The intake port is connected
Diagram of a crankcase scavenged 2-stroke engine in operation
Some SI engines are crankcase scavenged and do not use poppet valves. Instead the crankcase and the part of the cylinder below the piston is used as a pump. The intake port is connected to the crankcase through a reed valve or a rotary disk valve driven by the engine. For each cylinder a transfer port connects in one end to the crankcase and in the other end to the cylinder wall. The exhaust port is connected directly to the cylinder wall. The transfer and exhaust port are opened and closed by the piston. The reed valve opens when the crankcase pressure is slightly below intake pressure, to let it be filled with a new charge; this happens when the piston is moving upwards. When the piston is moving downwards the pressure in the crankcase increases and the reed valve closes promptly, then the charge in the crankcase is compressed. When the piston is moving upwards, it uncovers the exhaust port and the transfer port and the higher pressure of the charge in the crankcase makes it enter the cylinder through the transfer port, blowing the exhaust gases. Lubrication is accomplished by adding 2-stroke oil to the fuel in small ratios. Petroil refers to the mix of gasoline with the aforesaid oil. This kind of 2-stroke engines has a lower efficiency than comparable 4-strokes engines and release a more polluting exhaust gases for the following conditions:
They use a total-loss lubrication system: all the lubricating oil is eventually burned along with the fuel.
There are conflicting requirements for scavenging: On one side, enough fresh charge needs to be introduced in each cycle to displace almost all the combustion gases but introducing too much of it means that a part of it gets in the exhaust.
They must use the transfer port(s) as a carefully designed and placed nozzle so that a gas current is created in a way that it sweeps the whole cylinder before reaching the exhaust port so as to expel the combustion gases, but minimize the amount of charge exhausted. 4-stroke engines have the benefit of forcibly expelling almost all of the combustion gases because during exhaust the combustion chamber is reduced to its minimum volume. In crankcase scavenged 2-stroke engines, exhaust and intake are performed mostly simultaneously and with the combustion chamber at its maximum volume.
The main advantage of 2-stroke engines of this type is mechanical simplicity and a higher power-to-weight ratio than their 4-stroke counterparts. Despite having twice as many power strokes per cycle, less than twice the power of a comparable 4-stroke engine is attainable in practice.
In the USA two stroke motorcycle and automobile engines were banned due to the pollution, although many thousands of lawn maintenance engines are in use.citation needed
Ads on the Internet - is worth a look there cars?
The Internet is full of all kinds of automotive ads. They concern mainly the sale of used cars. Is it worth it to use the online services when looking for a car? It is certainly a very good solution if you do not have stalked the offer on the eye. You have to admit, however, that the majority of websites of the car in a good condition and at a reasonable price "spread" very quickly and to hunt down the network a good car you have to try hard. On the other hand, among the announcements automotive missing SELL they offer us to buy a good car, and really the facts are quite different.
The interior of the car shows the driver
In many newspapers or on websites related to the automotive industry really we find a lot of information about how to take care of the interior of our car. It is true that, without wanting to cleaning we fail to create a truly clean and neatly decorated the interior of the car, but everything can be seen glancing at, for example, the final result proposed by the authors of such articles of guidance. In many cases, clean the upholstery or perform similar operations does not require special cleaning products, which undoubtedly is a huge advantage. This allows us to perform complex cleaning of many elements in the interior of our car in the back garden or in the garage.