The airflow improvements offered by the Stage 2 system decreased the vacuum (inlet restriction) present from 2.22 inches to 1.33 inches. Minimizing the inlet restriction resulted in an increase on boost pressure from 8.5 psi to 8.9 psi. If we take the change in boost offered by the upgrade 0.44 psi and divide it by the original boost (8.5 psi), we see that boost increased by 5 percent (0.44/8.5 = 5 percent). If we take that 5 percent and multiply it by the original power number (502 hp), we get 25 hp (matching the power gain almost exactly). This percentage gain in power relative to the boost and vacuum loss was consistent up to 20 psi.
We have concentrated our efforts primarily on the throttle body and air intake system, but the intake manifold connecting the throttle body to the inlet of the supercharger is equally important. The largest, fastest, most powerful supercharger in the world can be severely limited by a poorly designed inlet system, including the intake manifold. The intake design is almost always a compromise, as it must maximize airflow while simultaneously fitting the tight confines of the engine bay. Given the rear entry of most twin-screw and Roots-style Mustang superchargers, it becomes difficult to package the intake manifold and supercharger in such close proximity to the firewall.
Recognizing the importance of inlet restrictions, Kenne Bell designed its Mammoth intakes to maximize flow for high-horsepower applications (available for a variety of popular Ford modular engines). As with the throttle body and air intake systems, vacuum present in the intake manifold will reduce both boost and power. Testing on the Mammoth intake revealed an increase of 56 hp at 22.8 psi of boost. Like the throttle body, the gains offered by the Mammoth intake manifold increased with the power output.
71 Extensive testing on the...
71 Extensive testing on the chassis dyno revealed that restrictions in the air intake system increase with the power output. A throttle body upgrade might be worth nothing on a stock motor, but it can be worth over 60 hp on a high-boost supercharged application.
8 Not confined to the chassis...
8 Not confined to the chassis dyno, extensive testing was performed on the engine dyno as well. Running 20 psi of boost on a 5.4L GT500 motor requires plenty of airflow.
9 In an effort to correlate...
9 In an effort to correlate the vacuum losses with the airflow, boost, and power gains, Kenne Bell tested not only throttle bodies, but complete air intake systems on its SuperFlow 1200 airflow bench. As you might expect, there is a direct correlation between the airflow and power gains. Less vacuum in the inlet system equals more boost out of the blower, and ultimately, more power from the motor. Sometimes less really is more.
Body Test —Kenne Bell Supercharged...
Body Test—Kenne Bell Supercharged 4.6L 3V The graph illustrates the same throttle body test run at two different power levels. Tested at 500 hp (8.5 psi on stock Three-Valve), the Stage 1 upgrade netted an extra 24 hp. The same test run at 15 psi resulted in a jump from 614 to 649 hp (up 35 hp).
Throttle Body Test —Kenne...
Throttle Body Test—Kenne Bell Supercharged 4.6L 3V The third test run on the supercharged Three-Valve motor was to perform the throttle body upgrade at 20 psi. Equipped with the stock throttle body, the Three-Valve produced 621 hp at a peak boost reading of 19.4 psi. After the Stage 1 upgrade, the boost jumped to 22.0 psi, and the power output shot up to 682 hp. (up 61 hp).
Mammoth Intake Upgrade — Kenne...
Mammoth Intake Upgrade— Kenne Bell Supercharged 3V Since the intake manifold that connects the throttle body to the supercharger is part of the total inlet system, restrictions in the intake will also affect the boost pressure and power output. Tested at 22 psi, the additional flow offered by the Mammoth intake over the Stage 2 system (1,350 versus 869 cfm) improved the power output by as much as 56 hp (from 682 to 738 hp). The key thing to remember is to eliminate any and all inlet restriction on a Kenne Bell (or other positive displacement) supercharged application.