Jim Smart
June 6, 2011

We're always looking for ways to improve fuel economy and performance in classic Mustangs. As time goes on, the time-proven carburetor is showing us how antiquated it can be at times with rough idle, lack of power at wide-open throttle, off-idle stumble and hesitation, and an inability to survive with today's harsh fuel additives. The carburetor certainly has its purpose and has for more than 100 years. However, if you're looking to improve both fuel economy and performance, Holley Performance Products has the solution with their new Holley Avenger EFI for four-barrel carbureted Mustangs.

Avenger EFI is a bolt-on, tunable throttle body electronic fuel injection system designed specifically for older carbureted automobiles. It bolts onto your Mustang's four-barrel, Holley pattern carburetor spacer, with electronics easily hidden from view to make it one of the stealthiest modifications for vintage Mustangs. Plug and play connectors make installation easy. And because Avenger EFI is self-tuning to your engine and driving conditions, it's a no-brainer system that adapts to your driving style. You can also fine-tune this high-tech EFI system via the hand-held tuner included in the kit. This means no laptop computer with special programming is required.

Gil Ruiz of Mustangs Etc. has a lot of experience as a fabricator, which is why we decided to consult with him on the best approaches to installing Holley's Avenger EFI. Gil has two basic approaches to this system. He either goes through the firewall with the ECU and harness or he finds a secure spot underhood away from heat, moisture, and dust.

Gil also suggests checking with your motor vehicle department about smog laws in your area. In most states, smog laws don't apply to older vehicles. However, if you have a newer carbureted vehicle like a '79-'85 Mustang, it may not be legal to install this system on your Mustang. Check laws in your area before plunking down the $1,900 suggested retail for the Holley Avenger EFI system.

How Does It Work?

Holley's Avenger EFI system isn't unlike those first throttle body injection (TBI) systems of the 1980s. Ford's Central Fuel Injection (CFI) was based on the same principle of injectors in a throttle body. However, Holley's Avenger EFI is a lot easier to install and tune. Fuel under pressure from the tank and pump feeds pulsing injectors, which pulse in rhythm with engine fuel demands. When the throttle is opened, fuel injector pulse width (duration open) increases to meter in more fuel and air. Fuel supply consists of 3/8-inch lines, electric fuel pump, filters, and hoses. There must also be a 5/16-inch return line that runs parallel with the fuel supply line for simplicity.

In order for electronic fuel injection to function properly, the fuel supply system has to know conditions throughout the engine, which comes from air and fuel temperature, throttle position, manifold vacuum, and oxygen sensors. In truth, the engine's computer doesn't know anything. Sensor input is based on resistance or simple on/off function. Step on the gas and you are working the throttle position (TPS) and manifold air pressure (MAP) sensors, which provide the ECU (electronic control unit) with the feedback necessary to increase fuel injector pulse width (fuel delivery). The EFI wiring harness is equipped with labeled Weathertight plugs that are easy to identify and install. It is impossible to get anything backwards.

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