Transitioning From Carburetor To Fuel Injection: A Comprehensive Guide

Carburettors are mechanical systems that have been replaced by electronic fuel injection (EFI) in newer vehicles. EFI offers greater fuel efficiency and improved performance, and it is also easier to adjust. While carburettors are still used in racing and classic vehicle restorations, EFI has been widely adopted by vintage vehicle owners. Converting from a carburettor to EFI involves a range of steps, from removing the carburettor and installing injectors in the intake manifold to setting up the electronics and tuning the chip that runs the EFI. The process can be complex and time-consuming, especially when converting from a carburettor to EFI on a motorcycle, and it may be more practical to buy a new vehicle with EFI.

Fuel injection conversion kits

Holley Sniper EFI Conversion Kits

Holley offers a range of Sniper EFI conversion kits that provide modern technology at an affordable price. The Holley Sniper EFI 2300 Self-Tuning Kit, for example, comes in a classic gold finish and includes a handheld display for easy monitoring and control. It is designed for bolt-on installation, with only four wiring connections required, and can support up to 650 horsepower.

The Holley Sniper 2 EFI Conversion Kit is another popular option, boasting a self-tuning ECU that eliminates the need for complex computer tuning. This kit also features a throttle body-mounted ECU, requiring no additional boxes to mount, and supports up to 650 horsepower with four 100 lb/hr injectors.

FiTech Fuel Injection Kits

FiTech offers a range of fuel injection kits that are designed for easy conversion from carbureted systems. The FiTech Go Street EFI 400 HP Self-Tuning Fuel Injection Kit is a popular choice, providing a force fuel system and a cast finish. It is designed to deliver better starts, more power, and improved throttle response.

The FiTech Go EFI Classic 4 Barrel Kit is another option, offering 650 horsepower and a classic gold finish. This kit includes an external ECU and a force fuel system, providing a complete solution for your conversion needs.

Summit Racing Fuel Injection Systems

Summit Racing offers a range of EFI systems from various top brands, including Holley, Edelbrock, and FiTech. These systems are designed to maximise power, efficiency, and performance, with many options being self-tuning and self-learning.

One example is the Holley Sniper 2 EFI 650 HP Base Fuel Injection System, which features a self-tuning throttle body, a black finish, and a 4150 flange. It can support up to 650 horsepower and includes an 800 CFM inline pump and a 3.5-inch display.

Another option is the Edelbrock Pro-Flo 4 EFI System, which offers a self-learning, sequential multi-port design and a satin finish. This kit is rated for up to 450 horsepower and is compatible with pre-1986 Small Block Chevy engines.

Tuner Tools Carb to EFI Kits

Tuner Tools offers drop-in and plug-and-play kits to convert carbureted cars to Electronic Fuel Injection (EFI). These kits are designed to be self-contained and require no additional computers to install. They are also self-calibrating and self-tuning in many cases, making the conversion process more accessible.

Additional Considerations

When choosing a fuel injection conversion kit, it is important to consider the specific needs and requirements of your vehicle. Factors such as horsepower, engine type, and compatibility with power adders should be taken into account to ensure the kit you choose will work seamlessly with your setup.

Additionally, it is worth noting that some kits may require additional components or modifications to complete the installation, so it is always advisable to carefully review the product specifications and instructions before making a purchase.

Removing the carburettor

Remove the Air-Cleaner Housing: Start by removing the air-cleaner housing, which covers the carburettor. Set it aside in a safe place.

Label and Remove Vacuum Lines and Wires: All the vacuum lines and wires connected to the carburettor need to be labelled and carefully removed. It is important to keep track of where each part goes to make reassembly easier.

Disconnect the Throttle Linkage: Disconnect the throttle linkage from the carburettor. If your vehicle has a kickdown linkage, disconnect and set that aside as well.

Disconnect and Stopper the Fuel Supply: Disconnect the fuel lines from the carburettor to prevent any leakage. Use a stopper or plug to prevent fuel from leaking out during the removal process.

Remove the Carburettor Nuts and Lift Off: The carburettor is usually secured to the intake manifold with nuts. Remove these nuts, then carefully lift the carburettor off the manifold. Place the carburettor in a suitable container to catch any remaining fuel.

Drain and Store the Carburettor: Allow the carburettor to drain completely. If it is in good condition, you can sell it as a used part. Otherwise, you can dispose of it at a junkyard.

Clean the Intake-Mating Surface: Before installing the new EFI unit, ensure that the mating surface of the intake manifold is clean and free of any debris or residue.

Install a New Gasket: Install a new carburettor-flange gasket to ensure a proper seal between the intake manifold and the new EFI unit.

