase is sealed and forms part of the induction process in gasoline and hot-bulb engines . Diesel two-strokes often add a Roots blower or piston pump for scavenging . The reed valve is a simple but highly effective form of check valve commonly fitted in the intake tract of the piston-controlled port. It allows asymmetric intake of the fuel charge, improving power and economy, while widening

4312-405: Is then where: The useful power of an engine with shaft power output can be calculated using a dynamometer to measure torque and rotational speed , with maximum power reached when torque multiplied by rotational speed is a maximum. For jet engines the useful power is equal to the flight speed of the aircraft multiplied by the force, known as net thrust, required to make it go at that speed. It

4410-409: Is under every circumstance more efficient than cross-flow scavenging. In a uniflow engine, the mixture, or "charge air" in the case of a diesel, enters at one end of the cylinder controlled by the piston and the exhaust exits at the other end controlled by an exhaust valve or piston. The scavenging gas-flow is, therefore, in one direction only, hence the name uniflow. The design using exhaust valve(s)

4508-455: Is used when calculating propulsive efficiency . Thermal energy is made up from molecular kinetic energy and latent phase energy. Heat engines are able to convert thermal energy in the form of a temperature gradient between a hot source and a cold sink into other desirable mechanical work . Heat pumps take mechanical work to regenerate thermal energy in a temperature gradient. Standard definitions should be used when interpreting how

4606-461: The Junkers Jumo 205 and Napier Deltic . The once-popular split-single design falls into this class, being effectively a folded uniflow. With advanced-angle exhaust timing, uniflow engines can be supercharged with a crankshaft-driven blower, either piston or Roots-type. The piston of this engine is "top-hat"-shaped; the upper section forms the regular cylinder, and the lower section performs

4704-620: The Lada Niva , Škoda Estelle , Polski Fiat ( design licensed from the Italian car manufacturer) and Yugo , the Trabant had negligible sales in Western Europe. A Trabant could be bought for as little as a few Deutsche Marks during the early 1990s, and many were given away. Although prices recovered as they became collectors' items, they remain inexpensive cars. In her Bodywork project, performance artist Liz Cohen transformed

4802-633: The Trabant 1.1 in 1990, the Trabant became symbolic of the former East Germany's stagnant economy and the collapse of the Eastern Bloc in general. Called "a spark plug with a roof", 3,096,999 Trabants were produced. Older models have been sought by collectors in the United States due to their low cost and fewer restrictions on the importation of antique cars . The Trabant also gained a following among car tuning and rallying enthusiasts. The German word Trabant , derived from Middle High German drabant , means 'satellite' or 'companion'. The car's name

4900-411: The Trabant 500 , Trabant 600 , Trabant 601 , and the Trabant 1.1 . The first model, the 500, was a relatively modern car when it was introduced. It featured detachable duroplast body panels on a galvanised steel unibody chassis, front-wheel drive, a transverse two-stroke engine, and independent suspension. Because this 1950s design remained largely unchanged until the introduction of the last model,

4998-405: The derivative with respect to time of the work done). The typically used metric unit of the power-to-weight ratio is W kg {\displaystyle {\tfrac {\text{W}}{\text{kg}}}\;} which equals m 2 s 3 {\displaystyle {\tfrac {{\text{m}}^{2}}{{\text{s}}^{3}}}\;} . This fact allows one to express

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5096-512: The expansion chamber , such as the Suzuki SAEC and Honda V-TACS system. The result is an engine with better low-speed power without sacrificing high-speed power. However, as power valves are in the hot gas flow, they need regular maintenance to perform well. Direct injection has considerable advantages in two-stroke engines. In carburetted two-strokes, a major problem is a portion of the fuel/air mixture going directly out, unburned, through

5194-474: The fundamental theorem of calculus has that power is given by F ( t ) ⋅ v ( t ) = m a ( t ) ⋅ v ( t ) = τ ( t ) ⋅ ω ( t ) {\displaystyle \mathbf {F} (t)\cdot \mathbf {v} (t)=m\mathbf {a} (t)\cdot \mathbf {v} (t)=\mathbf {\tau } (t)\cdot \mathbf {\omega } (t)} . where: In propulsion , power

