Mustang MonthlyHow To Engine
How To Add EFI To Your Engine
Electronic Fuel Injection (EFI) Buyer’s Guide
For the casual enthusiast, the romance of lifting the hood of your project car and swapping that old-fashioned carburetor for high-tech electronic fuel injection (EFI) was often shattered by the headaches of getting an early EFI system installed—never mind the tail-chasing tuning required to get it running half as well as that old carburetor. Fortunately for us, performance aftermarket companies felt our pain and now offer a range of EFI systems that aren’t just simpler to install, but don’t require a PhD in computer science to tune them. Heck, most entry-level systems tune themselves while you drive. Even us knuckle-busters can handle that.
The aftermarket EFI systems in today’s market range from simple carburetor-replacement throttle body injection systems (TBI), to full-on à la carte affairs that can control a nitrous-injected, turbocharged, variable-cam Ford Coyote V-8. We’ll hit the highlights of what’s available from the biggest aftermarket EFI suppliers in this buyer’s guide.
We intended to put the rough street prices for the individual kits, but there are so many options with each one, and some come with fuel systems while others don’t, so that wasn’t practical in this case.
Throttle Body Injection kits
Want benefits of EFI with the least amount of hassle? Then a throttle body injection kit is for you. Think of a throttle body injection (TBI) system as a computerized carburetor. Fuel still enters the intake manifold in the same way, but the carburetor’s jets, accelerator pump, power valve, and boosters are replaced with electronic fuel injectors controlled by a computer. TBI systems greatly simplify installation by retaining the carbureted intake manifold, throttle and trans linkage, and air cleaner, the but since they inject the fuel at the same place as a carburetor, throttle body injection systems can suffer from the same wall wetting and fuel distribution problems as a carburetor. So, ultimate performance is sacrificed for installation ease. Many kits incorporate the fuel pressure regulator into the throttle body or support “returnless” fuel systems to simplify installation.
Ideal for novice enthusiasts
Combines the benefits of EFI with simple installation
Direct carburetor replacement—retains existing manifold, linkage, and air cleaner
Self-tuning; no laptop required
Best for moderate horsepower engines with mild camshaft profiles
Limited tuning capability (some offer free laptop software for more advanced tuning)
User Level: Novice
Edelbrock E-Street 2
Edelbrock’s entry-level EFI system is the E-Street 2, which replaces a carburetor with a throttle-body injection unit. Like many in this category, it features a self-tuning strategy via a wide-band oxygen sensor, though calibrations can be tweaked via the “E Tuner App” that communicates via Bluetooth wireless to your favorite handheld device. A range of fuel system options are available.
FAST offers two throttle body systems, EZ-EFI, and EZ-EFI 2.0. Both feature self-tuning capability. EZ-EFI 2.0 is available in either a carburetor-look throttle body or a port-injected system. Calibration changes are made via a hand-held module (EZ-EFI) or a touch-screen module (EZ-EFI 2.0). A range of manifold and fuel system options are also available.
FiTech Go EFI 4
Focused on no-hassle performance, FiTech offers carburetor-replacement systems for mild to wild horsepower applications. The systems include a fuel pressure regulator integrated into the throttle body to reduce fuel system complexity. Tuning adjustments are made via an included handheld module.
Holley Sniper EFI/Terminator EFI
Known for decades for high-performance carburetors, Holley Performance Products has jumped into the EFI market with both feet. For those looking to switch from a carburetor, Holley offers several options. The company’s Sniper EFI system integrates the fuel pressure regulator into the throttle body to simplify installation. For those wanting to retain the classic Holley carburetor Double Pumper look, Holley offers the unique Terminator Stealth system. Many fuel system options are available, including Holley’s line of EFI conversion fuel tanks for classic applications (to see what’s involved in an installation of one of these systems, check out Zero Carbs on page TK of this issue).
MSD Atomic EFI
MSD’s EFI offering is centered on a throttle-body injection unit that’s aimed at the novice EFI enthusiast. The Atomic EFI unit integrates the fuel pressure regulator, electronic control unit (ECU), sensors, and injectors into the throttle body.
