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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

Another area where we found a significant difference was on the working end of the throttle body below the blades. Holley introduces fuel into the engine both from the large discharge hole directly below the injectors but also from several small holes drilled into the circumference of each throttle bore. The idea is to introduce fuel from multiple locations, especially at low throttle openings to enhance driveability.

Terminator also offers ignition control, should you want to integrate digital ignition control with the fuel. This offers advantages such as digital control over the timing curve that allows you to create a more specific timing map based on load and rpm. One way to simplify this conversion on a small- or big-block Chevy is to use the small-cap HEI-type distributor. The advantage here is these distributors are inexpensive and easy to find either used or new. On the Ford side, the system allows you to use a Ford TFI distributor. For our test, we retained our current MSD ignition system on the big-block so that the ignition remained the same for each TBI test.

Atomic EFI

Atomic is one of the latest iterations of the integrated throttle body fuel injection. The Atomic can accommodate any engine from 100 to 800 ci, with its only limitation being the injector output, which is limited to around 650 hp. This means that at 43 psi of fuel pressure the Atomic could easily supply fuel to a small 215ci Olds all-aluminum V8 as well as a monster 500ci Cadillac. Just as we were finishing this story, MSD announced an upgrade that now makes the Atomic compatible with both nitrous- and boost-ready supercharger packages. At press time, we didn't have any details on what makes the system boost-ready. The key with any claim is to look at the fuel flow potential of the injectors and compare them with the fuel required for your application.

As you might imagine, the Atomic will certainly allow ignition control if you so choose. A big advantage would be eliminating the archaic factory mechanical and vacuum advance mechanisms to allow non-linear tuning capabilities. If nothing else, you can do in a few keystrokes what used to take all afternoon to configure mechanical and vacuum advance curves. We did not integrate the ignition in our test, but it's reasonable to expect that we probably could have improved our fuel mileage by experimenting with the digital ignition curves, especially on the vacuum advance side.

The Atomic performed admirably feeding our 496ci, 590hp Rat. The driveability was excellent, and the fuel mileage was right there with the other systems, making this newest system an equal player among the four.

Edelbrock E-Street

When each of the TBI systems delivers similar benefits, it can often be the little things that can set one system apart. The Edelbrock E-Street's most notable feature is a large, 7-inch touch-screen Android tablet that offers Bluetooth wireless connection to the ECU. The tablet is not just essential for the initial setup but can also be configured as a gauge display. The wireless feature is attractive because it eliminates unsightly wires and allows user freedom to use the tablet apart from the vehicle. Plus, the tablet includes an antenna that allows it to be GPS-enabled by downloading software that will display vehicle speed. Even better, it also has Internet connectivity (Wi-Fi) for other tablet uses that have nothing to do with EFI. You might even consider permanently mounting the tablet in the dash. One small point was that our Android's battery life was shorter than anticipated.

If the number of pages in the instruction sheet is any indication, Edelbrock might be among the easiest to install since the EFI portion of the instruction manual is only 23 pages long. There is another 17 pages for the tablet, but even that only totals 40 pages. We configured the E-Street system in short order, and it quickly allowed us to start the engine and the big-block settled very quickly into an orderly idle. Our big camshaft (with 8 inches of manifold vacuum in gear) was no problem, and with our 4L80E in Overdrive, the E-Street delivered excellent light-throttle response, and quick stabs on the throttle to WOT were met with instant response. Overall, the only problem we encountered was in the cold-start test. For our 496ci engine, the E-Street delivered way too much fuel, requiring us to keep the engine running at 2,000-plus rpm for the first 45 seconds of operation before the engine began idling on its own. The problem was an over-rich, cold-engine enrichment program that unfortunately is not user-adjustable. Since the E-Street was the last of the self-learning systems to appear on the market, it's possible that feedback to Edelbrock from our experience will result in a software upgrade in the near future that will address this issue.

EZ-EFI 2.0

The most overwhelming fact about the EZ-EFI 2.0 system is its larger capacity. FAST has rated this throttle body with fuel flow potential to feed 1,200 hp. This is accomplished by including eight injectors compared to only four in the other systems. So if your engine has the potential to make 850 hp or more, the EZ-EFI 2.0 can handle it. Our first question concerned using this same monster TBI on a really tiny engine, such as a 4.8L (293ci) LS GM engine, for example. Controlling eight, 74-lb/hr injectors at idle on a small engine demands extremely short duty cycles that will cause control issues. FAST compensates by staging the injectors to fire only four at a time, which solves the dilemma. The advantage of these larger capacity injectors is that even at 850 hp the system is operating at a very comfortable injector duty cycle. So if big power is in your future, the EZ-EFI 2.0 can handle it.

While technically a different system, FAST also offers a separate kit called a multi-point upgrade that allows the use of the EZ-EFI 2.0 ECU with a multi-point fuel-injection system. So if we had an intake manifold with an injector in every port and a large throttle body upstream, we could control it all with self-learning EFI just like the TBI system. The advantage is the retrofit system is much less expensive than the TBI system (PN 30404-KIT).

Our experience with the EZ-EFI 2.0 was extremely positive. It did everything we asked it to do every time, and with its massive fuel potential, it's capable of even feeding a high-horsepower E85-fueled engine. If we had more time, we would have really liked to test this option.

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