What are the Differences Between Mustang H, X & Y Pipes?
First, and most clearly, they look different. As you can see as you can see from the diagram, they also have different flow patterns for the exhaust gasses to follow. Each is designed with a different strategy to flowing heat and gas from the manifold and was designed with different applications in mind. You'll want to make your selection based in part on the aftermarket and stock exhaust components currently on the car, as well as any future plans you might have for your Mustang.
X-pipe: Mid-pipes built with a crossover, or "X" shaped design, purposely cross exhaust streams to even out flow and streamline exhaust gasses through the rest of the system. X-Pipes are generally raspier and louder than H or Y-pipes and have been shown to provide slightly more power than their counterparts. You are likely to see most of the power gains higher in the rpm band with an X-pipe.
H-Pipe: An H-pipe is better at balancing sound and produces a more consistent, classic muscle car growl. It does less than an X-pipe in the way of balancing exhaust gasses but still flows quite well. H-pipes maintain the backpressure necessary for torque gains earlier in the rpm band, as opposed to the top-end power seen from an X-pipe.
Y-Pipe: A Y-pipe came standard on many late model V6 Mustangs and are sufficient for a mildly modded car. However, for those looking to install a power adder or make maximum horsepower, converting to a dual setup is ideal. The increased airflow from upgrading to an X or H setup gives you much more room to accommodate increases in horsepower and torque, relieving excessive backpressure.
What are the Similarities Between Mustang Mid-pipes?
Both aftermarket X and H pipes will provide increases in horsepower and torque, as well as change the sound and pitch of your exhaust note. X and H pipes also cross gas streams, helping to even out pulses in airflow caused by the firing order and subsequent airflow coming from the manifolds. While there are no more "true dual" setups (two straight pipes coming from either header with no cross-connection), the benefits reaped by the crossing of gasses between the two sides has left the days of true dual only to the past.
How to Choose The Right Mid-pipe For Your Mustang
So which one is right for you? Well, you first must decide on your plans for the car - if you are building a high-horsepower drag machine your choice will be different than a mildly modded street car. If you need a boost in low end torque, pick up an h-pipe. If it's high end horsepower later in the rpm band you seek, an x-pipe is the way to go. Keeping power in mind is important but most Mustang enthusiasts make their choice based on sound. Like previously stated - x-pipes provide a higher pitched, raspier note and can drone a bit whereas H-pipes produce a deeper, old-school muscle car growl. Personal preference will dominate and you can check out a sample sound clip on the product's page if you are unsure of which is right for you.