{{Short description|Automotive configuration}} {{Use dmy dates|date=October 2021}} {{More citations needed|date=October 2021}} [[File:Automotive diagrams 02C En.png|thumb|275px|F4 layout]]
In [[automotive design]], an '''F4''', or '''front-engine, four-wheel drive (4WD) layout''' places the [[internal combustion engine]] at the front of the vehicle and drives all four roadwheels. This [[car layout|layout]] is typically chosen for better control on many surfaces, and is an important part of [[rallying|rally]] racing, as well as [[off-roading|off-road]] driving. In terms of racing purposes, whether it be on-road or off-road, can be described as follows, <blockquote> A team that pursues the Weak LS4WD architecture will minimize the development cost of the [[front-wheel drive]] system at the expense of having a larger rear powertrain. The Weak architecture produces a vehicle with a large powersplit between the front and rear powertrains, while the Strong architecture recommends a vehicle with more similar power and torque requirements for the front and rear.<ref>{{cite thesis|last=Owen|first=Elliot Douglas|date=June 2018|url=https://dspace.mit.edu/bitstream/handle/1721.1/119907/1080309406-MIT.pdf|title=The Benefits of Four-Wheel Drive for a High-Performance FSAE Electric Racecar|publisher=[[Massachusetts Institute of Technology]]|oclc=1080309406|access-date=2021-10-02}}</ref> </blockquote>
Most four-wheel-drive layouts are front-engined and are derivatives of earlier [[Front-engine, rear-wheel-drive layout|front-engine, rear-wheel drive]], or [[Front-engine, front-wheel-drive layout|front-engine, front-wheel drive]] designs. The first origins of it were introduced in the 1820s from steam coach builders Burstall & Hill. This was then re-created by many other manufactures, such as "British engineer [[Bramah Joseph Diplock|Joseph Diplock]] patented a four-wheel-drive system for a traction engine, while in Vienna, Austria, [[Ferdinand Porsche]] developed an electric vehicle that also had all wheels driven, with an electric motor at each corner, as early as 1899". This layout is designed for off-road vehicles to have the most traction in strenuous situations without losing too much cargo space at the same time.<ref>{{cite magazine|url=https://www.hemmings.com/stories/article/the-origins-of-four-wheel-drive|title=The Origins of Four-Wheel Drive|magazine=[[Hemmings Motor News]]|date=December 2019|access-date=2021-05-05}}</ref> However, the 1903 [[Spyker|Spyker 60 HP]] was the first car built with an F4 drive layout.<ref>{{cite web|author=Malcolm McKay | url=http://www.classicandperformancecar.com/features/theknowledge/215358/fourwheel_drive.html |title=Four-wheel drive – The Knowledge | archive-url=https://web.archive.org/web/20090503012638/http://www.classicandperformancecar.com/features/theknowledge/215358/fourwheel_drive.html | archive-date=2009-05-03 | url-status=dead |publisher=Octane magazine | date=March 2008 |access-date=2009-05-24}}</ref>
This layout is also the drive train of choice for off-road [[pickup truck]]s and [[SUVs]]. It allows these vehicles to get the most traction without sacrificing cargo or passenger room. Part-time four-wheel drive vehicles frequently have a [[transfer case]] and no center [[Differential (mechanical device)|differential]], meaning, in many cases, the 4WD mode does not allow any difference in front and rear axle speeds. For normal road driving, these vehicles are shifted into [[Two-wheel drive|2WD]] mode, to prevent damage to the transfer case. Full-time four-wheel drive systems, on the other hand, cannot do without some kind of center differential.<ref>{{Cite web |first= |date=2023-02-16 |title=How 4WD, FWD, RWD and AWD all Work? |url=https://www.cardecent.com/meaning-of-4wd-fwd-rwd-awd/ |url-status= |access-date=2023-04-01 |website=Car Decent}}</ref> The purpose of four-wheel drive is to maintain optimal traction when manually selected. A vehicle has four-wheel drive when the front and rear driveshafts can be locked together to move at the same speed and send the same amount of torque to all four wheels.<ref>{{cite web|last=Markovich|first=Tony|date=2020-07-17|title=AWD vs. 4WD: Know the Differences|url=https://www.thedrive.com/cars-101/34829/awd-vs-4wd|website=The Drive|access-date=2021-05-05}}</ref>
Several four-wheel-drive vehicles have been built without a [[drive shaft]] between the front combustion engine and rear wheels; instead the rear wheels receive power and torque from a rear [[electric motor]]. This setup has been mainly used by [[hybrid electric vehicles]], although some conventional vehicles had also adopted the system.<ref>{{Cite web |date=2020-08-26 |title=Which Hybrids Have All-Wheel Drive? |url=https://www.autotrader.ca/editorial/20200826/which-hybrids-have-all-wheel-drive/ |access-date=2022-04-23 |website=AutoTrader.ca |language=en}}</ref>
==Examples== <gallery mode="packed"> File:Willys Jeep 1943.jpg|1943 [[Willys MB|Willys Jeep]] File:troller (uncropped).jpg|A [[Troller T4]] jeep File:2nd Jeep Liberty -- 08-16-2010.jpg|2008–2009 [[Jeep Liberty]] File:1993 Jeep Grand Cherokee Laredo - Blackberry with Crimson interior 17.jpg|Center transfer case sending power from the transmission to the rear axle (right) and front axle (left) File:Hmmwv-036.jpg|The [[HMMWV]] is a 4WD/AWD that powers all wheels evenly (continuously) via a manually lockable center differential, with [[Torsen]] differentials for both front and rear. File:Berlin Bicentennial Parade (7359013180).jpg|First-generation [[Dodge Power Wagon]] File:Land Rover Series 1 HT (cropped).jpg|[[Land Rover Series I]] File:Nissan Skyline GT-R R34 V Spec II.jpg|[[Nissan Skyline GT-R]] V Spec II (BNR34) File:2017-04-24 Mitsubishi Lancer Evolution X MR SST 17 (cropped).jpg|[[Mitsubishi Lancer Evolution X]] MR File:Subaru WRX STI - Blue (cropped).jpg|[[Subaru WRX]] STI File:Ferrari FF Newport Beach (8387695594).jpg|[[Ferrari FF]]; with a front mid-engine, four-wheel-drive layout File:Terenure, Co. Dublin - Ireland (6017584315).jpg|[[Audi Quattro]] File:GT-FOUR ST205.jpg|[[Toyota Celica GT-Four]] (ST205) </gallery>
==References== {{Reflist}}
{{Automobile layouts}}
[[Category:Four-wheel drive layout]]