Taken from here:
http://motortorque.askaprice.com/review ... n-z350.asp
At the heart of the 350Z lies a remarkable engine: the award-winning 3.5-litre V6 from Nissan´s ´VQ´ family. Voted one of the world´s best engines for a record 11 years in a row by influential American journal Ward´s Auto World magazine, the VQ engine is acclaimed across the world for its abundant power and smooth delivery.
But Nissan is not a company to rest on its laurels: the all-alloy, 24-valve twin cam unit, which was extensively redesigned for its role in the 350Z, has been further enhanced for the latest Z-car.
As befits a pure sports car, the changes target performance by enhancing the unit´s free-revving ability. First seen in the limited edition 35th Anniversary edition, launched earlier this year, the engine revisions raise power from 280PS to 300PS and move the rev limit from 6,600 rpm to a heady 7,000 rpm. Peak power is now developed at 6,400 rpm, some 200 rpm higher than previously.
The improvements have been achieved by traditional methods. In other words, the changes have been implemented not by simply ´chipping´ the engine´s electronic brain but by careful re-engineering of a number of key components.
With the aim of raising the rev limit and boosting power, the major changes allow the engine to breath more freely thanks to a redesigned intake duct. Along with new pistons and a revised camshaft profile, the intake manifold has also been shortened and widened. The timing chain and oil pump have been redesigned and electronic exhaust valve timing control has been adopted.
A number of other components have been lightened and stiffened to reduce internal friction and to enable them to withstand higher engine speeds. As well as raising power output and rev limits, the engine is now fully compliant with Euro IV emission regulations.
The changes have brought about a slight reduction in peak torque, which has fallen from 363Nm to 353Nm at 4,800 rpm. However the revised torque curve is far flatter than before and provides greater torque reserves at higher rpm. Torque delivery in the original 350Z fell off comparatively steeply once that 4,800 rpm peak had been reached. In the latest evolution the torque curve remains more linear as engine speeds rise: at 6,000 rpm, for example, the new engine delivers a full 20 Nm more torque than its predecessor could achieve.
What the changes mean in practice is simple: sharper acceleration through the gears. With the rev limit raised to 7,000 rpm, for example, maximum speed in third gear increases from 142 km/h to 150 km/h (88 mph to 93 mph). The benchmark 0-100 km/h (0-62 mph) figure has been cut from 5.9 seconds to 5.8 seconds (6.4 to 6.3 for the Roadster).