turbo

­In this article, we'll learn how a turbocharger increas­es the power output of an engine while surviving extreme operating conditions. We'll also learn how wastegates, ceramic turbine blades and ball bearings help turbochargers do their job even better. Turbochargers are a type of forced induction system. They compress the air flowing into the engine (see How Car Engines Work for a description of airflow in a normal engine). The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the charging. This can significantly improve the power-to-weight ratio for the engine (see How Horsepower Works for details).

­In order to achieve this boost, the turbocharger uses the exhaust flow from the engine to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 rotations per minute (rpm) -- that's about 30 times faster than most car engines can go. And since it is hooked up to the exhaust, the temperatures in the turbine are also very high.

The Basics
One of the surest ways to get more power out of an engine is to increase the amount of air and fuel that it can burn. One way to do this is to add cylinders or make the current cylinders bigger. Sometimes these changes may not be feasible -- a turbo can be a simpler, more compact way to add power, especially for an aftermarket accessory.

Where the turbocharger is located in the car.

Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.

One cause of the inefficiency comes from the fact that the power to spin the turbine is not free. Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back-pressure. This subtracts a little bit of power from the cylinders that are firing at the same time.

engine

In a piston engine, the same volume of space (the cylinder) alternately does four different jobs -- intake, compression, combustion and exhaust. A rotary engine does these sam­e four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next.

The rotary engine (originally conceived and developed by Dr. Felix Wankel) is sometimes called a Wankel engine, or Wankel rotary engine.

The Tang Dynasty was an imperial dynasty of China that lasted from 618 to 907. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire. The Tang Dynasty, with its capital at Chang'an, the most populous city in the world at the time, is regarded by historians as a high point in Chinese civilization—equal to or surpassing that of the earlier Han Dynasty—as well as a golden age of cosmopolitan culture. In Chinese history, the Tang Dynasty was largely a period of progress and stability, except during the An Shi Rebellion and the decline of central authority in the latter half of the dynasty. Like the previous Sui Dynasty, the Tang Dynasty maintained a civil service system by drafting officials through standardized examinations and recommendations to office. Two of China's most famous historical poets, Du Fu and Li Bai, belonged to this age, as well as the poets Meng Haoran, Du Mu, and Bai Juyi. Many famous visual artists lived during this era, such as the renowned painters Han Gan, Zhang Xuan, and Zhou Fang. There was a rich variety of historical literature compiled by scholars, as well as encyclopedias and books on geography. There were many notable innovations during the dynasty, including the development of woodblock printing, the escapement mechanism in horology, the government compilations of materia medicas, and improvements in cartography.

exam tips

It's bar exam season and new law grads across the country are gearing up for the most rigorous test of their lives. Here are a few tips to help you ace this all-important exam.

1. Establish a study plan. Establish a study strategy by outlining what you will study over the next month. While you don’t need to follow your plan to the letter, it can help guide your study efforts. Allocate 2-3 hours a day to practicing multi-state questions and the rest of your day to outlining the law and completing practice essays.
2. Create study sheets. To aid in memorizing black letter law, photocopy or retype your bar review outline, leaving the points of law blank. Create several copies and fill in the blanks. Putting pen to paper instead of repeating the material to yourself or a friend may aid in memorization and give you a better sense of how well you've mastered the material.
3. Schedule down time. Take time off from studying to relax and recharge. You don’t want to burn out in the last weeks before the exam.

An early 20th-century sail wagon, used in the sport of land sailing, in Brooklyn, New York. Land sailing is the act of moving across land in a wheeled vehicle powered by wind through the use of a sail. Although land yachts have existed since Ancient Egypt, the modern sport was born in Belgium in 1898.