Useful gadget for the car
Among the many highly advanced technological solutions can not fail to make life easier for drivers. A perfect example is the so-called parking sensor, which means that you can safely fit in the car, even in a small space. This gadget is not currently too expensive, and its value for the majority of drivers will be huge - definitely worth it to invest, as we move through the crowded city streets, and we have every day problems with the appropriate parking the car. This sensor, as well as many other facilities for drivers are becoming more popular, and above all, their price falls. This is certainly an argument for buying small appliances that make life easier on the road.
Some SI engines are crankcase scavenged
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
Content for beginners car fans
Cars are a rather complicated layouts and worth to each control you have knowledge of the most relevant information in this regard. First of all, take a look at the information on the basic elements of the construction of the car. These include not only the engine and steering wheel, but also many related parts, for example, with the propulsion system. More than one part of the car is completely black magic to people not connected in any way with the automotive industry. Some knowledge in this area is necessary, for example when driving course, but a lot of people quickly forget obtained message. It is worth it to remember, especially because it's easier, we can use the machine as we know it.