Turbo vision: a revolution in engine construction

Incredibly successful in Le Mans

Porsche was incredibly successful with the 917 in Le Mans and in the World Championship for Makes in 1970 and 1971. However, the governing body’s decision to only accept engines with a maximum displacement of three liters meant Porsche could not compete in the following season with the 4.5-liter engine. Hence the switch to the Canadian-American Challenge Cup. It was a paradise for the engineers as there were virtually no limits for their imagination and engineering expertise. Some of the competitors were competing in 800 PS, 8.0‑liter V8 engines, so Porsche needed an alternative to the tried-and-true 4.5‑liter V12 naturally aspirated engine in the 917. Experiments with a significantly heavier V16 power unit came to nothing because the handling wasn’t good enough. The solution was perhaps a turbo engine, but nobody at Porsche had any practical experience in this field. This technology was not even new – the first patent was filed in 1905. In the 1960s and 1970s, turbochargers were used in truck diesel engines, occasionally in automobile models for the road, and in oval track racing. The technology was not yet fully developed.

Valentin Schäffer, Helmut Flegl, Peter Falk, Günther Gutekunst, Gerhard Küchle, 917 LH, Le Mans, 1970, Porsche AG

The turbocharger principle is easy to explain

The turbocharger principle is easy to explain: the combusted air-fuel mix flows from the cylinder into the exhaust system, powering a turbine on its way. This is connected to a compressor wheel on the inlet side by a shaft. This pushes fresh air into the engine’s combustion chamber under pressure, allowing for more efficient combustion. Following the encounter in Teloché, the responsible engine developer Hans Mezger (1929–2020), Valentin Schäffer, and other engineers formed what would now be called a think tank. The 4.5-liter naturally aspirated engine in the 917 was to be fitted with two exhaust gas turbochargers to deliver up to 735 kW (1,000 PS). The team delivered some pioneering work – thereby creating the basis for the subsequent use of the turbo engine in series production. Confidentiality was a top priority.