FAQ’s About FAST™ XFI™ Fuel Injection

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Getting answers to technical electronic fuel injection questions is as simple as a phone call or email to the FAST™ EFI HELP™ techline. Experts are available to reply to your specific needs and are qualified to provide fundamental and advanced information.

Many who contact the techline are advanced in their knowledge of fuel injection. Some are not. In either case, FAST™ tech support is available to answer any fuel injection questions you may have. Here are some frequently asked questions and answers on the XFI™ Fuel Injection System.


Email EFI™ HELP
Read More About XFI™ Fuel Injection
XFI™ Installation Manual
Download XFI™ Software
FAST™ Website


Will the FAST™ XFI™ unit work with my OEM harness?
No, the XFI™ unit has a dedicated listing of harnesses for the engine layout, injector firing order, and ignition source. Since virtually every application will vary, we decided to make it as simple and straight forward as possible. Pick one of six main harnesses, one of eight injector harnesses, and one of a dozen ignition harnesses and you have everything you need.

Does the XFI™ unit require modification if I decide to go from a naturally aspirated set-up to a boosted application?
No, simply change the MAP sensor to a 2 bar, 3 bar, or 5 bar depending on how much boost your engine will see. Then build your tuning files according to your supercharged or turbocharged application.

I am currently running my XFI™ in bank to bank mode. Do I have to have my ECU reconfigured to run in sequential mode?
No, just add a camshaft position sensor and select "Sequential Mode" in the operational parameters window and you are in business. No modifications to the ECU are necessary.

What is the Qwik Tune™ feature in the XFI™?
The Qwik Tune™ feature allows you to build four separate calibration files or "tune ups" and save them in the system as cal files 0-3. Then, through one of our dash-mounted switches, you can select between these tune-ups without hooking back up to the system with a laptop. This feature gives you the ability to have a race fuel tune, pump gas tune, low boost tune, and high boost tune all loaded in to the ECU. Then, you can easily and quickly switch to the desired settings. There are endless possibilities for tune up combinations with Qwik Tune™.

Do I still need to run a mass air meter with the XFI™ system?
No, the XFI™ is a speed density system so it doesn't use a mass air meter. Speed density systems use the manifold pressure and air inlet temperature to calculate the volume of air entering the engine. Speed density allows you to do away with the mass air meter and also factors boost into the fuel and timing calculations.

Is a FAST™ system difficult to tune?
No, compared to most systems, the XFI™ with its C-Com XFI™ software is extremely user friendly. The Windows-based software is loaded with shortcut features such as the "L-Key" function. This function will automatically correct the volumetric efficiency table, at a given cell, to the desired air/fuel ratio using the wide-band O2 sensor. Anyone with a good understanding of general engine tuning and basic computer skills will have no problem using this system.

Can the XFI™ also function as a data logger?
Yes, as long as a laptop is connected to the XFI™, you can record data from all of the standard engine monitoring sensors, plus up to eight auxiliary sensors, such as oil pressure, fuel pressure, EGTs, drive shaft speed, input shaft speed, nitrous pressure, and many more. The data is displayed in an easy to view graph. You can also use our dash/data logger, Part #301417, which records data logs without a laptop in the vehicle.

How does the XFI™ work with nitrous?
The XFI™ will give the tuner total control of up to four stages of nitrous. You can supply fuel enrichment for the nitrous system as a "wet" system (fuel through the nitrous plate or nozzles), or as a "dry" system (fuel through the injectors). If the system is set up as a "dry" system, a separate fuel table is activated with the nitrous solenoids. The timing is also automatically retarded to the settings you select for each stage. There are activation parameters that must be met for the nitrous to activate and the subsequent stages are activated on a time based delay.


Email EFI™ HELP
Read More About XFI™ Fuel Injection
XFI™ Installation Manual
Download XFI™ Software
FAST™ Website