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.

The coils were easy, and the pulley swap for the Three-Valve bullet in our test Mustang continued that theme. It involves changing just two pulleys--on the crankshaft and water pump--as opposed to swapping three pulleys, as we do on pushrod engines and Two-Valve modulars (the alternator pulley is replaced on these two engines), and the task can be done in about an hour. The Granatelli Motor Sports pulleys we installed reduce crank and water-pump rotating speeds by 25 percent, which helps increase a trey-valve's rpm rate, and thus enables the engine to generate more power due to reduced drag on its crankshaft and water pump.

Granatelli Motor Sports' S197-Mustang cold-air-induction system was the fourth piece installed on Abraham's '06 'Stang. The kit is highlighted by its smooth-flowing cast-aluminum tube and bolts directly in place of the factory's airbox. The benefit in installing a cold-air kit for '05-up 'Stangs is twofold. First, it replaces the restrictive factory airbox and paper filter with a high-flowing performance filter. Second, by eliminating the really aggressive bend that's found in stock inlet tubes, the air has a cleaner/less turbulent direct flow to the throttle body.

The air-inlet tube for the cold-air/nitrous package comes from GMS with a Zex nitrous fogger nozzle already installed. However, the nozzle was removed for this stage of the project, which allowed us to gauge the CAI's impact on Abraham's 'Stang without any hint of the nitrous system. Although the GMS S197 cold-air system isn't supplied with a tune, we found that the influx of cooler high-pressure air affected the engine's air/fuel mixture to the point where it was definitely necessary to add fuel (14.7 at WOT).

Using the DiabloSport Predator, Ricardo selected the device's pre-programmed calibration for a comparable cold-air system, which is set up for a 90mm mass air, and we were instantly rewarded with safe (actually, rich) air/fuel of 11.8, 30 degrees of timing at WOT, and a final horsepower gain (from adding only the CAI) that was impressive, as you can tell from the dyno chart.

In the last four years, nitrous oxide use seems to have turned into a lost art of sorts when it comes to hopping up street/strip S197 Mustangs. That's not to say there aren't any nitrous kits that are compatible with the fuel-injected Three-Valve engines, because there are plenty. However, more and more enthusiasts are turning to supercharger and turbocharger systems to carry their Ponies to the big-power zone. Trust us--it doesn't have to be that way, especially when you're modifying your Mustang on a strict budget.

While the majority of our upgrades for Abraham's '06 GT affect naturally aspirated performance, we also added nitrous with a really cool, bolt-on system developed by Granatelli in conjunction with Zex. The GMS/Zex cold-air/nitrous system for '05-'09 Ponies is the most elaborate component in our upgrade package, and as such, took the most time to install. The kit is highlighted by the cold-air tube we detail earlier in this report, which is predrilled and tapped to receive a single fogger-style Zex nitrous nozzle. Also included with the nitrous package is a Granatelli Motor Sports' dual-window rpm switch, which we programmed to activate the nitrous shot between 3,000 and 6,000 rpm and only when the throttle is wide open.

We found that installation of the GMS/Zex S197 nitrous system is best handled by two people, as there are many tasks that must be performed to ensure it's done properly. GTR's Ricardo and Chris had the juice on and flowing in about four hours, and we headed back to the dyno to see what this final enhancement does for our test ride's power output. The photos and dyno details await you, so keep reading to see how our Three-Valve stocker fared when we started adding parts--and shooting juice.

On The Dyno
We gave GTR's Dynojet chassis dyno a serious workout during our quest for naturally aspirated power gains and major performance increases using nitrous oxide, putting no fewer than 24 runs on Abraham Becerra's '06 Mustang GT over the course of two days. As usual, baseline tests were done initially to determine the 'Stang's rear-wheel power in bone-stock trim, followed up by dyno runs after Ricardo Topete installed each bolt-on. An rpm window of 2,000-6,200 was maintained for the initial dyno pulls, as well as those with the bolt-ons.

