Front-engine, four-wheel drive layout

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Sketch of F4 layout

In automotive design, an F4, or Front-engine, Four-wheel drive layout places the internal combustion engine at the front of the vehicle and drives all four roadwheels. This layout is typically chosen for better control on many surfaces, and is an important part of rally racing as well as off-road driving.

Probably the best known user of this layout is Audi with its quattro four wheel drive system, which first appeared in the 1980 Audi Quattro road car.

This layout is also the drive train of choice for off-road pickup trucks and SUVs. It allows these vehicles to get the most traction without sacrificing precious cargo or passenger room. The center differential is often not present in these vehicles, the 4WD system is constantly splitting power between both axles when engaged.

For normal road driving, these vehicles are shifted into 2WD mode, preventing damage to the transfer case.

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