I've done a thread search and haven't got my question answered yet. What exactly does the X-pipe do other than take away the popping and lower the exhaust volume? I have a 4AT, and what will I gain from it?

Thanks

 

Ok, after reading about 50 of these posts let me explain the problem. The term "x-pipe" can mean so many things and has so many variables that one answer is difficult to provide.

If you are referring to the Bassani/Corsa/Magna flow style x-pipe that simply replaces the back half of your stock mid-pipe, then there's little to no horsepower gain at all. What it does do is help eliminate the burbling and backfiring/popping on decceleration with aftermarket cat-backs.

If you are referring to a complete replacement mid-pipe that has either no cats or Random Tech high-flow cats then there is some horsepower to be gained. By replacing the stock cats with high-flow units or deleting them completely, dynos have shown up to a 10 to 12 rwhp gain (off-road). Side effects are much louder exhaust and some gas/fumes smell during acceleration and idling.

And finally, if you are referring to the x-pipes that come as part of a matched set with long tube headers than the entire system can gain you up to 30 rwhp.

As you see it all depends on what x-pipe you're referring to....oh, and feel free to copy and paste this answer into the 10 other x-pipe posts currently running across four or five of the forums.

 

If you install an X-pipe aft of your stock cats and no other changes, you'd probably not see any change. Add performance mufflers and it will do as you point out for the noise, as it acts to balance each side.

I've yet to see any test proof where an X-pipe by itself actually provided any power increase.

 

The following information was taken from the Dr. Gas web site. (they've been building NASCAR exhaust systems for years)

Remember that radio and TV commercial about the piston engine going "Boing-Boing," when it out to go HUMM? Well, all V8 engines with 90 degree cranks, have an out of sync imbalance in their firing order between the right and left cylinder banks. Yes, they do go "Boing-Boing." The firing order imbalance is a necessary sacrifice for dynamic balance of the rotating and reciprocating crank, rods and pistons. Each time the firing order is completed (two full revolutional), two cylinders within each bank will fire and exhaust within 90 degrees of each other. These two cylinders will be exhausting into the header collector or exhaust manifold almost simultaneously. This overlapping condition creates a lot of back pressure and a pop sound. Meanwhile, the opposite exhaust manifold has no activity (or pressure) in it at all. This is where the characteristic, low harsh popping V8 sound comes from.

The most common way of reducing this out of sync imbalance is with rebalancing crossovers such as H pipes and over-and-under X style crossovers. These provide both noise reductions and efficiency (power) improvements. H pipes are effective only at low and mid range. The over-and-under X crossover works a little better but still does not completely rebalance the exhaust at high RPM.

Dr. Gas, Inc. has developed a new generation of crossovers that uses a tangentially siamese junction, in place of the H or over-and-under X. It evenly splits, smoothes, and synchronizes exhaust pressures at all engine speeds. The high and low pressure pulses in the two pipes are evenly imposed on each other, leveling out the pulse time history pressure differences between right and left cylinder banks. Re-synchronizing the exhaust pulses reduces back pressure, cancels sound, and provides additional scavenging. Tests have sound 6 dBa (75%) reduction in sound levels, and increases of 10 to 30 hp, and up to 40 ft-lbs. of torque! Economy, and throttle response are improved. Exhaust flow after the crossover is completely smoothed out. The job the headers started is finished.

One of the most appealing benefits of this system is the modified exhaust note. The deep growling and popping sound is replaced by a higher pitched smooth sound. The exhaust note is similar to a 180 degree header system without the nightmare of tubing.

Dr. Gas crossover kits replace the first 3 to 4 feet of the exhaust system with pre-bent mandrels pieces. Simply measure, cut and weld into place. The system is universal fit for most header applications. After the crossover, any type of dual exhaust, converters, or mufflers may be used with little or no effect on power. Vehicles that have problems meeting sound limits at local area tracks can also benefit with an increase in power tool. And so, the piston engine can go HUMM!