5292-479: The oil reservoir does not depend on gravity. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab , German manufacturers DKW , Auto-Union , VEB Sachsenring Automobilwerke Zwickau , VEB Automobilwerk Eisenach , and VEB Fahrzeug- und Jagdwaffenwerk , and Polish manufacturers FSO and FSM . The Japanese manufacturers Suzuki and Subaru did

5390-528: The 1960s due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was the piston could be made nearly flat or slightly domed, which allowed the piston to be appreciably lighter and stronger, and consequently to tolerate higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes, and compression losses. SAAB built 750- and 850-cc three-cylinder engines based on

5488-407: The 1960s, especially for motorcycles, but for smaller or slower engines using direct injection, the deflector piston can still be an acceptable approach. This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel/air mixture strikes the cylinder head , then follows the curvature of

5586-816: The British Embassy in Budapest , used a 1.1 (painted as close to British racing green as possible) as his diplomatic car . American Trabant owners celebrate the fall of the Berlin Wall with the Parade of Trabants, an annual early-November rally held in Washington, D.C. The event, sponsored by the privately owned International Spy Museum , includes street tours in Trabants, rides, live German music and displays about East Germany. The Herpa company,

5684-399: The German inventor of an early form in the mid-1920s, it became widely adopted in Germany country during the 1930s and spread further afield after World War II . Loop scavenging is the most common type of fuel/air mixture transfer used on modern two-stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop-scavenged, two-stroke engines. This operational feature

5782-427: The P 60. The updated P601 was introduced in 1964. It was essentially a facelift of the P 60, with a different front fascia, bonnet, roof and rear and the original P50 underpinnings. The model remained nearly unchanged until the end of its production except for the addition of 12V electricity, rear coil springs and an updated dashboard for later models. The Trabant's designers expected production to extend until 1967 at

5880-459: The Trabant 1.1 was discontinued. In total, 3.7 million Trabant vehicles had been produced. However, it soon became apparent that there was no place for the Trabant in a reunified German economy. Its inefficient, labour-intensive production line had only survived thanks to government subsidies. The Zwickau factory in Mosel (where the Trabant was manufactured) was sold to Volkswagen AG; the rest of

5978-477: The Trabant. It was technically equivalent to the West German Lloyd automobile, a similarly sized car with an air-cooled, two-cylinder four-stroke engine. The Trabant had a front, transversely mounted engine and front-wheel drive in an era when many European cars were using rear-mounted engines or front-mounted engines with rear-wheel drive. Its greatest drawback was its largely unchanged production;

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6076-752: The Trabants left the VEB Sachsenring Automobilwerke Zwickau factory in Saxony on 7 November 1957. It was a relatively advanced car when it was formally introduced the following year, with front wheel drive , unitary construction and independent suspension. The Trabant's greatest shortcoming was its engine. By the late 1950s, many small West European cars (such as the Renault ) had cleaner, more-efficient four-stroke engines, but budgetary constraints and raw-materials shortages mandated an outdated (but inexpensive) two-stroke engine in

6174-613: The air at four times the European average. A licensed version of the Volkswagen Polo engine replaced the Trabant's two-stroke engine, the result of a trade agreement between East and West Germany. The first prototypes were built in 1988, with pre-series cars appearing in 1989, but series production only began in May 1990 - By which time the two German states had already agreed to reunification . The locally built EA111-series engine

6272-423: The bore diameter for reasonable piston ring life. Beyond this, the piston rings bulge into the exhaust port and wear quickly. A maximum 70% of bore width is possible in racing engines, where rings are changed every few races. Intake duration is between 120 and 160°. Transfer port time is set at a minimum of 26°. The strong, low-pressure pulse of a racing two-stroke expansion chamber can drop the pressure to -7 psi when

6370-466: The car's two-stroke engine made it obsolete by the 1970s, limiting exports to Western Europe. The Trabant's air-cooled, 500 cc (31 cu in) engine—upgraded to 600 cc (37 cu in) in 1962–63—was derived from a pre-war DKW design with minor alterations during its production run. The first Saab car had a larger (764 cc), water-cooled, two-cylinder two-stroke engine. Wartburg , an East German manufacturer of larger sedans, also used

