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For a lot of enthusiasts, hearing the name “Holley” causes one’s brain to automatically append “four-barrel” – that’s how intertwined the company’s heritage is with performance carburetion. Of course, there’s much more to that history than just the iconic 4150 four-barrel. Since 1903, Holley has produced more than 250 million carburetors for everything from the original Model A Ford to aircraft, boats, and of course NASCAR and NHRA Pro Stock.

What’s not so commonly known, though, is how deep Holley’s electronic fuel injection roots reach as well, going back more than two decades. Per Holley Senior Engineer Doug Flynn, “Holley started offering aftermarket EFI systems in the mid-late 80’s. Holley used to manufacture a lot of OEM EFI parts as well, which most people don’t know.” Today, they offer the same sort of product range for their EFI systems as they do for their carburetors, with a fuel injection solution for everything from mild factory musclecar engines all the way up to max-effort forced induction racing combinations.

From left to right - Terminator (with throttle body injector unit), HP, and Dominator.

From left to right – Terminator (with throttle body injector unit and programming fob), HP, and Dominator.

Here, we’re going to take a look at the current lineup of Holley EFI systems and how they fit into the spectrum of different applications. There’s something here for everyone, from the six-second drag racer to the guy who just wants his favorite car to fire up and run right whether it’s cold or hot, and from the experienced tuner to the hobbyist who can’t picture cracking a laptop open in the garage.

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Terminator EFI

For those looking to dip their toe into the EFI waters for the first time, Holley’s Terminator series EFI systems are the perfect start. Designed as a direct replacement for any car running a 4150-style intake manifold, it’s easy to install and easy to set up. Because the injectors, most of the sensors, and the wiring comes built into the Terminator throttle body unit, there isn’t a lot of work involved in the installation. Besides pulling off the old carburetor and installing the throttle body in its place, the only major tasks involved are converting to a return-style EFI fuel system and installing the oxygen sensor via a bung in the exhaust. It’s about as simple as an EFI conversion can possibly be, in terms of mechanical work involved.

The Terminator EFI system is perfect for carb conversions where you want to preserve the look of your engine bay.

Terminator EFI Key Features

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  • Fully self-tuning ECU – No laptop required
  • 80 pound-per-hour injectors support 250-600 horsepower engines
  • Fits any 4150-style square flange intake
  • 950 CFM throttle body with CFD computer designed air-entry area
  • Available with a tumble-polished finish (PN 550-405, street price $2,009.95 at JEGS.com) or Holley’s exclusive Hard Core Gray (PN 550-406, street price $2,060.95)
The throttle body itself is a 950 CFM unit derived from Holley’s NASCAR throttle body. Those familiar with carb sizing might balk at at that number for smaller-displacement engines – typically putting a carburetor that big on a 300-horse small-block is asking for tuning headaches thanks to the mismatch in flow and the resulting weak vacuum signal to the carb. EFI is a totally different animal, though.

The Terminator system can support engines between 250 and 600 naturally aspirated horsepower, a range dictated by the capabilities of the four 80 pound-per-hour injectors mounted in the throttle body. The ECU doesn’t depend on a vacuum signal at the fuel discharge point to get the mixture correct, and as a result the system can handle such a wide spectrum of power and displacement. The injectors deliver fuel to the manifold through a proprietary annular discharge fuel ring for maximum flow and optimum fuel atomization, as well as even runner distribution side to side and front to back.

Computers Are Our Friends

One sticking point for a lot of people considering a switch to fuel injection is anxiety over having to tune it once the hardware is installed. For someone accustomed to jets and accelerator pump cams, the idea of punching numbers into cells on the computer is a show-stopper. Fortunately, with the Terminator, setup is handled via a hand-held programmer with a multiple-choice setup wizard. No computer experience is required to set it up – just scroll through the options and select what’s most applicable to your car to establish the starting point. Once you have the basic parameters set up, the system uses a wideband oxygen sensor to tune itself.

“The typical applications for the Terminator are such that the user can load the base calibration and its usually close enough for the car to run well without any further changes via the handheld tuner,” Flynn explains.

All of the setup work required to get the Terminator up and running can be done from this simple handheld controller. No laptop required, and once you've run through the setup wizard, the system continually self-learns to improve the tune.

