Modern cars and speed
Although having sporting a modern car very often remains just a dream for motorists, people with such cars more often appear on Polish roads. I must admit that this car really pose a huge threat to all road users. In sports cars do not feel the speed, and special arrangements are responsible for the fact that you can achieve really high speed driving. It is not only dangerous, but in some cases, even deadly. Despite the passionate driving fast sports car is not lacking, and for some of them the adrenaline during such driving is one of the most important experiences, so that they feel really good.
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
Gift for car lovers
What to buy a gift for fans of the automotive industry? Contrary to appearances, the possibilities are really a lot. We can decide to choose the professional literature, which concerns a favorite of the recipient by the model or brand of the car. When you want to select a small gift, certainly a great idea is to choose a key ring or other gadget that the person receiving the gift from us can be attached to keys to the car. Very nice idea on the web, but also a fun gift for a fan of the automotive industry is a shirt with an appropriate inscription. Here we can choose a really different graphics and manufacture of t-shirts with fun prints more than one person can really surprise. This t-shirt is a cool gift for a friend, brother or boyfriend.