Katerina Swanson
In 1957, Chevrolet became the first manufacturer to release a Rochester fuel-injection unit as an option for its full-size passenger cars and the two-seater Corvette. The Rochester fuel injection system was developed by the Rochester Products Division of General Motors and was first offered as a high-performance option on the Corvette and GM passenger cars in 1957. The Ramjet system, available on Chevy passenger cars from 1957 through 1959, was a continuous-flow port-injection system based on purely mechanical principles. Chevrolet continued to use fuel injection in its Corvette models until 1965, when it was discontinued in favour of the Chevrolet Big Block as a performance option.
| Characteristics | Values |
|---|---|
| Year of first Chevy fuel injection | 1957 |
| First Chevy model with fuel injection | 1957 Chevrolet Corvette Super Sport |
| Chevy fuel injection horsepower | 283 hp |
| Chevy fuel injection torque | 283 cu. in. V8 |
| Chevy fuel injection system | Rochester Ramjet |
| Chevy fuel injection type | Continuous-flow port-injection |
| Chevy fuel injection availability | 1957-1965 |
| Chevy fuel injection engineers | John Dolza, E.A. Kehoe, Donald Stoltman, Zora Arkus-Duntov |
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What You'll Learn
The Rochester Ramjet
The Ramjet is a continuous-flow port-injection system that is based on purely mechanical principles. It relies on vacuum and pressure signals to measure airflow and meter fuel. The two main sub-assemblies of the system are the air meter and the fuel meter. The air meter measures airflow into the engine and manages thermostatic warmup enrichment, fuel shutoff on overrun, and idle settings. The measurements are then sent via pressure and vacuum signals to the fuel meter, which contains the high-pressure fuel pump and controls the delivery of fuel to the injector nozzles.
The Ramjet system allowed a significant increase in engine performance, but its innovative design had several issues that affected reliability and tuning. For example, the system had problems with cold-start fuel enrichment, and the cranking signal valve was a source of reliability issues. The complicated nature of the system and the difficulty in troubleshooting and repairing it contributed to its demise.
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Corvette and passenger cars
In 1957, Chevrolet became the first manufacturer to release a Rochester fuel-injection unit as an option for its passenger cars and the two-seater Corvette. The Rochester Ramjet was an automotive fuel injection system developed by the Rochester Products Division of General Motors (GM). It was first offered as a high-performance option on the Corvette and GM passenger cars in 1957. The system was available on Chevy passenger cars from 1957 to 1959, and on Corvettes from 1957 to 1965.
The Ramjet system was based on purely mechanical principles, unlike later fuel injection systems that used electronics. It consisted of two main sub-assemblies: the air meter and the fuel meter. The air meter measures airflow into the engine and manages thermostatic warmup enrichment, fuel shutoff on overrun, and idle settings. These measurements are then sent via pressure and vacuum signals to the fuel meter, which contains the high-pressure fuel pump and controls the delivery of fuel to the injector nozzles.
The 1957 Chevrolet Corvette Super Sport was the first to feature high-performance Ramjet fuel injection. This system offered increased power and accelerator response, faster cold starts, smoother engine warm-ups, the elimination of carburetor icing, and better overall fuel economy. The continuous-flow injection system was initially chosen for its simplicity, and it allowed a significant increase in engine performance. However, the Ramjet system had some inherent issues that affected reliability and tuning, such as problems with the cold-start fuel enrichment.
In the late 1980s, GM began using MAF sensors in their Corvette production models, which provided a better reading of how much air was entering the engine and, in turn, how much fuel should be mixed with it. In the 1990s, they continued to make changes to their fuel injection systems, such as using different types of injectors and adjusting the injector sizes.
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Continuous-flow port-injection
The Rochester Ramjet is a continuous-flow port-injection system that was available on Chevy passenger cars from 1957 through 1959. Unlike later fuel injection systems that used electronics, the Ramjet is based purely on mechanical principles. It was developed by the Rochester Products Division of General Motors and was initially offered as a high-performance option on the Corvette and GM passenger cars in 1957. The system was discontinued in 1965 in favour of the Chevrolet Big Block as a performance option.
The Ramjet system consists of three main components: the intake manifold/plenum (also known as the "dog house"), the fuel meter, and the air meter. The intake manifold/plenum is the largest and most visible component, with two pieces: a base plate that doubles as a valley cover and injector nozzles, and the actual plenum. The plenum distributes air to the cylinders and serves as a mount for the fuel and air meter. The fuel meter contains a large fuel reservoir with a conventional float, needle and seat, and a positive displacement high-pressure pump. The air meter measures airflow into the engine and manages thermostatic warm-up enrichment, fuel shutoff on overrun, and idle settings. These measurements are sent via pressure and vacuum signals to the fuel meter, which then controls the delivery of fuel to the injector nozzles.
