KJ Jones Senior Technical Editor
July 1, 2009
Photos By: KJ Jones
Horse Sense: As late-model Mustangs continue to evolve, discovering the power-making (or power-losing) potential of basic bolt-on parts will forever be an important segment of the work we do with our favorite rides.

Once again, it's time for us to stop wondering about the performance-improving capabilities of different parts combinations for '05-'09 Mustang GTs. Our continuing mission is to find out through installing and testing pieces, and letting all of you know the real deal when we're finished.

Enhancements for S197s and their 4.6-liter, Three-Valve engines have come quite a long way since the cars were introduced back in late 2004. Today, Three-Valve cylinder head (porting) and cam technology have taken off, as has exhaust development and the much-talked-about supercharger and turbocharger systems that have surged to the forefront in the new-Mustang performance game.

Despite all the new and cool pieces and ideas we hear about, we also take time to jump back every now and then and revisit what can now be considered a classic tech concept for late-model Mustangs.

It's pretty much universally acknowledged that since about 1986, the affordable, basic Mustang bolt-on package has consisted of a post-catalytic exhaust system (mufflers); underdrive pulleys; cold-air induction; throttle bodies; upgraded coil packs (for '99-'09 GTs, Mach 1s, Cobras and Shelby GT500s); and aftermarket tuning. We've compiled and tested many variations of the basic package using parts from several different manufacturers in our control sets for each test. For the S197 bolt-on evaluation you're reading about right now, we decided to keep the product selection largely under one umbrella. With the exception of an after-cat exhaust (we're using Corsa Performance Exhaust's new system), Granatelli Motor Sports offers all of the basic parts necessary to take the first steps in modifying an '05-up Mustang. While our initial steps are focused on natural aspiration, we went beyond basic with this project effort and added a Zex nitrous system to Abraham Becerra's '06 Mustang GT after all of the GMS gear and Corsa muffs were in place.

All of the parts installing and all-important dyno testing for this review was handled by Ricardo Topete of GTR High Performance in Rancho Cucamonga, California, with assistance from GTR's lead technician, Chris Balster. Similar to Fox-body-and-later Mustangs, all of the basic bolt-ons for Ponies like Abraham's can be installed in a day or two by Mustang enthusiasts who are up for a good, do-it-yourself challenge.

An after-axle exhaust swap was the first order of business in the mega-upgrade session we planned for Abraham's bone-stock '06 Mustang GT, and Corsa's new, trick Ultimate Touring System was selected for the exchange. Ricardo had the new mufflers in place in 30 minutes, and the sound we experienced when the 'Stang roared on the dyno turned heads.

More impressive was the sound that we didn't hear inside the cabin area. The Corsas are unique in that they're designed to be quiet both inside and outside the car at cruising speed, but they let out a strong roar--audible outside only--when you step on the gas. On the inside, noise levels are so comfortable that a non-yelling conversation can be held even when the windows are down slightly. The drone that is common to other aftermarket exhaust systems is completely gone.

Because our plan was to eventually spray nitrous into Abraham's drone-free Three-Valve engine, we felt it was a good idea to enhance spark by adding hotter coil packs. Granatelli Motor Sports' Pro Series Xtreme coils were selected for this upgrade. They're specifically designed for nitrous-injected or supercharged/turbocharged applications that have a higher propensity for spark blowout than naturally aspirated stock engines. Keeping the candles lit at high rpm is critical when using power adders.