6468-459: The combustion chamber, and then is deflected downward. This not only prevents the fuel/air mixture from traveling directly out the exhaust port, but also creates a swirling turbulence which improves combustion efficiency , power, and economy. Usually, a piston deflector is not required, so this approach has a distinct advantage over the cross-flow scheme (above). Often referred to as "Schnuerle" (or "Schnürle") loop scavenging after Adolf Schnürle,

6566-704: The company became HQM Sachsenring GmbH . Volkswagen redeveloped the Zwickau factory into a centre for engine production; it also produces some Volkswagen Golfs and Passats . According to Richard Leiby, the Trabant had become "a symbol of the technological and social backwardness of the East German state." Trabants became a symbol of the GDR's serious flaws in the West after the fall of the Berlin Wall , when many were abandoned by their Eastern owners who migrated west. Unlike

6664-453: The crankshaft commonly spins in the same axis and direction as do the wheels i.e. "forward". Some of the considerations discussed here apply to four-stroke engines (which cannot reverse their direction of rotation without considerable modification), almost all of which spin forward, too. It is also useful to note that the "front" and "back" faces of the piston are - respectively - the exhaust port and intake port sides of it, and are not to do with

6762-415: The cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion , railway locomotives , and electricity generation . In a two-stroke engine, the exhaust gases transfer less heat to the cooling system than a four-stroke, which means more energy to drive the piston, and if present,

6860-458: The dielectric medium to nanopores and a very thin high permittivity separator. While capacitors tend not to be as temperature sensitive as batteries, they are significantly capacity constrained and without the strength of chemical bonds suffer from self-discharge. Power-to-weight ratio of capacitors is usually higher than batteries because charge transport units within the cell are smaller (electrons rather than ions), however energy-to-weight ratio

6958-400: The engine from end loads. Large two-stroke ship diesels are sometimes made to be reversible. Like four-stroke ship engines (some of which are also reversible), they use mechanically operated valves, so require additional camshaft mechanisms. These engines use crossheads to eliminate sidethrust on the piston and isolate the under-piston space from the crankcase. On top of other considerations,

7056-436: The engine's combustion chamber. The original liquid hydrogen turbopump is similar in size to an automobile engine (weighing approximately 352 kilograms (775 lb)) and produces 72,000 hp (54 MW) for a power-to-weight ratio of 153 kW/kg (93 hp/lb). In classical mechanics , instantaneous power is the limiting value of the average work done per unit time as the time interval Δ t approaches zero (i.e.

7154-415: The exhaust port in the cylinder, the hottest part of the engine, where piston lubrication is at its most marginal. The front face of the piston is also more vulnerable since the exhaust port, the largest in the engine, is in the front wall of the cylinder. Piston skirts and rings risk being extruded into this port, so having them pressing hardest on the opposite wall (where there are only the transfer ports in

7252-409: The exhaust port, and direct injection effectively eliminates this problem. Two systems are in use: low-pressure air-assisted injection and high-pressure injection. Since the fuel does not pass through the crankcase, a separate source of lubrication is needed. For the purpose of this discussion, it is convenient to think in motorcycle terms, where the exhaust pipe faces into the cooling air stream, and

7350-412: The fresh intake charge into the upper part of the cylinder, pushing the residual exhaust gas down the other side of the deflector and out the exhaust port. The deflector increases the piston's weight and exposed surface area, and the fact that it makes piston cooling and achieving an effective combustion chamber shape more difficult is why this design has been largely superseded by uniflow scavenging after

7448-466: The hydrocarbons and five times the carbon-monoxide emissions of the average 2007 European car. Its fuel consumption was 7 L/100 km (40 mpg ‑imp ; 34 mpg ‑US ). Since the engine was two-stroke , oil had to be added to the 24-liter (6.3 U.S. gal; 5.3 imp gal) fuel tank at a 50:1 (or 33:1) ratio of fuel to oil at each fill-up. Contemporary gas stations in countries where two-stroke engines were common sold

7546-443: The intake and exhaust ports in some two-stroke designs can also allow some amount of unburned fuel vapors to exit in the exhaust stream. The high combustion temperatures of small, air-cooled engines may also produce NO x emissions. Two-stroke gasoline engines are preferred when mechanical simplicity, light weight, and high power-to-weight ratio are design priorities. By mixing oil with fuel, they can operate in any orientation as

