The VK engine is a V8 piston engine from Nissan. It is an aluminum DOHC 4-valve design.

The VK56 engine was originally based on Nissan's VQ

Nissan VQ engine

The VQ is a V6 piston engine produced by Nissan with displacements varying from 2.0 L to 4.0 L. It is an aluminum block DOHC 4-valve design with aluminum heads. It is fitted with Nissan's EGI/ECCS sequential multi-point fuel injection system...

V6 rather than the VH

Nissan VH engine

The VH series consists of 4.1 and 4.5 liter engines built from 1989-2001 by the Nissan Motor Corporation. The design consists of a 90 degree V8 with an aluminum cylinder block that features a closed upper deck and a deep skirt. The cylinder heads are also aluminum with a DOHC 4-valve design and...

V8 used in previous Q45

Infiniti Q45

The Infiniti Q45 was a full-size luxury car sold by Nissan's Infiniti marque from 1990 until 2006. It is a rear wheel drive, four-door sedan powered by a V8 engine. Early generations were based on the automaker's Japanese-market flagship sedan, the Nissan President, while models produced after 1997...

/Cima

Nissan Cima

The Nissan Cima is a large luxury sedan produced by Nissan Motor Co., Ltd. for the Japanese market. The car's name is derived from Spanish for "summit". The hood ornament uses an image of an acanthus leaf. The acanthus leaf was commonly used by classical Greeks to make a wreath for use as a...

 models. Changes include: a variable polymer intake manifold, newly designed heads, and a larger drive by wire throttle chamber. The intake manifold directs air through different paths at different engine speeds to boost low-end torque or unleash high-end horsepower.
The 4.5 L (4494 cc) VK45DE was introduced in 2002 and is built in Yokohama

Yokohama

is the capital city of Kanagawa Prefecture and the second largest city in Japan by population after Tokyo and most populous municipality of Japan. It lies on Tokyo Bay, south of Tokyo, in the Kantō region of the main island of Honshu...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.