Looking for downpipes without cats-custom the only way?
After doing some reading it seems a good system that has electronic cut-outs gains very little from thee cutouts meaning that it is the good system making the power, cutouts maybe 7-8HP. I've got an idea for an exhaust I think will be good but can't start out with $800. downpipes that I plan on welding a set of cats into anyways. I am hoping for 25whp with the exhaust I have decided to put together. Just can't find a set of downpipes! How about the stock downpipes, anyone know the tubing diameter offhand? I don't want anything larger than 2.5" diameter and would prefer 2.25" to keep the velocity up so the scavenging effect works out well. I am planning on an X-pipe instead of the 2nd set of cats, no resonator and a Borla 400482 Turbo Pro XS muffler. The Borla's do not drone but are loud, the x-pipe should take some of the loudness out. Having a quiet freeflowing exhaust is important to me. It does not seem that there have been before and after dyno tests of many if any systems. I'll do the before and after, just need to have the downpipes reasonably priced. The Borla's also make good low end torque and that is what I'm after. Peak HP on a SC vehicle doesn't mean much as the peak HP is at redline.
Well do I have to go custom, work with the stock pipes or are there downpipes oriced where I can add $300. cats and labor and possibly a second muffler? Mark