So you bought a Mustang, either a brand new one or one of the few used ones that haven't been butchered by a previous owner. Most of us don't make it a week without modifying something on the car, and often the first mod is a high-performance exhaust. The benefits of a good exhaust are two-fold. One, it increases the power at the rear wheels. Two, it gives the car an audible attitude adjustment. Deciding on installing a performance exhaust brings with it some questions, however, such as the whole H-pipe versus X-pipe debate. Some believe that the H-pipe is the best flowing pipe of the two, while others say that the X-pipe is the better choice. Then, of course, you have to choose between catalytic converters or off-road (no cats) pipes. If you want the car to stay legal, there is no choice; you have to get the cats. But we know there are plenty of you out there that run off-road pipes, so there is still a choice in many cases.
We wanted to see which pipe design made the most power on an otherwise stock car. MagnaFlow Performance Exhaust is on the X-pipe side of the fence, claiming that the X design is much more efficient than the stock-style H-pipe, even in high-flow versions. We wanted to see for ourselves, so MagnaFlow agreed to let us test both an off-road (no catalytic converters) H-pipe and an X-pipe to prove which pipe produces the best performance and sound. We decided to go with the off-road pipes for two reasons. One, we wanted to see the differences between the H and X design without the flow hinderance of the
|
.
|
converters. Besides, if you're building a car specifically for a heads-up class, cats are not required so most racers will run the off-road pipes. The other reason was that MagnaFlow has not finished prototyping their catalytic converter X-pipe for the Mustang, so it wasn't even available for us to test. The test mule was a '99 Mustang GT with an automatic transmission that was in dire need of an attitude adjustment. The car was stock except for a K&N filter and a pair of 2-chamber Flowmasters. The mufflers gave it the bark, but the rest of the exhaust was stock, so the bite was not exactly Doberman-like.
The first step of the test was to baseline the car on MagnaFlow's chassis dyno. After making several runs on the dyno the car made a best of 224.7 horsepower and 273.6 ft-lbs of torque. After the baseline test, the original H-pipe with all six restrictive stock catalytic converters was removed. Removing the stock piece is quite a challenge, as the passenger-side front 02 sensor is a nightmare to remove. A long metal rod with a slotted end (like a screwdriver) was used to slide the 02 sensor apart. Once the sensors and bolts are removed the pipe can be removed.
The first pipe tested was the off-road H-pipe. This pipe gave the car a deep, aggressive exhaust sound. The increase in volume was also greeted with an increase in rear-wheel horsepower, as the car cranked out 235 horsepower and 286 ft-lbs of torque. That's a gain of 10.3 horsepower and 12.4 ft-lbs of torque, a significant improvement. MagnaFlow's opinion is that
|
