Editing Cosworth (section)

===The DFV (Double Four Valve)===
{{main|Cosworth DFV}}
[[File:Lotus 49-2.JPG|thumb|280px|A Ford-Cosworth DFV installed in the back of a [[Lotus 49]]]]
In 1966, [[Colin Chapman]] ([[Lotus Cars]] founder and principal of [[Team Lotus]]) persuaded Ford to bankroll Keith Duckworth's design for a new lightweight {{convert|3000|cc|1|lk=on|adj=on}} [[Formula One]] engine.<ref name=Cosworth.com/> Cosworth received the order along with the £100,000 that Ford felt it adequate to spend on such an objective. The contract stipulated that a four-cylinder Ford-based F2 engine would be developed as proof of concept (see the [[#FVA|FVA]] above) and that a pure Cosworth V8 would be built based on this.

The DFV design used a similar [[cylinder head]] to the one Duckworth had prototyped on the four-cylinder FVB unit on a custom Cosworth [[cylinder block]] and [[crankcase]], forming a single 90° [[V8 engine]], thus creating a legend in its own right, the '''DFV''' – meaning "[[Cosworth DFV|'''D'''ouble '''F'''our '''V'''alve]]". This engine and its derivatives were used for a quarter of a century, and it was the most successful in the history of [[Formula One]] / [[Grand Prix motor racing]]. Winning 167 races in a career lasting over 20 years, it was the product that put Cosworth Engineering on the map. Although originally designed for Formula One, the engine has been modified to be used in a range of categories.

The DFV won on its first outing, at the [[1967 Dutch Grand Prix]] in the hands of [[Jim Clark]], fitted to a [[Lotus 49]], and from 1968 was available for purchase to any F1 team that wished it. During the 1970s, it was common for almost the entire field (with the notable exception of [[Ferrari 312B|Ferrari]], [[BRM]] and [[Alfa Romeo in Formula One#Naturally aspirated engines (1960s and 1970s)|Alfa Romeo]] scoring wins and titles with V12 engines) to use one of these engines – this at a time when independent wealthy individuals could buy exactly the same engine off the shelf that was also being used by [[McLaren]] et al. Most teams just built a tub around a Cosworth DFV and a [[Hewland]] [[transmission (mechanics)|gearbox]]. It won a record 155 World Championship races, the last being [[Detroit Grand Prix|Detroit in 1983]], powering a [[Tyrrell Racing|Tyrrell]] driven by [[Michele Alboreto]].

Although the DFV (bore: {{convert|3.373|in|2}}, stroke: {{convert|2.555|in|2}}, displacement: {{convert|2992.98|cc|1|lk=on|abbr=on}}) with {{convert|410|bhp|kW PS|0|lk=in|abbr=on}} at 9,000&nbsp;rpm did not produce as much power as some of its rival 12-cylinder engines, it was lighter, resulting in a better [[power to weight]] ratio. In addition to being lighter, it was also made a structural part of the car itself, by placing load bearing arms to stress the block. These design aspects appealed tremendously to the genius of Colin Chapman who used them to the fullest extent.

The '''DFY''', introduced in 1982 was a further evolution of the DFV for Formula One, with a shorter stroke and a DFL bore (bore: {{convert|3.543|in|2}}, stroke: {{convert|2.316|in|2}}, displacement {{convert|2993.38|cc|1|abbr=on}}) with {{convert|520|bhp|kW PS|0|abbr=on}} at 11,000&nbsp;rpm, thereby producing more power, but still unable to fight against the turbocharged cars of the day. It was the advent of [[turbocharger|turbocharged]] engines in Formula One which sounded the death knell for the venerable DFV, and in 1986 Cosworth returned to the lower formulae preparing the DFV for the newly created [[Formula 3000]], with the installation of a compulsory 9,000&nbsp;rpm rev limiter, which scaled power back from 500 to {{convert|420|bhp|kW PS|0|abbr=on}}; the DFV remained in this class until 1992 and the DFY until 1995. By this time the Cosworth '''AC''' V8 replaced the DFV/Y in F3000 and was the dominant engine in the class until it became a spec-series in 1996 using a Zytek-Judd V8. The final F3000 engines gave {{convert|500|bhp|kW PS|0|abbr=on}}, almost equalling the 1983 DFV which gave {{convert|510|bhp|kW PS|0|abbr=on}} at 11,200&nbsp;rpm.

In Formula One, a new DFV-based design was introduced for the new {{convert|3500|cc|1|abbr=on}} normally aspirated rules in 1987. The '''DFZ''' was produced as an interim model, but in 1988 Cosworth created the DFV's final evolution, the '''DFR''', which soldiered on in F1 with smaller teams until 1991, scoring its last points – including a pair of second places by [[Jean Alesi]] – with [[Tyrrell Racing|Tyrrell]] in 1990.

The DFV has recently been given a new lease of life as a result of interest in Classic F1 racing, which was given a World Championship status by the FIA in 2004.

{{anchor|DFX}}{{anchor|DFS}}{{anchor|DFL}}

====DFV variants====
The DFV spawned a number of derivations. In 1968; Cosworth created the DFV's first derivation, a {{convert|2500|cc|1|lk=on}} version for the [[Tasman Series]], the '''DFW'''. DFV to DFW conversion simply involved substitution of a short-stroke crank and longer connecting rods.

[[File:Cosworth DFX engine.jpg|thumb|left|200px|Cosworth DFX]]
[[File:CosworthDFSV8engine.JPG|thumb|right|200px|Cosworth DFS]]
One of the most successful and longest-lived projects of Cosworth has been its [[Champ Car|CART]] / [[Champ Car]] engine programme. In 1975; Cosworth developed the '''DFX''', by destroking the engine to {{convert|2650|cc|1|abbr=on}} and adding a [[turbocharger]], the DFX became the standard engine to run in [[United States Automobile Club|IndyCar]] racing, ending the reign of the [[Offenhauser]], and maintaining that position until the late 1980s. Ford backed Cosworth with creating a new interim design for IndyCar racing in the late 1980s, the '''DFS''', which merged DFR technology into the ageing DFX design, but it was eventually rendered obsolete by advancing technology.

While designed as an F1 engine, the DFV was also used as in endurance racing, although its flat-plane crank design led to destructive vibrations putting stress on devices surrounding the engine, especially the exhaust system. The first sports car to use a DFV, the [[Ford P68]], failed to finish a single race because of repeated mechanical and electrical failures. Despite this handicap the DFV won the [[24 Hours of Le Mans]] twice in its original 3.0 Litre form for Mirage in 1975 and Rondeau in 1980, who were able to attain sufficient reliability by de-tuning the motor.

The '''DFL''' for endurance racing was developed for the 1982 season to replace the DFV. It came in two versions: one with {{convert|3298|cc|1|abbr=on}} and the other with {{convert|3955|cc|1|abbr=on}}. While neither competed well in the [[Group C]] (C1 Class) the former was adapted to the C2 Class (700&nbsp;kg minimum weight, 55 Litres fuel, 5 refuelings/1000&nbsp;km) starting in 1984. During the latter half of the 1980s it was the most popular motor for that class, with successful championship campaigns and five class wins at the 24 Hours of Le Mans. The latter version's severe lack of reliability caused it to fall out of use by 1985.

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