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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

Professional Products Powerjection III

We originally intended to test the Powerjection III unit because it also is a self-learning EFI throttle-body system. But that was until we opened the box and began reading the instructions. One of our criteria for this test was the fact that you could load the entire system on the car without the need for a laptop. Unfortunately, the Powerjection III requires a laptop to load the software into the computer, which it then imparts to the ECU that is integrated into the throttle body. From reading the instructions, we were going to have to make several critical changes to the base fuel program in order to create a usable package for our big-block Rat motor, since the software was designed for a 350ci engine. This complexity and the requirement for a laptop computer led us to not attempt to test the Powerjection III. It does appear to offer all of the basic amenities of the other systems, and it is also about $400 less expensive than the least expensive of our test systems.

Cold Start

Here's the only area where we discovered minor difficulties with a couple of the systems. Since this is more of a subjective evaluation, we decided to grade the systems on a 1-to-10 scale with 10 being best. Because we don't have access to a freeze room and we live near the ocean, our so-called cold-start is questionable since the coldest temperatures were in the mid-50 degrees F. With each system, we merely turned the ignition on to cycle the fuel pump, waited a few seconds and then tried to start our big 496.

A couple items are worth discussing. It's entirely possible that colder temperatures would produce different results. Unfortunately, cold-start is not a tuning function in some of the systems, although the EZ-EFI 2.0 offers access and the Holley at least gets you in under the "after start enrichment" category. If we hook a laptop up to the Terminator (which you can do after upgrading the software), the Holley instructions do give a simple procedure for tuning the cold-start, which is welcome.

The EZ-EFI 2.0 performed the best with a subjective score of 9 out of 10. This did require us to wait the two seconds necessary to allow the ECU to command the prime circuit, and you can actually hear the injectors cycling. If you encounter a problem, the EZ-EFI 2.0 allows you to modify the cold-start parameters, which is an improvement over the original version that was not user-adjustable. The Holley system does not require you to wait on startup and quickly settled into a stable idle. When we revved the engine once, it stalled on idle recovery, but immediately re-started without hesitation. We gave the Terminator an 8 rating.

The Atomic on cold-start was nearly as good as the other two with a stable idle and no hesitations on acceleration and no stalling. We gave it an 8 only because it was slightly richer than we would prefer. The Edelbrock cold-start test was problematic in that while the engine started easily, we had to manually maintain a 2,000-rpm engine speed to keep the engine running. Once the engine built some heat, the idle stabilized, and everything was fine. The reason for this was because our WBO2 sensor indicated a very rich mixture around 10:1 AFR. In speaking with the people at Edelbrock, they are aware of the problem and offered to alter our software to compensate. Because of this, we gave it a 6 for just the cold-start section. We expect that by the time you read this, Edelbrock engineers will have improved the cold-start program to minimize the excessively rich AFR.

HP Claims

In all these systems, the power limitations are not based on airflow but rather restrained by fuel flow of only four injectors. This is probably why FAST decided to up its game with the EZ-EFI 2.0 by doubling the injector count to eight injectors. FAST could have made the injectors smaller but instead sized them at 74 lb/hr. We decided to do the math on all these systems to see how the hp claims compare to the formula. The basic formula is:

Injector size x 0.85 (85 percent duty cycle) / 0.50 BSFC = hp per injector

There are several variables in this formula that require explanation. First is the duty cycle; this industry standard is intended to avoid running an injector at more than 85 percent of the time to improve injector life. A 100 percent duty cycle means the injector is open all the time, which leads to overheating and eventual failure. The second variable is the brake-specific fuel consumption (BSFC) number. This represents the number of pounds of fuel the engine burns (at WOT) per horsepower per hour. The industry standard is 0.50 lb/hp-hr. We've seen many dyno tests with engines now performing in the 0.45 and even 0.40 range at peak torque. These lower BSFC numbers are typical of today's current crop of Ford Mod, GM LS, and Chrysler Hemi engines that burn less fuel to make the same horsepower compared to older engines.

Another variable affecting injector output is fuel pressure. Any injector rating in lb/hr must include fuel pressure for accuracy. Most aftermarket injectors are rated at the industry standard 43 psi (3 bar). An easy way to increase injector output is to increase the fuel pressure from 43 psi to 60 psi. This can improve injector output by 18 percent. We will give you both the manufacturers' numbers and our calculated numbers.

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