7644-553: The latest, and East German designers and engineers created a series of more-sophisticated prototypes intended to replace the P601; several are displayed at the Dresden Transport Museum . Each proposal for a new model was rejected by the East German government due to shortages of the raw materials required in larger quantities for the more-advanced designs. As a result, the Trabant remained largely unchanged for more than

7742-475: The model year. The Monte Carlo Rally variant, 750-cc (with a filled crankshaft for higher base compression), generated 65 hp. An 850-cc version was available in the 1966 SAAB Sport (a standard trim model in comparison to the deluxe trim of the Monte Carlo). Base compression comprises a portion of the overall compression ratio of a two-stroke engine. Work published at SAE in 2012 points that loop scavenging

7840-681: The oil pump of a modern two-stroke may not work in reverse, in which case the engine suffers oil starvation within a short time. Running a motorcycle engine backward is relatively easy to initiate, and in rare cases, can be triggered by a back-fire. It is not advisable. Model airplane engines with reed valves can be mounted in either tractor or pusher configuration without needing to change the propeller. These motors are compression ignition, so no ignition timing issues and little difference between running forward and running backward are seen. Power-to-weight ratio Power-to-weight ratio ( PWR , also called specific power , or power-to-mass ratio )

7938-487: The other - the inlet pipe having passage to the crankcase only when the two cutouts coincide. The crankshaft itself may form one of the members, as in most glow-plug model engines. In another version, the crank disc is arranged to be a close-clearance fit in the crankcase, and is provided with a cutout that lines up with an inlet passage in the crankcase wall at the appropriate time, as in Vespa motor scooters. The advantage of

8036-478: The partition of Germany, Auto Union re-established itself in West Germany (ultimately evolving into Audi ), leaving VEB Sachsenring with the two stroke engine inherited from DKW. The Trabant was the result of a planning process which had been intended to design a three-wheeled motorcycle. In German, Trabant is an astronomical term for a moon (or other natural satellite) of a celestial body. The first of

8134-442: The perception of sports car like performance or for other psychological benefit . Increased engine performance is a consideration, but also other features associated with luxury vehicles . Longitudinal engines are common. Bodies vary from hot hatches , sedans (saloons) , coupés , convertibles and roadsters . Mid-range dual-sport and cruiser motorcycles tend to have similar power-to-weight ratios. Power-to-weight ratio

8232-434: The piston covering and uncovering the ports as it moves up and down in the cylinder. In the 1970s, Yamaha worked out some basic principles for this system. They found that, in general, widening an exhaust port increases the power by the same amount as raising the port, but the power band does not narrow as it does when the port is raised. However, a mechanical limit exists to the width of a single exhaust port, at about 62% of

8330-439: The piston is at bottom dead center, and the transfer ports nearly wide open. One of the reasons for high fuel consumption in two-strokes is that some of the incoming pressurized fuel-air mixture is forced across the top of the piston, where it has a cooling action, and straight out the exhaust pipe. An expansion chamber with a strong reverse pulse stops this outgoing flow. A fundamental difference from typical four-stroke engines

8428-550: The power band. Such valves are widely used in motorcycle, ATV, and marine outboard engines. The intake pathway is opened and closed by a rotating member. A familiar type sometimes seen on small motorcycles is a slotted disk attached to the crankshaft , which covers and uncovers an opening in the end of the crankcase, allowing charge to enter during one portion of the cycle (called a disc valve). Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members with suitable cutouts arranged to rotate one within

8526-431: The power-to-weight ratio purely by SI base units . A vehicle's power-to-weight ratio equals its acceleration times its velocity; so at twice the velocity, it experiences half the acceleration, all else being equal. If the work to be done is rectilinear motion of a body with constant mass m {\displaystyle m\;} , whose center of mass is to be accelerated along a (possibly non-straight) line to

8624-466: The principles remain the same, the mechanical details of various two-stroke engines differ depending on the type. The design types vary according to the method of introducing the charge to the cylinder, the method of scavenging the cylinder (exchanging burnt exhaust for fresh mixture) and the method of exhausting the cylinder. Piston port is the simplest of the designs and the most common in small two-stroke engines. All functions are controlled solely by

