The Story Of Fuel Injection
Audio Brief
Show transcript
This episode details the historical evolution of engine fuel delivery, from early carburetion and mechanical systems to modern electronic injection and Gasoline Direct Injection, highlighting key technological shifts and regulatory impacts.
There are four key takeaways from this discussion. First, technological evolution is problem driven, with each major fuel system innovation arising to solve specific challenges related to fuel type, performance, or emissions. Second, pioneering innovations often lay the conceptual groundwork for future success, even if they fail commercially. Third, the transition from mechanical and analog systems to software driven digital control was the key enabler for modern engine performance, efficiency, and emissions compliance. Finally, modern Gasoline Direct Injection systems maximize efficiency by enabling sophisticated combustion strategies, only possible through high pressure direct injection and precise digital management.
Early carburetion prepared fuel for combustion, but faced limitations with less volatile fuels. Mechanical injection addressed these needs, especially for diesel. The subsequent shift to electronic fuel injection was driven by performance demands and stricter government emissions regulations, which acted as a major catalyst for innovation.
The Bendix Electrojector, introduced in 1957, was the first electronic fuel injection system. Despite its commercial failure due to unreliability, it established the foundational concept of electronic fuel delivery. This paved the way for successful systems like Bosch’s later analog and digital ECUs.
The progression from hardwired analog ECUs to microprocessor driven digital ECUs revolutionized engine management. Digital systems convert sensor data to digital values, determining ideal injector cycles entirely through flexible software. This software driven approach enabled comprehensive engine control, improving performance, efficiency, and emissions compliance.
Gasoline Direct Injection represents the state of the art, injecting fuel at very high pressure directly into the combustion chamber. This enables advanced combustion modes such as stratified charging. Stratified charge allows for air fuel mixtures as high as 80:1, achieving unmatched fuel efficiency at low to medium engine loads, which is impossible with port injection.
These advancements underscore a continuous drive for greater precision, efficiency, and environmental performance in engine technology.
Episode Overview
- Traces the evolution of engine fuel delivery, starting with the basic principles of carburetion and progressing through early mechanical injection systems.
- Highlights the pivotal transition from mechanical to electronic fuel injection (EFI), beginning with the Bendix Electrojector and Bosch's subsequent analog systems.
- Explains how government emissions regulations became a major catalyst for innovation, leading to the development of closed-loop feedback and digital engine management.
- Compares key technologies and control strategies, such as speed-density versus air-flow metering and analog versus digital electronic control units (ECUs).
- Details the principles and advantages of modern Gasoline Direct Injection (GDI), including its ability to achieve ultra-lean combustion for improved efficiency.
Key Concepts
- Fuel Preparation: The essential process of preparing liquid fuel for combustion through three stages: metering (matching fuel to oxygen), atomization (creating fine droplets), and vaporization (turning it into a gas).
- Carburetion: The earliest method of fuel preparation, using a Venturi to meter and vaporize fuel, which was eventually superseded due to its limitations with less volatile fuels.
- Mechanical Fuel Injection: A category of "airless" injection systems, primarily developed for diesel engines, including jerk pumps, rotary pumps, unit injectors, and the foundational common rail system.
- Electronic Fuel Injection (EFI): The revolution in fuel delivery, enabled by the transistor, which uses electronic sensors and solenoid injectors for precise control. It began with the Bendix Electrojector and was refined by systems like Bosch's D-Jetronic and L-Jetronic.
- Air Mass Measurement Methods: Two primary strategies for determining the amount of air entering an engine: the speed-density method (calculating based on pressure, temperature, and RPM) and air flow metering (directly measuring air volume or mass).
- Analog vs. Digital Control: The technological progression from early analog ECUs with hardwired logic to modern digital ECUs that use microprocessors and flexible software "maps" for comprehensive engine management.
- Gasoline Direct Injection (GDI): The current state-of-the-art technology that injects fuel at very high pressure directly into the combustion chamber, enabling advanced modes like stratified charging for efficiency and homogeneous charging for power.
Quotes
- At 0:01 - "In the internal combustion engine, a tank full of liquid fuel is directly unusable." - This quote establishes the core problem that all fuel systems are designed to solve: preparing liquid fuel for efficient combustion.
- At 16:06 - "...led to the introduction of the first electronic fuel injection system, the Bendix Electrojector, in 1957." - This marks the pivotal moment when electronics were first applied to control fuel delivery in automobiles, setting the stage for all modern EFI systems.
- At 19:07 - "It was so unreliable that Chrysler had even offered to replace it with carburetors at no charge." - This quote powerfully illustrates the commercial failure of the Bendix Electrojector, highlighting that groundbreaking technology can fail if it's not ready for real-world application.
- At 27:27 - "Digital ECUs do not directly tie the various engine sensors to the injector control signal, but rather convert them to a digital value and indirectly determine the ideal injector duty cycle... completely in software." - This explains the fundamental shift from fixed hardware-based control in analog systems to the flexible, software-driven logic of modern engine management.
- At 33:26 - "[Stratified charge allows] overall air-fuel mixtures as high as 80:1, allowing for unmatched fuel efficiency at low- to medium-engine loads." - This highlights the primary advantage of GDI's stratified charge mode, achieving ultra-lean combustion that is impossible with port injection.
Takeaways
- Technological evolution is problem-driven, with each major fuel system innovation—from carburetors to GDI—arising to solve specific challenges related to fuel type, performance, or emissions.
- Pioneering innovations often lay the conceptual groundwork for future success even if they fail commercially, as seen with the Bendix Electrojector paving the way for Bosch's reliable EFI systems.
- The transition from mechanical/analog systems to software-driven digital control was the key enabler for modern engine performance, efficiency, and emissions compliance.
- Modern GDI systems maximize efficiency by enabling sophisticated combustion strategies, like stratified charging, that are only possible through the combination of high-pressure direct injection and precise digital management.
