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]

The factory outlet of the DP is 2.75 inches, this one is more than enough for me instead of paying more for an aftermarket DP. The DP's that "look tidy" are horrible on performance. DP's and headers need to hold in the heat, which is what cast iron does best. Stainless and chrome dissipate too much heat making the exhaust cooler and more dense. And the DP is right in front of the radiator fans with outside air being blown over them as you're driving. Once the exhaust gets cooler it expands and gets harder to push, this directly affects performance. If I have a 3" exhaust system with a chrome header or DP the exhaust might flow like a 2.5" system or less. This is why you see drag cars with a slow flaring individual exhaust setup. The headers are the exhaust piping and they start out as a couple inches and gradually flare out to 4 inches or so. This allows the exhaust to flow smoothly as it expands and gets more dense coming out the pipe, and they didn't have to pay enormous amounts of money for a cast iron one.

I said all of this to say...I now have a 2.75" cast iron DP. I paid jcbass7 $30 for the cat part on my trip home and brought it back with me, and I've had the blitz cast DP for a while. Since the factory DP has a 2.75 outlet, and the inside of the blitz DP is pretty roomy, I now have a "real" downpipe. So you can take your factory one to a steel place and get some money for it and then buy a "real" downpipe that is shiny and takes away HP, heatwrapping it will make the flow better, but there goes the nice looks. Or you can buy a more expensive aftermarket cast DP to get the same thing that you would for hollowing out the cast iron one.

This post has been edited by match220: May 12, 2012 - 1:38 PM