The Mean Streets: FAST EFI Upgrade

By Richard Holdener/Photos By Author

How do you improve the output and drivability of your SBF? Just add the XFI Street EFI system!

Losing control is not usually a good thing (okay, maybe once in a while!), but not having full control of the tune on your performance motor is definitely bad. The advent of self-tuning EFI systems has simplified converting a carbureted performance motor to modern fuel injection.

These systems, like the EZ-EFI offered by FAST, rely on the oxygen sensor to provide information to the ECU to determine the air/fuel mixture. The ECU then compares the current air/fuel reading to the desired reading, and automatically adjusts accordingly. Assuming you have input the proper desired air/fuel mixture for the conditions, these self-tuning EFI systems can greatly improve things like drivability and fuel mileage over a conventional carburetor. The problem that often occurs with carburetion is, there is usually some sort of compromise.

Very rarely can you get the exact desired air/fuel at idle, cruise and WOT with a carburetor. Since a carburetor cannot be tuned for specific rpm and load conditions, it is often necessary to settle for the best overall (compromised) combination.

To illustrate the potential gains offered by upgrading from carburetion to fuel injection, we took FAST up on their offer of testing an XFI Street system. Having previously run a small-block Ford with the self-tuning, EZ-EFI management system, we wanted to explore the possibility of tuning the combination ourselves. Luckily, FAST offered just such an upgrade in the form of the XFI Street management system. Designed as an upgrade to the EZ-EFI system, the XFI Street utilized the same wiring harness and throttle body employed on the self-tuning EZ-EFI system.

The XFI Street was also available as a complete system with the throttle body and harness. According to FAST, the XFI Street was designed as a cost-effective alternative to enthusiasts wanting complete control of their normally aspirated combinations without the need to step all the way up to the complete, high-end stand-alone systems. The XFI Street can be used with the four-hole, EZ-EFI throttle body or, with a different harness designed for multi-port injection. We liked that the XFI Street also featured data logging when connected to a laptop computer.

To put this system to the test, we employed it on one of our favorite Ford test motors, the BPE 306. Originally supplied as a crate short block, the BPW test motor included a late-model, 5.0L hydraulic-roller block (bored .040 over) machined to accept a cast crank, 5.155-inch rods and hypereutectic pistons. Also present was a healthy hydraulic roller cam (.543/.554, 218/226 112 lsa), lifters and a front cover. The short block also featured an oiling system that included a production Mustang oil pan, pick up and high-vol oil pump.

To complete the 306 Ford, we installed a 50-oz damper, a set of BPE as-cast, 190-cc aluminum heads and dual-plane, Eliminator intake from Speedmaster. Additional touches included a 650-cfm, four-barrel carb, billet distributor and 1 ¾-inch, long-tube headers. After adjusting the air/fuel (with jetting) and timing, the carbureted BPE 306 produced peak numbers of 371 hp at 6,100 rpm and 367 lb-ft of torque at 4,000 rpm. This was a healthy, carbureted small-block Ford ready for action, but we were not done yet. Now it was time to take it to the streets!