Fuel Injection Vs Carburetor: Is It Worth The Switch?

There are several reasons why you might want to consider changing your fuel injection to a carburetor. Carburetors are simpler and easier to adjust, and they're a good choice for classic cars or occasional-use vehicles. However, fuel injection offers improved fuel efficiency, increased power, better throttle response, and reduced emissions. It also provides improved horsepower and torque due to more efficient air/fuel mixing and the precise timing of fuel delivery. Additionally, fuel-injected engines are generally easier to start, especially in cold conditions. For these reasons, fuel injection can be a worthwhile investment for daily drivers, performance vehicles, or situations where fuel efficiency and emissions are significant concerns.

Fuel injectors: Choose the right type and size for your engine

Fuel injectors are an essential component of a fuel injection system, and choosing the right type and size for your engine is crucial. Here are some factors to consider when making your decision:

Type of Fuel Injector

The two main types of fuel injectors are throttle body injection (TBI) and multi-port fuel injection (MPFI). TBI is a simpler and more cost-effective option as it serves as a carburetor replacement, and you won't need to change your intake manifold. However, MPFI offers better fuel distribution and engine performance. It involves injecting fuel above the intake valve of each port, resulting in more efficient fuel delivery.

Engine Needs and Performance Goals

Consider the specific needs and performance goals of your engine. Factors such as horsepower, fuel type, and engine modifications play a significant role in choosing the right fuel injectors. Determine your horsepower goal and fuel type (e.g., gasoline, ethanol, or race gases) to select the appropriate injector size and flow rate.

Fuel Injector Size

The size of the fuel injectors is critical. Bigger injectors do not always translate to more power. If your engine cannot handle the extra fuel, it may lead to flooding and damage. On the other hand, if your engine modifications require more fuel, ensure your injectors can deliver enough to avoid a lean condition, which can cause sluggish performance or piston damage.

Fuel System Requirements

Fuel injection systems operate at higher pressures than carbureted systems. Ensure your fuel system can meet these requirements by installing a high-pressure fuel pump and a fuel pressure regulator. Additionally, consider the fuel lines, rails, and the return line from the engine back to the fuel tank.

Electronic Control Unit (ECU)

Fuel injection systems require an ECU to adjust fuel delivery and ignition timing precisely. Choose an ECU that can manage these functions and ensure you have the necessary sensors, such as throttle position, air intake temperature, and oxygen level sensors.

Wiring Harness

You will need a wiring harness designed for a fuel injection system to connect the ECU to the fuel injectors, sensors, and other electronic components. Ensure the wiring is done correctly to avoid issues.

Tuning and Maintenance

After installation, proper tuning is essential to optimize performance and fuel efficiency. This involves adjusting the fuel map within the ECU. Keep in mind that fuel injection systems may require specialized knowledge or equipment for maintenance and repairs.

In conclusion, when choosing fuel injectors, consider your engine's specific needs, performance goals, and the type of fuel injection system you plan to use. Consult with a reputable mechanic or tuner to ensure you select the right type and size of fuel injectors for your engine.

Fuel pump and pressure: Install a new, high-pressure fuel pump and regulator

Fuel pump and pressure are key components of a fuel injection system's performance. A good fuel pump will ensure the engine gets a consistent volume of fuel, and the right pump for your system will depend on the type of fuel injection you have.

Throttle body injection (TBI) systems are a cheaper and simpler way to switch from a carburetor to fuel injection. They act as direct carburetor replacements, so you won't need to change your intake manifold. However, they lack some of the capabilities of multi-port fuel injection (MPFI) systems.

MPFI systems are a better approach to EFI conversion in almost all applications. They offer better fuel distribution and a better-running engine. All original equipment manufacturers (OEMs) moved to multi-port systems around 20 years ago.

Regardless of the type of fuel injection you choose, you will need a fuel pump that can deliver at least 255 liters per hour or more, depending on the horsepower of your engine. EFI systems usually operate at pressures between 43 and 60 psi, compared to the 5 to 7 psi of carbureted systems.

Most EFI systems require a return line from the engine back to the fuel tank, but returnless solutions are available. However, you will still need a fuel line that supports EFI fuel pressures to deliver fuel from the tank to the engine.

An external pump will be easier to install but will be loud and must be mounted properly, while an in-tank fuel pump will be more involved but will be submerged in fuel and remain cooler.