The continuous-flow system permits the use of a rotary vane pump, which does not require timing to the engine. The fuel pump is a positive-displacement, rotary-vane type with a splined shaft for connection to the accessory drive system of the engine. The system includes a spring-loaded, diaphragm-type relief valve, with the diaphragm chamber vented to atmospheric pressure. Fuel enters at the swirl well of the vapor separator, where the swirling motion separates the vapor from the liquid fuel. The vapor is drawn from the top centre of the swirl well and directed into the vapor return line, which carries it back to the fuel tank.
The Bendix inline stem-type regulator injection system (RSA) is another example of a continuous-flow system. It measures engine air consumption and uses airflow forces to control fuel flow to the engine. The fuel distribution system to the individual cylinders is achieved through the use of a fuel flow divider and air bleed nozzles. A fuel metering section is also included, and some fuel injectors are equipped with an automatic mixture control unit. The airflow consumption of the engine is measured by sensing impact pressure and venturi throat pressure in the throttle body.
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Mechanical vs electronic systems
The Rochester Ramjet, an automotive fuel injection system, was first introduced to the Corvette and other Chevy passenger cars in 1957. This mechanical system, developed by the Rochester Products Division of General Motors, was based on vacuum and pressure signals to measure airflow and meter fuel. It was discontinued in 1965 in favour of the Chevrolet Big Block as a performance option.
Mechanical fuel injection systems, such as the Rochester Ramjet, rely on mechanical principles and linkages to control fuel delivery. They offer a direct approach, with a rotary or inline pump providing individual fuel bursts for each cylinder. While mechanical systems can provide sufficient performance for constant speed or electric power applications, they have limitations in matching engine power delivery to application requirements. Tuning a mechanical injection system can be laborious, and it may only optimise the cruise condition.
On the other hand, electronic control systems offer greater flexibility and accuracy in fuel injection. They utilise an electronic control unit (ECU) to monitor engine speed and load through various sensors. This allows for the alteration of fuel injection rates to deliver the right power as needed. Electronic systems enable multiple fuel injections into the cylinders during the compression cycle, building up fuel vapour to efficiently control engine speed and power output.
Electronic systems provide stable operation across different power levels and simplify the trimming of individual cylinders. They are particularly beneficial for machines requiring a faster engine response to the applied load, such as excavators, loaders, and forklift trucks. Additionally, electronic control systems are often necessary to meet emissions standards, as they ensure the accurate control and reduction of combustion by-products.
While electronic systems offer advantages in terms of flexibility, accuracy, and emissions control, mechanical systems have their advantages in certain applications. Mechanical systems are suitable for light loaders and static equipment with a constant load on the engine, such as screeders, crushers, and electric power generation.
In summary, the choice between mechanical and electronic systems depends on the specific requirements of the machine and its intended use. Electronic systems excel in situations demanding variable engine responses, emissions compliance, and efficient power management. In contrast, mechanical systems suffice for applications with constant speed or load requirements, offering a more direct and mechanically linked approach to fuel injection.
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1957: The year of fuel injection
The 1957 Chevrolet Corvette Super Sport was a game-changer for the automotive industry. It was the first to feature high-performance Ramjet fuel injection, developed by a team of engineers led by John Dolza and manufactured by GM's Rochester carburetor division. This system offered increased power and accelerator response, faster cold starts, smoother engine warm-ups, improved fuel economy, and the elimination of carburetor icing. With a combination of high performance and efficiency, the 1957 Corvette became the quickest production car in the world, out-accelerating the Mercedes 300SL.
The "Ram Jet" Rochester mechanical continuous-port injection system was designed by a team of GM engineers, led by Zora Arkus-Duntov and Ed Cole, who had been working on the project since 1955. The biggest advantage of fuel injection was its ability to distribute the fuel-air mixture equally to all cylinders, resulting in a smooth and instantaneous response. This was a significant improvement over traditional intake manifolds, which could vary by up to 15% between cylinders due to the length of the runners.
The 1957 Corvette's fuel injection system consisted of three main components: the intake manifold/plenum, the fuel meter, and the air meter. The intake manifold/plenum was the largest and most visible component, with the fuel meter and air meter mounted to the right side. The fuel meter contained a large fuel reservoir with a conventional float, needle, seat, and a positive displacement high-pressure pump. The pump was driven by a flex cable attached to the distributor, running at half engine speed and varying pressures depending on engine rpm.
Despite its impressive performance and technological advancements, the Rochester FI system was considered too expensive for its time, with a cost-benefit ratio that was unattractive to most buyers. Additionally, in April 1957, Bill France, Sr. banned fuel injection from NASCAR, further reducing the incentive to develop and market fuel injection systems for passenger cars. However, the 1957 Corvette and its fuel injection technology remain a significant milestone in automotive history, showcasing the potential of fuel injection and paving the way for future advancements.
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Frequently asked questions
Chevy started using fuel injectors in 1957 with the Chevrolet Corvette Super Sport.
The first Chevy to use fuel injectors was the 1957 Chevrolet Corvette Super Sport.
The 1957 Chevrolet Corvette Super Sport used the Rochester Ramjet fuel injection system.
The Rochester Ramjet fuel injection system is a continuous-flow port-injection system that relies on vacuum and pressure signals to measure airflow and meter fuel.