8722-701: The propulsive power of a jet or rocket engine is transferred to its vehicle. An electric motor uses electrical energy to provide mechanical work , usually through the interaction of a magnetic field and current-carrying conductors . By the interaction of mechanical work on an electrical conductor in a magnetic field, electrical energy can be generated . Fluids (liquid and gas) can be used to transmit and/or store energy using pressure and other fluid properties. Hydraulic (liquid) and pneumatic (gas) engines convert fluid pressure into other desirable mechanical or electrical work . Fluid pumps convert mechanical or electrical work into movement or pressure changes of

8820-714: The same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, due to increasingly stringent regulation of air pollution . Eastern Bloc countries continued until around 1991, with the Trabant and Wartburg in East Germany. Two-stroke engines are still found in a variety of small propulsion applications, such as outboard motors , small on- and off-road motorcycles , mopeds , motor scooters , motorized bicycles , tuk-tuks , snowmobiles , go-karts , RC cars , ultralight and model airplanes. Particularly in developed countries, pollution regulations have meant that their use for many of these applications

8918-520: The top or bottom of the piston. Regular gasoline two-stroke engines can run backward for short periods and under light load with little problem, and this has been used to provide a reversing facility in microcars , such as the Messerschmitt KR200 , that lacked reverse gearing. Where the vehicle has electric starting, the motor is turned off and restarted backward by turning the key in the opposite direction. Two-stroke golf carts have used

9016-591: The vehicle (which had become symbolic of Bulgaria's NATO accession) to the National Historical Museum of Bulgaria . In 1997, the Trabant was celebrated for passing the moose test without rolling over, as the Mercedes-Benz W168 had; a Thuringian newspaper's headline read, "Come and get us, moose! Trabi passes A-Class killer test". The Trabant entered the world of diplomacy in 2007 when Steven Fisher, deputy head of mission at

9114-516: The vehicle itself. In the sport of competitive cycling athlete's performance is increasingly being expressed in VAMs and thus as a power-to-weight ratio in W/kg. This can be measured through the use of a bicycle powermeter or calculated from measuring incline of a road climb and the rider's time to ascend it. A locomotive generally must be heavy in order to develop enough adhesion on the rails to start

9212-425: The vehicle's modest performance. Its curb weight was about 600 kg (1,323 lb). When it ceased production in 1989, the Trabant delivered 26 PS (19 kW) from 594 cc (36.2 cu in) displacement . It took 21 seconds to accelerate from zero to its top speed of 100 km/h (62 mph). The engine produced a very smoky exhaust and was a significant source of air pollution : nine times

9310-569: Was given the model code BM 820 by the East Germans; the plant also made 1.3-liter versions for the Wartburg 1.3 (BM 860) and the Barkas utility vehicle (BM 880). The model, the Trabant 1.1, also had minor improvements to its brake and signal lights, a renovated grille, and MacPherson struts instead of a leaf-spring-suspended chassis. By April 1991, after only eleven months,

9408-481: Was inspired by the Soviet Sputnik satellite. The cars are often referred to as "Trabbi" or "Trabi". Produced without major changes for nearly 30 years, the Trabant became the most common automobile in East Germany. It came to symbolize the country during the fall of the Berlin Wall in 1989, as images of East Germans crossing the border into West Germany were broadcast around the globe. Manufactured by

9506-657: Was quieter and cleaner than its predecessor. The 1.1 had front disc brakes, and its wheel assembly was borrowed from Volkswagen . It was produced from 1989 to 1991, in parallel with the two-stroke P601. Except for the engine and transmission, many parts from older P50s, P60s and 601s were compatible with the 1.1. In mid-1989, thousands of East Germans began loading their Trabants with as much as they could carry and drove to Hungary or Czechoslovakia en route to West Germany–the so-called "Trabi Trail". Many had to get special permission to drive their Trabants into West Germany. The cars did not meet West German emissions standards and polluted

9604-541: Was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ, and Walter Kaaden. Loop scavenging, disc valves, and expansion chambers worked in a highly coordinated way to significantly increase the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha, and Kawasaki. Suzuki and Yamaha enjoyed success in Grand Prix motorcycle racing in

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