Horse Sense: As with most X-pipe designs, MagnaFlow's is said to offer performance improvements without an obnoxious exhaust note to turn you deaf. As you will see by the Dyno Doings sidebar, we did make some nice power numbers, but our exhaust was none the quieter-although it wasn't any louder either. We can only suspect the Steeda side-exit after-cat system, which exits right at the side windows, keeps the exhaust note close to what it was before (with the stock H-pipe) due to its exit location. The sound is truly sweet when it bounces off traffic or close buildings, so we're not complaining.
The MagnaFlow Tru-X Crossover...
The MagnaFlow Tru-X Crossover Pipe system features 211/42-inch, mandrel-bent tubing, two high-flow converters, and stainless steel construction. Mounting hardware is included, but you might want to pick up a new right exhaust manifold gasket since sometimes they are damaged during removal of the old H-pipe.
Our 3g GT's exhaust modifications to this point have been limited to the Steeda side-exit exhaust kit. While the kit looks awesome and has a great sound to match, our P-1SC-blown '01 needs more. If there's one thing blower cars like, it's bigger exhaust. There's no need to throw big bucks on the intake side of things right away, as the blower is forcing the air into the engine, artificially increasing the volumetric efficiency of the engine, if you will. Of course, intake-side modifications will still reap some horsepower benefits, but the exhaust side of the equation is where your money will be better spent (in street applications at least).
To that end, we wanted to help our 3g GT exhale a little more easily, while retaining the converters (we have to live on this big rock, too, you know). Since we hope to install a 5.0 stroker mod motor at some point, we opted to avoid the headache of installing headers on our Two-Valve at this time. That left us with but one area to wrench on-the stock four-cat H-pipe that sat between the stock headers and our previously installed Steeda side-exit system.
We placed a call to MagnaFlow for its Tru-X crossover pipe with con-verters (PN 93335). We've installed MagnaFlow's after-cat systems before with great results. And though its newest Tru-X is for Fox 5.0s (see "Ignite the Future," Mar. '02, p. 171), our past experience with the part's fit and design is what had us picking up the phone and calling MagnaFlow.
Lugo Performance's Eddie Burke...
Lugo Performance's Eddie Burke begins our stock H-pipe removal by disconnecting and removing the forward O2 sensors. The plugs are difficult to reach as they are up high at the back of the block. A long, small-shank screwdriver is the ticket for popping free the connectors.
Of course, we usually can't install a part without dyno testing it. So, to make everything right in the world, not only did we have the great folks at Lugo Performance install our new MagnaFlow Tru-X high-flow-cat crossover pipe, but we also had them twist the dyno rollers. Dyno king Eddie Burke was all too happy to get behind the wheel of his favorite yellow project car and beat it to within an inch of its warranty to see what our new Tru-X system was worth.
Though we lost a bit of baseline power from our previous pulls-likely due to increased heat and humidity since our last test-we found a gain of 34.8 hp and 21.4 lb-ft of torque from the addition of the X-pipe. These are solid numbers that are no doubt helped by the fact that our 3g GT's ATI P1-SC blower (or any blower for that matter) really likes a free-flowing exhaust.
After wrapping up our back-to-back testing on the Mustang MD-1750 dyno, we had Eddie run an "unloaded" test to see what kind of numbers we should expect on a dyno, such as a Dynojet. Eddie says experience with customer cars shows the unloaded MD runs are within a couple horsepower of the same car run on a Dynojet.
Completely remove the rear...
Completely remove the rear attaching hardware for the stock H-pipe. As this hardware will not be reused, Eddie slides back the Steeda ball-socket flanges and threads the factory nuts on to the H-pipe for storage.
With the rear of the stock...
With the rear of the stock H-pipe free, remove the H-pipe to manifold retaining nuts. Work the four nuts a little at a time to loosen the H-pipe without it falling.
It takes only a bit of shaking...
It takes only a bit of shaking to loosen the ball-socket flanges from the cast-iron manifolds, which allows the H-pipe to drop out of the car.
A comparison shot of the stock...
A comparison shot of the stock H-pipe and MagnaFlow Tru-X shows the large radius bends for better flow, and the less-restrictive, twin-converter design.
When swapping the rear O2...
When swapping the rear O2 sensors from the old H-pipe to the new MagnaFlow, make sure you have the correct sensor for the side of the system on which you are working. The rear O2 sensors are side-specific and color keyed by their harness connectors, blue for the left and pink for the right.
The front O2 sensors are not...
The front O2 sensors are not side-specific and can be installed now or in the car, whichever is easier. Don't forget to apply fresh antiseize to the threads.