Shift from EZ self-learning to programming power with FAST
By Richard Holdener/Photos by Cindy Bullion
The FAST EZ-EFI is an impressive little fuel injection system with plenty going for it, including affordability, ease of installation, and (best of all) self-learning tuning technology. Seriously, is there a better upgrade you can make on your street rod than removing a carb and bolting on a fuel injection system that pretty much tunes itself ?
If you’re not familiar with the EZ-EFI system, think of it as fuel injection 101. It is the type of system that first-timers use to replace that faithful carburetor they know and love. Let’s face it, carburetion works well, but fuel injection provides the ability to dial in the air/fuel mixture under every possible combination of load and rpm.
By comparison, carburetors are considerably more limited. Sure, it’s possible to get a carbureted motor tuned well at idle, wide-open throttle, and even part throttle, but just try leaning out the mixture under cruise conditions at just 2,300 rpm. This is where fuel injection shines, and what makes a system like the EZ-EFI so attractive.
The entry-level FAST EZ-EFI system is very cost effective and bolts right in place of a conventional squarebore carburetor. Hook up is simple, requiring only a few sensors, such as coolant temp, manifold pressure, and the all-important oxygen sensor.
The O2 sensor is really the key to the success of the EZ-EFI, as this allows the system to selftune based on the readings gathered through the exhaust. The system allows the user to input the desired air/ fuel values for different load and rpm ranges. Then, all you have to do is idle or drive the vehicle and let the sensor and ECU do the rest.
Using readings from the oxygen sensor, the EZ system adjusts the fuel supply to the motor until the actual air/fuel levels match the desired air/fuel targets. The EZ-EFI then creates a new fuel map, so the system is not constantly trying to make massive adjustments. Of course, it is necessary to load in a few engine parameters, like displacement, to give the system a starting point, but once set, the EFI will keep things running smooth and easy from cold starts to huge altitude changes. Try that with a carburetor!
As good as the EZ-EFI system is, there are naturally limitations, such as being best on mild engine combinations. The critical element seems to be cam timing and the associated idle vacuum (or lack thereof ). Because the system relies on a manifold pressure signal, when the idle vacuum drops near or below 10 inches due to more aggressive cams and engine combinations, the EZ-EFI is challenged when it comes to optimizing the fuel requirements.
To put this number into perspective, a stock V-8 (of any make) will usually produce near 20 inches of vacuum at idle. Wilder cam timing can also wreak havoc on high-rpm fueling.
The enthusiasts that work at Memphis- based FAST recognized that a great many performance applications featured cam timing that might be a step or two beyond the ideal target of an EZ-EFI system, but still not require an advanced, stand-alone XFI management system. For these special applications, FAST has introduced their XFI Street Management EFI system.
So, what makes the XFI Street system different than the EZ? The major offering is laptop programmability. Once the parameters have been loaded in the EZEFI, the system runs in closed loop, using the oxygen sensor to dial in the target air/fuel. While the XFI Street system can also be run in closed loop using the oxygen sensor, users are also able to manually program adjustments.
This tuning ability affords the XFI Street system more flexibility to handle low idle vacuum or wilder cam timing. The XFI system also features data logging, advanced diagnostics, and can even be used on individual-runner induction systems.
The versatility of the XFI Street system is impressive, as systems are available for use with the EZ-EFI throttle body, multi-port injection, and as a simple ECU retrofit for existing EZ-EFI systems. So, whether you’ve upgraded that mild crate motor with a new cam and heads, or started fresh with a lumpy big or small block, the new XFI Street EFI system has you covered. SRL
SOURCE: Fuel Air