Basic principles of 2-stroke engines
I am extremely lucky to have among my friends that of Mr. Jesús Ortiz, INTA's Aeronautical Technical Engineer, whose specialty is, precisely, explosion engines. Thus, I have asked you to technically illustrate, in a brief and easy-to-understand way, about the technical foundations of this type of thruster:
[your_quote]
'The two-stroke engine was designed in 1878 by Dugal Clerk and has been applied to both forced-ignition and compression-ignition engines. In this type of engine, a working stroke is obtained for each revolution, so that with the same displacement and revolutions as a four-stroke engine, theoretically its power should be double. This, together with the fact of its simplicity of construction, generally lacking distribution systems and having a very simple greasing, makes it a very attractive solution.
The two-stroke consists of two ports, one of the exhaust located above the other of the intake and of a transfer duct, which communicates the crankcase of the engine with the upper part of the cylinder, being the piston in its race through the cylinder the one that opens or close the ports.
[/ su_quote]
[su_youtube_advanced https=»yes» url='https://youtube.com/watch?v=ZjEj4Uv5sLw' width='480′ height='360′]
[your_quote]
When the piston moves from the crankcase to the cylinder head, compression and intake are performed simultaneously. The piston compresses the gas mixture between it and the cylinder head and in turn generates suction in the crankcase, so that when the piston uncovers the intake port, fresh gases (fuel, air and oil mixture) enter the engine. When the piston reaches top dead center and the mixture is ignited, the piston begins its downward stroke, which in addition to producing the energy necessary for the movement of the crankshaft compresses the mixture that previously entered the engine. Continuing its downward movement, the piston uncovers the exhaust port and subsequently the transfer port that allows fresh mixture to enter the cylinder from the crankcase. When the piston reaches bottom dead center, the expansion and exhaust phase is complete.
Unfortunately, this type of mechanics presents the problem of short circuit, which consists in that part of the fresh gases escape through the port of
escape due to process concurrency. In addition, the times available for intake and exhaust are short, which also affects the renewal of gases.
[/ su_quote]
[your_quote]
Another important factor to take into account is the operating temperature: since there is an ignition per revolution, compared to a four-stroke propeller, at the same revolutions we will have twice as many ignitions, which implies a higher stress thermal.
At present, the use of two-stroke engines is focused on the sectors of minimum and maximum powers. Provoked ignition engines are used in the low range, having application in motorcycles, outboards, etc. Compression ignition engines are used for the high power range, working at low revolutions and including supercharging and more complex distribution systems, achieving high performances and good specific powers. They are used mainly for ships and power plants. "
[/ su_quote]
The main brands and their prices
I will focus on the world of classic cars, deliberately leaving aside the microcar brands, whose peculiarities can be discussed in another article later.
[su_note note_color = »# f4f4f4 ″]
DKW Auto Union
It manufactured automobiles from 1928 to 1963. Its range was exclusive of two-stroke vehicles, producing 2, 3, 4 and 6 cylinder engines for them. It manufactured its models in Germany and South America –Brazil and Argentina-.
DKW prices vary greatly, depending on the stage of manufacture and the model. In general, prewar sedans (F1 to F8) do not exceed 15.000 euros, always for vehicles in good condition. Cabrios are around 30.000, and some special roadster versions (F5 or F7) reach 40.000. A separate case are the rare F1, Schwebeklasse, P-15 or F-600 units, whose prices are not easily measurable given their exclusivity and rarity.
If we talk about vehicles from the 40s, 50s and 60s, in general sedans will not exceed € 15.000, nor convertibles 15-20.000. Between 1.500 and 4.000, the Mungas. A very special case are the Monza and the V6 prototypes, whose difficulty of acquisition makes them highly valued pieces by German collectors, mainly, reaching in some cases figures that reach six digits. Undoubtedly, they are, today, the 2 most expensive and difficult to find times.
[/ su_note]
[su_note note_color = »# f4f4f4 ″]
IFA
After World War II, DKW's main factory, Zwickau, was in East Germany. With this base the IFA brand was created, whose first mission was not the manufacture of vehicles, but the recovery or restoration of the DKW survivors of the war. After this stage and from 1949 to approximately 1955, it began to manufacture automobiles as such, most of the engine parts being the same as those of the 2-cylinder DKWs.
In recent years, their prices have only risen: the most common model, the F8, follows prices parallel to its twin brother, the DKW F-8. But always with 4.000-5.000 euros less for the relative from the east.
Wartburg
Starting from IFA and the F9 model, the Wartburg firm is resurrected in 1956 from oblivion, and becomes in charge of manufacturing the new 2-stroke, three-cylinder models from East Germany. Its activity was very intense, and it exported a good number of units of its W311 and W353 to all of Europe, which would be produced in a 2-stroke cycle until 1983, when it adopted a VW engine.
The Wartburgs, in general, are simple vehicles to maintain, whose biggest Achilles heel is the poor quality of the plate. Their prices, really affordable, and almost always below 3.000 euros. Only some cabrios will reach 6.000-7.000.
[/ su_note]
[su_note note_color = »# f4f4f4 ″]
Trabant
An icon of the cold war, It was at the time the most economical vehicle in East Germany. 2-stroke units were coming out of its factory in Zwickau until 1989. More than 3.000.000 Trabants were built, all equipped with its little 2cc 2-cylinder 600-stroke engine. In Germany they are wanted and have a fairly active club; and their prices, in general, do not exceed 1.000-3.000 euros.
SAAB
After the world war, the adoption of these types of propellants seemed good for Scandinavian climates. With this premise, Saab decided to enter the automotive world by creating a technologically advanced vehicle, comfortable and easy to maintain in any circumstance. This is how the Saab range was born, with its 92 and 93 models as the spearhead. It would not be until well into the 60s when it was decided to take the step towards 4-stroke engines.
The Saab two-stroke market is not very wide, and, in general, its prices are between 7.000 and 15.000 euros, depending on the versions. The most valued are the Montecarlo, the vitaminized version of 93, with three carburettors and other improvements. By the way, together with the DKW 3 = 6, they are the only two 2T vehicles with which the Historic Monte Carlo can be raced.
[/ su_note]
[su_note note_color = »# f4f4f4 ″]
eucort
National representative of these engines. Its range was exclusive of two-stroke mechanics, with 2 and 3 cylinders. It had a representation of some importance in the world of competition at the national level. Their prices are not known, given the null offer of the market. [/ Su_note]
[su_spoiler style = »fancy» title = 'VIDEO AND INFOGRAPHIC CREDITS' show = 'false']
♠ Rainer nyberg
♠ Harald sakshaug
♠ A.Schierwagen
[/ Su_spoiler]