3" Exhaust vs 2.5" Exhaust... - ModernCamaro.com - 5th Generation Camaro Enthusiasts
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post #1 of 10 Old 08-08-2012, 10:57 PM Thread Starter
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3" Exhaust vs 2.5" Exhaust...

Hey guys, just wondering which size you would get and for what reason. I have the factory exhaust with a dealer installed GMPP axle-back...and the entire system is 2.5". I'm considering going with an aftermarket 3" cat-back but I'd like some advice. Personally, I don't think a 2.5" will do me any good over what I already have but I could be wrong. So please tell me what you chose (or would choose) and why. Thanks!

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post #2 of 10 Old 08-09-2012, 08:17 AM
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A few reasons to go to a 3" system:

1. You are planning on exceeding 600-650 bhp (the generally recognized ceiling for a 2.5" system)

2. You are going to use or are using Forced Induction

3. You want a deeper exhaust tone with no rasp


A few reasons NOT to go to a 3" system:

1. In and of itself, a 3" system won't net you much in the way of HP unless you are very heavily modded.

1a. Requires a change to headers to really take advantage of the 3" system

2. Depending on the material/design of the 3" system you can actually ADD weight to the car.

3. Makes accessing the diff drain plug (among other things) very difficult

4. Some systems are difficult to get/keep aligned and require you to shim the stock tunnel brace for clearance or replace it

These are my experiences with my car along my modification path, YRMV. Others will chime in with their thoughts I'm sure...

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post #3 of 10 Old 08-09-2012, 12:30 PM Thread Starter
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Well I am planning on forced induction in the future. But I don't need or want more than 600 RWHP max. Plus I don't like having to deal with fitment issues. So I guess 2.5" will suffice. Since I already have the axle-back I guess all I need to get is some aftermarket tubing from the cats to the axle and I'll be set. Thanks for the info!!

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post #4 of 10 Old 08-09-2012, 01:08 PM
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Quote:
Originally Posted by Chapel View Post
Plus I don't like having to deal with fitment issues. So I guess 2.5" will suffice. Thanks for the info!!
I have a Magnaflow 3" system and it clears my Hotchkis Max Chassis Brace's center tunnel section though it took some adjustment and flipping some bolts upside down....

I'm def not saying all systems have fitment issues or that they can't be overcome, just pointing it out....

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post #5 of 10 Old 08-09-2012, 05:34 PM
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even with 2.5" aftermarket catback systems, is that they ought to be mandrel bent so they won't have the flow restrictions like the stock pipes. Which if you check have a couple sections that have sizeable flat spots.

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Last edited by Nancygrl; 08-09-2012 at 05:38 PM.
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post #6 of 10 Old 08-10-2012, 10:30 AM Thread Starter
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Quote:
Originally Posted by Nancygrl View Post
even with 2.5" aftermarket catback systems, is that they ought to be mandrel bent so they won't have the flow restrictions like the stock pipes. Which if you check have a couple sections that have sizeable flat spots.
Yea good idea...thanks!! I'll check for that when I start shopping around!!

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post #7 of 10 Old 08-10-2012, 10:49 AM
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Remember, you will lose torque with a larger pipe.

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post #8 of 10 Old 08-10-2012, 11:16 AM
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Quote:
Originally Posted by patriotpa View Post
Remember, you will lose torque with a larger pipe.
That's why I stayed with a 2.5" catback.

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post #9 of 10 Old 08-14-2012, 04:15 PM
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Just go headers back straight pipes lol
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post #10 of 10 Old 08-19-2012, 01:45 PM
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Well... 2.75" Piping is pretty reasonable.
Straight flow no resonator = increase HP / TQ

But if you willing to add more FI, then 3" inch piping is alternative option.
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