A Close Look At Edelbrock's Pro-Flow EFI - Injection Is Nice

Stepping up to a modern fuel injection system for your vintage Mopar has always been somewhat like putting a complicated puzzle together. Since no comprehensive bolt-on kits are offered by the players in the market, it has come down to finding an intake you like, adding the injectors, fabbing this and adding that, finding a source for sensors and wiring-and, of course, the ECU-and then just making it work. Get all your favorite injector parts together and set it up-how hard is that? For most guys like us weaned on carburetors, it's pretty hard. What if the whole setup came in a box, with all the parts to make it go? Man, that would be nice, kinda like getting a new toy when you were a kid, and the batteries were already inside.

When we heard rumors that Edelbrock was developing an electronic fuel-injection package to retrofit onto Mopar V8s, it caught our attention. When we found out they already had the big-block system prototyped and running in a test vehicle, we wanted to know more. We snooped around at Edelbrock, where we were informed the system was going through its final calibration and testing program. We were invited to have a look. Edelbrock's Pro-Flow systems have been around for several other applications, and they set the standard for comprehensive EFI retrofit kits. Edelbrock's philosophy is to get the groundwork done, both in terms of the hardware component and electronics, to make the conversion to EFI as simple as possible.

Why EFI?
Why go to EFI? The next time you go out to drive your late-model truck, think about how well it works. Twist the key, and it will fire immediately. Put it in gear, and it doesn't die. Step on the gas, and it goes. It starts, runs, and goes-simple desires, really, but the kinds of things you don't always get unless you keep your carb tuned. When was the last time you needed to pop the hood on a factory EFI vehicle and poke around with a screwdriver to get it to idle? Once it's set up, an EFI system can't be beat for reliable and consistent service. Edelbrock's objective was to take care of getting it set up, so the end user can simply enjoy the drive.

Carburetors work on the basis of pressure differential and are primarily dependent on orifice flow for calibration. A carb is fairly rigid in its metering ability, since the flow of fuel and the mixture in the various circuits is established by the orifice sizing of jets, air bleeds, emulsion tubes, and so on. Changes in pressure differential from vacuum or air velocity control the flow through the metering orifices. To alter the fuel curve, the calibrated orifices of the various carb circuits need to be physically changed, as in jet changes, air bleed changes, or altering various drillings in the carb body.

Fuel injection doesn't directly rely on anything happening at the injector to determine the fuel-flow requirements. Instead, the electronic control unit directly controls the injector output, and in turn relies on sensors to gather information on fuel requirements. The Edelbrock system takes inputs of throttle position, manifold pressure, coolant and intake air temperature, and the readings from an oxygen sensor in the exhaust to calculate the fuel requirements in real time as the engine is operating. More precise control of the quantity of fuel delivered is possible, with injectors mounted in each cylinder's inlet runner, and the fuel distribution becomes as close to ideal as possible.

In addition to controlling the fuel system, modern EFI systems take over the mechanical functions of ignition timing and turn them over to the EFI's electronic control unit. The electronics in the ECU can control timing with more flexibility than the linear action of the springs, weights, and vacuum diaphragm of a mechanical distributor. In controlling both the timing and fuel requirements, an EFI system offers the possibility to manage the engine's systems more accurately than traditional carbs and distributors.

Think about it-with only the processor in control of the timing and fuel delivery, each can be continually "tuned" to the engines' requirements under a particular instant's operating conditions. The ECU's processor takes in information from the various systems' sensors, relaying the engine's operating parameters. It then responds according to a schedule depicted by programmed "maps" of the required fuel and spark settings. While that sounds pretty trick, one of the greatest difficulties in producing an aftermarket EFI system is in the development of the ECU and its software.

Pro-Flow To Go
In developing the electronic controls for OE engine applications, the manufacturers have the luxury of programming the ECU to operate a specific engine combination, since each engine is identical in specifications. One of the difficulties in creating a control unit for aftermarket retrofits is that each customer's engine varies in its specific combination. The ECU must provide a baseline map to allow it to run, and have the flexibility to be fine-tuned to an individual's engine requirements. Edelbrock provides for these needs by preprogramming the ECU with fuel and spark maps that are developed in real-world testing, and then allowing the maps to be adjusted or custom-tailored to the application. The idea is to provide a product similar to one as-delivered from Edelbrock. This will allow the customer to optimize the control maps for his or her engine's requirements. Fine-tuning is done by a hand-held, plug-in calibration module.

The calibration module provides for the adjustment of both the fuel and spark functions of the ECU. On the fuel side, intuitive menus go through adjustments of idle speed and mixture, cold-start enrichment, closed-loop fuel, transitional and global fuel modifiers, as well as a map based upon an rpm/vacuum matrix. On the ignition side, there are controls for altering the timing on a global or overall setting, or in an rpm/vacuum matrix. There is quite a bit of tuning flexibility designed into the system. Really, as complicated as it may sound, the tuning procedure is straightforward, and Edelbrock provides detailed instruction on the tuning aspects of the system.

Mechanically, the Pro-Flow system is a comprehensive retrofit EFI system based on a high-flow, single-plane intake manifold, which mounts the injectors, fuel rails, bypass-style regulator, and a high-flow 1,000-cfm throttle body. The standard injectors are rated at 22-lb/hr fuel flow for applications up to 475 hp, with optional 44-lb/hr injectors available to handle up to 700 hp. The MAP sensor, TPS, and idle air control are mounted to the throttle body.

The only additional sensors to install are the air and coolant temperature sensors and an oxygen sensor, which screws into a bung welded to the exhaust headpipe or header collector. On the ignition side, a distributor designed to work in conjunction with the ECU is provided, as well as an ignition amplifier. An E-core coil is required with this ignition. To provide for the required fuel pressure, Edelbrock supplies a Walbro external fuel pump, which must be plumbed to the fuel system, with a return line from the fuel-pressure regulator to the fuel tank.

To put its system to the test, Edelbrock fitted the new big-block Pro-Flow system to the 440 in a '70 Plymouth GTX. This vehicle was used as the engineering mule to work out the base calibration setting for the system in two levels of tune-Edelbrock's Performer and Performer RPM packages. Edelbrock's facility is equipped with a SuperFlow eddy-current dyno, which can simulate load and road operating conditions.

When we arrived at Edelbrock, R&D engineer Doug Stalter had the GTX strapped to the dyno and was working on the base calibrations. This dyno development program resulted in the various fuel and spark maps encoded in the ECU's software for the 440 application. Doug demonstrated the fine-tuning process that can be accomplished by the customer with the supplied calibration module. As we watched what could be accomplished at the push of a button with the electronic engine management system, we were impressed by the ease of tuning changes. Edelbrock has put serious time into the development of these EFI systems; as usual, they've done the homework ahead of time so the customer doesn't have to.