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post #1 of 72 (permalink) Old 08-18-2014, 03:23 AM Thread Starter
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Exhaust Overhaul

I'm kinda new to the site but so far loving it. I have an 08 LS 5-speed.

The only performance mod I have so far is a K&N short ram intake, the rest is all visual.

I'm planning on doing custom exhaust, bending the pipes myself and everything. I have a mandrel and welder. The only thing that confuses me is what diameter pipe to go with, I want either 2.5" or 3". I'm pretty sure stock is either 1.75" or 2" so it sounds like a big jump, which is whats confusing me.

Would it be robbing my engine if I went with 3" pipe? Also, any recommendations on header and dp with a high flow cat?
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post #2 of 72 (permalink) Old 08-18-2014, 05:34 AM
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If you plan on going forced induction then go 2.5". If you don't then go 2.25". You can go bigger and stay N/A if you also own a honduh


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post #3 of 72 (permalink) Old 08-18-2014, 06:19 AM
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2.25" is arguably perfect for NA. Just don't expect any real power from it.

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post #4 of 72 (permalink) Old 08-18-2014, 09:06 AM
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3" is also good for forced induction


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post #5 of 72 (permalink) Old 08-18-2014, 09:55 AM
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The bigger it is the deeper the tone. Obviously don't go too big. I'd go with what pj and moneyman said. But I'd probably do 3" if you're turbod or supercharged
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post #6 of 72 (permalink) Old 08-18-2014, 10:15 AM
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Unless you in the 400+ HP range there's no point in going over 2.5''

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post #7 of 72 (permalink) Old 08-18-2014, 12:59 PM
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Read up about exhaust scavaging and proper velocity.

A full 2.5" system would be just fine, you won't notice anything better or worse from a 2 1/4" system anyways...Shorty ZZP Header/2.5" Downpipe/2.5" catback.

Done and done.

My LAP 2.2 made just shy of 140 WHP and 160 WTQ with just an intake/catback, so expect a little more, I'm sure. Especially with the manual transmission.

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Previously dumped on BC Xtreme Low's...RIP LOWLYFE :(
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post #8 of 72 (permalink) Old 08-21-2014, 06:23 AM Thread Starter
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Thank you and sorry for taking so long to reply.

I don't plan on doing turbo or supercharging, so it seems like the max I should go is 2.5" then.

I'm going to look into this a little more and see if it would just be worth it to get a 2.5" shorty header and downpipe, high flow cat, and the GMPP cat-back.
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post #9 of 72 (permalink) Old 08-21-2014, 07:15 AM
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GMPP catback is 2.25", but it'll pair well with a ZZP 2.5" DP. Look into the mid length header/dp combo and go with the 1.5" primaries and 200 cell cat. Wideband is nice to have but not necessary.

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post #10 of 72 (permalink) Old 08-21-2014, 09:23 AM
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With a motor that makes not that much power...and just changing the exhaust and not really anything else...a wideband probably wouldn't make any difference unless you had two cars side by side on the dyno.

The Racekar - SOLD!: http://www.youtube.com/watch?v=fIW9XK_WMR4
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Previously dumped on BC Xtreme Low's...RIP LOWLYFE :(
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