Welcome to the North American Subaru Impreza Owners Club Tuesday September 2, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC General > General Community

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 10-14-2012, 10:41 AM   #1
anthony12052
Scooby Specialist
 
Member#: 178973
Join Date: May 2008
Chapter/Region: NWIC
Location: small town oregon
Vehicle:
2000 2.5RS
gray/silver

Default catted exhaust gets rid of turbo sound? :(

i have a catless dp and the last 2 exhausts "invidia n1, stock" i've been able to hear the turbo spooling just fine.
i installed a tsudo catted catback and now cant hear it
thought i'd share some useless happenings with you
* Registered users of the site do not see these ads.
anthony12052 is offline   Reply With Quote
Old 10-14-2012, 11:21 AM   #2
coldmm803
Scooby Newbie
 
Member#: 229343
Join Date: Nov 2009
Location: Allentown, PA
Vehicle:
12 WRX SWP sedan
09 LGT RIP

Default

there is no cat in the catback
coldmm803 is offline   Reply With Quote
Old 10-14-2012, 11:48 AM   #3
ThunderDent
Scooby Newbie
 
Member#: 334948
Join Date: Oct 2012
Location: WV
Vehicle:
2013 WRX - Limited
Dark Gray Metallic

Default

Cat-back exhaust means the piping from the end of your CAT to the exhaust tips.

Turbo back exhaust means from the turbo exit until the exhaust tips ( which will contain the cat.)

cats are restricted in the US to Cali standards, so motor companies only have to pay to certify them here once (around $1M per vehicle engine change). Probably looking at 600 cell count or so.

Turbo engines work best with high flow (unlike NA engines), so you want to match proper cat flow, exhaust tubing (ID) size, resonator boxes, bends in the exhaust, etc to maximize your exhaust flow.

If you run no cat then obviously you will have max flow. But in todays cars you will throw error codes to the face with O2 sensors, emmisions, etc. It's best to get an aftermarket setup (as long as you dont live in Cali) with a High Flow Cat (HFC) that is is around 200-250 cell count which will open up the exhaust flow tremendously and that are set up to keep the O2 sensors in check.

More airflow (whether you straight pipe it or run a hfc, is going to let your turbo spool faster increasing your boost pressure=more horsepower).

It's also worth noting that tubing diameter on the exhaust is a factor with back pressure and bigger is not always better. Generally you look for 3-3.5" after the turbo outlet depending on the size, if you run a hfc, the rest of the test pipe after it will make a gradual transition to 3", and then your downpipe (where all the controvery lies) will be 2.5-3". The rest of the system should be at about 2.25-2.5" depending on your hp.

It's worth noting that an increase in downpipe size does NOT show hp gains. It will however change the tone on your exhaust.

Then you have to consider the silencers/boxes/mufflers/resonators, whatever you want to call them. Theyneed to be less restrictive and higher flowing. This equals more hp and better sound.
ThunderDent is offline   Reply With Quote
Old 10-14-2012, 12:03 PM   #4
ThunderDent
Scooby Newbie
 
Member#: 334948
Join Date: Oct 2012
Location: WV
Vehicle:
2013 WRX - Limited
Dark Gray Metallic

Default

These principles hold for most turbo engines.

I'm not crazy familiar with the subarus yet other than what I saw opening the hood on the new WRX, and seeing manifold/turbo/downpipe, and intercooler on top (sooo small in comparison to the one on my Audi which is 3" thick.) I didnt see the cat on the WRX when looking so its either in the dp, or further down the system. Technically, the further away from the turbo you can get it, the better off you'll be.

My Audi runs a huge freakin cat butted ip right off the turbo. Then to downpipe, center silencer. Mid-muffler, then split to 2 boxes on the back. All running at 2.25". It's killing me.

So I'm changing it up. I've already put on a bigger S3 turbo (my intercooler is really large already, and IMO, too big an intercooler is bad too as you losr boost). Turbo out is at 3.5", putting on a hfc (250 cell count), with test pipe posterior to the cat that transitions from 3.5 down to 3". Then downpipe that transitions down to 2.5", replacing primary silencer with large straight through resonator for sound/tone deepening. 1 high flow mid-muffler, splitting to 2 hemholtz resonator boxes on the rear (all 2.5" piping throughout), and then opening to 3.5" tips.

Lots of things to consider wgen you are running a turbo set up.
ThunderDent is offline   Reply With Quote
Old 10-14-2012, 02:58 PM   #5
ThunderDent
Scooby Newbie
 
Member#: 334948
Join Date: Oct 2012
Location: WV
Vehicle:
2013 WRX - Limited
Dark Gray Metallic

Default

Another note I forgot to mention is turbo size vs intercooler size in relation to the dreaded turbo lag.

I had awful lag problems with a small turbo and a huge intercooler. Once I changed that ratio by bumping the turbo up to get a better ratio between the two.... Not much lag now at all.

With a small turbo pushing boost into such a large chamber, it was horrible on the lag.
From what I've driven of the WRX, I haven't felt much lag, so the two must be paired pretty well.

The WRX turbo spool is way quieter, I can tell u that. However, it's new and that may change with the break-in.

More airbox flow will also help decrease lag.
ThunderDent is offline   Reply With Quote
Old 10-14-2012, 03:06 PM   #6
cvananden
Scooby Newbie
 
Member#: 326698
Join Date: Jul 2012
Chapter/Region: Tri-State
Location: Bayonne NJ
Vehicle:
2006 WRX Ltd.
San Remo Red

Default

If this information is correct, I have just learned way more about the turbo back system than I knew already....but I'm a newb.

