Stock 4dr 2013 si exhaust, 2.5 or 3.0

Deeblo · Nov 15, 2013

Hey all,

I've got nearly 13k on my 2013 Si, and I find it's not quite as nice sounding as I want it to be, and the local muffler shop is willing to do a catback for ~150, either magnaflow or flowmaster, but they're saying 3" is too big for an N/A motor.

I've read through a couple of the threads on here (all 11 pages of the magnaflow, and 3 pages for the 2.7 or 3.0) and it seems people either already have supporting mods, or are inconclusive about the sizes.

If I've read all the info right, the stock exhaust is 60mm, or ~2.3", which means a 2.5 would be at least a minor improvement. But, will a 3.0 give any improvement, or is the exhaust shop right and it'll actually rob me of power?

I'm mostly looking for just sound, but I do eventually want (read as: 2 years or so from now) to get a dp, replace the cat converter, a sri, and a tune, but for now I can only get the exhaust (wife's orders, plus I am in the process of restoring a camaro, so most of the funds are going there.)

TL-DR - 2.5 or 3.0? Is 3.0 too big?

Thanks all!

EffBee6fromthe209 · Nov 15, 2013

First off what year camaro.?

Second off if you want exhaust get it done right.
I'm Willing to bet they will use a crush bender so literally your stock exhaust will flow better.
If you want sound do a simple axleback.call it a day.
The sharp turns under the car will render a crushbent exhaust useless.
The si likes a 3 inch exhaust ONLY if you do supporting mods.the biggest exhaust you can go stock is 2.5 to 2.75.as long as its mandrel and not crush bent.

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FantaSI · Nov 15, 2013

Go with Invidia Q300

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Deeblo · Nov 15, 2013

Thanks for the info.

1984 Z28 with 3" back into dual flowmaster's. It's got a 4bolt 350 out of a 71 c10 that I'm rebuilding with an edelbrock intake mani, 3/4" spacer, edelbrock 600cfm carb, and I'm hoping she'll be a screamer.

I'll ask them about it being mandrel bent.

Thanks again for the insight!

EffBee6fromthe209 · Nov 15, 2013

I have a 383 stroker that would give it a nice whiplash effect paired with a nice high stall converter.
But is it 2 bolt or 4bolt.
If its out of a c10 might be 2 bolt.
Decent for a mild build tho.give it some real nice oomph.

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Deeblo · Nov 16, 2013

Haven't pulled the block apart, I was told it was resleeved and rebuilt, but.. not 100% sure. Previous owner got it down and started building it back up, left it with no intake manifold on it, loose lifters, loose valve covers, and all the parts on the front taken off except the timing chain.

But, I did run the block numbers and the head numbers, everything seems to match with a 350 4 bolt.

I passed on the exhaust today, talked to the manager and he said he'd only do a muffler and tailpipe for their special. Bastards. Looks like it's another wait until Tax returns before I can get some sound to the civic.

EffBee6fromthe209 · Nov 16, 2013

Buy a TLM and take it to them and have them make it into a tail pipe at the flange.
The TLM runs you maybe like 55-65 off eBay and paired with the stock resonater it'll give you a much different sound without the major drone

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immajackuup · Nov 16, 2013

everything 3inch just like my penis!!

FantaSI · Nov 16, 2013

I'm sorry to hear that. 3 inches long must be tough on your love life. Lol

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Sports Buzz · Jan 12, 2014

Ya, I thought everything was BIG in Texas?

ericc191 · Jun 14, 2014

What size is the stock exhaust? 2 inches?

Red13Si · Jun 14, 2014

~2.3"

K24Z7FTW · Apr 29, 2015

Is that 2.3 " just for 12-13? Didnt the 14-15 model SI's get a slight larger exhaust?

rgregory14 · Oct 1, 2015

I would like to know the same thing someone told me they were 2.5"

EffBee6fromthe209 · Oct 2, 2015

No.same.

Stock 4dr 2013 si exhaust, 2.5 or 3.0

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