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.
This is a basic layout of...
This is a basic layout of the Holley Avenger EFI system, but it could apply to any fuel injection system. There are two lines for pressure and return. Any unused fuel under pressure is regulated at the return line after the injectors to both control fuel pressure and get fuel back to the tank. Pressure line is 3⁄8-inch while return is 5⁄16-inch.
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.
1 Holley’s new self-tuning...
1 Holley’s new self-tuning Avenger EFI is a stealthy bolt-on throttle body fuel injection system for classic Mustangs. This is the 700-cfm system (#550-400) engineered for up to 400 horsepower applications. The Avenger EFI 4V TBI system hides beneath your air cleaner and is undetectable at first glance. Even the pressure and return fuel lines cannot be seen because they enter from behind. The complete system includes four-barrel throttle body, harnesses, electronic control unit (computer), electric fuel pump and filters, fuel pump block-off plate, clamps and attaching hardware, gaskets, throttle position sensor, coolant temperature sensor, and an oxygen sensor that installs just beyond exhaust manifolds or headers.
2 This is the 700-cfm Holley...
2 This is the 700-cfm Holley Avenger EFI throttle body sporting four 65 lb/hr injectors, which tucks neatly beneath most stock and aftermarket air cleaners and will mount on top of a Holley 1850/4150/4160 or Autolite 4100/4300 manifold pattern. It is also available in two 900-cfm sizes for up to 500 and 600 horsepower applications. What makes this throttle body work so well is time-proven GM electronic engine components you can purchase from any auto parts store. The fuel pressure regulator is located in back between pressure and return lines.
3 Here’s the throttle position...
3 Here’s the throttle position sensor (TPS) and connection for the intake air temperature sensor. The harness feeds four Bosch injectors positioned above the throttle bores and plates.
4 This is the idle air bleed...
4 This is the idle air bleed solenoid, which controls idle speed by electronically inducing a mild vacuum leak to regulate idle speed, which is how idle speed is controlled in most electronic fuel injection systems. To raise idle speed, it allows more air. To lower idle speed, it allows less air.
5 The Holley Avenger EFI...
5 The Holley Avenger EFI has four injectors positioned above four throttle bores. The base system is 700 cfm, which may seem like a lot for a 289 or 302, but it is the correct size for engines up to 400 horsepower.
6 The throttle body base...
6 The throttle body base plate is the same four-barrel pattern as the Holley 1850/4150/4160 and Autolite 4100/4300.
7 The days of carburetor...
7 The days of carburetor adjustment and tweaking are over. Here’s the Holley Avenger EFI Engine Management System (ECU) and hand-held programmer. You can locate the ECU just about anywhere. We suggest locating it away from heat, moisture, and road dust for optimum performance. You can locate the ECU inside the cabin underdash (which mandates boring a hole for harness passage) or locate it in a safe place underhood.
8 We like the Avenger EFI’s...
8 We like the Avenger EFI’s ease of installation, including these Weathertight connectors with their silicone seals and multifunction design. You cannot get it backwards. Each plug is mission specific. This is the two-pin power supply harness with 10-amp fuse, which is full-time battery power. The other two multiplex plugs feed to the engine and switched power.
9 Each connection is labeled...
9 Each connection is labeled so you’d have to work really hard at messing this installation up. The entire harness is braided for protection and is aesthetically pleasing. Once installed, it’s hard to know it’s there. Power connections must be solid and reliable, with one constant live and the other switched. And remember, negative ground connections are as important as positive.
10 There are two fuses for...
10 There are two fuses for constant and switched circuit protection. One lone relay activates the in-line electric fuel pump.
11 A single oxygen (O2) sensor...
11 A single oxygen (O2) sensor gauges exhaust gas oxygen content to help the ECU determine proper fuel mixture.
12 The oxygen sensor must...
12 The oxygen sensor must be located within 10 inches of the exhaust collector on a stock manifold or header. If you’re running long-tube headers, it should be located in the header collector (secondary) tube. You can weld in the oxygen sensor bung included in the kit or purchase a strap-on sensor bung.