The injectors simply push...
The injectors simply push into the intake bosses and are held in place by the fuel rail. Lube the O-rings with a little white lithium. FAST recommended 42-lb/hr injectors (rated at 45 psi), which are good for up to about 650 horsepower. Injector size is fairly critical to overall performance. Too small, and you'll limit power and risk going lean. Too big gains you nothing on the top end but will likely cause idle and low speed issues. Jeff recommends that your injector duty-cycle at max power be no more than about 80 percent (our Hemi was at 70) and the duty cycle at idle be no lower than about 21/2 percent. That way you have room for the XFI system to protect against any lean conditions that might occur and you'll have fine enough control on the low end for good idle and low speed operation. Jeff has also found that a vacuum referenced fuel pressure regulator will help make a little oversized injector appear smaller, run better, and be easier to tune down low.
One upgrade you will need to make, though, is to an EFI compatible fuel system. You'll need a pump capable of providing the volume of fuel necessary for your power level and can also maintain the proper fuel pressure (normally 45 psi) at the injectors. A bypass regulator and return fuel line will also be necessary. The guys at FAST can help you with parts selection if you are not sure.
Programming the software is what usually scares most people away from EFI, and while FAST's C-Com XFI software has a large amount of capability built into it, once you start to break it down into its individual components, you'll be able to logically move through the system and you'll likely be amazed at the amount of control that you have. If you can tune a carb and a distributor and know how to read your plugs, you'll do fine with this software. If there is a trick to it, it's knowing what your engine needs in terms of fuel and timing throughout its rpm and load range.
This FAST throttle body works...
This FAST throttle body works much like a carb except, of course, that it's dry, flowing only air. This is one of the major advantages of fuel injection. Because the intake only flows air, you won't have any of the fuel distribution problems that you can have with a carburetor. The FAST system even allows you to tune the A/F ratio (and timing) for individual cylinders.
At the heart of the software are three tables or "maps" that control the amount of fuel delivered at every rpm and load, the amount of timing needed at a given rpm and load, and a target air/fuel ratio table. In each case, the load level is represented on the vertical scale and rpm on the horizontal scale. Knowing how to initially set up each of these will put you well on your way to setting up your tune. Fortunately, FAST has a number of base maps to help you get started. It's really not any different from tuning a carburetor and a distributor; you need to know that you have safe timing and air/fuel ratios at the start so you don't damage your engine on the first pull. It's been said that you can be rich all day but you can only be lean once. That's good advice.
There are basically three ways you can tune your FAST equipped engine: on an engine dyno, on a chassis dyno, or on the street. An engine dyno will probably allow the most accurate tune as you'll have complete control over rpm and load conditions, and you can easily measure the results of any changes that you make. However, cold start, cold run, and accelerator enrichment settings may need to be tweaked some once you are on the road.
Once you have the injectors...
Once you have the injectors and fuel rails in place, you'll need to connect them. We did it with some braided line. A -8 to -6 reducer is first O-ringed into the rail followed by a -6 90 degree elbow. Be prepared to fit your own line per your application. The opposite ends of the rails will be connected for fuel in and fuel return.
A chassis dyno is a real good place to put the finishing touches on an engine dyno tune, but it also works well by itself. If you are installing EFI on an engine that is already in the car, then this is the way to go. You'll be able to simulate real world driving conditions while closely monitoring your engine. You still may have cold start and run tuning to do because you need the basic engine tune in place first and it's unlikely you'll be able to let your car sit on the dyno long enough for your engine to go stone cold again.
Based on their experience (and probably that of your dyno operator) FAST will be able to help you get these types of settings close enough to get you out cruising.
On the back of the throttle...
On the back of the throttle body is the idle-air control motor or IAC. It provides and controls the amount of air needed to maintain the idle speed that is set into the ECU. Below it are three vacuum ports. The center will supply the power brake booster. The right hand one is for the MAP sensor. The left is unused for this application.
Tuning on the street can be done, but you'll need a lot of patience and a buddy to watch the engine condition on your laptop. Running your engine through all possible rpm and load conditions is going to be problematic since there is no way to safely and legally make full power runs. Also, street tuning by itself is just not the way to get the most out of your EFI investment because there is no direct way to measure any changes you make. An hour's worth of time on a chassis dyno will pay instant dividends.
However you decide to tune your engine, you'll greatly benefit from becoming familiar with the software's data logger feature. Once activated, it will record all of the sensor data so that you can go back over an entire dyno pull and see moment by moment the information that's coming from up to fourteen different sensors. Essentially, you can "relive" any period of engine time in slow motion.
Most any distributor can be...
Most any distributor can be used with the FAST system as long as the mechanical timing can be locked out since all timing functions are set and controlled by the XFI box. This is a dual-sync distributor from FAST. The FAST dual-sync distributor also has a cam sync that allows sequential injection instead of simply squirting bank to bank. Cam sync tells the XFI which cylinder is firing so it can control each injector individually. On a mild engine like this, either method works great. It's when you get more radical and especially with blown, turbo, or nitrous applications that it's nice to have control over individual cylinder's A/ F ratios and timing. Note the water temp sensor below.
The throttle position sensor...
The throttle position sensor or TPS tells the XFI module not only the actual throttle position, but also how fast it may be opening or closing. This is critical for accelerator enrichment functions.
Our FAST distributor had a...
Our FAST distributor had a small interference issue with the Indy manifold. After a little grinding on the intake, they were able to play nice together.