All of the setup work required to get the Terminator up and running can be done from this simple handheld controller. No laptop required, and once you’ve run through the setup wizard, the system continually self-learns to improve the tune.

For those who’d like to put together their EFI experience from the ground up, the Terminator also has room for growth built right in. The Terminator shares its ECU design with Holley’s HP EFI system (more on that in a moment), and with a free download from Holley, the Terminator’s programming can be upgraded to HP spec to allow things like nitrous or boost.

Here at the Power Automedia garage, we’ve installed and tested the Terminator on a 383-powered K5 Blazer, and appreciated the improvements in drivability, fuel economy, and performance we experienced thanks to the swap. While anyone contemplating a switch from a carburetor will appreciate the instant cold starts, lack of vapor lock issues, and responsiveness the Terminator provides, in an off-road application like that, a big added benefit is no float bowl slosh. Off-camber slopes don’t faze the Terminator EFI system – as long as there is fuel around the pickup in the tank, it will make it to the cylinders. The same goes for applications like road racing or drag racing, where high g-loads can give carbureted engines fits as the jets are intermittently uncovered at the worst possible moments.

Like all of Holley's EFI family, the HP's processing unit is environmentally sealed so that it can be mounted in the engine bay or inside the vehicle.

Like all of Holley’s EFI family, the HP’s processing unit is environmentally sealed so that it can be mounted in the engine bay or inside the vehicle.

HP EFI

While there are plenty of enthusiasts who will find the Terminator EFI perfectly suited to their needs, Holley knows that no two builds are the same. For those who want the flexibility of multi-point port injection, or are looking to run a late-model EFI engine, Holley’s HP EFI provides the solution. “Holley now offers plug and play harnesses for the ultra-popular LSx engines, as well as late Model HEMI engines and Ford Modular and Coyote (with the VVT locked) as well,” says Flynn.

HP EFI Options

550-602GRHolley has put together plug and play packages, ECU and harness combos, and even complete intake manifold setups to let you run practically any internal combustion engine under the sun with the HP EFI. Here’s a partial list of applications…

HP EFI combines the same processing brains used by the Terminator EFI with one of a number of different plug and play packages, or it can be used a-la-carte with your own custom harness. For those looking to retrofit a small or big block Chevy, they even have complete packages including a throttle body and intake manifold to go along with the HP system.

The HP offers numerous advantages over a reprogrammed OEM computer, including integrated single channel wide band oxygen sensor control that works with NTK or Bosch sensors, 2GB internal datalogging, integrated boost control, eight channel Distributorless Ignition (DIS) outputs capable of directly driving “smart” ignition coils or Holley DIS coils, four-stage progressive nitrous control, and the ability to work with an external third-party traction control system.

Lest you think that the HP is strictly a race EFI system, though, keep in mind that it’s also well-suited for street applications. It’s got four programmable inputs and the same number of outputs that can be configured to run electrical accessories like a radiator fan or electric water pump, and it has the same powerful self-tuning capabilities that make the Terminator so easy to set up and run.

Holley’s HP EFI is so advanced and powerful, in fact, that it’s standard equipment on the 2013-up COPO Camaro. The number of different configurations available is always growing (see the sidebar for a small sample), so if what you’re looking for doesn’t exist straight off the shelf at the moment, Holley can help you out with a custom setup.

In addition to using a laptop to control the HP EFI system, Holley also offers an optional color touch screen that allows convenient operation right from the driver's seat. It uses an industry-standard mount and offers an SD card port for loading and saving data.

In addition to using a laptop to control the HP EFI system, Holley also offers an optional color touch screen that allows convenient operation right from the driver’s seat. It uses an industry-standard mount and offers an SD card port for loading and saving data.

Dominator EFI

Holley EFI uses a 31×31 base fuel table, with adjustable X and Y axes. This provides the resolution necessary for precise tuning, especially with 2, 3, and 5 bar MAP sensors.

Holley EFI uses a 31×31 base fuel table, with adjustable X and Y axes. This provides the resolution necessary for precise tuning, especially with 2, 3, and 5 bar MAP sensors. For a deep dive into the Dominator’s capabilities, check out our full review.

At the top of the ladder in Holley’s EFI system offerings is their Dominator system. The Dominator has all of the features of the HP and adds more engine and peripheral systems control on top of that – it’s designed to be the last engine management system you’ll ever need. The Dominator can be set up to tune the engine on its own just like the HP and Terminator systems, but instead of using a single wideband oxygen sensor, it offers better resolution by using dual-channel control.

