We disconnected the negative battery cable, and Saul routed the wires from the controller's harness into the 'Stang's cockpit. Wiring is simple, as it's only a matter of connecting five color-coded wires from the harness to their corresponding components (red/switched 12V, yellow/any negative fuel-injector harness wire, green/Boost Cooler pump, black/ground, and gray/Boost Cooler touch-screen display). Four additional wires extend from the other side of the controller and allow optional components such as a fluid-level switch, auxiliary 12V output, SafeInjection trigger, and flow-signal output. Unfortunately, time constraints forced us to hastily plumb and wire the system for basic operation in this tech exercise, but we've cleaned things up considerably since this photo was taken.
These photos depict the bread and butter of the Stage 3G Boost Cooler system's True 2d Injection Control, which uses engine fueling and boost pressure to ensure accurate injection of water-methanol. We used this vacuum T-fitting to tap into a boost source and spliced the controller's Yellow wire into the negative/ground side of the injector harness (also a yellow wire on our XFI harness) at the number-one cylinder.
The kit includes wire-splice connectors for this task, but we recommend directly splicing it into the injector harness and securing the connection with solder. Protect it with shrink tubing to reduce the chances of grounding the circuit, which could cause an injector to hang open and possibly damage the engine.
The first step in dialing in the water-meth system is selecting the setup mode on the LCD touch-screen controller and entering information the controller requires (boost psi to start injection, flywheel horsepower, nozzle size, and pump size) for programming the injection's amount and rate. With the setup data entered, we made a series of dyno runs with the system in peak-and-hold mode to determine the peak duty cycle for our new fuel injectors. Stage 3G's injection control algorithm is based on 85 percent duty cycle, which our 150-lb/hr injectors are below. Once injector duty cycle has been confirmed (48 percent), we subtracted that amount from 85 and entered the remainder (37) as the amount of gain (fine-tuning percentage) to the injection curve.
Harv of HMS Performance is the man when it comes to manipulating FAST's XFI engine management system. While theoretically, our 150-lb/hr fuel-injector upgrade is actually better suited for a 1,100-plus horsepower application, it didn't take Harv long to duplicate the 811 horsepower we saw with maxed-out 650cc injectors, and then extend the engine's performance envelope by finding more than 10 additional horsepower and 22 lb-ft of torque. This thing can easily make more horsepower with an intercooler, but the tune is safe and the engine now makes more than enough horsepower for the street," says Harv. With the big injectors, you'll lose the crack-of-the-key starting that is one of the cooler aspects of fuel-injected, high-horsepower street cars (we now have to give the engine a little throttle for cold starts), but that's about the only thing you give up when you run big injectors. The car's driveability will still be fine."
We checked spark plugs and were happy to see their cocoa brown color return with the changes Harv made in the XFI fuel tables. Initial hits on the dyno with the bigger injectors brought about heavy black smoke that's the telltale mark of a rich mixture, and early inspections of the plugs confirmed it. Harv dialed a good air/fuel burn and smooth idle into our coupe's bullet, and then manipulated timing and decreased fuel to allow water-methanol to make the difference we were looking for in terms of lowering our engine's inlet-air-charge temperature without sacrificing any of the performance we gained during the dyno session.
The monitor screen displays real-time data for injector duty cycle, boost pressure, and water-meth injection rate. The Stage 3G system allows you to fine-tune the injection rate up or down on the fly by simply touching the screen to add or subtract gain.