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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

Test Mule

When it came time to evaluate these TBI systems on our 496ci-powered '70 Nova test car, the old saying, "Beat it like a rented mule," became a war cry. We first assembled the Nova to test electronic overdrive transmission controllers ("In Control," Mar. '12) using the 496 we flogged for our big-block oval-port cylinder head test in the Mar. '08 issue. That combination made 590 hp and 620 lb-ft of torque with a set of Brodix oval-port heads and a mild Comp hydraulic roller camshaft. Next, we plugged in a boneyard refugee 4L80E with a TCI lockup 10-inch torque converter and finalized the drivetrain with a Currie-built 3.55:1-geared limited-slip 9-inch Ford rearend. We bolted on a set of P275/40R17 Toyo Proxes R888 soft-compound tires on a set of Weld Racing wheels and then discovered we needed a set of Competition Engineering Slide-A-Link traction bars to keep the rear tires firmly in contact with the pavement. We also previously had installed a Rick's Tanks stainless steel fuel tank with a Walbro in-tank electric pump that was capable of feeding our voracious Rat. With that, we were ready to take on these four TBI fuel-mixers.


The hardest part of installing any EFI system is building the fuel-delivery system. We've covered that in another section of this story. The next step is much easier—installing the WBO2 sensor. It's important to locate the sensor in the top half of the exhaust pipe to prevent cold-start condensation from possibly damaging the sensor. All of the kits supply a bung that is not difficult to install but does require welding. Make sure that the upstream portion of the exhaust leading to the WBO2 sensor is leak-free. This is critical to ensuring the WBO2 sensor works properly. With this accomplished, the only challenge left is finding a suitable home for the ECU and routing the wiring.

Unpacking a TBI box might be slightly intimidating because of all the wiring and connectors, but don't let it get to you. The connections are all pre-terminated, and each sensor has its own dedicated connector. You can't get them confused because they will only connect to the proper sensor, and each is labeled. There are roughly 10 sensor hookups to perform along with full-time 12-volt power and ground and a switched 12v trigger wire. You'll hear this more than once in this story, but it is essential that the constant 12-volt connection be hooked directly to the battery to minimize electrical noise. Hooking the wires to the battery uses it as a kind of filter or capacitor that minimizes electrical feedback that can otherwise cause untold ECU problems. Make sure that the switched 12-volt power source is live even when the engine is cranking. If not, the engine will probably not start. We chose to build a separate insulated terminal-fed power from a relay that offers system voltage whenever the ignition switch is turned on.

This may sound like we've over-simplified the process, but not really. You will still need to read the instructions. But the main thing that will require some installation time is professionally routing the wires. We'll admit that in the rush to install each of these systems, we just zip-tied each ECU wherever it was convenient because it was going to be quickly replaced by the next box, so we don't have a true installation time. Our best estimate would be four to six hours, not counting the fuel system. We installed the Phantom pump assembly in roughly three hours with an additional two hours to route and install the second (return) fuel line. So any of these system installations could be accomplished in a weekend. Ed Taylor helped us install a first-generation EZ-EFI in roughly 10 hours on our '65 El Camino, including the Phantom fuel system. We did cut a few corners on the ECU wiring that will need to be addressed, but you can use this as a guide.

Fuel Delivery

The underlying truth behind any EFI system is the fact that it will only be as good as the fuel-delivery system. So in order to be EFI successful, you must provide a qualified fuel-delivery system. There are several ways to approach fuel delivery, but based on our 25-plus years of experience with EFI systems, there's really only one way to go. We don't have the space to go into why a return-less system could work or the several reasons why an externally mounted pump is not the best idea for a typical muscle-car fuel system. Let's just cut to the chase and declare that if you really want your EFI-fed car to run properly in all conditions, do yourself a favor and follow our lead.

We've written perhaps a dozen stories over the years on fuel-delivery systems. Each of the four TBI manufacturers has its own fuel pump and delivery system because they have to give you that option. The key to a quality delivery system is an electric high-pressure pump that's capable of continuous fuel flow at 43- to 60-psi fuel pressure, do this with a minimum of noise, and finally to be robust enough to provide years of service with minimal maintenance. Any good fuel-delivery expert will tell you that this requires an inline, in-tank fuel pump. Inline pumps actually pump fuel through the inside of the pump around the spinning armature. This keeps the pump cool. Mounting the pump inside the fuel tank immerses it in fuel, which further enhances cooling. An in-tank pump uses the weight of the standing column of fuel to push it into the pump so it does not have to work to draw the fuel into the pump. External pumps must create a low-pressure area (which can cause vapor lock) when required to draw fuel vertically. Pumps are much better at pushing than pulling fuel. Externally mounting a pump in a muscle car usually then uses the stock fuel tank pickup. The problem here is that when the fuel level drops, fuel slosh during acceleration or cornering uncovers the pickup, fuel pressure drops, and the engine hesitates or bogs. This can work as long as you keep the fuel level above half full, but frankly, that's lame. There's a better way.

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