Porsche Variable Turbine Geometry (VTG)

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The 911 Turbo has always been synonymous with performance. Now the car is more capable than ever thanks to a new twin turbo system featuring Variable Turbine Geometry (VTG).

porsche variable turbine geometry vtg

On a conventional turbocharger, the exhaust flow drives a turbine that is connected to a compressor in the air intake tract. By ‘squeezing’ the incoming air, the amount of oxygen in a given volume is increased. Since compression also causes an increase in temperature, the air must be passed through an ‘intercooler’ unit. With more oxygen present in each cylinder charge, more fuel can be burned yielding greater energy. Since higher exhaust pressures generate corresponding loads on the intake side, the intake pressure must be carefully controlled in order to protect the engine. On the new 911 Turbo, the boost pressure is limited using wastegate valves that bypass excess pressure around the twin exhaust turbines.

Another important factor is the size of the turbo unit. Since a smaller turbine has a lower mass, it generally responds more quickly to increasing pressure, spinning up easily to its optimum speed. The key disadvantage of using a smaller turbo is that the back-pressure generated at higher engine speeds causes a significant reduction in performance. Resistance is caused by the smaller cross-sectional area through which the exhaust is required to flow. Larger turbo units, which create lower back-pressure at higher rpm, take considerably longer to spin up under power due to the large cross-sectional area and relative inertia of the heavier turbine. Generally, this type of turbo will only be effective in the medium rpm range. This phenomenon, known as ‘turbo lag’, means there is virtually no turbocharging effect at lower engine speeds. To overcome this problem, the twin water-cooled turbochargers on the 911 Turbo feature Variable Turbine Geometry (VTG). With this technology, the gas-flow from the engine is channelled onto the turbines via electronically adjustable guide vanes. By changing the vane angle, the system can replicate the geometry in all types of turbo, large or small.

With Variable Turbine Geometry (VTG), it is possible to achieve higher turbine speeds, and thus higher boost pressure, at lower engine rpm. Cylinder charging is significantly improved, with a corresponding increase in both power and torque. Maximum torque is reached at lower rpm and is retained across a wider rev range. A full 460 lb.-ft. is available from as low as 1,950 rpm up to 5,000 rpm. Every throttle input is met with exceptional response and phenomenal acceleration. When the boost pressure reaches its maximum value, the guide vanes are opened further. By varying the vane angle, it is possible to achieve the required boost pressure over the entire engine speed range. As a result, there is no need for excess-pressure valves as found on conventional turbocharged engines.

Matching the superlative performance of the car is the efficiency with which it is generated. In spite of the increase in power and torque, the 911 Turbo offers a further reduction in fuel consumption.

(source: Porsche)

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Porsche Paisley   by Parkoffka.
Porsche 904 Carrera GTS Coupe : 1964   designed by Ferdinand Alexander Porsche.
Porsche 356 Coupe : 1951   50 produced between 1949 and 1951.
Porsche 911/997 Turbo : 2008   
Porsche 928 : 1987   
Porsche 997 911 Targa 4S : 2007   Eleven series continues to grow.
Porsche Boxster RS 60 Spyder : 2008   Limited Edition of 1960.
Porsche Boxster S : 2005   
Porsche Carrera GT (targa) : 2004   612 Horses. You can go on if you want to
Porsche 928 (Panamera) : 2006   2012 Porsche 928.
Porsche Boxster : 2010   
Porsche 959 : 1987   113 were delivered in 1987 and another 179 in 1988.
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Lohner Porsche : 1899   300 of the Lohner-Porsche chassis were sold until 1906.
Porsche's 100,000 997 911   
Porsche 911/993 Carrera S Coupe : 1997   Only 3,714 produced in 1997.
Porsche 356 Nr.1 Roadster : 1948   
Porsche Boxster S : 2007   More horses.
Porsche Cayman S : 2006   
Porsche Design Edition1 Cayman S : 2008   Exclusive all-black special edition. Only 777 available.
Porsche 911/997 Targa : 2009   
Porsche 901 : 1964   82 built.
Porsche releases info & photos of 2009 911 models   New Generation 911s Combine Increased Performance with Better Fuel Efficiency
Porsche Cayenne GTS : 2008   Ultimate handling Cayenne.
Porsche Cayenne S Transsyberia : 2010   Tribute to the three-time rally winner.
Porsche Gives First Official Peek of New Panamera   
Porsche number 1   Pebble Beach Concours d'Elegance to Display The First Porsche Sports Car
Porsche Reports U.S. Sales for August 2008   
Porsche : First Place for the Fourth Time in a row   J.D. Power Quality Study
Porsche : Engine of the Year   Strong and Innovative.
Porsche Boosts Brand Value   
Magna Steyr to Help Make Mid-Engine Porsches after 2012   
Porsche Boxster S Design Edition 2 : 2008   500 units will be produced worldwide.
Porsche Increases its VW Stake to 35.14 Per Cent   
Porsche Boxster/Cayman facelift leaked   
Porsche October 2008 sales   A decrease of 50%.
Porsche Panamera Gran Turismo : 2010   Worldwide Debut in Spring 2009.
Porsche Boxster S : 2009   Introduced at the 2008 Los Angeles Motor Show.
Porsche 911 Carrera RS 2.7 : 1972   Voted the "Dream Car of the Year".
Porsche 911 GT3 : 2010   Launched at the Geneva Motor Show on March 3, 2009.
Porsche Cayenne GTS Design Edition 3 : 2010   Fewer than 100 units in the United States.
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