Per Flynn, “If you want two wideband oxygen sensors, drive by wire, or electronic transmission control, you have to have the Dominator. Other than that, the decision point comes down to, ‘how many inputs and outputs do I need?’ For most any track or serious street car application, especially with power adders, you’ll find out quickly that there are tons of great uses for all the extra inputs and outputs the Dominator offers.”

For ease of installation, Holley also offers a wide range of Dominator and HP wiring harnesses both in unterminated form for custom applications as well as ones designed to interface with factory connectors.

When we were looking for an engine management setup for our in-house 275 Drag Radial Camaro, dubbed “BlownZ,” we turned to the Dominator EFI system. Considering that the ProCharger F-1X-12 blown 440 cubic inch LS under the hood has propelled it to a best time of 7.09 seconds in the quarter mile, and a best trap speed of 202 miles per hour, you can see that the Dominator is capable of handling just about any high performance application.

Look closely and you can see the Dominator ECU riding shotgun in BlownZ.

Look closely and you can see the Dominator ECU riding shotgun in BlownZ.

We’ve also had hands-on experience with the Dominator in our quest to produce 1,000-plus horsepower with a Whipple-supercharged LSX376-B15. Running that engine on the dyno at Westech, we found that the datalogging functions and ease of making changes on the fly really helped to quickly dial in the tune and reach our goals. We’ve also taken an in-depth look at the Dominator previously – if you’re in the market for a high-end racing EFI system, be sure to check out that article as well.

A closer look at the Dominator mounted in our 275 Drag Radial Camaro. One of the big strengths of both the HP and Dominator EFI systems is their ability to easily interface with external electronics, like ignition boxes, traction control, and datalogging systems.

A closer look at the Dominator mounted in our 275 Drag Radial Camaro. One of the big strengths of both the HP and Dominator EFI systems is their ability to easily interface with external electronics, like ignition boxes, traction control, and datalogging systems.

Like the HP, the Dominator isn’t strictly for race cars or crazy, high-horsepower engines, though. It has the same intelligent self-tuning ability as the HP and Terminator, and where it really shines is in the area of user-configurable inputs and outputs. Racers might use them to run multiple stages of nitrous oxide or water/methanol injection, but for street applications, those same controls can be used to operate things like an air conditioning compressor or auxiliary cooling fans.

“If you can send an email, you have the ‘computer skills’ needed to operate the laptop with Holley EFI,” Flynn asserts. “The lack of knowledge usually comes down to pure tuning or a lack of basic understanding on how EFI systems operate.  A person that is truly a good carb tuner, and there aren’t a ton, has the tuning skills needed.  Their issue is usually just plain being scared of punching keys. Once they get over that, they usually love EFI, as it doesn’t have tuning compromises faced with a carburetor.”

Since the Dominator has the native ability to integrate with drive-by-wire throttle controls and GM electronic automatic transmissions, it’s an excellent choice for engine swaps.  Rather than a patchwork of separate controls, pretty much any electronic function can be managed by the Dominator, making for a cleaner and more reliable installation with fewer headaches.

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On the engine dyno at Westech, the Dominator’s software made for a quick initial setup and easy tweaks to get our LSX376-B15 in the zone.

Suitable for Any Need or Budget

The Holley EFI family has a solution for pretty much any need. If you’re replacing a carburetor for better cold starts, drivability, economy, and performance on a classic musclecar, and want a system that is easy to install and set up, the Terminator is an excellent choice. Doing an engine swap, but don’t want the hassles of trying to get a factory computer to play nicely with the components you’ve teamed up? The Holley HP is all over that job. And if you need a no-compromises, does-it-all engine management system for your race engine that covers your needs today and has room for growth tomorrow, then the Dominator EFI system is tailor-made for you.

Having worked with Holley quite a bit over the years, we also have to give proper credit to their staff for providing accessible expertise and advice as good as you’ll find in the automotive aftermarket. Their century-plus experience mixing fuel and air, combined with the fact that they’re enthusiasts at heart, makes for products that really feel like they are designed with the end user in mind. If you’re in the market for EFI at any level, from basic carb replacement to full-race, do yourself a favor and give Holley a look.