The most popular EZ-EFI conversion is a throttle-body injection system, which uses a 1,000-cfm throttle body that is a direct replacement for a 4150 carb. With this conversion the carburetor on an existing intake manifold is simply replaced with the throttle-body injection unit from FAST, along with the electronics and fuel system to make it work. The throttle body includes four 85-lb/hr injectors, making the system good for engines up to 600 hp, and these TBI units can be ganged in tandem for a dual-quad installation of upward of 1,000 hp. The real upshot of this arrangement is that as far as the engine is concerned, you are just replacing the carb with the throttle body and its associated components. The EZ-EFI system is a fuel-only EFI, so all of the ignition functions are still handled by the existing distributor or ignition system.

Although the EZ-EFI in its most basic form is a simple replacement for a carburetor, the same smart electronic controls are also capable of supporting port fuel injection. This covers modern engine applications such as GM’s LS, Ford’s new Coyote, or Chrysler’s Hemi. The FAST EZ-EFI facilitates simplified retrofits of these engines into earlier cars or street rods without the necessity of dealing with the complex OEM engine management system and wiring. For applications where port injection is preferred as a retrofit, the EZ-EFI is adaptable to existing port EFI installations as an adaptive fuel control electronics package, or as a complete retrofit for popular applications, including the manifold, fuel rails, injectors, and air-only throttle body.

The problem from an enthusiast’s point of view is that tuners and dynos cost money, and most end users are not ‘tuners.’

While the self-tuning capability is the calling card of the EZ-EFI system, there is still the capacity to provide user inputs to influence the tune. From the target air/fuel ratio to such nuances as “accelerator pump shot duration,” the system allows inputs to influence the tune. If you want to know how your machine would perform on the dragstrip with a little bit richer mixture, the tuning capabilities are there with a simple entry via the handheld display. FAST also offers the same self-tuning technology in their higher-end engine management systems.


While many enthusiasts instantly identify Holley with their famous line of carburetors, Holley was early to embrace the concept of the aftermarket retrofit EFI system. These systems have been regularly updated from the primitive dials and dip switches of the earliest controls, to the state-of-the-art electronics of today. As might be expected, Holley has jumped to the forefront of the trend to self-tuning engine management, with a full-spectrum line of new ECUs with these capabilities. These new control boxes come in three series: Avenger, HP, and Dominator.

Unlike the carbs by the same names, these various EFI systems are all suitable for a full range of applications, with the difference being the capabilities of the ECU itself. All have the self-learning capacity, which allows these units to dial-in their own tune. The Avenger is the most basic of the three ECUs. It has the fewest features but includes everything you need for a typical carburetor-to-EFI conversion. This system is ideally suited as a retrofit to a throttle-body type injection system, or to run a multiport injection system in a batch-fired strategy. The Avenger uses a simple handheld tuning module for easy set-up, and allows for user inputs for setting the tuning parameters. The Avenger can be run as a fuel-only control, but also has ignition control capabilities allowing computer controlled ignition timing if desired.