The Engine Control Unit (ECU), often referred to as the “brain” of a modern vehicle, is responsible for managing a multitude of functions, from engine performance and fuel efficiency to emissions control and safety systems. But when did this critical piece of automotive technology first make its debut? The answer takes us back to the late 1950s, marking the beginning of a fascinating journey of innovation that has revolutionized the way cars operate.
The Dawn of Electronic Control: Bendix Electrojector (1957)
The title of “world’s first engine control unit” is widely credited to the Electrojector system developed by the Bendix Corporation, now part of Honeywell International Inc. Introduced in 1957, this pioneering system was commercially available in the 1958 Chrysler 300D and Chrysler Imperial models. The Electrojector was a bold step towards electronic fuel injection (EFI), aiming to replace traditional mechanical fuel injection systems with a more precise and responsive electronic alternative.
At the heart of the Electrojector system was the Electronic Control Unit (ECU). This early ECU was tasked with the crucial job of managing fuel delivery to the engine. It achieved this by processing data from various sensors that monitored engine conditions. Based on these sensor inputs, the ECU would calculate and control the amount of fuel injected into the engine cylinders. This marked a significant departure from purely mechanical systems, offering the potential for improved engine performance and fuel economy.
However, the Electrojector system, while groundbreaking in concept, faced significant hurdles in its early implementation. Reliability issues plagued the system in its initial run. The technology of the late 1950s was still nascent in terms of robust and dependable electronic components for automotive applications. Despite its innovative design, the Electrojector system was ultimately discontinued after a short period due to these challenges. Nevertheless, its significance cannot be overstated. It was the crucial first step, laying the essential foundation and proving the concept for future generations of engine control units. The Electrojector demonstrated the potential of electronic control in automobiles and paved the way for the sophisticated ECUs we see in vehicles today.
Bosch D-Jetronic: Refining the ECU (1967)
The patents and knowledge gained from the Electrojector project were acquired by Bosch, a German automotive component giant. Bosch took on the challenge of refining the early ECU technology and transforming it into a reliable and commercially viable system. In 1967, Bosch introduced the D-Jetronic system. This system represented a significant leap forward in ECU technology. The “D” in D-Jetronic stands for “Druk,” the German word for pressure, highlighting its reliance on manifold pressure as a primary sensor input for fuel injection calculations.
The D-Jetronic ECU utilized analog circuitry and was a marvel of engineering for its time. It was built without microprocessors or digital logic, instead relying on approximately 25 transistors to perform all the necessary processing. This analog ECU was capable of sophisticated fuel management for its era, offering improvements in performance and emissions compared to older mechanical systems.
The Bosch D-Jetronic system found its way into a range of European luxury and performance vehicles during the late 1960s and early 1970s, showcasing its growing acceptance and capability. Notable examples include:
- Mercedes-Benz: Models like the 250E, 280, 300, 350, and 450 benefited from the D-Jetronic’s enhanced fuel control.
- Porsche: The iconic Porsche 914 also adopted the system.
- Saab: The Saab 99E was another early adopter.
- Volkswagen: Certain Type 3 and Type 4 models utilized D-Jetronic.
- Volvo: Models including the 1800E, 1800ES, 142, 144, and 164E.
- Citroën: The technologically advanced Citroën SM and DS models.
- BMW: Early versions of the BMW 3.0Si.
- Jaguar: The Jaguar XJ-S and XJ12 initially incorporated D-Jetronic.
Interestingly, the D-Jetronic system, even with later modifications incorporating a Lucas-designed timing mechanism and branding on some components, continued to be used in the Jaguar V12 engine (XJ12 and XJ-S) until 1979. This longevity speaks to the system’s effectiveness and the gradual pace of technological change in automotive electronics during that period.
Analog to Digital: L-Jetronic and LH-Jetronic
Building upon the foundation of the pressure-controlled D-Jetronic, Bosch further innovated with the L-Jetronic system. Introduced after D-Jetronic, the “L” in L-Jetronic stands for “Luft,” German for “air.” This indicated a shift towards air-flow measurement as a primary input for fuel calculations, making it an air-controlled analog engine control unit.
A significant advancement in the L-Jetronic system was the use of custom-designed integrated circuits (ICs). This integration of components led to a simpler and more reliable ECU compared to the earlier D-Jetronic, which was built using discrete transistors. ICs marked a step towards miniaturization and increased processing power within the ECU.
The evolution continued with the LH-Jetronic system, representing the birth of digital fuel injection systems. The LH-Jetronic, introduced in 1982 in Volvo 240 models destined for California (likely due to stringent emissions regulations in California), marked a pivotal transition from analog to digital control in ECUs.
LH-Jetronic systems were favored by Scandinavian car manufacturers and also found applications in sports and luxury cars produced in smaller volumes, such as the Porsche 928. Common variants included LH 2.2, utilizing an Intel 8049 (MCS-48) microcontroller with typically 4 kB of program memory, and LH 2.4, employing a Siemens 80535 microcontroller (based on the Intel 8051/MCS-51 architecture) and a significantly larger 32 kB program memory on a 27C256 chip.
These early digital ECUs, like LH-Jetronic, addressed critical pain points for car owners. They provided solutions for:
- Cold Start Management: Improved cold starting performance and reliability.
- Fuel Economy: Significant improvements in fuel efficiency through more precise fuel metering.
- Emissions Control: More controlled and reduced exhaust emissions, increasingly important for environmental regulations.
