EFI And XFI Essentials - Demystifying EFI

To create that landscape, we turn to one of the C-Com's numerous customizable tables: Fuel Ratio vs. RPM & MAP (manifold absolute pressure). In speed/density mode, the ECU first determines the volume of air being consumed by the engine. Then it looks to this table to determine what air/fuel ratio is the target and how much fuel is needed to hit it, and then makes any necessary corrections. The target air/fuel ratio table is a critical part of the calibration in speed/density mode, but the optional Alpha-N mode does not use it as part of the base fuel calculation; it simply references injector pulse width from the base fuel table. Got that? Don't worry; it's all in the book.

The XFI's C-Com software isn't just full of tables of numbers that make your eyes glaze over, 3-D graphics are available to help tuners visualize the landscape they are creating. It's also very helpful for spotting any accidently overlooked or mistyped areas of the tables.

The table on the right shows the line that the engine actually followed through the ratio cells during a dyno run; the green dot follows the line and shows where the engine is at each rpm. All of this is replayable, thanks to the XFI's data logger, as well as the chart on the left that shows a sampling of sensor readings for 8.5 seconds overlaid. The lines are viewable separately for clarity, or overlaid with your choice of readings.

It's not all about pure horsepower; we were particularly amazed by how many minor adjustments are available in the XFI for tuning manners and driveability. The Idle Speed vs. Coolant Temperature chart (shown) is one of a dozen or so options for dialing in an engine's cranking temperament.

Since we had the benefit of attending class at Westech, we had dyno cells on hand to see the FAST systems in action. Westech's dyno and engine expert, Steve Brule, was the maestro at the SuperFlow controls.

First up was the FAST EZ EFI. There's no tuning class available for these because they simply don't require it. This one was dropped on this basically stock small-block Chevy, and it was up and running to perfection within minutes.

Next, we had an LS equipped with FAST XFI as well as FAST's LSX intake and 102mm throttle body. Getting everything dialed-in is a more time-intensive process, but the payoffs can be huge for those with radical combinations or power adders. XFI's Qwik Tune stores up to four different profiles, which are accessed with the flick of a switch. That means you can drive around town on a street tune and have multiple track tunes ready-a two-stage nitrous tune for example.

Toward the end of the day, the classroom time became more informal with Macy opening up the floor to the students to discuss specific questions or problems, or for going back over areas they are unclear on. This was particularly useful since Macy could reference his own experience racing XFI-equipped cars.

There's no final exam, but there is a certificate of completion handed out that's great for our garage, but would also be an ideal wall hanger in a professional tuning shop to promote customer confidence.