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Nothing says performance like a great exhaust system. The right combination of mufflers, pipes, and converters can increase power and transform the sound of your vehicle from zero to superhero. And for anyone who wants to get the most from a performance exhaust system on their V8 or V6 powered vehicle, a crossover setup is crucial. These simple but proven components not only add power and greater drivability to a vehicle, they can also significantly improve the sound of the exhaust system too.
A crossover is a way of joining both tubes of a dual exhaust, which increases the efficiency of the system particularly at lower speeds. “Crossovers equalize the pressure differences between the left and right cylinder banks on a V-style engine,” says Mark Emerson of Holley. “So you help with exhaust pulse scavenging, you get better throttle response, and an improvement in torque. Crossovers also cut down some of the drone in an exhaust system, because it’s cancelling out some of those frequencies.”
For many vehicle owners, the improvement in sound quality alone is enough to justify adding a crossover, says Emerson. “We get a lot of customers who say things like, ‘I love the sound of my car, but it’s getting a lot of drone – do you recommend a better muffler?’ And I usually tell them to first add a crossover. You’re going to have better throttle response, better drivability. And lot of times just adding the crossover will eliminate noise issues instead of having to redo the mufflers.”
There are several types of crossovers, each with its own advantages. An H-pipe is simply a short length of tubing that runs between the two main pipes of the exhaust system, thereby connecting them. It’s the easiest method of adding a crossover to an existing exhaust system – you don’t need to relocate the main tubes, and it’s relatively simple to install the pipe close to the optimum location. “H-pipes are kind of the original design,” explains Emerson. “You’re just taking the two tubes and adding a straight connection between them. It’s the easiest to install if you have the pipes already on the vehicle and you don’t want to reroute the whole system – you just find a good crossover point and add that tube in there.”
Worth noting, the pipe used to join the two main tubes on an H-pipe system doesn’t have to be the same size as the tubes that make up the rest of the system – exhaust pulses aren’t actually flowing through that crossover, just sound waves and pressure differences. So a 2.25” to 2.50” diameter exhaust system can use a 2.0” crossover tube, and 3.0” system can use a 2.25” crossover tube.
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In contrast to an H-pipe system, an X-Pipe design has the two main exhaust tubes merged for a short section to form the crossover. Like H-pipe systems, X-pipes improve scavenging and low-speed power. But an X-pipe also generally adds power further up the RPM range. On the negative side, however, X-pipes can be more difficult to add to an existing exhaust system. And because this type of crossover requires both main exhaust tubes to merge together, it can be harder to get the crossover at the optimum placement in some applications.
H-pipes and X-pipes also change the exhaust tone in different ways. But that’s not to say one sounds ‘better’ than the other – it depends on your own personal preference. “H-pipes tend to cancel out more of the high-pitch frequencies,” explains Emerson. “You end up with a deeper bass to your overall tone, which gives you more of a traditional muscle-car type of sound. By comparison, X-pipes cancel out more of the bassier frequencies, so you end up with a higher-pitched tone. On some applications, it gives the car more of a European type of sound.”
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To combine many of the advantages of an H-pipe with the benefits of an X-pipe, Flowmaster offers its Scavenger X-Pipe systems. These exhaust systems have a carefully engineered port shape for the crossover, which enhances its scavenging effect. “Our Scavenger X-Pipe systems use our patented D-Port technology,” says Emerson. “At the connecting point of the tubes, instead of just taking the two round pieces and welding them together, we flatten out one side and it looks like the letter ‘D.’ We weld those two flat sides together.
“As the exhaust pulse goes through that shape, it increases the velocity of it,” continues Emerson. “It has a stronger signal or pull to the other side behind it for the exhaust pulse on the other cylinder bank, so it maximizes the scavenging effect like an X-pipe does. But with the D-Port, you get those benefits both at low and high rpm. And the D-Port design also tends to cancel out more of the high pitch frequencies like an H-pipe and retain that low, deeper tone. It gives you more of a traditional muscle car sound, but with the benefits of a modern style X-pipe – the best of both worlds.”
Fitting a crossover to a vehicle with dual exhaust is relatively straightforward. From an exhaust-flow standpoint, there’s an optimum location for the crossover to be mounted to achieve the best performance. And there’s a simple trick for finding where that point is on your car. “Ideally, the crossover should be within eight to 18 inches of the end of the collectors,” says Emerson. “An easy way to find where the ideal crossover point is on an existing system is to spray some cheap flat-black paint on the tubes and then run the vehicle, get it up to temp, and then see where the paint starts burning off the most. That’s the ideal crossover point.”
That said, much of the placement of a crossover setup on a vehicle comes down to where there’s room for it; the ideal point for a crossover often isn’t the easiest or most practical place to add one. “The closer you can get the crossover to the collectors the better,” explains Emerson. “But a lot of times, that ideal point would have you putting the crossover right through the transmission pan or something like that. So, typically, right behind the transmission ends up being the best place to put it.”
The easiest and most effective way to add an exhaust crossover to your vehicle is with a full exhaust system from Flowmaster. These are designed to fit your vehicle precisely, giving you maximum advantage but with fast and easy installation. These systems are available for a wide range of cars and trucks, and they give you all the benefits of a crossover, with bolt-on ease. Or you can add a crossover to any vehicle by choosing from the wide array of crossover components offered by Flowmaster, White Box, Flowtech, Scott Drake, and Dinan.
So which is better for your car, an H-pipe or an X-pipe? In all honesty, you really can’t go wrong with either. Both offer significant improvement to the tone and overall sound level. And as far as power advantages are concerned, the differences between the two are relatively small. More than anything else, the choice of H-pipe vs. X-pipe typically comes down to what you want your exhaust to sound like and which is easiest to fit onto your vehicle.