- Engine Diagnostics: Basic diagnostic capabilities to aid in troubleshooting engine issues.
- Engine Idling Speed: Stable and controlled engine idling speed.
Microcontrollers Era: 1980s and Beyond
The late 1970s and early 1980s witnessed the burgeoning influence of power electronics on automotive systems, setting the stage for the widespread adoption of microcontrollers in ECUs and other vehicle systems. In 1978, Cadillac took a step towards digital dashboards by introducing a microprocessor-controlled “trip computer” in their Seville model, powered by a custom Motorola 6802 microcontroller. Ford also entered the digital control arena with their Electronic Engine Control systems (EEC-1 & EEC-2), utilizing Toshiba’s 8-bit TLCS-12 PMOS microcontrollers.
The underlying technology driving this revolution was the emergence of metal-oxide-semiconductor (MOS) technology. Key inventions like the MOSFET (MOS field-effect transistor) at Bell Labs in 1959, the power MOSFET by Hitachi in 1969, and the single-chip microprocessor at Intel in 1971, were foundational. These advancements in semiconductor technology made it possible to create powerful, compact, and relatively affordable microcontrollers suitable for automotive environments.
The 1980s and 1990s became decades of rapid expansion for automotive electronics. Microcontrollers became increasingly integral to:
1980 to 1990:
During this decade, microcontrollers began to find more applications in vehicles, although systems were still less complex compared to today’s standards. Examples of microcontrollers used during this time include:
- Intel 8051: Despite its late 1970s introduction, the 8051 continued to be widely used in automotive applications due to its versatility.
- Motorola MC6805: Released in the early 1980s, it was employed in automotive control systems, including engine management.
- Intel 80186 and 80188: These early 1980s microprocessors found use in some automotive control and monitoring systems.
- Hitachi H8 Family: Introduced in the mid-1980s, the H8 family was used in automotive control and other embedded systems.
- Zilog Z80: While famous for personal computers, the Z80 also saw limited use in certain automotive applications during this period.
It’s important to note that microcontroller usage was still focused on specific functions like engine control and basic electronic systems. The level of integration and sophistication would dramatically increase in the following decades.
1990 to 2000:
Advancements in the 1990s led to greater microcontroller integration for diverse vehicle functions. Examples of automotive microcontrollers from this era include:
- Motorola MPC5xx Series: Introduced in the mid-1990s, the MPC5xx series (later Freescale, now NXP) became widely popular in automotive ECUs, especially for engine control.
- Intel 80C196 Family: This family found applications in automotive control systems, including engine management.
- Mitsubishi 16-bit Microcontrollers: Mitsubishi Electric’s 16-bit microcontrollers were used for automotive control and monitoring.
- Microchip PICmicro Microcontrollers: The PICmicro family, introduced in the early 1990s, was used in various embedded control systems, including automotive.
- Hitachi SH-2 and SH-3: The SuperH (SH) series found applications in automotive ECUs.
- STMicroelectronics ST10 Family: Designed for automotive applications, including engine control and body electronics.
These microcontrollers contributed to more sophisticated electronic control within vehicles, providing increased processing power for various systems.
2000 to 2010:
This period saw accelerated advancements with more powerful and specialized microcontrollers entering the automotive market:
- Freescale (NXP) MPC55xx and MPC56xx Series: Building on the MPC5xx, these were designed for automotive powertrain applications, offering enhanced performance.
- Renesas RH850 Series: Specifically designed for automotive control, including powertrain and body control.
- Infineon TriCore AURIX: Evolved to offer improved performance for safety-critical automotive applications.
- STMicroelectronics SPC5 Series: Targeted automotive applications, with features for engine management and safety systems.
- Microchip dsPIC DSCs: Digital Signal Controllers used for motor control and power management in automotive applications.
- Texas Instruments C2000 Series: With real-time control capabilities, used in automotive motor control and power electronics.
These microcontrollers enabled advanced features such as electronic stability control, adaptive cruise control, and more efficient engine management systems.
2010 to 2020:
The trend continued with even more sophisticated microcontrollers to support increasingly complex vehicle electronics:
- NXP S32K1 and S32K3 Series: Enhanced performance, security, and connectivity for automotive applications.
- Infineon AURIX 2nd Generation: Addressing growing demands for automotive safety and performance.
- Renesas R-Car Series: Including microcontrollers for infotainment and Advanced Driver Assistance Systems (ADAS).
- STMicroelectronics SPC58 Series: Addressing powertrain, body control, and safety systems.
- Texas Instruments TMS570 Series: Evolved for safety-critical real-time control applications.
- Microchip SAM V7 Series: High-performance solutions for motor control and communication interfaces.
These microcontrollers were vital for enabling autonomous driving, connected cars, and advanced safety features that became prominent in this decade.
The automotive microcontroller market reflects this growth, valued at USD 11.56 Billion in 2022 and projected to reach USD 21.64 Billion by 2030, with an 8.15% CAGR from 2023 to 2030. The increasing electrification of vehicles and the growing demand for advanced features are driving this expansion, ensuring microcontrollers will continue to be at the heart of automotive innovation.
In conclusion, the journey of the ECU from the Bendix Electrojector in 1957 to the powerful microcontrollers of today is a testament to continuous innovation in automotive technology. From managing basic fuel injection to orchestrating complex vehicle systems, the ECU has become indispensable, and its evolution mirrors the remarkable progress of the automotive industry itself.
