anyone ever hollow out their downpipe? Options

[match220]

I'll be running a 3" high flow cat with 2.5 reducers on each side, I just noticed that the stock Gen III 3sgte downpipe has a cat built into it. I know some downpipes will kill drill bits and others you can pound out with a hammer if you spend a few hours..lol. I want to hollow it out though, are the downpipe internals hard to gut?

[match220]

delusionz and pressure2,
I just read your comments and responded quickly before I left this morning. In earlier posts I wasn't saying it was better than a "well crafted" downpipe. So to recap this thread a little...Someone had mentioned buying a cheap ebay one, which was when I started talking about how they dissipate too much heat and add resistance as exhaust expands and slows down. The ones I was talking down about were cheap ebay ones, I didn't say my stock hollowed out one would be better than a well-crafted one, I said it would be as good as a real one with a 2.75 outlet. Pressure2 mentioned getting a real one for $60-$85, which I disagree with because the cheaper ones are cheaply made, it's pretty hard to find a nice one for that price. Anyway, when I looked carefully at the inside yesterday I saw the bends and different size diameters which sucks on performance.. and I actually can't find my blitz DP right now, which also sucks, so now I'm stuck with the factory one until the find the blitz upper. I thought the factory DP would be smoother and straighter inside than what it actually is.

Anyone can bend some metal to spec and put some flanges on it. They are usually chrome or thin stainless and I wouldn't put it on my car unless it was free. The "well crafted" ones that you mentioned will be thick stainless or titanium, maybe even cast which aren't as popular. These are the ones that hold in heat better than the cheap ones. Heat wrapping a cheap ebay DP would probably work out great, but on that note, heat wrapping your whole exhaust would work out even better. A ton of velocity is lost as the heat is lost, and also as pipe diameters change from being large to small. Bernoulli's principle starts to be factored in, as diameters change from small to large the velocity drops and as it changes from large to small the velocity increases. The more times we allow exhaust to expand and contract in the exhaust system the more energy is lost. I've done extensive study on exhaust flow, thermodynamics, and how the laws of physics affect our exhaust systems, I almost designed exhaust systems for a local exhaust place, that's actually the area of performance that I've been most fascinated with and wanted a job in for a while. I would be more than happy to write up an article with references if I have enough time if someone would pin it, or verify it first before it's pinned.