1962-1963 Oldsmobile F-85 Jetfire

1962-1963 Oldsmobile F-85 Jetfire Engine Development

The 1962 Oldsmobile F-85 Jetfire's sidedraft single-barrel carburetor and turbo body were tucked neatly under a hood trimmed by twin windsplits.
The 1962 Oldsmobile F-85 Jetfire's sidedraft single-barrel carburetor and turbo body were tucked neatly under a hood trimmed by twin windsplits.

A team of Oldsmobile engineers under Gilbert Burrell, the division's chief engine designer, worked with Garrett AiResearch on the 1962 Oldsmobile F-85 Jetfire's turbocharger development.

"A turbo-supercharger unit . . . could have been designed that would have resulted in much higher high-speed power output, but this would not have given the tremendous torque increase in the road-speed or normal driving range," Burrell told Road & Track in 1962. "We wanted a hot-performing street job, not a high-speed race car."

Oldsmobile engineers decided on a small-diameter turbo unit to keep weight down and also speed up response. They also chose to employ an integral waste-gate, an idea borrowed from aircraft turbos, to drain off some of the exhaust gases and limit the amount of boost. Unless a limit was designed into the system, the turbocharger might run dangerously fast.

They determined that the turbo would be restricted to a boost of five pounds per square inch (psi). At five psi above atmospheric pressure, a waste-gate relief valve caused a portion of the exhaust gases to bypass the turbine wheel, which governed impeller speed and the amount of air being pumped.

Despite their inherent efficiency (compared to a supercharger), turbochargers had a couple of drawbacks. First, they were subject to intense heat from the exhaust gases that drove their impellers. Turbocharged engines were also prone to detonation (pinging), due to carbon buildup that resulted -- especially when using certain grades of fuel.

To help prevent pinging, Chevrolet lowered the compression of its turbo-charged Corvair. Oldsmobile took a different path, keeping the compression at 10.25:1 but employing an innovative fluid-injection system. Kept in an under-hood reservoir, "Turbo-Rocket Fluid" was an equal-parts mix of distilled water and methyl alcohol, along with a bit of rust inhibitor.

Whenever the driver tromped the gas pedal, this tank was pressurized, causing a small amount of fluid to be injected into the air-fuel mix just before it reached the intake-side impeller. As the fluid evaporated, it absorbed heat from the intake air, holding down combustion-chamber temperatures and preventing detonation.

Depending on the driver's pattern, according to historian Vance, the full reservoir could last anywhere from 200 to 2000 miles. Should the fluid run low, an indicator light inside the car would flash a warning. If it ran out, a throttle-body valve closed to prevent full-power acceleration.

That was one of several safety features that ironically caused the turbo-charged engine to be deemed troublesome. There were others. The wastegate itself, for instance, had twin diaphragms. If those failed, the fluid-reservoir cap would pop off as a final measure to prevent an overboost situation.

The Jetfire's Garrett TO-3 turbocharger sat crossways atop the engine, with a special single-throat, side-draft Rochester carburetor on the left and the exhaust system on the right. The entire installation added about 36 pounds to engine weight. The placement of the turbocharger did not impede access to spark plugs or the distributor.

To cope with the extra horsepower, the Jetfire V-8 had special pistons and heavier-duty main bearing caps, along with heavy-duty aluminum alloy for bearing inserts and what Oldsmobile called a "performance-tailored" fuel pump and connecting rods. Intake valves were aluminum-coated, and the distributor and coil worked at higher voltage. A bigger radiator was installed, too.

Read more about the Jetfire's features by continuing to the next section.

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