T-top Coupe’s engine has always...
T-top Coupe’s engine has always been directed by FAST’s XFI EFI system. During the project’s down time, we sent the original XFI processor back to FAST, where it was upgraded with new XFI technology (2.0). The engine-management system’s new features, which include Qwik Tune Technology and advanced forced-induction controls, are highlighted by a cool “self-learning” function that literally brings brand-new engines to smooth idle and good driveability shortly after they’re started for the first time. Intelligent Traction Control also is now included in XFI 2.0 processors. We didn’t have time to experiment with ITC during this test, but we definitely plan on trying it out. Upgrades are available in two forms: software only for $49.95 and a software/ECU package for $99.95.
Engines in our T-top project car have always been commanded by FAST's XFI fuel-injection system. We've had great success using XFI for engine management, and consider it one of the best stand-alone EFI units for aggressive street/'strip Mustangs.
During the coupe's rebuilding period, we received word that XFI was also being revamped. And, of course, we immediately had interest in trying it with our new engine and intercooled Paxton Novi superchargers (2000 and 2500).
The new XFI, Version 2.0, retains many of the features of the first-gen system. However, engineers at FAST and tuning consultant Brian Macy of Horsepower Connection have brainstormed and developed quite a few new functions for the new ECU. Features such as Intelligent Traction Control and Self Learning are among the new additions to XFI, which give both amateur and experienced tuners the ability to dial in Mustangs for just about any driving condition.
We sent the 'Stang's original XFI processor back to FAST, and a few weeks later received the upgraded 2.0 ECU (FAST performs the hardware upgrade for $99.95). We were fortunate enough to catch up with Brian Macy for help with nailing down calibrations for our Mustang. (Brian travels all over the country giving classroom lectures, tuning in dyno sessions, and consulting with FAST on XFI features.)
Our tuning with XFI 2.0 took place over the course of two days in your tech editor's driveway, where preliminary parameters were established. It continued in the dyno cell at Extreme Automotive, where we set out on our mission to make big steam.
We called on Horsepower Connection's...
We called on Horsepower Connection's (
www.horsepowerconnection.com) Brian "The Professor" Macy for assistance with tuning Project T-top Coupe. Brian is considered one of the nation's top EFI tuners (and EFI University instructor). As a consultant to FAST engineers, Brian also is heavily involved with XFI's development and beta testing of its new features.
Our tuning experience began...
Our tuning experience began right in the driveway of Tech Editor KJ Jones's house, where Brian first adjusted the throttle body's idle screw so the engine would idle on its own. From there, an update is made in XFI's Throttle Follower table that sets the minimum IAC position to 10 (nearly closed).
After that, Brian set the...
After that, Brian set the idle speed in the Idle Speed vs. Coolant Temperature table to 900 degrees (when the engine is warmed up and with the IAC position at 10). These changes ensure that the IAC has enough adjustment to maintain idle rpm when the transmission is put in forward or reverse gear, and when starting from or coming to a complete stop.
When tuning with XFI (or any...
When tuning with XFI (or any other higher-end, aftermarket engine-management system), syncing actual timing with XFI's timing values is critical. XFI 2.0 has a new Fixed Timing Test Mode function within its Operational Parameters section. Using this feature is as easy as clicking on a check box and setting the value to 15 degrees.
With the engine running, timing...
With the engine running, timing is verified by looking at XFI 2.0's Spark Table and seeing 15 degrees at both the crank and the Spark BDTC value. With timing locked down and all timing modifiers turned off, Brian adjusts the distributor until actual timing matches the XFI value.
The next segment of establishing...
The next segment of establishing a basic tune for our new setup involves installing the car on a chassis dyno and setting up conservative air/fuel (Target A/F table) and timing (Base Spark table) values using established parameters from calibrations developed for engine/power-adder combinations similar to ours. With the high probability of T-top Coupe being used in varying altitudes, Brian tunes using XFI's Load Indexed Speed Density. With this setting, XFI 2.0 performs a barometric check and compensation every time the ignition is turned on.
The fuel side of the air/fuel...
The fuel side of the air/fuel mixture is manipulated next. Through the Base VE table, Brian adds and subtracts fuel based on closed-loop O2 sensor readings. With the engine held at 3,000 rpm, and then moving the throttle from light throttle to WOT, we were able to see how far air/fuel was from our target. Fixing the fuel curve is done by changing the value in each cell by the O2 correction-percentage amount, first in the Target Air/Fuel table and then in the Base VE table, until total correction is less than 5 percent.
Periodically consulting XFI...
Periodically consulting XFI 2.0's 3D graph gives tuners a visual idea of how calibration changes affect engine performance, as the data is completely real time. From an overall "tune" perspective, a gradual and smooth curve like the graphic shown here is desired.
FAST engineers have incorporated...
FAST engineers have incorporated Qwik Tune Technology into XFI 2.0. The new feature gives tuners the ability to save as many as four individual tunes in the ECU (for various fuel octanes, street driving/track racing, with different rev limits, and so on), which can be selected at any time through a simple two-position or four-position switch. We’re setting the coupe up with two calibrations for now—no-boost/low-boost street driving with VP Racing Fuels’ 100- or 109-octane street fuel (or even 91-octane pump gas in a pinch), and max-effort performance using VP’s Q16 race gas.