4.6L Cobra Intake Test: Stock vs. Aviator
The Aviator intake featured a dual-runner system much like the FR500 intake. Judging by the peak power numbers alone, you might be tempted to think the stock Cobra motor offered only 10 hp over the Aviator, but this is why we go through the trouble of running these graphs that illustrate the entire power curve. Below 3,000 rpm, the Aviator actually held the edge, but from 3,700 rpm to 6,800 rpm, the factory Cobra intake offered some serious power gains. The dual-runner Aviator intake offered slightly better power for the next 200 rpm (to 7,000 rpm), but the impressive midrange torque offered by the Cobra manifold would make it the clear choice on this combination. That the Aviator will not fit under the stock hood is another possible deterrent to running it in place of the Cobra piece.
The first order of business was to run the Cobra motor with the stock '01 intake. Not surprisingly, it performed quite well on this modified mod motor, posting peak numbers of 408 hp and 383 lb-ft of torque. |  | 
Due to its dual-runner design, the factory 4.6L Aviator intake is often plugged on the Internet as the poor-man's FR500. Equipped with the Aviator intake, the 4.6L produced 398 hp and 352 lb-ft of torque. |
4.6L Cobra Intake Test: Stock vs. FR500
Like the Aviator intake, the FR500 featured a trick, dual-runner design that offered basically two intakes in one. Unfortunately, even the dual runners couldn't match the Cobra intake in the all-important midrange. Below 3,400 rpm, the short runners on the FR500 bettered the factory Cobra intake, but from 3,900 rpm to 6,500 rpm, it was all Cobra. Above 6,500 rpm, the FR500 pulled away thanks to the short secondary runners. For maximum effort motors that regularly exceed 7,000 rpm, the FR500 intake has something to offer, but like the Aviator-which is closer in power to the factory intake than the FR500-the FR500 is not ideally suited to a mild Cobra motor.
Removing the lid of the FR500 intake revealed the secondary throttle blades that opened to activate the short (high-rpm) runners. The Aviator intake shared this design philosophy, though the lengths and cross section differed. |  | 
Pricey to be sure, the FR500 intake from Ford Racing Performance Parts offered light-weight magnesium construction, a trick dual-runner design, and plenty of peak power. Equipped with the FR500 intake, the mod motor produced peak numbers of 422 hp and 346 lb-ft of torque. |
4.6L Cobra Intake Test:Stock vs. Sullivan Intake (with Elbow)
The Sullivan intake was run in three different configurations: two EFI and one carbureted. Isn't it ironic that the carbureted combination produced a higher peak power reading than any of the EFI configurations? The reason the carbureted combination produced the best power was the introduction of fuel into the intake well before the head ports (where it's injected in EFI configuration). The introduction of fuel actually helps reduce the intake charge temperature, which, in turn, helps improve power production. Since the Sullivan intake was basically a single-plane carbureted intake, it was only natural that it be run in carbureted form as well as with the elbow (the oval Accufab throttle body) and the four-hole throttle body. As indicated by the graph, the short-runner Sullivan intake produce exceptional power past 6,000 rpm-bettering the stock intake by nearly 50 hp at 7,000 rpm-but lost power from 3,000 rpm to 6,000 rpm.
The Sullivan intake was tested in a number of different configurations, including this front-mount elbow designed to accept the factory Cobra throttle body (or suitable aftermarket version). Equipped with the Sullivan intake, the motor produced 432 hp and 349 lb-ft of torque. |  | 
To ensure adequate flow for the Sullivan elbow (and intake) we installed a single-blade throttle body from Accufab. |