K.J. Jones
February 7, 2007
Gonzolo Topete's S197 sits on the Dynojet 224X chassis dyno at GTR High Performance, awaiting another turn on the rollers. The 'Stang is lowered, it has been given an X-shape crossover exhaust pipe, and it wears dubs on all four corners, but it's otherwise virgin. It's a perfect candidate for the type of bolt-on testing we have in mind.

Horse Sense: Power-mad enthusiasts should be careful when selecting various parts for improving their Mustang's appearance. The test ride in this story suffered a 10hp loss when the stock 17-inch wheels and tires were replaced with a 20-inch combination. A mere 3 inches in wheel diameter can bring on performance-killing weight. You probably don't think about that when you're buying the bling, but the dyno exposes it every time.

We can't help but get excited by the fervor with which Mustang enthusiasts have embraced modifying their brand-new Ponies, sometimes almost immediately after they've arrived at home from the car's maiden voyage from the dealership.

While the mods 'Stangbangers are currently making to their '05-'07 'Stangs can be classified as mild, wild, and everything in between, the one thing that seems to remain constant is the upgrades almost always involve installing an aftermarket part or system, stepping up the power output of the 4.6, Three-Valve engine sitting under the hood. This type of Mustang upgrading to make power isn't anything new. Improving a Mustang's rear-wheel horsepower and torque has always been the name of the game for dedicated enthusiasts. We're always experimenting with different methods of gaining more oomph for the powerplants motivating our favorite ponycars-especially these new ones.

Meet the players in our exercise. Shown are Gibson's 2 1/2-inch post-axle mufflers (PN 319001; $439.00) and Steeda's new S197 cold-air induction system, featuring an improved, high-flow intake tube (PN 555-3131; $379.95). This CAI requires recalibrating the PCM, as the stock fuel and timing parameters are not capable of effectively processing increased airflow. SCT's XCalibrator 2 flash tuner (PN 388-9415; $399.00) is available for use with the Steeda CAI. The tuners come loaded with programming that updates a PCM's fuel and timing calibrations, enabling the S197's computer to function without hassle. The March Performance underdrive crank pulley (PN 01158; $114.36) is the same unit that works on '99-'04 Mustang GTs.

For this exercise, we're taking a trip back to the future by installing and dyno-testing a collection of parts proven to be bonafide best-bang-for-the-buck methods of producing commendable, bolt-on power for post-'79 V-6 or V-8 Mustangs. Many diehard 'Stang junkies probably already know what we're getting at, but for readers who are not quite sure what parts we're talking about, they include: cold-air induction systems, post-catalytic exhaust (crossover tubes and mufflers), and underdrive pulleys.

This trifecta (and a gear swap) is probably the most tried-and-true group of proven Mustang upgrades ever discussed in any Mustang magazine. Countless tests show that increasing air volume/ velocity, reducing drag from serpentine belts, and setting up a freer-flowing exhaust system establishes a collective starting point for hopping up a 5.0 or 4.6, mainly because these upgrades are relatively inexpensive.

Thankfully, not much has changed for these three entry-level bolt-ons in the last 20-or-so years since they hit the 'Stang scene. They're still extremely popular, and despite this new age of calibrating PCMs with handheld flash tuners and custom chips, they're also not too complex when it comes to installing them.

In this report, we're covering our installation of S197 products from Gibson Performance Exhaust (after-axle mufflers), March Performance (underdrive crank pulley), and Steeda (CAI with high-flow inlet elbow and required SCT XCalibrator 2 flash tuner) on a new '06 'Stang GT. We'll also show how they measure up against the rollers of the Dynojet chassis dyno at GTR High Performance in Rancho Cucamonga, California. Our thanks go out to GTR's co-owners Gonzolo and Ricardo Topete, who came through for us and made this project a smooth effort. Gonzolo owns the 5,000-mile Mustang that's featured in this report. His brother Ricardo handled not only all the dyno testing, but also the parts installation, with help from GTR technician Dan Ellebracht.

In the following captions, check out the highlights of our day, as well as the all-important results of how our stock 4.6 responded to the new pieces.

Photo Gallery

View Photo Gallery

We gave Gonzolo's 'Stang a baseline run on GTR's Dynojet prior to starting our project. We tested it again after each piece was installed. Ricardo was mindful of maintaining ambient and engine temperatures throughout our testing, with a large surface fan and a gauge pointer at center for each engine pull. He also adhered to a strict 2,000-6,000-rpm range for every dyno run.

Our findings were interesting. In stock trim (except for the 20-inch wheels and X-shape exhaust crossover), the GT put down 263.80 hp and 289.42 lb-ft of torque at the rear tires, which is about the average performance we've seen for stock S197s with five-speed transmissions.

After bolting on the Gibson mufflers, the stock 4.6 showed a slight gain in power (265.32) and some loss on the torque side (285.96). This loss of torque really doesn't surprise us; we attribute the decrease to the slight reduction of backpressure due to the freer-flowing Gibsons.

Adding the March underdrive crank pulley resulted in a more significant jump in horsepower (7.81) and torque (10.63 lb-ft). The Three-Valve's performance surpassed its stock numbers, and air/fuel ratios ranged between 13.5 and 13.7 from 3,500 rpm to our cutoff at 6,000.

Steeda's cold-air intake system with SCT's tuning was our last installment, and again we saw gains. On the horsepower side, the increased airflow and PCM calib-ration resulted in 17.06 more horses and 7.64 lb-ft of torque at the rear wheels of the test Mustang. But we also saw significantly leaner air/fuel levels (14.1). SCT's XCalibrator 2 allows users to add small percentages of fuel to stabilize the air/fuel ratio. Although our testing officially concluded, Ricardo used the tuner to make adjustments that resulted in a much better 13.1 ratio, with a gain of 2 more horsepower and lb-ft of torque.

Overall, we netted 26.39 rwhp and 14.61 lb-ft of torque at the peaks and more at the big end with this simple collection of bolt-ons that'll set you back just more than $1,300 if you're a retail shopper. This cold-air tuning, underdrive pulley, and free-flow exhaust collaboration is definitely a sure thing for S197 Mustangs.