Our test stocker responded well to all of the parts in our selection, showing impressive but not overwhelming naturally aspirated power-and-torque gains that are on par with data we've recorded in similar bolt-on parts evaluations for stock S197s. As we expected, the addition of a Granatelli Motor Sports/Zex cold-air/nitrous-oxide system proved to have the biggest impact on the stock Three-Valve, taking the 'Stang's rear-tire horsepower close to the 380 mark, with more than 450 lb-ft of tire-shredding torque.

 BaselineCorsa ExhaustGMS CoilsGMS PulleysGMS CAI
RPMHPTQHPTQHPTQHPTQHPTQAF
2,400121.86266.67122.88268.91123.69270.69125.17273.92102.27223.8118.00
2,{{{600}}}131.85266.33132.25267.14133.64269.95135.92274.56108.54219.2618.00
2,800144.47270.99145.30272.55146.11274.07148.27278.12117.88221.1018.00
3,000152.38266.77153.12268.06154.26270.07157.15275.13131.89230.8816.70
3,{{{200}}}163.12267.72163.70268.68165.68271.93168.54276.{{{62}}}146.31{{{240}}}.1416.47
3,400178.81276.21179.73277.62181.{{{57}}}280.47185.72286.88159.74246.7616.17
3,600194.55283.83195.89285.79197.76288.51201.58294.10190.10277.3415.17
3,800207.96287.42208.49288.16211.01291.65214.98297.13200.52277.1515.00
4,000222.00291.49223.76293.81225.40295.95230.34302.43213.89280.8315.48
4,200236.18295.34239.18299.09241.22301.65245.01306.39227.75284.8114.{{{90}}}
4,400244.47291.82248.17296.24250.03298.45255.32304.77248.36298.0614.63
4,600252.19287.94255.39291.60258.74295.42263.99301.41256.40292.7614.36
4,800259.85284.32262.66287.40267.27292.44273.10298.82264.70289.6314.39
5,000266.63280.08270.22283.84273.75287.55280.16294.29273.64287.4414.47
5,200267.73270.42272.35275.08276.49279.26282.54285.37277.79280.5814.10
5,400266.65259.35270.78263.37274.87267.34281.74274.03277.37269.7814.36
5,600266.89250.31271.17254.33275.62258.50281.90264.39277.74260.4814.26
5,800268.00242.69272.01246.32275.12249.13283.77256.96280.82254.2914.33
6,000266.77233.52271.40237.57274.15239.98283.17247.88282.75247.5014.29
6,200261.87221.83265.53224.92271.60230.08280.{{{80}}}237.87279.75236.9814.12
 {{{Diablo}}} TuneNitrousDifference
RPMHPTQAFHPTQAFHPTQAF
2,400123.37269.8711.84120.03262.6611.77-1.83-4.01-6.23
2,600133.30269.2711.73130.49263.5911.79-1.36-2.74-6.21
2,800146.04273.9311.56143.61269.3811.61-0.86-1.61-6.39
3,000154.68270.7911.56151.53265.3212.31-0.85-1.45-4.39
3,200166.96274.0211.26226.38371.5513.2063.26103.83-3.27
3,400183.81283.9311.66283.40450.7310.52104.59174.52-5.65
3,600200.31292.2311.75272.48397.6210.1477.93113.79-5.03
3,800212.56293.7911.58304.97421.4911.1097.01134.07-3.90
4,000230.35302.4511.78328.97431.9611.28106.97140.47-4.20
4,200252.04307.8511.76337.81422.4211.30101.63127.08-3.60
4,400257.29307.1211.69346.81413.9711.29102.34122.15-3.34
4,600266.61304.4111.52358.78409.6511.09106.59121.71-3.27
4,800275.98301.9811.48363.08397.2711.06103.23112.95-3.33
5,000284.19298.5311.56366.15384.6111.2199.52104.53-3.26
5,200286.26289.1311.74369.13372.8211.25101.40102.40-2.85
5,400286.58278.7311.82374.40364.1511.27107.75104.80-3.09
5,600288.43270.5211.88379.21355.6711.10112.32105.36-3.16
5,800290.96263.4711.92378.13342.4110.85110.1399.72-3.48
6,000291.86255.4811.86371.50325.2110.77104.7391.69-3.52
6,200289.83245.5211.86367.67316.590.00105.8094.76-14.12