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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

The critical point here is that by the stroke of a few keys you can create a system that runs exactly as you commanded. This kind of tuning requires days with a carburetor or hours with older EFI systems. All of this is predicated on the performance of the oxygen sensor, but the technology involved with wideband oxygen sensors has improved so much in the past few years that this kind of dependable performance is possible and all without having to earn a degree in computer science.

System Overview

Functions MSD Atomic Edelbrock E-Street FAST EZ-EFI 2.0 Holley Terminator
PN 2910 3600 30400-KIT 550-405
Price: Summit Racing $2,125 $2,198.97 $1,999.95 $1,999.95
Throttle Body 4150 4150 4150 4150
CFM Rating 1,000 1,000 950 950
Manuf. Claim HP 625 600 1,200 600
No. Injectors 4 4 8 4
Fuel Press. Sensor Yes Yes Yes Optional
Wet N2O Upgrade Yes No Yes Yes
Handheld Screen Yes Yes Yes Yes
Color Touch Screen No Yes Yes Optional
Fan Control Yes Yes Yes Yes
Rev Limiter (fuel) Yes Yes Yes Yes
Timing Control Yes No Yes Yes
No. Pages in Manual 26 40 72 35
Software Upgradable Yes Yes Yes Yes
Laptop Required No No No No


Each of these closed-loop EFI systems operates in a similar manner. The ECU measures the critical engine parameters and creates a fuel-delivery schedule based on the inputs from the sensors. Most of these sensors are located on the throttle body itself, making the connections easy since they can only be attached to their intended sensor. So you can't screw up. The following are definitions for each sensor so you can see how each measures a certain engine function.

MAP (Manifold Absolute Pressure): Each of these EFI systems operate under Speed Density. This system assumes a certain level of volumetric efficiency based on displacement and creates a base fuel map that then establishes the amount of fuel delivered to the engine, given by its position on the fuel map, which is based on rpm and load. The MAP sensor converts the manifold vacuum level into a zero-to-5-volt signal to the ECU so it knows how much load the engine is currently experiencing.

TPS (Throttle Position Sensor): This simple device is much like a rheostat that converts the motion of the throttle into a zero-to-5-volt signal that tells the ECU how far the throttle is opened.

IAT/MAT (Inlet Air Temperature/Manifold Air Temperature): This sensor converts the inlet air temperature into a zero-to-5-volt scale, which helps the ECU to decide whether to richen the mixture when the air temperature is cold or make it lean when the air is hot.

CTS (Coolant Temperature Sensor): This converts engine temperature into a scale that the ECU uses to trim mixture.

IAC (Idle Air Control): This is actually a stepper motor controlled by the ECU that is used to maintain idle speed. When the engine is idling, generally a small amount of air is bypassed around the throttle blades through the IAC to maintain the commanded engine idle speed.

FPS (Fuel Pressure Sensor): All these systems use an FPS to monitor fuel pressure because this is critical to flowing sufficient fuel through the injectors. All of these systems are designed to operate between 43 and 60 psi.

RPM (Revolutions Per Minute): This is a critical input into the ECU since all the fuel and driveability programs are based on engine speed. Systems like the EZ-EFI 2.0 require a signal conditioner to establish a good signal to the ECU when using an HEI distributor.

WBO2 (Wideband O2): The wideband oxygen sensor is the critical feedback sensor used to help each self-learning system to adapt to the individual requirements of each different engine. The sensor actually measures the amount of free oxygen in the exhaust and calculates an air/fuel ratio from that measurement. This is why it's critical to seal any leaks in the exhaust system to minimize inaccurate (lean) O2 readings.

Fuel Mileage

Our fuel mileage test constituted the same, mostly highway, 105-mile loop that included one 15-minute stop to test for heat soak starting and roughly a dozen stop lights. To make the mileage test fair to the carburetor, we spent an afternoon (hours longer than it took to configure any of the EFI systems) tuning the Holley until we could get roughly a 13.9:1 air/fuel ratio at our 65-mph cruise speed. Had our test involved much more stop-and-go driving, the carburetor mileage would have suffered dramatically. As a side note, getting 14 mpg out of a near-600hp 496ci is pretty damn good. The 4L80E overdrive with the TCI lockup converter was a major factor. Our highway mileage rpm hovered around 2,300 rpm, and we commanded 13.9:1 air/fuel ratio for all four tests. We didn't try a leaner air/fuel ratio, but it's possible that we might have been able to wrestle even better mileage with a leaner AFR.

MSD Atomic Edelbrock E-Street Holley Terminator FAST EZ-EFI 2.0 Holley 950 HP carb
14.4 mpg 14.2 mpg 14.2 mpg 14.5 mpg 14.2 mpg

Holley Terminator

So what makes the Terminator a possible best buy? What intrigued us was the ability to upgrade. Holley doesn't make a big deal of this, but the Terminator ECU is exactly the same as the one you buy for the HP or Dominator systems. This means that everything the Dominator system offers can be achieved by upgrading from Terminator. This means you don't have to sell your Terminator system if you later decide to add multi-point EFI or go to a multi-stage nitrous system. You do have to purchase additional wiring harnesses, but all the software is already there. Did you know that you can even control a 4L60E or 4L80E electronic overdrive transmission with the Dominator? If expandability is important to you, the Holley offers loads of potential.

Within the areas a handheld unit will give you access, Terminator offers plenty of additional tuning abilities. Under the Advanced Tuning category, you have multiple area access. We didn't have to go into them to allow our engine to run properly since the stock tune was very good, but it's comforting to know that the access is there should you want to perform a little fine-tuning. One example is that the rpm activation of closed loop is set to zero, which means the Terminator runs in continuous closed loop. But the system does offer the ability to increase the rpm to perhaps 1,500 to compensate for big overlap camshafts. The problem with big cams is that free oxygen from valve overlap enters the exhaust system and fools the WBO2 sensor into thinking the engine is running lean. Removing the closed-loop idle fuel control would allow you to manually tune the idle AFR to improve idle quality.

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