Dual Exhaust Type
 

What is considered a real dual exhaust? Does the Nismo Z have a real dual exhaust?

"True Dual" exhaust setups don't have a mid-pipe crossover.

I'm sure wikipedia has this but anyways, m4a1mustang is right about the true duals.

:google:

Exhaust
 

If that's the case, very few sports cars have dual exhaust. Even the Skyline GTR and M3 has either a X or H pipes. What's the advantage/disadvantage of having a true dual exhaust.

Crossover will help scavenging and allow to produce some extra power at higher end.

It depends on the engine design and firing pattern but carefully designed exhaust system and position of the X or H pipe will cancel out resonance and make less noise inside the cabin as well. Deducing from that True dual should have louder/more aggressive note and should have more in-cabin noise.

I have Agency Power true dual exhaust BTW. I thought it was going to have 'some' drone but after talking to one of other member who installed AP exhaust, I realized that the video they posted was not an accurate representation of in-cabin noise. After burning off some residues (watever it is inside the muffler/resonator that was burning) I have practically zero drone, and exhaust actually quieted down a lot, which i thought would be otherwise. As far as HP/TQ gain goes, we might be able to compare the difference with H/X after I get it dyno-ed with HFC install. If I'm not too happy with the result, I might get my buddy to fab up some X or H pipe and put'em on.

Nevertheless, I think it all depends on the quality of the steel and design of the exhaust and varying size of resonator/muffler.

"H pipe produces higher low end torque whereas X pipe produces higher torque in higher speed."

Take my advice for a grain of salt, I'm no expert mechanic, but from my understanding, difference of HP/TQ in our engine doesn't seem to create immense amount of change with or without X pipe.
But it seems, in certain cases, depending on the design of the exhaust, H pipe introduce some rasp or "farts" to our engine (research videos!)

"True" dual will produce more aggressive sound and steeper torque curve partially due to loss in low end torque and thereby produce lower 'hp' gain from calculation.