Upgrading To Electronic Fuel Injection: Essential Changes To Know

Electronic Fuel Injection (EFI) is a system that replaces the need for a carburetor, which mixes air and fuel. EFI injects fuel directly into an engine's manifold or cylinder using electronic controls. While EFI has been standard in the auto industry for decades, it is less common in smaller engines. The primary benefits of EFI are automatic altitude adjustments, more consistent power, and better fuel efficiency. However, the system is more costly and complex than carbureted engines, potentially leading to higher repair costs. Installation of EFI typically involves replacing the carburetor with a throttle body fuel injection system and may require additional modifications, such as the use of a high-pressure electric fuel pump.

Replacing the carburetor

The carburetor has been the primary device for supplying fuel to the combustion engine for most of its existence. However, over time, the carburetor has become more complex and harder to maintain, with some engines requiring up to five different circuits to handle all operating requirements.

Electronic Fuel Injection (EFI) is a more modern and efficient way of introducing fuel into the engine. It involves injecting fuel directly into the engine's manifold or cylinder using electronic controls. This technology has been used in the auto industry for decades and has gradually replaced carburetors.

The last carburetor-equipped car came off the assembly line in 1990, and since then, all cars sold in the United States have fuel injection systems. This shift was driven by stricter emissions requirements, which carburetors could not meet.

There are several benefits to using EFI over carburetors. EFI provides automatic altitude adjustments, more consistent power, and better fuel efficiency. It also eliminates the need for a choke, making it easier to start the engine in both hot and cold conditions. Additionally, EFI engines produce fewer emissions due to more accurate air-fuel mixtures and better fuel atomization.

However, there are also some downsides to EFI. The system is more costly than a carbureted engine, and repair costs tend to be higher due to its complexity.

Converting a carbureted engine to EFI can be challenging and expensive, but it is possible with the help of aftermarket conversion kits. One such kit is the "EZ-EFI" system by Fuel Air Spark Technology, which is designed to be relatively simple to install and does not require custom programming. This system is compatible with various engine makes, styles, and cylinder configurations. The only requirement is that the intake manifold has a standard Holley "square bore" opening.

The process of installing the EZ-EFI system involves removing the carburetor, inlet fuel lines, and mechanical fuel pump. The EZ-EFI throttle body is then mounted to the intake manifold, and the throttle and transmission linkage are reconnected. The system also includes a fuel-pressure regulator, which needs to be installed, and a high-pressure fuel line.

The control unit should be mounted in a secure location away from heat sources and connected to the battery and the throttle body using the provided wiring harness. Additionally, a wide-band oxygen sensor is required to allow the system to determine the proper air-fuel ratios while driving.

Once the physical installation is complete, you will need to input specific data about your engine into the control module, including cubic inch displacement, the number of cylinders, desired idle speed, and engine redline. After this, you can start the engine, and the computer will begin learning and making real-time adjustments to the air-fuel mixture.

Injecting fuel into the engine

The fuel injector is supplied with pressurised fuel by the fuel pump and is capable of opening and closing multiple times per second. When energised, an electromagnet moves a plunger that opens the valve, allowing the pressurised fuel to squirt out through the nozzle. The nozzle is designed to atomise the fuel, creating a fine mist that can be easily burned.

The amount of fuel supplied to the engine is controlled by the amount of time the fuel injector stays open, known as the pulse width. This is, in turn, controlled by the engine control unit (ECU) or engine control module (ECM). The ECU/ECM uses input from various sensors, such as the mass airflow sensor, oxygen sensor, throttle position sensor, coolant temperature sensor, voltage sensor, and manifold absolute pressure sensor, to determine the appropriate amount of fuel to be supplied and make real-time adjustments to the air-fuel ratio.

The fuel injectors are mounted in the intake manifold, spraying fuel directly at the intake valves. A fuel rail supplies pressurised fuel to all the injectors, ensuring a steady supply of fuel delivered at the required pressure.

By injecting fuel directly into the engine, the fuel injection system provides several benefits, including improved fuel efficiency, reduced emissions, better throttle response, and enhanced cold start-up capabilities.

