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Car Craft’s Giant EFI Test

We Test Four Self-Learning Throttle-Body EFI Systems on a Rat-Motor Nova

By , Photography by Ed Taylor

Electronic fuel injection has come a long way in the last 30 years. Early aftermarket systems were complex, slow, and the user had to combine the unique talents of computer software user and accomplished engine tuner. The duo of high price and complexity kept all but the heartiest car crafters away. When the first adaptive systems came on the scene several years ago, many were skeptical, but these systems have now had the benefit of experience to become, for the most part, the simple-to-use-and-install systems they are advertised to be. We decided that what the world needed was an unbiased test of each of the four most popular systems to see just how easy they are to install and whether they can indeed deliver on the promise of better driveability and maybe a mileage improvement, too.

The four self-learning EFI systems we chose to evaluate are the MSD Atomic, FAST EZ-EFI 2.0, Edelbrock E-Street, and Holley Terminator EFI. All of these systems use a dedicated, standard 4150 flange throttle body with integrated injectors, making it a simple switch from a carburetor. That part is very easy. However, it is the implementation of a quality fuel-delivery system that is essential to a durable, trouble-free throttle body fuel injection (TBI) system. Our suggestion is to build the fuel-delivery system first and ensure its performance before you tackle the TBI.

This is also a good place to warn that these self-learning EFI systems are not a cure for a worn engine with two cylinders with burnt valves. On the other hand, we all know that most carbureted performance engines tend to run at a rich air/fuel ratio (AFR) nearly all of the time. Our experience with carburetors is that you can tune them to efficiently operate at steady-state levels like highway cruise or idle. The problem is that, unlike a boat, cars operate a majority of the time in transient conditions where the throttle is constantly moving. It is in these transient conditions where EFI can have a distinct advantage over a carburetor. When fitted with a wideband oxygen sensor (WBO2), it becomes obvious very quickly that carburetors suffer from very rich conditions in deceleration. All of the EFI systems we tested maintained a much leaner AFR when the throttle blades were closed and the rpm was descending, while a carburetor tends to nearly flood the engine with fuel. Combined with carburetor tuning that creates a rich condition on acceleration, EFI is probably at its best compared to a carburetor in transient, part-throttle, in-town traffic. We didn't simulate that specifically in our mileage test, but our guess would be that any of these systems would deliver far-superior around-town mileage, showing perhaps 2–4-mpg improvements when compared to a carburetor.

Our EFI test involved bolting on these four, self-learning EFI throttle-body systems to evaluate each in terms of how well they performed on our 496ci Rat '70 Nova test mule. We also evaluated these systems for ease of installation, how easy they were to configure, and how quickly each system could get your car running down the road with a feedback, self-learning fuel-injection system. That part was pretty easy because all of these kits performed equally well, a couple better than others in one particular test. Overall, the simplicity of the designs is what makes them attractive.

The reason for this simplicity is that in the past the end user had to create his own base fuel (and spark) maps. This first required a laptop computer along with a rather large knowledge base of engine fuel requirements at different engine speeds and loads, and knowledge of how to make all that work within the limitations and complexities of the EFI system's software. Even among the least-expensive EFI programs (like MegaSquirt), configuring the system demands specific software, computer, and engine expertise. Conversely, these newest, self-learning systems do not require a laptop, and anyone with newbie engine knowledge can program the simple inputs necessary to make the system work.

So while some may rant against the complexity of technology, here is an example of how the technology makes things easier and still delivers excellent performance for a reasonable cost while minimizing the technical expertise. We bolted each of these systems on our big-block and within a few minutes of completing the installation, we were driving down the road enjoying excellent throttle response.

As we completed the testing on these systems, everybody had the same question: "Which system is the best?" We think the answer depends upon what you want. That's not the question-dodging politician's answer that it sounds like. Instead, all four of these systems performed very well (with a couple minor hiccups), so from a performance standpoint, we would not hesitate to recommend any of these systems for the average sub-500hp street car. So then the question becomes less about performance and more about options or opportunities that one system offers that the others don't. As an example, if upgrading to a more sophisticated EFI system down the road is very important, then the Holley Terminator system offers great potential for expansion. If your plan is to bolt on an EFI kit and never touch the engine again except to change the oil and plugs once a year, then the least-expensive kit is probably the best. If you are an electronic geek who is attracted to the idea of an Android tablet included with the EFI system, then Edelbrock's E-Street system might be worth the price. If appearances are important, the MSD Atomic has by far the smallest, least-obtrusive wiring harness, since the ECU is integrated into the throttle body. And if your carbureted big-block already makes 800 normally aspirated horsepower, or you like the idea of converting to E85 fuel, then the EZ-EFI 2.0 is the only choice. We could go on, but you get the point. This test is perhaps the most complex we've taken on because of the dozens of similarities and variables across these four systems. We've done our best to illustrate as many ideas and opportunities as possible, but declaring a "winner" is something that only you can do. That's the beauty of being in this situation—you have four clear choices and you really can't make a bad decision. So let's get to the details.

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