A gas turbine inserted in the exhaust stream can be used to turn a compressor, which supercharges the engine by pumping more air into it. And the more air and fuel an engine ingests, the more power it produces.
Like so many things automotive, turbocharging has a long history. In 1905 Alfred Buchi, a Swiss engineer, patented an exhaust-driven supercharger for use on a diesel engine. Buchi planned to use pressure as high as 30 pounds per square inch (psi), a very high pressure even today.
As 1920 approached, research on turbocharging was under way in the United States to try maintaining sea-level performance in aircraft engines in the thinner air of high altitudes. Dr. Sanford Moss of the General Electric Co. spearheaded this work, eventually becoming known as the "Father of Turbocharging."
In 1918 Moss fitted a GE turbo to a Vl2 Liberty aircraft engine and tested it at Pikes Peak, an altitude of 4267 metres (14,000 feet). At this altitude it developed 230 horsepower in naturally aspirated form. With the turbo installed its power jumped to 356, a dramatic demonstration of the effectiveness of turbocharging.
Turbocharging gradually gained acceptance in aircraft -- the turbocharged 1937 Boeing B-17 "Flying Fortress" bomber was a landmark -- and really flowered during the Second World War. It wasn’t until 1962, however, that they found their way onto production passenger cars.
Oldsmobile pioneered the use of turbochargers in production cars with the introduction of the 1962 F-85 Jetfire Sport Coupe in April of that year. It beat Chevrolet’s turbocharged Corvair Monza Spyder to market by about a month. The F-85 had been introduced as a trim and attractive compact Oldsmobile in 1961, powered by an overhead valve, 3.5-litre aluminum V8 that developed 155 horsepower. For 1962 an optional 185-horsepower version of the same engine was offered, although still naturally aspirated.
But the real news for 1962 was the addition of an even hotter version, the turbocharged "Turbo-Rocket" engine, which brought the horsepower up to 215.
The engineers had done their homework in an attempt to make the turbo installation durable and trouble-free. To counteract detonation, or pinging, with the high 10.25:1 compression ratio, a fluid-injection system was fitted.
1963 Jetfire Coupe: Oldsmobile pioneered the use of turbochargers.
This device, commonly known as water injection, uses a mixture
of half water and half methyl alcohol carried in an underhood reservoir.
The fluid was injected into the intake manifold when maximum power was
called for, and the rate of use varied with the heaviness of the driver’s
foot. Under easy driving one might get up to 3,600km (2000 miles) out of
a quart; a hot rodder could use it all in 360 km (2,00 miles).
The internal components of the engine, such as pistons and bearings
were beefed up to withstand the higher operating pressures due to turbocharging.
A larger radiator was also fitted.
In the further interest of engine durability, maximum turbo boost
pressure was limited to a conservative five psi.
The Jetfire proved much quicker than the normally aspirated models.
The zero to 6o mph (96km-h) acceleration time dropped from 10.9 seconds
in the 185-horsepower model (it was 14.0 for the 155 horsepower) to a very
respectable 8.5, as reported by Car Life magazine’s testers. The Jetfire’s
zero to 8o mph (130 km-h) time was improved to 16.4 seconds from the 185’s
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 three
mph higher --107 mph (171 km-h) compared with 104 mph (166 km-h).
Alas, GM’s brave experiment didn’t last long. In an era of cheap
and plentiful gasoline, there wasn’t much incentive for powerplant innovation.
More power was easier and less expensive to obtain with a bigger, thirstier
engine. And if there is one thing Detroit really knew, it was how to turn
out millions of huge V8s.
Oldsmobile offered the turbo engine for just two model years,
producing a total of 9,607 of them. Chevrolet would carry on with its turbo
until 1966, by which time its air-cooled flat-six was developing 180 horsepower
from 2.7 litres (164 cu in.).
Turbocharging then disappeared from the automobile scene until
1975 when Porsche introduced it on its evergreen 911 sports car. Saab followed
in 1977 with its turbocharged Saab 99.
Although their popularity has waned somewhat since, they are still
in use, particularly on diesel engines for which they are especially well
suited.