The last time we took a look at Project Aerio we revealed what it took to turbocharge the 2.0-liter J20A engine. With the fabrication side of things done, it's now time to show you what it takes to add proper fuel tuning to our boosted powerplant. The Aerio's fuel system still utilizes a return line, saving us a lot of problems in setting up the upgraded fuel system.
To begin, we lined up the following equipment: Vortech 12.1:1 fuel pressure regulator and Holley 190 LPH fuel pump and, for the all-important fine tuning, an A'PEXi Super Air Flow Converter, aka, the S-AFC. Since the Turbonetics Racegate we're using right now is equipped with an adjustable 3-to 6-lb spring, we backed off on the set screw to allow 3 psi of boost pressure.
While we were at 3 psi we installed the Vortech FMU. As we stated earlier, the vehicle is equipped with an O.E. fuel return line. The Vortech unit is considered an inline regulator and not a replacement. What this means is the unit works off boost pressure, while the factory unit controls fuel flow under vacuum. The FMU hooks up inline with the return line and it must "T" into a vacuum source. When the regulator detects boost, it uses the boost pressure to close off the fuel return line, creating more pressure. The amount of regulation depends on the ratio of the FMU. Its ratio is based on additional fuel pressure versus boost pressure. For example, for every 1 psi of boost the regulator will compensate an additional 12 psi of fuel pressure. Considering our Aerio runs a factory-regulated fuel pressure of 38 psi, and we're planning to run 7 psi of boost, this technically means we'll get an additional 84 psi of fuel pressure at max boost pressure.
Next in the line up was our Holley fuel pump. The unit we chose is a 190 LPH pump. This pump is designed to work with the FMU in the sense that it's a high-pressure pump rather than high-volume. One thing you must remember is we haven't started playing with the injector pulse width yet, only the fuel pressure. This is the main reason we're working with fuel pressure for the coarse tuning of the project.
Last in the lineup was the A'PEXi S-AFC. This is as fine as we get in our fine tuning, other than hacking into the ECU and changing the aforementioned injector pulse width. The S-AFC has always been a flawless fuel-tuning tool, and since it modifies airflow signal to increase or decrease injector duty cycle, wiring is a matter of finding the correct signals on the ECU. Unfortunately for us, the A'PEXi wiring schematics do not include Suzuki's Aerio. For that, your beloved 2NR technical editor had to figure out how to wire it into the Aerio, and now he's giving you the info free of charge. What a nice guy I am.
Dyno Time
For weeks, the joke around the office has been, "When are we going to blow up the Aerio on the dyno?" Everyone here had a chance to see the car's connecting rods, and we were able to speculate on how strong the engine would be under boost. It appeared that 7 psi would be no problem for the stock rods, but boosting any higher would be risky. With the car on the dyno we made an initial pass with the boost set at 4.5 psi and only the Vortech regulator installed; the end result was 171.4 hp, with a mid- to high-rpm air/fuel ratio ranging from 12.9:1 to 13.1:1. This signified it was time to install the Holley fuel pump. All preliminary testing was done on a Dynamic Test Systems chassis dyno located at XS Engineering. The best part of this dyno is it gives us information on the fly so we can let off the throttle before we damage the engine. Data logging includes a knock sensor, air/fuel ratio, boost pressure and air temperature.