Richard Holdener
December 13, 2006
Our never-ending quest for horsepower took us to MagnaFlow for an exhaust upgrade.

Here we are again, looking for ways to make more power from the '96 4.6-liter Two-Valve residing in the engine bay of Project Redheaded Step Child. Though we jumped the gun a bit in Part 1 by immediately testing minor bolt-on components, we stepped back in Part 2 and treated the 200K mod motor to some much needed TLC.

The list of high-maintenance components included new plugs, wires, and coil packs along with fresh Lucas synthetic oil, a new fuel filter, and an Accufab adjustable fuel-pressure regulator. We even replaced the well-worn accessory belt, something we noticed when performing the installation of the BBK underdrive pulleys. With the V-8 now ready for more power upgrades, we went to MagnaFlow for a few exhaust modifications-after all, what goes in must also come out.

Exhaust modifications rank right up there with mass air, throttle body, and pulleys in terms of popularity, and for good reason. They cannot only unearth additional power, but they also can alter the very character of the Mustang by replacing the mellow stock system with something altogether more menacing.

Given the relatively modest power output offered by the near stock, pre-PI mod motor, we were actually somewhat appreciative of the quiet demeanor. The last thing we wanted to do was draw unwanted attention from a nearby LS1, 350Z, or WRX. Don't get us wrong-if we pulled up next to them, it was most certainly go time. It just sucks to have to hope for wheelspin or a missed shift from your opponent in order to be competitive. Though the minor mods performed in Part 1 were worth a few extra ponies, we weren't even up to the power output of a stock PI engine, let alone one of the other more modern musclecars.

Last time out, Project RSC received a handful of basic bolt-ons, including a throttle body and plenum, a set of underdrive pulleys, and a custom chip. When tested at Powertrain Dynamics, the 200,000-mile 4.6 pumped out 209 hp at the wheels. Despite running on a DynoJet chassis dyno at both places, the power was down to just 199 hp in baseline form at MagnaFlow. We can't explain the difference in power between the dynos, but the new numbers repeated three times in a row and are a perfect example of why we reestablish a new baseline before we start swapping parts.

As luck would have it, the gang at MagnaFlow offered us not only a stainless steel performance after-cat exhaust for the '96 GT, but also a trick Tru-X X-pipe system. The Tru-X system was designed to replace the factory H-pipe. In 1996, Ford relied on no less than six catalytic converters to meet emissions. Not surprisingly, the use of six catalytic converters had a less-than-positive effect on exhaust flow. In addition to having to force the exhaust flow through the converters, the factory H-pipe also suffered from excessive tight-radius bends. The combination of the tight-radius bends and triple converters (per side) made us look forward to replacing the stock system with the much-improved Tru-X system offered by MagnaFlow.

Though not technically an emissions-legal part, the car will pass the sniffer portion of the stringent California test (we know this for a fact), if not the actual visual portion. Only a performance-savvy inspector will likely catch the X-pipe, since the MagnaFlow system did feature (obviously effective) catalytic converters. We liked the idea of having the cats in place since enthusiasts should continue to do their part to keep the air clean. Performance and reduced emissions are not mutually exclusive. Given the power gains offered by the replacement of the factory cats, we'd say there is probably little power left to be had from the removal of the two remaining cats-that is, until we step up the power level with cams, ported heads, and a new intake. We'll be taking a look at long-tube headers and a cat-less X-pipe in the near future, but for now, we like the idea of being clean and mean.