Install the New EFI Unit: Carefully position the new EFI unit onto the intake manifold, ensuring proper alignment. Secure it in place with the appropriate fasteners, being careful not to over-tighten them.

Check Throttle Linkage Operation: Ensure that the throttle linkage moves freely and has a full range of motion after the installation of the new EFI unit. If there are any issues, you may need to use a spacer plate.

Reconnect the Throttle Linkage: Reattach the throttle linkage to the new EFI unit, transferring any necessary hardware from the carburettor. Adjust the throttle as needed.

By following these steps, you will have successfully removed the carburettor and prepared the engine for the installation of the electronic fuel injection system. Remember to have all the necessary tools and safety equipment before beginning any work, and always refer to vehicle-specific instructions for the best results.

Installing injectors in the intake manifold

Step 1: Remove the Old Carburetor

Before installing the injectors, you must first remove the old carburetor. Start by disconnecting the fuel lines and hoses that are attached to the carburetor. Then, use a wrench to remove the nuts that secure the carburetor to the manifold. If the carburetor is still in good condition, you may be able to sell it as a used part; otherwise, you can dispose of it at a junkyard.

Step 2: Prepare the Intake Manifold

Most intake manifolds can be modified to accept injectors by welding in bungs. This process may require the expertise of a machine shop, especially for the welding. Once the welding is complete, you should have a spot for each injector, and these should slide into place with o-rings to create a seal.

Step 3: Install the Injection Fuel Rails

The injection fuel rails will also need to be machined to fit your specific engine. Depending on the conversion kit you are using, it may come with a ready-to-go manifold that accepts injectors. Many companies also produce ready-to-go injector manifolds that can be purchased separately.

Step 4: Connect the Fuel Injectors

With the manifold and fuel rails in place, you can now connect the fuel injectors. Ensure that the injectors are securely seated in the manifold and that all connections are tight to prevent leaks.

Step 5: Test and Adjust the System

Once the injectors are installed, you will need to test and adjust the system to ensure it is functioning correctly. This may involve tuning the chip that runs the electronic fuel injection (EFI) system and setting up the electronics. It is recommended to get an aftermarket system as it is very difficult to reprogram a factory control unit.

Step 6: Post-Installation Checks

After the installation is complete, it is important to perform a thorough inspection of the engine and fuel system. Check for any leaks or loose connections and ensure that all sensors are properly installed and functioning. Test drive the vehicle to ensure that the engine is running smoothly and that there are no issues with the fuel injection system.

Converting from a carburetor to fuel injection can be a challenging task, but with careful planning and execution, it is certainly achievable. Always refer to the instructions provided with your specific conversion kit and seek professional assistance if needed.

Installing the throttle body

The throttle body regulates the air going into the valves. Universal models are the easiest for conversions.

To install the throttle body, first, bolt the throttle body on and hook it up at the throttle linkage. This is connected to the accelerator pedal. An idle air controller is needed with the EFI throttle body. This goes into a small passage that pushes extra air past the throttle plates. It opens or closes the passage depending on how much air is needed in the manifold. Most throttle bodies come with an IAC already installed.

The throttle body portion of the assembly contains the throttle plates, idle air control valve, and throttle position sensor. The fuel body houses the fuel pressure regulator and one or two fuel injectors. The vehicle’s fuel pump moves fuel from the gas tank to the throttle body assembly. Then a computer, often referred to as the powertrain control module (PCM), activates the TBI injectors. The injectors spray fuel into the throttle body bore and above the throttle plates.

To control fuel pressure, the fuel pressure regulator routes excess fuel back to the fuel tank.

Installing the sensors

In order for the EFI system to monitor and change the injection, several measurements need to be taken. If they're not already in place, several sensors need to be installed. These include an oxygen sensor, manifold air pressure sensor, air temperature sensor, coolant sensor, and throttle position sensor.

These sensors are fairly easy to install, as most simply screw into the engine. The kit should contain everything you need. If not, there are sensor packages available.

The oxygen sensor provides the ECU with information about how the fueling in the engine is doing. From these exhaust readings, the system will add or subtract fuel as needed until it meets the target air/fuel ratio for that particular combination.

The manifold air pressure sensor, also known as the MAP sensor, is part of the engine's electronic control system. It measures the amount of air entering the engine, which is then used to calculate the appropriate amount of fuel to inject.

The air temperature sensor measures the temperature of the air entering the engine, which is important for the EFI system to optimize the fuel injection process.

The coolant sensor monitors the temperature of the engine coolant, which helps the EFI system ensure the engine is running at the optimal temperature.

The throttle position sensor measures the position of the throttle valve, which indicates how much air is entering the engine. This information is used by the EFI system to adjust the fuel injection accordingly.

Frequently asked questions