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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

It's important to note that because every engine is different, your BSFC numbers might be better or worse than our estimates. That's one reason why having access to injector duty cycle numbers on the ECU's display is important. For example, if you have an engine that actually does make 550 hp and you command a 12.5:1 AFR at WOT, you can run the engine up to max power rpm and have a friend watch the injector duty cycle on the output screen. If at any point the ECU indicates more than 90 percent duty cycle, you know that your engine needs more fuel to supply the commanded AFR. This does not necessarily mean the engine is running too lean. Experimenting with different AFRs will show if the engine wants more or less fuel. This is why having another tuning aid like injector duty cycle is helpful.

We must also point out that just because some of these systems may not necessarily supply 600 hp worth of fuel at 43 psi doesn't mean they don't perform. Frankly, most of these EFI systems will find their way onto engines making less than 500 hp, in which case all these systems have more than enough injector "head room" to accommodate normally aspirated performance upgrades like better heads or a bigger camshaft.


In the early TBI self-learning systems, no one offered the opportunity to run a nitrous system. With these latest versions, a couple of systems are now compatible. Among the four systems, MSD, FAST, and Holley offer nitrous configurations. The EZ-EFI 2.0 system will work with the classic "wet" nitrous plate–type system, where both nitrous and fuel are introduced into the intake manifold. There is a Nitrous Setup category you can click on that allows you to select the target AFR, as well as a target total timing number. But the nitrous target timing number (effectively a nitrous retard) only works if the ignition is integrated with the EFI package. Otherwise, you will need to trigger a separate nitrous retard.

The advantage of using closed-loop feedback AFR control is that if the additional fuel supplied by the nitrous plate is slightly rich, the WBO2 will indicate this situation and the ECU will immediately respond to meet that commanded AFR. This has the potential to produce a measurable advantage over a straight carbureted nitrous application. This is basically how the Holley system is also intended to be used, but you will have to perform the free upgrade to the HP version of the software, and this will require a laptop. But it's easy—just buy your laptop buddy lunch.

Software Upgrades

When it comes to electronics, we have come to expect that after the device goes out the door, there will be upgrades. The same is true with EFI systems. The ease with which you can do this will depend upon which system you are working with. One thing to keep in mind is that if you do upgrade, any specific changes you made the existing software will be lost, so it's best to track the changes you've made in a written record that will make it easier to input them back into the ECU once the upgrade is complete.

As an example, because the Edelbrock system uses the Android tablet, software improvements might be a little easier since you can quickly access the upgrade off the Internet and then load it to the ECU. We watched a short video by MSD that showed how to upgrade the software, which involves removing the micro-SD card from the ECU, purchasing an SD card reader, and then accessing the new software from Atomic's website to upgrade the card using the reader. The Terminator system is designed so that a laptop is not needed. However, if you desire to go into the system to make changes that are not currently allowed, Holley engineer Doug Flynn told us that with a laptop and an inexpensive USB cable you can download the Holley V2 software into your laptop and then use that to upgrade the Terminator system. The EZ-EFI system also accommodates updates via the Internet. In all cases, should the manufacturer come up with software improvements, all it takes is a relatively simple upgrade to bring your older system up to date. That's the beauty of electronics.

Throttle Body Horsepower Potential

Manufacturer MSD Atomic Edelbrock E-Street FAST EZ-EFI 2.0 Holley Terminator
Injector Size 80 lb/hr; 43 psi 63 lb/hr; 43 psi 74 lb/hr; 43 psi 80 lb/hr; 43 psi
Number of injectors 4 4 8 4
Manf. HP Claim 625 600 1,200 600
Calc. HP 43 psi 0.50 BSFC 544 428 1,006 544
Calc. HP 43 psi 0.45 BSFC 604 476 1,118 604
Calc. HP 60 psi 0.50 BSFC 643 595 1,187 643
Calc. HP 60 psi 0.45 BSFC 713 660 1,313 713
Inj. Duty Cycle Display No Yes Yes No

Parts List

Description PN Source Price
Competition Eng. Slide-A-Link C2100 Summit Racing $409.97
RacePak IQ3 dash 250-DS-IQ3 RacePak 250.00
Edelbrock Universal Reservoir 3605 Summit Racing 545.87
Aeromotive Phantom system 18688 Summit Racing 549.87
Aeromotive bypass regulator 13129 Summit Racing 139.97
FAST in-tank fuel pump kit 307501 Summit Racing 1,297.97
FAST retrofit kit 30405 Summit Racing 1,249.97
Pro. Prod. Powerjection III 70020 Summit Racing 1,569.97
Dominator display screen 553-103 Summit Racing 681.84

Holley Performance Products
1801 Russellville Rd.
Bowling Green
KY  42101
Quick Fuel Technology
129 Dishman Lane
Bowling Green
KY  42101
7805 Barton Street
KS  66214
2700 California St
CA  90503
Moroso Performance Products
80 Carter Drive
CT  06437
MSD Performance
1350 Pullman Dr., Dock #14
El Paso
TX  79936
Rick’s Tanks
Fuel Air Spark Technology
3400 Democrat Road
TN  38118
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