Main article: 2-stroke engine
The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consist of:
Power: While the piston is descending the combustion gases perform work on it?as in a 4-stroke engine?. The same thermodynamic considerations about the expansion apply.
Scavenging: Around 75° of crankshaft rotation before BDC the exhaust valve or port opens, and blowdown occurs. Shortly thereafter the intake valve or transfer port opens. The incoming charge displaces the remaining combustion gases to the exhaust system and a part of the charge may enter the exhaust system as well. The piston reaches BDC and reverses direction. After the piston has traveled a short distance upwards into the cylinder the exhaust valve or port closes; shortly the intake valve or transfer port closes as well.
Compression: With both intake and exhaust closed the piston continues moving upwards compressing the charge and performing a work on it. As in the case of a 4-stroke engine, ignition starts just before the piston reaches TDC and the same consideration on the thermodynamics of the compression on the charge.
While a 4-stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust. The work required to displace the charge and exhaust gases comes from either the crankcase or a separate blower. For scavenging, expulsion of burned gas and entry of fresh mix, two main approaches are described: Loop scavenging, and Uniflow scavenging, SAE news published in the 2010s that 'Loop Scavenging' is better under any circumstance than Uniflow Scavenging.6
Automotive industry - economy
Around the world, there were about 806 million cars and light trucks on the road in 2007, consuming over 980 billion litres (980,000,000 m3) of gasoline and diesel fuel yearly.7 The automobile is a primary mode of transportation for many developed economies. The Detroit branch of Boston Consulting Group predicts that, by 2014, one-third of world demand will be in the four BRIC markets (Brazil, Russia, India and China). Meanwhile, in the developed countries, the automotive industry has slowed down.8 It is also expected that this trend will continue, especially as the younger generations of people (in highly urbanized countries) no longer want to own a car anymore, and prefer other modes of transport.9 Other potentially powerful automotive markets are Iran and Indonesia.10 Emerging auto markets already buy more cars than established markets. According to a J.D. Power study, emerging markets accounted for 51 percent of the global light-vehicle sales in 2010. The study, performed in 2010 expected this trend to accelerate.1112 However, more recent reports (2012) confirmed the opposite; namely that the automotive industry was slowing down even in BRIC countries.8 In the United States, vehicle sales peaked in 2000, at 17.8 million units.13
How to check the car before you buy?
Used cars are much less expensive than acquiring your dream vehicle straight from the showroom. Not surprisingly, it is a very popular way to quickly obtain necessary sometimes the vehicle. What can you do to buy certainly a good car? Very often it is recommended to select a proposed us a car to the garage. The perfect solution would be that if we had a friendly workshop where our friend after a review by a special software this car could tell us a lot about him. Experienced car mechanics unhindered see if the car has already passed through some accident or has other hidden defects, which would like to avoid a potential car owner.