2007 Porsche 911 - Review

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Enlarge PhotoThe basic structure of the familiar six-cylinder boxer engine remains virtually unchanged with the powerplant of the previous 996. Instead, most of the changes involve the adoption of the variable turbine geometry (VTG) turbochargers whose internal vanes directly modify the passage of exhaust gases to vary the amount of air flow through the turbo depending on the level of revs coming from the engine. In effect, this makes the engine much more responsive lower in the rev range and provides good power delivery right through till the ends of the tachometer. The VTG technology has already been proven a success with diesel powered cars, but in the case of the petrol powered six-cylinder 997 Turbo there were fears that the main turbo unit wouldn’t be able to withstand exhaust temps in excess of 1,000°C (modern turbodiesel exhaust temps are around 700-800°C). The problem was solved by employing special heat resistant material and the use of new methods of simulation that allowed engineers to design and test turbo components before mass production. In addition, the conventional method of using oil to draw heat from the turbo has been added to the engine’s water cooling system. Maximum power is 480hp at 6,000rpm with torque of 620Nm coming on from just 1,950rpm.

Even more power is available for models equipped with the optional Sports Chrono Package. Pressing the Sport button on the center console makes several adjustments to the engine management and suspension settings, providing more response thanks to Porsche’s new Overboost function. With the throttle floored, the blades of the VTG turbo are angled so that they increase boost pressure by 2.9psi for up to 10 seconds, increasing peak torque to an earth moving 680Nm. When accelerating from 80 to 120km/h in fifth gear, our recorded times fell from 3.8 seconds to 3.5 seconds with Overboost switched on.

Porsche also offers VarioCam Plus valve-lift technology for its entire 911 range, a valve-timing system that optimizes engine breathing and refinement, while reducing fuel consumption and exhaust emissions. During low load situations valve-lift is limited to just 3.6mm, reducing friction and resulting in a 10% improvement for emissions and fuel consumption over the 996 mill. At the other end of the scale, when power is demanded, valve-lift is increased to a maximum of 11mm, which ensures efficient air flow and minimal losses.

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