Multi-Port Injection kits
Multi-port fuel injection (MPFI) kits address many of the fuel distribution problems of TBI (and carburetor) systems by including a special intake manifold with one injector in each intake port. Many systems use the same ECU and self-tuning software as their TBI kits to lower the tuning hurdles, but offer more advanced tuning capability via a laptop computer. Because there is one injector per cylinder, MPFI systems can use smaller injectors to control higher horsepower engines.
More precise fuel delivery and control than TBI systems
Ideal for high horsepower, wild camshaft combinations
Some systems offer better hood clearance than carburetor or TBI systems
Self-tuning, though advanced tuning is possible via laptop software
Some systems support automatic transmission control, nitrous injection, boost control, and other advanced features
Installation more complex than TBI systems
Extracting maximum performance and efficiency often requires laptop tuning
User Level: Intermediate
Edelbrock Pro-Flo 3
The Pro-Flo 3 EFI system from Edelbrock is a step up from its entry-level E-Street 2 systems by replacing the TBI unit with port-injected manifolds. The Pro-Flo 3 system offers sequential control of each fuel injector, the ignition curve, idle control, coolant fans, rev limiter, and more via the company’s E-Tuner app. The system can tune itself via the included wide-band oxygen sensor, and can drive a CDI ignition (no separate ignition box is required).
FAST EZ-EFI 2.0
FAST offers its self-tuning EZ-EFI 2.0 with either a carburetor-look throttle body or a port-injected system. Calibration changes are made via a touch-screen module. FAST claims it includes the market’s only fuel pulse damper, a device that absorbs pressure waves in the fuel system. EZ-EFI 2.0 supports both return and returnless fuel systems running both standard gasoline and E85.
FiTech Go Port EFI
FiTech offers their no-hassle approach in a port-injected version for popular Ford engines. The systems include a 900-cfm throttle body that integrates many of the necessary sensors, hand-held tuner, and wide-band self-tuning capability. The ECU is integrated into the throttle body, which eliminates the mounting and harnessing tasks of other systems.
Holley HP EFI
Holley’s HP EFI builds on the company’s self-tuning TBI systems by adding a port fuel injection manifold and more advanced tuning capability. Holley’s HP systems can tune themselves via the included wide-band oxygen sensor, or via a laptop (a touch-screen hand-held module is optional). A wide range of fuel system options is available, including Holley’s line of EFI conversion fuel tanks for classic applications.
Advanced Fuel Injection systems
For sophisticated combinations and late-model engines, often the best solution is an advanced fuel injection system. These systems have powerful computer processors that can support complex engine functions such as drive-by-wire throttles bodies, traction control, transmission control, boost and nitrous control, and variable camshaft timing. These systems require installation and tuning by an experienced professional.
Powerful processors handle complex functions such as traction control and variable camshaft timing
Ideal for specialized applications and complex late-model engines
Components are often purchased individually, which can increase cost
Tuning and installation are best performed by an experienced professional
User Level: Advanced
AEM Electronics Infinity
AEM initially gained notoriety by developing aftermarket components for the sport compact market, but has since specialized in offering specialized electronics for today’s late-model vehicles. Their latest offering is the Infinity ECU, which delivers high-end motorsports capabilities at a sportsman-level price point. The AEM Infinity is powerful enough to control many aspects of today’s sophisticated powertrains that include drive-by-wire throttle, variable camshaft timing, and boost, launch, traction, and knock control. AEM offers a full range of sensors and application-specific harnesses for many late-model engines. If you can build it, the AEM Infinity ECU can probably control it.
Edelbrock Pro-Flo Sportsman
Sophisticated, high-horsepower engines are targets for Edelbrock’s Pro-Flo Sportsman EFI system. Edelbrock partnered with high-end supplier EFI Technology, Inc. to offer a system with fully-sequential fuel injection, real-time tuning, dual-calibrations that can be switched on-the-fly, electronic boost control, four-stage nitrous control, on-board data logging, and much more.
FAST XFI Sportsman and 2.0
For ultimate control and flexibility, FAST offers its XFI Sportsman and XFI 2.0 systems. The systems’ virtually limitless options include trans-brake creep control, boost control, progressive nitrous, self-tuning, switchable tunes, CAN communication, transmission control, and data logging. A wide range of harnesses to fit different vehicles and applications are available.
