Longitudinal engine

In automotive engineering, a longitudinal engine, also sometimes known as a north-south engine, is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back.

Most rear wheel drive vehicles use this engine orientation, while most modern front wheel drive vehicles use a side-to-side transverse arrangement. An exception is most Audi vehicles (those using platforms designed to accommodate the Torsen-based quattro four wheel drive system) which continue to use the longitudinal layout, and Saab until the Saab 9000.

Position placement of longitudinal engines

Engines may be placed in three main positions within the motor car:
* front engine - where the engine is mounted under the bonnet/hood, over the front axle (sometimes ahead of the front axle),
* rear engine - where the engine is mounted where the boot/trunk would normally be, either over, or to the rear of the rear axle,
* mid engine - where the engine is mounted between the front and rear axles, usually where the rear seats would be sited.

Common types longitudinally placed engines

This is a list of typical examples of types of engines which can be placed in motor vehicles:
* in-line or straight engine - where two, three, four, five, six, and even eight cylinders are placed in a single plane,
* V engine - where two, four, six, eight, ten, twelve, or even sixteen cylinders are placed in two separate planes, looking like a "V" when viewed from the end of the crankshaft,
* flat or boxer engine - where two, four, six or more cylinders are arranged in two diametrically horizontally opposed planes,
* W engine - where two (narrow angle) vee engines are siamesed together (within 180°), where at eight, twelve or sixteen cylinders are arranged in four separate planes,
* H engine - where two vee engines are siamesed together (greater than 180°), where at eight, twelve or sixteen cylinders are arranged in four separate planes,