The badge said TAG. The engine was Porsche.
How it happened
Porsche's most successful Formula 1 involvement happened without a Porsche logo on a car. Between 1983 and 1987, Porsche supplied turbocharged V6 engines to McLaren under the TAG brand. The cars were McLaren MP4/2 chassis with engines built in Weissach. TAG was Techniques d'Avant Garde, a Saudi-owned holding company that owned a controlling stake in McLaren and paid for the engine development.
Ron Dennis ran McLaren. He had taken over the team in 1981 and was rebuilding it. The Cosworth DFV engine that had dominated F1 through the 1970s was no longer competitive against the new turbocharged engines being developed by Renault, Ferrari, and BMW. McLaren needed a turbo.
Dennis approached Porsche through TAG's Mansour Ojjeh. Porsche had no Formula 1 program of its own and no commercial interest in starting one. But the company would design and build a Formula 1 engine on contract. The result was a 1.5 liter twin-turbocharged V6, designated TAG TTE PO1 internally, developed under the technical direction of Hans Mezger.
The engine
The TAG-Porsche V6 was a 90-degree configuration with twin KKK turbochargers. The first running prototype produced approximately 600 horsepower. Race trim by 1984 produced approximately 750 horsepower at 11,500 rpm. Qualifying trim produced approximately 850 horsepower with higher boost pressure.
The engine was specifically tailored to the McLaren MP4/2 chassis designed by John Barnard. Barnard wanted a compact, narrow engine that would allow him to design a tightly-packaged chassis with optimized aerodynamics. The TAG-Porsche fit that requirement. The engine was approximately 130 millimeters narrower than the contemporary Renault and Ferrari turbo V6s.
The fuel economy of the engine was also significantly better than the competition. This mattered because Formula 1 in the mid-1980s had fuel-quantity restrictions. Each car was allowed only 220 liters of fuel per race, and the most powerful turbo engines of the era struggled to complete races within that allowance. The TAG-Porsche engine consistently could.
1984
The McLaren MP4/2 with the TAG-Porsche engine launched in 1984. Niki Lauda and Alain Prost drove. They won twelve of the season's sixteen races between them. Lauda won the World Drivers' Championship by half a point over Prost. McLaren won the World Constructors' Championship.
1985 and 1986
In 1985 Alain Prost won the Drivers' Championship. McLaren won the Constructors' Championship. The car was now established as the dominant package on the grid.
In 1986 Alain Prost won the Drivers' Championship again. McLaren finished second in the Constructors' standings to Williams-Honda. The Honda turbo engine that Williams was using had begun to match the TAG-Porsche on outright performance, and the development gap between teams was narrowing.
1987
For 1987 the McLaren chassis remained competitive but the TAG-Porsche engine was no longer the class of the field. Honda had advanced. Alain Prost finished fourth in the Drivers' Championship. McLaren finished second in the Constructors'.
The contract with McLaren ended after the 1987 season. McLaren moved to Honda engines for 1988 and went on to dominate that era with Senna and Prost. Porsche moved on to Indycar (the Porsche-March-Cosworth program) and various racing efforts, but the brief Formula 1 collaboration with McLaren had ended.
Why the TAG name was used
Porsche AG did not want a Porsche-branded engine on a McLaren. The brand association of having Porsche power a competitor's championship car was awkward. Both companies had production sports cars in the market and competed for buyers in the same segment. TAG was a holding company without a competing product portfolio. Branding the engine as TAG-Porsche, with Porsche as a minority technical partner rather than the primary identity, kept the relationship cleaner.
This is why the average racing fan does not associate the 1984 to 1986 World Championships with Porsche. The car was a McLaren. The engine was a TAG. The Porsche connection was real but deliberately understated.
The legacy
The TAG-Porsche engine is considered one of the most successful Formula 1 power units of the turbo era. Three World Championships in three years is a record very few engine manufacturers ever match. The engineering work that went into the engine, particularly the fuel economy and thermal management approaches, fed directly into Porsche's parallel production engine development through the 1980s. Some of the same principles that made the TAG-Porsche V6 efficient went into the 944 Turbo and the contemporary 911 program.
The TAG-Porsche V6 chassis from the McLaren MP4/2 era now live in private collections and museums. The cars trade rarely. A 1984 Lauda Championship-winning chassis would likely bring north of $10 million if offered at auction, though none has been offered publicly in over a decade.