Bolting up 3" DP/cat to 2.25" exhaust? Help!

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Old Feb 13, 2006 | 08:13 AM
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Default Bolting up 3" DP/cat to 2.25" exhaust? Help!

I'm upgrading from a greddy kit on my stock D16Y8 this spring, and I'm going to be running a ramhorn manifold with a SC50 .48 a/r and 3" downpipe.

I plan on running a 3" Carsound high-flow cat (should I get the short one or the regular size?) with the 3" downpipe (NO TEST PIPES FOR ME).

My question is, how can I bolt up a 3" high-flow cat to my 2.25" DC Sports exhaust? I don't plan on upgrading my exhaust any time soon, because it's sooooo quiet I love it! I'll probably upgrade to a full 3" exhaust next summer though, when I get another car for a daily driver.

Will I need some sort of adaptor? Thanks in advance for the help
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Old Feb 13, 2006 | 12:06 PM
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Default Re: Bolting up 3" DP/cat to 2.25" exhaust? Help! (boostincoupe)

bump!
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Old Feb 13, 2006 | 12:10 PM
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3" > 2.25" = pointless, dont bother getting the 3" if you plan on keeping your exhaust
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Old Feb 13, 2006 | 12:11 PM
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Default Re: (sk8shorty012)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sk8shorty012 &raquo;</TD></TR><TR><TD CLASS="quote">3" &gt; 2.25" = pointless, dont bother getting the 3" if you plan on keeping your exhaust</TD></TR></TABLE>

If you could read, I'm upgrading next summer. I need something for this year.
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Old Feb 13, 2006 | 12:20 PM
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the point is, you might as well wait for to put on the kit or run without an exhaust cause 3" &gt; 2.25" = teh sux0r. If you cant do a kit completely, then dont do it. Itd be like getting everything for a turbo kit minus a turbo, but not having enough funds for the turbo. Basically, either upgrade to 3" now or dont get the kit yet, youd just be wasting money getting an exhaust shop to fab you some custom adapter or whatnot, just wait til you can do it all at once...
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Old Feb 13, 2006 | 12:26 PM
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Default Re: (sk8shorty012)

Go to autozone or pepboys and see if you can find a reducer.

I'd get the short cat, get the reducer, and the flanges needed to put everything on.

-Put on your DP, put on the short cat, weld on a two bolt flange to one end, weld on a 2 bolt flange onto the 3" end of the reducer, and weld on another flange onto the 2.25" side of the reducer to match your DC sports exhaust.

Make sense? If not I can try to make up a diagram as to what I mean.

-Nick
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Old Feb 13, 2006 | 12:27 PM
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Any exhaust shop should be able to build you a reducer.. While not optimal, it will get your by until you add a 3" exhaust.
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Old Feb 13, 2006 | 12:35 PM
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Default Re: (Project-D)

Just so you know, the reason I reccomended the short cat was so you would have room to fit in a reducer.
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Old Feb 13, 2006 | 12:49 PM
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or just do a 3'' d p&gt; E-cut out befor the cat &gt; reducer to the cat &gt; 2.25 exhaust. So while strolling around it's quite and when racing open the cutout
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Old Feb 13, 2006 | 12:52 PM
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From: Destroying turbo ITR motors in Minneapolis, MN, U.S.A.
Default Re: (six7one)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by six7one &raquo;</TD></TR><TR><TD CLASS="quote">or just do a 3'' d p&gt; E-cut out befor the cat &gt; reducer to the cat &gt; 2.25 exhaust. So while strolling around it's quite and when racing open the cutout</TD></TR></TABLE>

I might end up going that route, since it'll be mainly a street car.
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Old Feb 13, 2006 | 12:58 PM
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Default Re: Bolting up 3" DP/cat to 2.25" exhaust? Help! (boostincoupe)

check out kteller.com they have reasonable priced 3 inch cat back bolt up exhaust systems. you would be restricting your exhaust with 3" dp going into a 2.25 exhaust. I don't think it will be any louder than the 2.25.
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Old Feb 13, 2006 | 05:11 PM
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it won't be restricting cuz of the cut out
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Old Feb 13, 2006 | 05:23 PM
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The autozone here has reducers for a couple bucks a piece. I don't think they have a 3" to 2.25", but they would have a 3" to 2.5", then you could stick a 2.5" to 2.25" on there. It's ghetto, but it would work.
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Old Mar 4, 2006 | 04:32 PM
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Default Re: (bubs)

Thanks for the tips fellas, I'll be sure to check that stuff out this week.

Which Carsound cat do I order? I was looking on eBay at the Magnaflow Carsound units, and they have a universal one, then a cat for "smaller engines".

Which one do I order???

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Old Mar 4, 2006 | 04:39 PM
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When you build your DP, just taper the end of it and allow the DP to insert into the cat. Weld brackets on THE DP so you can utilize the stock cat bolts and springs.

I have a 3" DP to my 2.25" exhaust and it does suck. I made 330whp at the tire with the exhaust and then a whopping 410whp without it.

Good Luck!
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Old Mar 4, 2006 | 05:23 PM
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Default Re: (jDMJeRk)

80 HP difference becasue of a small exhaust!!!?!?
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Old Mar 4, 2006 | 05:54 PM
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Default Re: (themorphious)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by themorphious &raquo;</TD></TR><TR><TD CLASS="quote">80 HP difference becasue of a small exhaust!!!?!?</TD></TR></TABLE>
80whp; even worse!

with exhaust, 10psi (MBC)=330whp
open 3" DP 14psi (We didnt change the fuel maps or the MBC, an open DP allowed the turbo to spool more boost)=410whp
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