Also, I don't know about the newer WRX's, but in my 06...the cat is in the downpipe.
cvananden is offline   Reply With Quote
Old 10-14-2012, 08:30 PM   #7
wrx~god
Scooby Newbie
 
Member#: 58755
Join Date: Apr 2004
Location: out there
Vehicle:
2011
satin white pearl

Default

my 04 rex, 04 sti, 11sti, and all of my friends sti's only have a cat in the stock downpipe. Their cat backs don't have cats. Hmmmmm. I think i'll weld one on just for the hell of it and see if other's can figure it out.
wrx~god is offline   Reply With Quote
Old 10-14-2012, 08:40 PM   #8
cvananden
Scooby Newbie
 
Member#: 326698
Join Date: Jul 2012
Chapter/Region: Tri-State
Location: Bayonne NJ
Vehicle:
2006 WRX Ltd.
San Remo Red

Default

I believe this holds true up until 06 and then the precat is removed?

cvananden is offline   Reply With Quote
Old 10-14-2012, 08:52 PM   #9
scx89
Scooby Specialist
 
Member#: 269388
Join Date: Jan 2011
Chapter/Region: SCIC
Location: SoCal SD / LA
Vehicle:
2011 Impreza WRX
obp

Default

No cat after dp for 11'wrx
scx89 is offline   Reply With Quote
Old 10-14-2012, 09:15 PM   #10
dave07
Scooby Newbie
 
Member#: 291349
Join Date: Aug 2011
Chapter/Region: MAIC
Location: Maryland
Vehicle:
2013 Mustang GT
Black

Default

Quote:
Originally Posted by scx89
No cat after dp for 11'wrx
My 2009 doesn't have a cat after the down pipe. They must have stuck the 2 cats in the down pipe in the 08+.
dave07 is offline   Reply With Quote
Old 10-14-2012, 09:15 PM   #11
ThunderDent
Scooby Newbie
 
Member#: 334948
Join Date: Oct 2012
Location: WV
Vehicle:
2013 WRX - Limited
Dark Gray Metallic

Default

Thanks for the diagram. Shocked to see 3 cats on the WRX. I suppose if you changed the downpipe and went turbo-back exhaust, that you could eliminate one of the 2 posterior cats. They are probably all.small cell ones since there are so many.

Any idea what the ID of the downpipe and of the rest of the piping is?

Also wonder how much flow restriction that intake silencer adds.

Seems to me if you were going to eliminate a cat, it would be the one in the downpipe right after the turbo. It would help the exhaust sound a bit as well I would think, plus help the turbo spool quicker.
ThunderDent is offline   Reply With Quote
Old 10-14-2012, 09:19 PM   #12
ThunderDent
Scooby Newbie
 
Member#: 334948
Join Date: Oct 2012
Location: WV
Vehicle:
2013 WRX - Limited
Dark Gray Metallic

Default

Oh, my bad, so after 06, that diagram would not have the precat, and after '11 it also wouldn't have the dp cat. So my '13 only has the single rear cat before the resonator? Is that correct?
ThunderDent is offline   Reply With Quote
Old 10-14-2012, 09:26 PM   #13
dave07
Scooby Newbie
 
Member#: 291349
Join Date: Aug 2011
Chapter/Region: MAIC
Location: Maryland
Vehicle:
2013 Mustang GT
Black

Default

The downpipe has 2 cats in it. The mid pipe has no cats in it...just a resonator. This only holds true for 08+ wrx's. I just checked the parts diagrams.
dave07 is offline   Reply With Quote
Old 10-14-2012, 09:29 PM   #14
HinshawWRX
Medium Frank
Moderator
 
Member#: 140114
Join Date: Feb 2007
Chapter/Region: MAIC
Location: Common Sense, VA
Vehicle:
2014 Porsche
GT3 (Currently on Fire)

Default

That diagram isn't technically 100% accurate for the 06/07 anyways. Once Subaru switched to the 2.5L for the WRX, they got rid of the catted up pipe.
HinshawWRX is offline   Reply With Quote
Old 10-14-2012, 09:45 PM   #15
seanvetter123
Scooby Specialist
 
Member#: 174476
Join Date: Mar 2008
Chapter/Region: NWIC
Location: B-ham, WA
Vehicle:
2002 Impreza RS
BRP

Default

that diagram is for the 2002-2005 wrx. After that they got rid of the cat in the up pipe. As far as the cat's after the turbo, I don't know.

Last edited by seanvetter123; 10-14-2012 at 09:48 PM. Reason: woops, had the wrong years.
seanvetter123 is offline   Reply With Quote
Old 10-14-2012, 09:54 PM   #16
dave07
Scooby Newbie
 
Member#: 291349
Join Date: Aug 2011
Chapter/Region: MAIC
Location: Maryland
Vehicle:
2013 Mustang GT
Black

Default

There is no silencer for 08+ WRX's as well.
dave07 is offline   Reply With Quote
Old 10-15-2012, 11:26 AM   #17
cvananden
Scooby Newbie
 
Member#: 326698
Join Date: Jul 2012
Chapter/Region: Tri-State
Location: Bayonne NJ
Vehicle:
2006 WRX Ltd.
San Remo Red

Default

Well I did say it was up to 06 (when it changed)

I think there is a newer diagram floating around, but I can't find it right now.
cvananden is offline   Reply With Quote
Old 10-15-2012, 12:19 PM   #18
coldmm803
Scooby Newbie
 
Member#: 229343
Join Date: Nov 2009
Location: Allentown, PA
Vehicle:
12 WRX SWP sedan
09 LGT RIP

Default

Quote:
Originally Posted by dave07 View Post
There is no silencer for 08+ WRX's as well.
Do you mean the intake silencer or resonator in the mid pipe? My '12 has a resonator haven't look at the intake.
coldmm803 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 07:43 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.