2005 Ford Mustang GT Vortech, HP Performance, & Vex Upgrade

Sure, there are always the minor mods, which most of us choose strictly from a cost standpoint. Things like cold-air intakes, programming, and even headers or exhaust mods all yield decent performance gains. The problem is, unlike the previous Two-Valve motor, the Three-Valve is in such a higher state of tune that big power gains are not going to come from simple bolt-ons. You'll have to look at cams or changes in displacement to really make a difference.

It doesn't matter whether it comes from a bottle, a supercharger, or even a pair of turbos, adding power with supernatural aspiration will yield gains only dreamed of by the all-motor crowd.Rather than gains of 10, 20 or even 30 hp, boost and/or juice can yield gains of 100, 200, or even 300 hp. That my friends, is what supernatural is all about!

To ready the 4.6L for dyno use, we installed a set of JBA long-tube headers and a FAST management system, and swapped out the stock injectors for a set of 65-pounders, also from FAST.

It should be noted that the Three-Valve motors feature two electronic systems that make dyno testing difficult. The first is the electronic throttle, which we got around by converting to manual activation. Simple vice grips allowed us to create our very own drive-by-wire.

The last hurdle was the variable cam timing. Unfortunately, the FAST management system couldn't control the variable cam timing, so we were forced to run the cams in a locked position. This is not a big deal since all tests were run in the exact same configuration, but it would be nice to have the extra power offered by retarding the cam at higher engine speeds.

Run in stock trim with the long-tube headers, the 4.6L produced 361 hp at 5,800 rpm and 381 ft-lb of torque at 4,300 rpm.

For our mod motor, we chose a wet EFI system from Zex. The Zex wet kit combines the nitrous and fuel into a single fogger, and injects that mixture into the throttle body. As with most kits, the amount of fuel, nitrous, and eventual power is controlled through jetting. For our test, we installed 150hp jetting, but made sure to optimize bottle pressure with a bottle heater.

Adding the 150hp shot from the Zex nitrous kit increased the power output from 361hp and 381 lb-ft of torque to 510hp and a stump-pulling 562 lb-ft of torque. All this additional power came at the touch of a button. No wonder nitrous oxide is so popular.

For our test motor, we chose a blower kit from Vortech Engineering, but there are a number of kits available from a variety of sources. The Vortech kit features a reverse-rotation Si supercharger, but we elected not to run the intercooled system.

Our previous fuel system upgrades would now come into play, as the supercharger was first configured to produce a peak boost pressure of 11 psi at 6,200 rpm. So equipped, the 4.6L produced 559 hp at 6,200 rpm and 513 lb-ft of torque at 5,300 rpm. A quick pulley change netted an increase in boost pressure to 13.7 psi, and with it an increase in peak power to 613 hp and 545 lb-ft of torque. Without the intercooler, that was about as far as we dared push the stock motor, despite the use of race fuel.

Run at the higher boost level, torque production exceeded 500 lb-ft from 4,200 to 6,200 rpm. All cranked up in intercooled form on an otherwise-stock Three-Valve motor, this same Vortech supercharger kit pushed the author to 192 mph in an '05 Mustang during a top speed test.

The turbo kit certainly had the power potential if you have the motor properly built to withstand the intended output. For our needs, we limited boost on this stock motor first to just 6.2 psi, then to 11 psi. The reason for limiting the boost pressure was that the motor produced so much torque that we began to fear for the strength of the internals.

On this stock 4.6L application, the twin turbos improved power output from 361 hp and 381 lb-ft to 500 hp and 530 lb-ft at just 6.2 psi. Imagine that-adding 140 hp with just 6 psi of boost.

The question now is not which form of supernatural aspiration is better, but which one works best for you?