The DFV (Double Four Valve) was originally designed by Cosworth in 1967 for Formula One, funded by Ford. A turbocharged Indy car variant was first developed privately by the Vels Parnelli Jones team for the 1976 USAC IndyCar season, against the initial objections of Cosworth founder Keith Duckworth. The Parnelli-Cosworth took its first victory at the 1976 Pocono 500 driven by Al Unser, followed by two further wins that season.
Cosworth moved quickly to control the program themselves, poaching two key engineers from the Parnelli team and establishing facilities in Torrance, California, to develop and market the engine. The unit was formally named the DFX — a turbocharged Indy car variant of the DFV architecture. Henceforth it became the standard power unit for top American open-wheel competition.
The DFX replicated in American racing what the DFV had achieved in Formula One: total domination with a package that was competitive, reliable, and widely available to customer teams. The engine won the Indianapolis 500 in ten consecutive years from 1978 through 1987, a record of sustained dominance at a single event that has never been surpassed. Winners during that stretch included Al Unser (1978), Rick Mears (1979, 1984), Johnny Rutherford (1980), Bobby Unser (1981), Gordon Johncock (1982), Tom Sneva (1983), Danny Sullivan (1985), Bobby Rahal (1986), and Al Unser again (1987).
In CART competition the DFX was similarly dominant. CART championships from 1979 through 1987 were won by DFX-powered drivers, with the exception of one season. Notable champions included Rick Mears (1979, 1981, 1982), Johnny Rutherford (1980), Al Unser (1983, 1985), Mario Andretti (1984), and Bobby Rahal (1986, 1987). The engine powered 81 consecutive Indy car victories between 1981 and 1986, and accumulated 153 total victories during its competitive life. By the time it was replaced, the DFX was developing over 840 horsepower.
For a period in the early 1980s some DFX engines were badged as Fords, giving the engine the Ford-Cosworth designation by which it was widely known during that era. The Ford branding reflected the historical relationship between Ford and Cosworth from the original DFV program.
In 1986 General Motors financed Ilmor Engineering to build a rival to the DFX, resulting in the Ilmor-Chevrolet Indy V8. Ford responded by commissioning Cosworth to redesign the DFX, incorporating improvements from the Formula One DFR. The updated engine, introduced in 1989 as the DFS (for short stroke), was fielded by Kraco Racing with Bobby Rahal and Dick Simon Racing with Arie Luyendyk. Rahal won one race at the Meadowlands in 1989, but the program did not achieve the dominance of the DFX era. The Kraco team subsequently switched to Chevrolet, and by 1992 the Ford Cosworth XB replaced the DFS with limited success.
The DFX's record in American open-wheel racing represents one of the most complete periods of engine dominance in motorsport history. Its ten consecutive Indianapolis 500 victories between 1978 and 1987 remain unmatched. The engine's success was built on the same engineering foundation that had won twelve Formula One drivers' championships — the DFV architecture designed by Keith Duckworth — adapted for the methanol fuel, high-boost turbocharging, and oval-circuit requirements of American championship racing. Its displacement by the Ilmor-Chevrolet program from the mid-1980s onward marked the end of an era in which a single engine family had shaped the competitive landscape of top-level American open-wheel racing for more than a decade.