Holley Dominator EFI
For high-end enthusiasts and racers with sophisticated powertrains, Holley’s Dominator EFI fits the bill. Advanced features such as drive-by-wire, nitrous and boost control, transmission control, and even direct injection are all supported by Holley’s flagship system. Harnesses for Ford’s Modular and Coyote are even offered.
Salvage Yard and OEM Injection systems
If you’re installing a late-model engine in your project, sometimes the easiest path to getting it up and running is to commandeer the EFI system from a late-model donor car. This is a great option for engines that are bone stock, or slightly modified from stock. Unfortunately, this route has become treacherous over the years as vehicles’ electronic systems become more integrated into (and interdependent on) the other functions of the car. For example, the computer may not allow the engine to start if the computer doesn’t receive confirmation from the chassis computer that the brake pedal is depressed. However, an experienced tuner may be able to “turn off” or “fool” the computer into running the engine, as well as tune for engine modifications. Thankfully, some manufacturers (through their performance aftermarket divisions) offer simplified OEM-based electronics packages to run their late model engines.
Often lower cost than aftermarket EFI systems
Designed to control complex late-model engines
Simplifies wiring and connections because harness is designed to fit engine
Can often control an OEM automatic transmission
Some OEMs offer simplified electronics packages to run their late model engines
Limited technical support
Ability to accommodate modifications is limited by the OEM processor
Interdependent/integrated systems often won’t work properly without companion chassis harnesses and computers
User Level: Depends on system chosen
A common EFI swap, especially in the days before the proliferation of aftermarket EFI kits, was to use stock 5.0, Cobra, or GT40 EFI manifolds, wiring, and ECU from a Fox-body Mustang, as seen on this early car.
An essential part of any modern electronic fuel injection system is getting feedback on its operation. EFI systems gather information from various sensors (e.g., coolant temp, manifold air pressure, throttle position), and reference a “fuel map” to know how much fuel to inject. But was that the right amount? The system reads the oxygen (O2) sensor to get the answer. If it’s off its target, most systems can “learn” to trim or add fuel when it sees those sensor readings again.
In the infancy of aftermarket EFI, most entry-level systems used a “narrow-band” oxygen sensor. If your car came with EFI from the factory, them most likely it uses a narrow-band oxygen sensor. It’s essentially a “rich/lean switch” that only tells the EFI system if the air-fuel mixture is leaner or richer than 14.7:1. If you’re tuning your engine to run 12.5:1 air-fuel under load, a narrow-band O2 sensor isn’t gong to help, since it’ll only tell you “that’s richer than 14.7:1, pal.” Here’s where a “wide-band” oxygen sensor comes in.
Most modern aftermarket EFI systems use a wide-band oxygen sensor. This sensor reads the amount of oxygen in the exhaust over a “wide” range (typically air-fuel ratios from 5:1 to 22:1). Modern aftermarket EFI systems use a wide-band O2 sensor to read, (and often self-adjust) the air-fuel ratio to meet the desired target and refine the system’s internal calculations so it’s closer to the target next time.
Fueling the Burn
Aside from some additional wiring, one of the biggest differences between a carbureted setup and one for EFI is how the fuel gets from (and often returned to) the fuel tank. Most carbureted fuel systems run at a lower pressure (6-ish psi), and only have a single fuel line that sucks fuel from the tank and delivers fuel to the carburetor. EFI systems usually require roughly 44 psi, and a regulator that circulates the fuel from the fuel tank, to the engine, and back to the tank via a return line.
Often, one of the first hurdles when converting from a carburetor to an EFI system is installing a high-pressure fuel system with a return line back into the tank. A few different companies have come up with innovative ways to skin this cat. One method is installing a small sump inside the engine compartment that contains the high pressure pump and return plumbing. Another is a returnless system that either incorporates a regulator inside the fuel tank, or “modulates” the fuel pump to deliver fuel based upon the demands of the engine.
But these innovations are currently the exception rather than the rule. The conventional method is to run a return line back to the tank. Many companies offer solutions to simplify this task, including drop-in retrofit pump modules to complete EFI-conversion fuel tanks.