Forced-induction motors present extreme challenges in terms of power management, fuel consumption, and exhaust gas temperature. The good news is that XFI 2.0 offers a variety of features that deal with these challenges quite well. The system now has a three-port boost control solenoid for controlling the wastegates. It can be operated off either manifold pressure or compressed CO2. For flexibility, it can be plumbed to either add boost or to remove boost from the wastegate. Likewise, the XFI 2.0 software has both an open loop and even closed loop feature for boost control. Utilizing closed loop control, you can target the amount of boost that you want, and it will maintain that boost. If you utilize the open loop mode, then the solenoid pulse width changes over time. Since the XFI 2.0 software has the option to drive multiple injectors, it makes managing large quantities of fuel much easier. We have customers who run two or three injectors per cylinder on applications that require a lot of fuel delivery. XFI 2.0 also has an optional EGT system that allows monitoring exhaust temperature in each cylinder.
A great perk of the XFI 2.0 system is that it includes an internal data logging system. This eliminates the cost and complexity associated with installing a separate external data acquisition system. XFI 2.0 can monitor all of the engine parameters such as rpm, throttle position, coolant temperature, air temperature, and air/fuel ratio, just to name a few. With an external data acquisition system, additional sensors must be purchased to log these parameters. XFI 2.0 also features additional inputs that can be used for several more external sensors. By utilizing these additional inputs, it can monitor fuel pressure, oil pressure, wastegate pressure, backpressure, and driveshaft speed. The XFI system can also be combined with the FAST touch-screen dash that allows for even more inputs as well as hours of data-logging capacity.
Naturally aspirated and forced-induction motors call for vastly different tuning strategies. Much like a naturally aspirated combination, the air/fuel ratio of a forced-induction motor at idle and cruise speed is between 13.0:1 and 15.0:1. However, as boost increases, the fuel demands are much greater than that of a naturally aspirated combo. Between 14.5 and 29 psi of boost, an air/fuel ratio of 11.8:1 to 12.5:1 is common. At boost levels beyond that, the air/fuel ratio can get as rich as 10.0:1. As far as spark timing is concerned, ignition advance varies greatly depending on fuel type and inlet air temperature. In steady state cruising, anywhere from 25-35 degrees of timing is common. Between 14.5 to 29 pounds of boost, timing can range anywhere from 15-30 degrees. Beyond that level of boost, timing can drop as low as 12 degrees of advance. At any rate, forced-induction motors are very sensitive to changes in air/fuel ratio and spark advance, so it’s extremely important to get the tune dialed in right. CHP