Oldsmobile F-85 Jetfire Turbo
Turbocharging has a seductive allure for engineers because it recovers “free” energy just by inserting a gas turbine into an engine’s exhaust stream. This spins a compressor, or supercharger, which pumps more air into the engine than it breathes normally. And more air and fuel in means more power out. Turbocharging history dates back in the early twentieth century to 1905 when Swiss engineer Alfred Buchi patented an exhaustdriven supercharger for a diesel engine using pressures as high as 2.1 bar (30 pounds per square inch (psi), 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.’s Sanford Moss who became known as the “Father of Turbocharging.” In 1918 Dr. Moss tested a Liberty V-12 aircraft engine at Pikes Peak, 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’s effectiveness. Turbocharging gradually gained acceptance in aircraft – the 1937 turbocharged Boeing B-17 “Flying Fortress” bomber being a landmark - and flowered during the Second World War. It was also used in heavy duty 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’t until 1962 that they first appeared on production passenger cars. In April, 1962 Oldsmobile scooped the industry by pioneering passenger car turbocharging with the 1962 F-85 Jetfire Sport Coupe. Based on the Olds Cutlass, the Jetfire beat sister division Chevrolet’s 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 an optional 185-horsepower version of the same engine was offered. But the much bigger news for 1962 was the even hotter version, the turbocharged “Turbo-Rocket” engine which brought horsepower up to 215, the then vaunted one horsepower per cubic inch. Engineers did their homework to make the turbo installation durable and troublefree. To counteract detonation, or pinging, with the high 10.25:1 compression ratio they fitted fluid injection. This device commonly known as water injection introduced “Turbo Rocket Fluid,” a mixture of half water and half methyl alcohol into the intake manifold to keep things cool when high boost was demanded. The fluid was carried in a reservoir and consumption varied with the heaviness of the driver’s foot. Driven moderately a litre may give up to 3,200 km (2,000 mi.), but a hot rodder could use it all in 360 km (200 mi). Internal engine components including pistons and bearings were strengthened to withstand turbocharging’s higher internal operating pressures. A larger radiator was fitted to dissipate, the extra engine heat, and to further protect engine durability the 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 (60 mph) 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 (80 mph) time improved to 16.4 seconds from the 185’s 20.2. The Jetfire was engineered more for midrange passing and hill climbing performance than for high speed. Thus its top speed was only 5 km/h (3 mph) higher at 172 km/h (107 mph). This was because further engine durability was assured by reducing boost to four psi above 121 km/h (75 mph). Alas GM’s brave futuristic experiment soon faded. In an era of cheap North American gasoline there wasn’t 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 aircooled 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 and is standard on diesels. Some gasoline engines have two turbochargers, and the rare one, four.