London Taxi smoking exhaust Buses in public space
Public transport is of utmost importance. You can quickly reach the first place, above all those who do not own a car. On the other hand, using the bus or smaller buses can get rid of the problem of parking the, which is often quite confusing for drivers. The bus ride makes it not need to be focused on driving. It is not surprising that this mode of transport is still often used on Polish roads. True, much of the buses is a machine that would give longer to the museum associated with the automotive industry, but there is also a really modern, rich in many of the features of vehicles on the road. The use of the exclusive bus is a feature of organized tours and I must admit that this is undoubtedly advantage of long journeys.
Some SI engines are crankcase scavenged
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
Źródło: https://en.wikipedia.org/wiki/Internal_combustion_engine
Testing of very expensive vehicles
The opportunity to test the car before buying enjoys considerable popularity among customers as well as all other interested parties. Test drive the opportunity to try a bit of luxury as an exclusive brand cars also offer ride exposed for sale cars. I must admit that in this case, it is often true fan event for the automotive industry, which for years had dreamed about it, to go for a car ride, which in everyday terms will not be able to afford. It is no wonder that many people going to a car dealership just to try these wonderful, but exorbitantly expensive machinery. Especially in big cities simulating the role of the potential customer it is fairly easy to do and quite common.