Welcome to the North American Subaru Impreza Owners Club Thursday July 28, 2016
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo)

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 09-02-2001, 03:43 PM   #1
2.0 guy
Scooby Specialist
 
Member#: 5670
Join Date: Apr 2001
Location: Round Rock, TX
Default exhaust/OBDII/CEL questions

In talking with a Subaru tech, he said that you needed to keep 2 cats on the car...

Someone else had told me that its really just a matter of where you mount the 2nd O2 sensor and that if its farther back, you are less likely to get a CEL...

So, if I were to get an up-pipe and a down-pipe, but keep the stock cat back section, that would eliminate 2 of the 3 cats, leaving the main cat only...

So, technically, would that set off a CEL?

Granted, the stock exhaust is a bit of a bottleneck, but is it a BIG bottleneck?

I'd like to keep some of the quietness of stock, but its kind of exciting thinking of the up-pipe, downpipe and a Unichip... That would make the car look stock and sort of sound like stock, but run like stink

any ideas on CELs. I guess its not a big deal having a CEL, but it would be nice to avoid them alltogether...

Is my info on the the 02 sensor location triggering/not triggering the CEL correct?

Thanks!
Mike
* Registered users of the site do not see these ads.
2.0 guy is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 09-02-2001, 04:49 PM   #2
Austin
Scooby Guru
 
Member#: 7089
Join Date: May 2001
Chapter/Region: NWIC
Location: Western Wa
Vehicle:
2016 STi

Default

First of all, by law you need to keep all the cats that came on the car. If they get damaged, you can replace them, but other than that...

You get a cel from having not enough difference in the values sensed by the front and rear o2 sensors. Placement (as far as the way the exhaust hits it) is important, but if you pull the cat from the uppipe and the down pipe, you're left with only the third cat in the front midpipe. The rear o2 sensor is right at the front of the third cat, so you've just pulled both the cats between the o2 sensors, and you'll get a cel.

Also, there are variances between car/car so doing something that did not give someone else a cel could possibly give you a cel.
Austin is offline   Reply With Quote
Old 09-02-2001, 05:30 PM   #3
2.0 guy
Scooby Specialist
 
Member#: 5670
Join Date: Apr 2001
Location: Round Rock, TX
Default

First off, I'm aware of the legal issues... if the car would pass the state emissions with just a single cat, I'd be content with that. I don't want a "illegal" car, but if the sniffers say the car is clean enough with just the one cat, thats good enough for me...

Then again, if the Unichip does wonder like its supposed to, I'd probably be content with just that, and no exhaust work...

I noticed that some exhaust systems have a option to mount that last O2 sensor after the cat (can't remember which one it was).

So I guess that having the up-pipe, downpipe AND a cat-back that allows mounting the O2 after the cat could "theoretically" allow you to run with no CEL...

I'd assume that the Unichip alone gives more performance than a full exhaust (turbo back + up-pipe) and allows you to remain emissions legal, so maybe that is the best route to go...

Thanks for the info on CELs.






Quote:
Originally posted by Austin
First of all, by law you need to keep all the cats that came on the car. If they get damaged, you can replace them, but other than that...

You get a cel from having not enough difference in the values sensed by the front and rear o2 sensors. Placement (as far as the way the exhaust hits it) is important, but if you pull the cat from the uppipe and the down pipe, you're left with only the third cat in the front midpipe. The rear o2 sensor is right at the front of the third cat, so you've just pulled both the cats between the o2 sensors, and you'll get a cel.

Also, there are variances between car/car so doing something that did not give someone else a cel could possibly give you a cel.
2.0 guy is offline   Reply With Quote
Old 09-02-2001, 06:03 PM   #4
en3d
Scooby Specialist
 
Member#: 5238
Join Date: Mar 2001
Location: Bay Area, CA
Vehicle:
GGA Black

Default

You only need one cat and the O2 sensor behind it. So either a cat in the downpipe or midpipe and have the sensor behind the cat. that will give you the readings that it expects and not trigger a cat effiency CEL code.

