Originally Posted by Jordo!

You are presuming a great deal of experimentation and fine tuning on the part of a given company based on the assumption that they have no prior experience with similar set-ups and are devoted to milking every last hp. The price tells you nothing about that, so buyer beware.

I highly doubt the design of these sytems are generated empirically through trial and error either -- the impact of runner length on headers, collector design, diameter of piping vs peak torque, are all well known, and these principles can be applied to new vehicles without completely reinventing the wheel every time.

On that note, the choice of an X, H, or Y pipe for a given set-up was probably determined on the basis of theory and expectation rather than trying various iterations to see where power was gained or lost for this engine... and that is why we see all three designs rather than a few variations on one.

The major pain is making it all fit on a specific vehicle and keeping emissions in check. Speaing of emissions, any systems that includes high flow cats or test pipes probably won't pass emissions, so that isn't a concern, so much as the goal is to fool the secondary O2 into believing the cat as designed by the factory is still on there and working.

Like I said, I'm guessing maybe 2 iterations, probably mainly for reasons of fitment. If there's more going on, one of the "Names" should share the details, as it would be of great interest to many of us I think to see all of the time, effort, and experimentation that was happening behind the scenes before the final design was sent off for production.

As far as sound, most of these kits use pretty standard mufflers and resonators -- I think the Saclam kit is the only one I've seen with a really unique looking design.

That said, my guess is most of these systems are derivitive of the VQ35HR exhausts (or, shocker, the OEM VQ37HR one) anyway.

And if I had a lift and a good welder willing to work for beer, I absolutely could design an exhaust system. As WarmandSci noted, it's not THAT complicated if you know something about intake and exhaust systems, especially when you are just talking everything after the cats. Header design is a bit more complicated, and designing an intake manifold without a flowbench is probably a waste of time.

Again, I'm just talking cat back exhausts here -- designing a turbo or S/C set up is quite a bit more complicated, as is designing (or improving upon a design) for an IM or header.