Turbocharging has a seductive allure for engineers because it recovers 鈥渇ree鈥� energy that is otherwise lost. A gas turbine inserted into an engine鈥檚 exhaust stream will spin a compressor, or supercharger, which pumps more air into the engine than it would breathe normally. And more air and fuel in means more power out.
Turbocharging history dates back in the early 20th century to 1905, when Swiss engineer Alfred Buchi patented an exhaust-driven supercharger for diesel engines using pressures as high as 2.1 bar (30 pounds per square inch), considered high even today.
As the 1920s approached, turbocharging research was under way in the United States in a quest to maintain sea-level performance in aircraft engines at high altitudes. The work was spearheaded by General Electric Co.鈥檚 Sanford Moss, who would become known as the 鈥淔ather of Turbocharging.鈥�
In 1918 Dr. Moss tested a Liberty V-12 aircraft engine at Pikes Peak, Colorado at an altitude of 4,267 m (14,000 ft). Naturally aspirated, it developed 230 horsepower; with a GE turbocharger fitted power jumped to 356, a dramatic demonstration of turbocharging鈥檚 effectiveness.
Turbocharging gradually gained acceptance in aircraft 鈥� the 1937 turbocharged Boeing B-17 鈥淔lying Fortress鈥� bomber being a landmark 鈥� and flowered during the Second World War.
It was also used in heavy-duty industrial engines, and by the 1950s turbos were becoming popular on line-haul diesel trucks. Turbos were used in a few automobile racing engines, but it wasn鈥檛 until the 1960s that they first appeared on production cars.
In April 1962, Oldsmobile scooped the industry by pioneering passenger鈥攃ar turbocharging on the 1962 F-85 Jetfire Sport Coupe. Based on the Olds Cutlass, the Jetfire beat sister division Chevrolet鈥檚 turbocharged Corvair Monza Spyder to market by about a month.
The F-85 had been introduced in 1961 as a trim, attractive compact Oldsmobile powered by an overhead valve, 3.5-litre (215 cu in.) 155-horsepower aluminum V-8. For 1962, a 185-horsepower version of this engine was available.
But the much bigger news for 1962 was an even hotter version, the turbocharged Jetfire 鈥淭urbo-Rocket鈥� engine that brought horsepower up to 215, the then-vaunted one horsepower per cubic inch.
Engineers did their homework to make the turbo installation durable and trouble-free. To counteract pre-ignition with the high 10.25:1 compression ratio they used fluid injection, commonly known as water injection. It introduced 鈥淭urbo Rocket Fluid鈥� 鈥� a mixture of half water and half methyl alcohol 鈥� into the intake manifold to keep things cool under higher boost conditions.
The fluid was carried in a reservoir, and consumption varied with the heaviness of the driver鈥檚 foot. Driven moderately, a litre might give up to 3,200 kilometres, but a hot rodder could use it all in 360 km.
Internal engine components including pistons and bearings were strengthened to withstand turbocharging鈥檚 higher internal operating pressures. A larger radiator was fitted to dissipate the extra engine heat. To further protect engine durability, maximum turbo boost pressure was limited to a conservative 0.34 bar (5.0 psi).
The Jetfire proved much quicker than normally aspirated models. Car Life (5/62) reported that zero to 97 km/h acceleration dropped from 10.9 seconds in the 185 horsepower model (it was 14.0 for the 155 horsepower) to a very respectable 8.5. Zero to 129 km/h time improved to 16.4 seconds from the 185鈥檚 20.2.
The Jetfire was engineered more for mid-range passing and hill-climbing performance than for high speed. Thus its top speed was only 5 km/h higher at 172 km/h. This was because further engine durability was assured by reducing boost to four psi above 121 km/h.
Alas, GM鈥檚 brave futuristic experiment soon faded. In an era of cheap gasoline, there wasn鈥檛 much real incentive for powerplant innovation. More power was easier and less expensive to obtain with a larger, thirstier engine, and Detroit loved V-8s.
Oldsmobile offered turbocharging for just two model years, producing a somewhat disappointing total of 9,607 F-85s. Chevrolet carried it on until 1966, by which time its air-cooled flat-six Corvair was developing 180 horsepower from 2.7 litres (164 cu in.).
Turbocharging then disappeared from the automobile scene until 1975, when Porsche revived it on the evergreen 911 sports car. Saab followed in 1977 with its turbocharged Saab 99.
General Motors got back into turbos in 1978, this time to address fuel-economy concerns. To retain eight-cylinder performance with six-cylinder economy, Buick turbocharged its 3800 V-6 and called it the Grand National. Performance enthusiasts loved it.
Now when even higher fuel-economy standards require smaller but still powerful engines, turbocharging is offered by virtually all car manufacturers. It is the engineers鈥� saviour again, just as the catalytic converter and electronics were in the 1970s and 80s.