One thing that people forget is that a turbo back exhaust may not net you the biggest HP, but it is extremely important when you go down the path of mods on a turbo car. you can increase boost with the unichip/boost controller all you want but an exhaust allows the exhaust gas to exit faster. turbo cars less backpressure is better.
en3d is offline   Reply With Quote
Old 09-02-2001, 08:01 PM   #5
gtguy
Scooby Guru
 
Member#: 2184
Join Date: Aug 2000
Location: Highland Park, Ill., USA
Vehicle:
2005 Legacy GT wagon
Platinum Silver Metallic

Default

The Unichip is tuned for an axle-back exhaust, and panel filter like a K&N. T'would be interesting to see if folks like JaMa, who are running the Unichip with a turbo back system are getting faster times than those running a cat-back, then axle-back.

This might be a case where more money isn't necessarily better, though it might be theoretically.

Anyone?

Kevin
gtguy is offline   Reply With Quote
Old 09-02-2001, 08:41 PM   #6
Tuning Factory Inc.
Vendor
 
Member#: 3600
Join Date: Jan 2001
Location: Detroit, Michigan, USA
Default

I have the cat before the turbo removed as well as the last cat before the exhaust removed. Zero problems and response is MUCH better although I do want to tear out the last cat soon. Just waiting for my flanges to get my downpipe in production.
Tuning Factory Inc. is offline   Reply With Quote
Old 09-02-2001, 09:30 PM   #7
Austin
Scooby Guru
 
Member#: 7089
Join Date: May 2001
Chapter/Region: NWIC
Location: Western Wa
Vehicle:
2016 STi

Default

Yeah... I'd never seen the innards of a cat before, but when I had my stock uppipe out I looked at the cat in it. OMFG! Definitely no light can get through - it's got to be a MAJOR flow restriction. Like corrugated cardboard packed as tight as they could get it.

Oh, and 2.0 guy - I didn't mean to say you didn't know the legal crap, what I was amazed about was that anyone representing Subaru would say that, essentially, it's okay to remove one cat. (I would expect him to say NO, of course you can't modify your car in any way, esp. cat convervters!)
Austin is offline   Reply With Quote
Old 09-03-2001, 12:10 AM   #8
2.0 guy
Scooby Specialist
 
Member#: 5670
Join Date: Apr 2001
Location: Round Rock, TX
Default

Austin,

I hope I didn't sound like I was snapping back at you, because I wasn't...

I too was amazed, but the dealer is mod-friendly. They just are sure to warn the consumer that if a mod caused the problem, then the warranty is toast...

I think he only meant that you could remove the cats as they pertain to the CEL and not the legal ramifications of doing so...

basically, he didn't say it was illegal (since it is), he just said what one should do to make sure you don't get a CEL...

So, Austin, you have the cat-less up-pipe? Any other mods? I'm not really planning on going the Imprezer/alfriedesq route, but I just want to maximize what I have right now, or maybe some mild mods...





Quote:
Originally posted by Austin

Oh, and 2.0 guy - I didn't mean to say you didn't know the legal crap, what I was amazed about was that anyone representing Subaru would say that, essentially, it's okay to remove one cat. (I would expect him to say NO, of course you can't modify your car in any way, esp. cat convervters!)
2.0 guy 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Exhaust CEL question- midpipe installation preacher#1 Newbies & FAQs 5 12-13-2006 08:33 PM
Exhaust CEL question StealthfishWRX Newbies & FAQs 3 08-03-2005 10:35 PM
What stores test OBDII CEL codes for free? Sephro New England Impreza Club Forum -- NESIC 11 02-23-2005 04:21 PM
Where do you connect the OBDII CEL code reader? disque71 Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 3 07-02-2004 05:43 PM
What is a cheap/simple OBDII CEL reset device svxr8dr Engine Management & Tuning 21 09-06-2003 06:08 PM

All times are GMT -4. The time now is 08:07 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2016 Axivo Inc.
Copyright ©1999 - 2016, North American Subaru Impreza Owners Club, Inc.