"H" pipe vs "X" pipe

[guruatbol]

Ok, for all you race performance guys. I have heard a couple different things from different people and they all contradict one another.

So my question is simple and I would like some theory behind it as well.

What is better, and "H" pipe or an "X" pipe on my exhaust. I have an "H" on the 65 and an "X" on the 67. This is where the contradiction comes in. I had two shops tell me two different things. I think they just wanted to justify what they were doing.

So, what is the theory behind both?

Mel

 

[AzPete]

My thoughts....the H pipe is more for just balancing out the exhaust with duals so the sound and back pressure is better/equal....mainly back pressure which improves MPG slightly. The X is there for a bit better scavenging of the exhaust and possibly a slight increase of HP. Not a seat of the pants increase but a dyno shown increase.

Unless you need every single HP number, either will work good for the street. Higher HP motors benefit from the X.

Again...my thoughts.

 

[Horseplay]

My opinion and experience is that any cross-over pipe does have a benefit over a dual exhaust without, as Pete details. I'm sure by the design an "x" may allow a smoother flow that could translate to improved power but I have to believe this would only occur at higher RPM and not equal a very big number. I'm in complete agreement that any benefit of one over the other (outside of perhaps sound preference) would not play out on a street car.

 

[Anonymous]

The X will make gains only found on a dyno sheet. The biggest difference is the tone. I went with the X pipe cause it made fabbing the side exhaust much simpler.

 

[Norm Peterson]

Ok, for all you race performance guys. I have heard a couple different things from different people and they all contradict one another.

So my question is simple and I would like some theory behind it as well.

What is better, and "H" pipe or an "X" pipe on my exhaust. I have an "H" on the 65 and an "X" on the 67. This is where the contradiction comes in. I had two shops tell me two different things. I think they just wanted to justify what they were doing.

So, what is the theory behind both?

Mel

Waking this topic up . . .

An X does tend to make smallish gains over an H up in the higher revs, though the biggest difference in normal driving is the sound.

It also tends to be relatively more effective at doing this when the mufflers are a little more restrictive.
The thing that gives duals and H pipes the classic V8 rumble also indicates that very briefly each muffler is providing slightly higher resistance to the exhaust flow, because of the overlap between the pulses when two cylinders in the same bank fire in sequence.

In the thumbnail, exhaust system pulsing with true duals and to a slightly lesser extent the H look like the top chart. An X (and a large single) like the bottom. The rumble even plots up as a rougher, choppier sound. What I haven't figured out is how to plot how an X sounds as you hit its midrange resonance. Probably need a 3-D chart for that and I'm not that ambitious so these "snapshots" are all I've got.


Norm

 

[cmayna]

Norm,
Good info. Thanks