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.