When installing a new fuel pump, it is important to follow the manufacturer's instructions carefully to avoid damage to your vehicle or injury to yourself. The pump should be mounted on the chassis, in a vertical position with the pump motor on top. It should be located at the rear of the vehicle, below the lowest point of the tank, to ensure an adequate fuel supply. The pump should not be mounted in a closed area, such as the vehicle's trunk, and care should be taken to avoid exposing the pump and fuel lines to moving parts and hot areas, such as the exhaust.

When connecting the fuel lines, use the same size flexible hose as the original equipment and avoid unnecessary restrictions such as sharp bends and undersized fuel fittings and hoses. All fuel line connections must be leakproof, and a thread sealant with Teflon is highly recommended.

If you are installing a high-pressure pump, a pressure regulator must be installed in the line between the pump and the carburetor. The regulator should be positioned as close to the carburetor as possible, minimizing exposure to heat sources. The regulator pressure can be adjusted by loosening the regulator locknut and turning the adjustment screw.

Intake manifold: Replace or modify to accept injectors

Replacing or modifying an intake manifold is a complex process that requires careful planning and execution. Here are some detailed instructions and considerations for the task:

Replacement Process:

• Remove the old intake manifold: Start by removing the air filter and air filter container. Pay close attention to the removal process, as you will need to reconnect all the parts during the installation of the new manifold.
• Open the hose clamp: Use a flathead screwdriver to open the hose clamp and remove the carburetor's fuel line and any attached vacuum lines.
• Disconnect the throttle links: Remove the screws attaching the links to the throttle using a screwdriver.
• Loosen the carburetor and intake manifold nuts: These nuts are typically located on the four corners of the carburetor.
• Remove the distributor: Loosen the connecting bolts with a wrench to remove the distributor.
• Detach the upper radiator hose: Use a flathead screwdriver to loosen the screws and detach the upper radiator hose from the intake manifold.
• Loosen the bolts fastening the intake manifold to the engine.
• Clean the engine surface: Ensure that the engine surface is clean and free of debris.
• Prepare the new intake manifold: Check for any leaks from the gaskets and apply gasket sealant on both sides of each gasket.
• Install the new intake manifold: Fit the new manifold into place next to the engine block and secure it by screwing in the bolts.
• Reinstall the components: Reinstall the upper radiator hose, distributor, carburetor, links to the throttle, carburetor fuel line, vacuum lines, and air filter.

Modification Process:

Modifying an intake manifold to accept injectors involves machining the manifold to create ports for the injectors. Here are some key considerations and steps for this process:

• Select the appropriate injectors: Choose injectors that are compatible with your vehicle and engine specifications. Common options include the Bosch-type injectors.
• Determine the required port size: The port size will depend on the type of injector you choose. For example, Bosch injectors typically require two different diameters in a stepped fashion to ensure a proper seal for the O-rings.
• Machining the manifold: You will need to machine the manifold to create the injector ports. This can be done using a mill, drill press, or other appropriate tools. Ensure that the finish is smooth and that the port size is accurate to ensure a proper seal for the injector O-rings.
• Install the injectors: Once the ports are machined, you can install the injectors into the manifold. Ensure that they are securely seated and that the O-rings are properly sealed.
• Modify the fuel system: Converting to fuel injection may require modifications to the fuel system, including upgrading the fuel pump and adding a return line from the engine back to the fuel tank.
• Upgrade the ignition: Consider upgrading the ignition system to take full advantage of the fuel injection system. This may include adding an ignition box or making adjustments to the timing curve.
• Tuning and calibration: Once the intake manifold modification is complete and the injectors are installed, you will need to tune and calibrate the fuel injection system to ensure optimal performance. This may involve adjusting fuel pressure, airflow, and other parameters.

It is important to note that modifying an intake manifold to accept injectors is a complex task that requires a good understanding of mechanics and access to the appropriate tools and equipment. If you are unsure about any aspect of the process, it is recommended to consult a professional or seek advice from experienced individuals.

Electronic Control Unit (ECU): Manage fuel delivery and ignition timing

If you're considering changing your fuel injection to a carburetor, it's important to understand the role of the Electronic Control Unit (ECU) in managing fuel delivery and ignition timing. The ECU is essentially the "brain" of a vehicle, controlling various subsystems of an internal combustion engine. It takes readings from sensors and interprets the vehicle's needs to make adjustments to the engine's fuel delivery circuits and ignition timing. This ensures that the proper air-fuel mixture is ignited at the optimal time in the combustion chamber, maximizing power and fuel efficiency.

