I thought it was like having two sets of exhausts, i.e. 2 cats and keeping everything separate from the manifolds to the tailpipes. But I must be wrong because I've seen kits for Escalades and 350Z's and it's clearly not the case.

Now, when I look at the info on the new G35, they say it has true duals, and it clearly from the Nissan documentation have what's called an "efficient merging structure" which follows the equal length manifolds and front pipe. After the merging structure they once again separate, and are those the 2 cats afterwards before going to the mufflers? Can anyone explain this exhaust system, and also what constitutes true duals? Thx!

 

"A true dual exhaust system means that it starts at the catalytic-converter spot and has two separate pipes that go back to the muffler(s). If the tubes cross, that is okay, as long as they separate again. Now there are variations on this. It can go into one muffler and have two exhaust outlets or it can go into one muffler and have one exhaust outlet. Or it can go into two mufflers, each with one exhaust outlet. Those with two mufflers are typically "true-true-dual" exhausts like what is shown in the new 2007 G35. - 350Z-Tech"

True-True Dual Exhaust System


Ram-Air Dual Intake System

 

It seems to me now, that the key in an oversimplified way is that a true dual has more than one cat. Obviously the new G35 exhaust was not simply bolted on for looks...and so I think that merging structure has to do with perhaps equalizing the pressure?

Oddly I found some info online that the Pontiac GTO has true duals from the factory. The thing is under the car it looks like what I thought constituted true duals--complete separation from the manifolds back. But on the GTO, they send the right pipe over and it comes out under the bumper as twin pipes on the left, not one on each side. I would have previously assumed that's not a dual exhaust system, it looks like the current 3 or G35!