Richard Holdener
March 29, 2010

If you own an '05-up Mustang GT, chances are you've been looking into ways to make it faster.

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.

The other option is to forgo natural aspiration and look into something a little more, shall we say, supernatural. We aren't talking about performance voodoo dolls or chicken sacrifices, but rather artificial aspiration.

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 illustrate the kind of gains available from supernatural aspiration, we took a stock 4.6L motor from an '05 Mustang GT and subjected it to both boost and juice.First up was a nitrous kit from Zex, followed by a Vortech supercharger. The final from of supernatural aspiration came from a twin-turbo kit from HP Performance in Roswell, New Mexico.

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.

Juice It!
We started our supernatural assault with chemical warfare. The history and make up of nitrous oxide has been covered in detail on numerous occasions-what you should know is that the important part of nitrous oxide is the oxygen it supplies. When nitrous oxide is injected, the chemical compound is broken down and releases the free oxygen molecules. Combined with additional fuel (to maintain the proper air/fuel ratio), the oxygen burns and produces exceptional power gains.

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.

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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.

Get Blown
What would any list of supernatural mods be without supercharging? Adding a supercharger to a Three-Valve is a no brainer, especially once you see how easy it is to make serious power.

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.

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The supercharger kit required installing the factory water pump (we ran a Meziere electric pump on the NA and Zex combinations), along with all the accessories. A single belt was employed to run the accessories, as well as the supercharger.

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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.

Turbocharge It
Putting the final super in supernatural was a twin-turbo kit from HP Performance. The kit features a pair of 57mm Garrett turbos, a pair of Tial wastegates, and a pair of blow-off valves. Naturally, the turbo system was equipped with a front-mounted, air-to-air intercooler. When run on a Four-Valve Terminator crate motor, this same system produced nearly 1,000 hp at 20 psi of boost.

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.

HP Performance now offers an equally powerful single turbo kit for the '05-up Mustangs, as well as a full array of kits for 5.0L and modular Mustangs. Hellion Power Systems and a few others also offer suitable turbo kits.

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.

Things really got serious once we upped the boost pressure to 11 psi, as the Three-Valve produced 624 hp and 664 lb-ft of torque. Torque production exceeded 600 lb-ft from 3,500 to 5,400 rpm, making this one serious torque monster. Even down at 3,000 rpm, the twin-turbo motor belted out 575 lb-ft of torque-so much for turbo lag!

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

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HP Numbers
Stock, 150hp Zex, Vortech (13.7 psi), HP Turbos (11 psi)
RPMSTKZEXVORTUR
3,000193192225328
3,300213212252367
3,600247248312427
3,900272301349476
4,200304392401525
4,500324482450569
4,800341496486593
5,100357506525612
5,400358509560624
5,700357509582620
6,000361510599614
6,300355461613NA

TQ Numbers
Stock, 150hp Zex, Vortech (13.7 psi), HP Turbos (11 psi)
RPMSTKZEXVORTUR
3,000338337394575
3,300339339402584
3,600361362456623
3,900367406470641
4,200380491502655
4,500278562525664
4,800373542535649
5,100367521540630
5,400348495545607
5,700329469536571
6,000316446524538
6,300296384511NA