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Open Loop VS Closed Loop

lambda open loop example

Open Loop VS Closed Loop

Open-loop and closed-loop are two different modes of operation for engine control systems, particularly fuel injection systems. They describe how the engine control unit (ECU) adjusts fuel delivery based on feedback from sensors.

Open-vs-closed-loop lambda

Open Loop

  1. Principle: In open-loop operation, the ECU determines fuel delivery based solely on pre-programmed fuel maps or tables. These maps are configured by the manufacturer or tuner and provide a fixed relationship between engine parameters (such as engine speed and load) and the amount of fuel injected.
  2. No Feedback: Open-loop systems do not rely on feedback from sensors to adjust fuel delivery. Instead, they use predetermined fuel maps that are designed to provide adequate fueling under typical operating conditions.
  3. Simplicity: Open-loop operation is relatively simple and requires minimal sensor inputs. The ECU does not need to continuously monitor exhaust gases or other parameters to adjust fuel delivery, which can reduce system complexity and cost.
  4. Limitations: Open-loop systems may not provide optimal fueling under all operating conditions. They are less able to compensate for changes in engine load, fuel quality, or environmental factors such as altitude or temperature variations.
  5. Performance Tuning: Open-loop systems are commonly used in performance tuning applications, where fuel maps can be customized to optimize engine performance and power output under specific conditions.

You can often find open loop and closed loop maps inside our TunerPro XDF definitions and inside our WinOLS OLSX mappacks.

Here below an example of Honda Civic 1.5L VTEC Turbo 182CV (L15B engine):

example of closed and open loop with tunerpro

In the context of engine control systems, “open-loop” refers to a mode of operation where the engine control unit (ECU) determines fuel delivery based solely on pre-programmed values or maps without relying on feedback from sensors to adjust fueling in real-time. Here are some key characteristics and features of open-loop operation:

  1. Pre-Programmed Fuel Maps: Open-loop systems use predefined fuel maps or tables that establish the relationship between engine parameters (such as engine speed, load, and temperature) and the corresponding amount of fuel to be injected into the engine cylinders.
  2. No Sensor Feedback: Unlike closed-loop systems, which continuously monitor sensor inputs such as exhaust gas oxygen concentration (O2 sensor) or air-fuel ratio (lambda sensor), open-loop systems do not rely on feedback from sensors to adjust fuel delivery. Instead, fueling is determined solely by the values stored in the fuel maps.
  3. Simplicity: Open-loop operation is relatively simple and straightforward, requiring minimal sensor inputs and processing. The ECU does not need to continuously monitor sensor data or adjust fueling in real-time, which can reduce system complexity and cost.
  4. Limited Adaptability: Because open-loop systems do not adjust fuel delivery based on real-time sensor feedback, they may be less adaptable to changes in operating conditions such as variations in fuel quality, altitude, temperature, or engine wear. This can result in less precise fueling and potentially suboptimal engine performance under certain conditions.
  5. Performance Tuning: Open-loop systems are commonly used in performance tuning applications, where fuel maps can be customized or optimized to achieve specific performance objectives such as maximizing power output or improving throttle response. Tuners can adjust fueling parameters based on dyno testing or empirical data to optimize engine performance under different operating conditions.
  6. Emissions Control: While open-loop systems may provide adequate fueling for performance-oriented applications, they may not be as effective in controlling emissions compared to closed-loop systems. Without real-time sensor feedback to adjust fuel delivery, open-loop systems may struggle to maintain optimal air-fuel ratios for emissions control, potentially leading to higher levels of pollutants in the exhaust gases.