The ECU plays a crucial role in managing fuel delivery by controlling the fuel injection system. It determines the correct mixture ratio by considering factors such as engine demand, temperature, and airflow. For example, when you press the accelerator pedal, the throttle flap opens to allow more air into the engine. The ECU, using input from the Mass Air Flow (MAF) sensor, adjusts the amount of fuel injected to maintain the ideal mixture ratio. This dynamic adjustment of the mixture ratio ensures that the engine operates at full throttle without wasting fuel.

The ECU also controls the ignition timing, determining when to ignite the spark in petrol engines. By using a Crankshaft Position Sensor, the ECU precisely times the activation of the injectors and ignition system. This timing is critical to ensure that the air-fuel mixture is ignited at the optimal moment for efficient combustion. The ECU's ability to manage ignition timing contributes to improved engine performance and fuel efficiency.

Additionally, the ECU can adjust fuel delivery based on environmental conditions, such as cold climates. It makes the necessary adjustments to ensure a smooth start and trouble-free operation, regardless of the weather. This capability enhances the vehicle's reliability and performance in various conditions.

Furthermore, the ECU can monitor various components and engine systems, including oil condition and maintenance schedules. By analyzing data from sensors within the engine, the ECU can determine the optimal intervals for scheduled maintenance. This helps vehicle owners stay on top of maintenance tasks and potentially avoid costly repairs.

In conclusion, the ECU plays a vital role in managing fuel delivery and ignition timing, resulting in improved fuel efficiency, enhanced engine performance, and reduced emissions. Its ability to make real-time adjustments based on various sensors and environmental conditions ensures that the vehicle operates at its peak power and economy level. Therefore, when considering changing from fuel injection to a carburetor, it is essential to recognize the significant advantages that the ECU provides in modern vehicles.

Wiring harness: Connect the ECU to the fuel injectors and sensors

While converting a carbureted engine to a fuel injection system has its benefits, it is a complex process that requires careful consideration of the costs and benefits. One of the critical steps in this conversion is connecting the ECU (Electronic Control Unit) to the fuel injectors and sensors, which is done through a wiring harness. Here is a detailed guide on the wiring harness installation process:

A wiring harness is essential to connect the ECU to the fuel injectors, sensors, and other electronic components in a fuel injection system. This harness serves as the nervous system of the engine, ensuring precise communication and control. The process of connecting the ECU involves the following steps:

Understanding the ECU: The ECU is the brain of the engine, controlling fuel injection, ignition timing, and other engine parameters. It uses digitally stored equations and numeric tables to optimize engine performance and emissions.

Identifying Sensors: The ECU relies on input from various sensors to make decisions. These sensors include the mass airflow sensor, oxygen sensor, throttle position sensor, coolant temperature sensor, voltage sensor, manifold absolute pressure sensor, and engine speed sensor, among others.

Selecting the Correct Wiring Harness: Choose a wiring harness specifically designed for fuel injection systems, ensuring it has the necessary connectors and wiring diagrams to facilitate the connections between the ECU, fuel injectors, and sensors.

Disconnecting the Battery: Before beginning any electrical work on the vehicle, disconnect the battery to ensure safety and prevent short circuits.

Removing the Old Wiring: Carefully remove the existing wiring associated with the carburetor. This step ensures a clean slate for installing the new wiring harness.

Installing the New Wiring Harness: Follow the provided instructions or a vehicle-specific guide to route and connect the new wiring harness. Ensure that all connections are secure and that the wiring is protected from potential abrasion or heat sources.

Connecting the ECU: Using the new wiring harness, connect the ECU to the fuel injectors and sensors. Refer to the wiring diagram to identify the correct pins or connectors for each component.

Testing and Verification: Once the connections are made, reconnect the battery and perform a thorough test of the vehicle's systems. Ensure that the ECU is communicating correctly with the fuel injectors and sensors, and make any necessary adjustments.

Tuning: After installation, the fuel injection system will require tuning to optimize performance and fuel efficiency. This step typically involves adjusting the fuel map within the ECU based on feedback from the sensors.

It is important to note that converting to a fuel injection system is a complex process that requires mechanical and electrical expertise. Working with a qualified mechanic who has experience with such conversions is highly recommended. Additionally, sourcing an EFI kit that includes the necessary components, such as the Holley self-tuning EFI kits, can streamline the process.

Frequently asked questions