Oxygen sensors

The oxygen sensor's role is to inform the ECU about the oxygen levels in the exhaust, which indicates how rich or lean the fuel mixture is. Based on this data, the ECU can make the necessary adjustments to the air-to-fuel ratio, ensuring the engine runs efficiently and meets emissions standards.

The oxygen sensor is typically placed before the catalytic converter to provide feedback on the combustion process. The sensor reads the amount of free oxygen in the exhaust and converts these levels into voltage, which is then interpreted by the ECU.

Additionally, the oxygen sensor helps the ECU maintain a specific air-to-fuel ratio, typically around 14.7:1 at part-throttle, which engineers refer to as stoichiometric or the ideal chemical balance. Deviations from this ratio can result in increased emissions and reduced engine efficiency.

The EZ-EFI system, for example, includes a wide-band oxygen sensor that works in conjunction with the ECU to fine-tune the air-fuel mixture. This sensor is required for the system to determine the proper air-fuel ratios while driving and is typically mounted just behind the exhaust header collector.

Engine control unit

The engine control unit (ECU) is the brain of the electronic fuel injection (EFI) system. It is a computer that controls all the electronic components of the engine and makes decisions about the air/fuel ratio or spark timing. The ECU uses a formula and a large number of lookup tables to determine the pulse width for given operating conditions. The ECU also adjusts the idle speed, eliminating the need for manual adjustments.

The ECU requires a voluminous stream of sensor information to make proper decisions. For a bare-minimum EFI speed-density system to operate, it needs to know the engine RPM, throttle position, engine load from intake-manifold vacuum (manifold absolute pressure or MAP), and preferably coolant temperature. Other sensors include mass airflow (MAF), knock sensors, inlet air temperature sensors, and oxygen sensors. The oxygen sensor, usually placed ahead of a catalytic converter, is the only feedback sensor that informs the ECU of what happened after the combustion process. It reads the amount of free oxygen in the exhaust, which is extremely useful for the ECU to maintain a given air/fuel ratio.

The ECU uses the information from the sensors to fine-tune fuel consumption and delivery so that the air-to-fuel ratio is just right. It increases the fuel rate as soon as the throttle valve opens to prevent hesitation when the gas pedal is first pressed. The ECU also adjusts the spark timing, ignition timing, and injector pulse width.

The ECU can be integrated with automatic transmission controls and referred to as a powertrain control module (PCM) or vehicle control module (VCM).

Fuel pump

A fuel pump is a crucial component of an electronic fuel injection system. It is responsible for supplying pressurised fuel to the fuel injectors, which then spray it into the engine. The fuel pump ensures that the fuel is delivered at the required pressure and flow rate, enabling the precise metering and delivery of fuel to the engine.

In the context of installing electronic fuel injection, one of the key changes involves upgrading the fuel pump. A high-performance, high-pressure electric fuel pump is typically required to ensure sufficient fuel supply at the necessary pressure. This is especially important when using a multi-point or multiport fuel injection system, where each cylinder has its own fuel injector. The electric fuel pump replaces the mechanical fuel pump commonly found in carbureted engines.

The electric fuel pump is designed to deliver fuel at a higher pressure, typically around 43 pounds per square inch, which is significantly higher than the pressure required for carbureted systems. This higher pressure ensures that the fuel can be atomised into a fine mist, enabling more efficient combustion. It is important to select a fuel pump that matches the fuel flow rate requirements of the injectors to ensure optimal performance and avoid issues such as fuel starvation.

Additionally, the fuel pump's location and mounting are important considerations. It should be mounted securely and as far away from heat sources as possible to prevent damage and ensure reliable operation. The fuel lines connecting the pump to the fuel tank and the injectors should also be of sufficient size and quality to handle the required fuel flow rate without restrictions.

Overall, upgrading to a high-performance electric fuel pump is a crucial aspect of installing electronic fuel injection, ensuring that the engine receives a steady supply of pressurised fuel for efficient combustion and improved performance.

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