Overall, open-loop operation provides a simple and effective means of fuel delivery control, particularly in performance tuning applications where precise fueling is critical for maximizing engine performance. However, open-loop systems may have limitations in terms of adaptability and emissions control compared to closed-loop systems, which adjust fuel delivery based on real-time sensor feedback.

lambda open loop example

Closed Loop

  1. Principle: In closed-loop operation, the ECU adjusts fuel delivery based on feedback from sensors that measure engine parameters such as exhaust gas oxygen concentration (O2 sensor), engine speed, throttle position, and coolant temperature.
  2. Feedback Control: Closed-loop systems continuously monitor sensor inputs and adjust fuel delivery in real-time to maintain a target air-fuel ratio (typically stoichiometric, around 14.7:1 for gasoline engines) or lambda value. The ECU compares the measured air-fuel ratio to the desired target and makes adjustments to the fuel injector pulse width accordingly.
  3. Adaptability: Closed-loop systems are more adaptable to changes in operating conditions compared to open-loop systems. They can compensate for variations in fuel quality, altitude, temperature, and engine wear, providing more consistent and reliable fueling across a wide range of conditions.
  4. Emissions Control: Closed-loop operation is essential for meeting emissions regulations, as it allows the ECU to optimize fueling to minimize harmful emissions such as hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx).
  5. Fuel Efficiency: Closed-loop systems can also contribute to improved fuel efficiency by maintaining the optimal air-fuel ratio for combustion. By continuously adjusting fuel delivery based on sensor feedback, the ECU can achieve more efficient fuel combustion and reduce fuel consumption.

In the context of engine control systems, “closed-loop” refers to a mode of operation where the engine control unit (ECU) continuously monitors feedback from sensors and adjusts fuel delivery in real-time to maintain a target air-fuel ratio or other desired parameters. Here are some key characteristics and features of closed-loop operation:

  1. Sensor Feedback: Closed-loop systems rely on feedback from sensors to monitor engine parameters such as exhaust gas oxygen concentration (O2 sensor), engine speed, throttle position, coolant temperature, and intake air temperature. These sensors provide real-time data to the ECU, allowing it to adjust fuel delivery accordingly.
  2. Real-Time Adjustments: Based on the feedback from sensors, the ECU adjusts fuel delivery in real-time to maintain a target air-fuel ratio or lambda value (the ratio of air to fuel in the combustion mixture). The ECU compares the measured air-fuel ratio to the desired target and makes adjustments to the fuel injector pulse width to achieve the target ratio.
  3. Adaptability: Closed-loop systems are highly adaptable to changes in operating conditions such as variations in fuel quality, altitude, temperature, and engine load. By continuously monitoring sensor data and adjusting fuel delivery accordingly, closed-loop systems can maintain optimal engine performance and emissions control across a wide range of conditions.
  4. Emissions Control: Closed-loop operation is essential for meeting emissions regulations, as it allows the ECU to optimize fueling to minimize harmful emissions such as hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). By maintaining the correct air-fuel ratio for combustion, closed-loop systems can reduce emissions and improve air quality.
  5. Fuel Efficiency: Closed-loop systems can also contribute to improved fuel efficiency by optimizing fuel delivery for efficient combustion. By maintaining the optimal air-fuel ratio, the ECU ensures that fuel is burned efficiently, minimizing fuel consumption and maximizing fuel economy.
  6. Diagnostic Capabilities: Closed-loop systems offer diagnostic capabilities that allow the ECU to detect and diagnose engine problems in real-time. For example, if the O2 sensor detects a lean or rich air-fuel mixture, the ECU can trigger a diagnostic trouble code (DTC) and illuminate a warning light on the instrument panel to alert the driver to a potential issue.

Overall, closed-loop operation provides precise control over fuel delivery and engine performance by continuously monitoring sensor feedback and adjusting fueling in real-time. This method of operation offers adaptability, emissions control, fuel efficiency, and diagnostic capabilities, making it the standard for modern engine control systems.

In summary, open-loop operation relies on predetermined fuel maps without sensor feedback, while closed-loop operation adjusts fuel delivery in real-time based on feedback from sensors. Closed-loop systems offer greater adaptability, emissions control, and fuel efficiency compared to open-loop systems, making them the standard for modern engine control systems.

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