three cats, one must die - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > General Technical Discussions > Engines & Drivetrain > three cats, one must die

Savvy Billet LED Tail LightsLight up the holidays with LED lights from JeepHutIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 08-03-2005, 12:47 AM   #1
copbait
Member
 
Join Date: Jun 2005
Location: San Diego, CA
Posts: 355
three cats, one must die

I think my XJ has three cats. I see two off the manifold with O2 sensors before and after, and then there is what looks like another on the bottom just before the muffler.

I'm wondering, is the bottom one a cat, or is it just a resonator? It is flanged at both ends, so I am thinking of having a straight pipe built with flanges so I can easily swap between the pipe and cat for off-road purposes.

Since I already have two cats inline, I'm thinking that swapping in a straight pipe shouldn't make it any louder, the only effect should be an increase in performance. Has anyone done something like this on a three cat system and what were the results?

copbait is offline   Reply With Quote Quick reply to this message
Unread 08-03-2005, 09:39 AM   #2
bcar240
Registered User
 
Join Date: Jan 2005
Posts: 69
The one close to the muffler is probably a resonator. I don't think anyone would use that many cats unless a previous owner had emissions problems and tried to pass by adding cats. Either way, from my experience, removing a cat makes for a pretty big difference in exhause volume, but that is because the exhaust is flowing better, which is why it increases performance.
bcar240 is offline   Reply With Quote Quick reply to this message
Unread 08-03-2005, 12:31 PM   #3
copbait
Member
 
Join Date: Jun 2005
Location: San Diego, CA
Posts: 355
I read that after '00 they started making all systems CA emissions compliant, so it wouldn't suprise me if it was a third cat. Will pop it off today and check it out...
copbait is offline   Reply With Quote Quick reply to this message
Unread 08-04-2005, 06:49 PM   #4
Tshark299
Registered User
1987 YJ Wrangler 
 
Join Date: Mar 2004
Location: Upstate NY
Posts: 2,352
All 3 are cats. You can tell the 3rd one is a cat because you should be able to see an o2 sensor before and after it. Replacing it with a straight pipe would be possible as long as you don't have emissions inspections where you live. You would need to buy an o2 sensor simulator for the rear-most sensor though or else the computer will detect the missing cat and you'll get a check engine light.

I know if i did that here in NY it would never pass inspection though.
__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
Tshark299 is offline   Reply With Quote Quick reply to this message
Unread 08-04-2005, 07:13 PM   #5
coorsmgood
Registered User
2010 JK Wrangler 
 
Join Date: Jul 2005
Location: Fort Worth, Texas
Posts: 875
http://www.jeepforum.com/forum/showt...p?t=181192read this it may help
__________________
2010 4 door wrangler stock for now in burnt orange longhorns style!!
coorsmgood is offline   Reply With Quote Quick reply to this message
Unread 08-05-2005, 05:57 AM   #6
copbait
Member
 
Join Date: Jun 2005
Location: San Diego, CA
Posts: 355
I verified, the third one is just before the muffler, and it's flanged at both ends, so I will have a straight pipe with flanges welded up to swap out.

IMO it's ridiculous to have THREE cats on a vehicle, two should be plenty sufficient to do the job right the first time.
copbait is offline   Reply With Quote Quick reply to this message
Unread 08-05-2005, 08:53 PM   #7
brandoncrone
Registered User
1996 ZJ 
 
Join Date: May 2004
Location: Saranac Lake, New York
Posts: 614
The problem with the whole 3 cats is that the 4.0 engine is a dinosaur....no offense, its the most durable engine on the market as far as I'm concerned, its very dirty and the only way Chrysler could get it to meet California emissions was to add the two cats up by the manifold to 'clean' it up (I mean steal a little more power away!) That is the reason why it is not in production anymore, I guess too much retooling and designing to make it more efficient.
__________________
Dodge/Chrysler/Jeep Technician 14 Years
ASE Master Certified
L1 Advanced Engine Performance
brandoncrone is offline   Reply With Quote Quick reply to this message
Unread 08-08-2005, 11:34 AM   #8
denverd0n
Registered User
 
Join Date: Jul 2004
Location: Colorado
Posts: 730
Quote:
Originally Posted by brandoncrone
That is the reason why it is not in production anymore...
What's not in production anymore? The 4.0? I beg to differ. It is still the standard engine on several of the newest models of Jeeps.
denverd0n is offline   Reply With Quote Quick reply to this message
Unread 08-08-2005, 04:31 PM   #9
Tshark299
Registered User
1987 YJ Wrangler 
 
Join Date: Mar 2004
Location: Upstate NY
Posts: 2,352
Quote:
Originally Posted by denverd0n
What's not in production anymore? The 4.0? I beg to differ. It is still the standard engine on several of the newest models of Jeeps.
What he means is that it's being phased out right now. The 4.0 is available on only one current Jeep model, the TJ, which is actually Jeep's oldest model right now. When the new Wrangler comes out next year the 4.0 will be gone forever.
__________________
'87 YJ Laredo - 4.0L, AX-15, NP231, 4.10s: 3.5" BDS, 31" Muds

'95 XJ - Donated drive train to the YJ, Parted out the rest

'51 CJ-3A - Buick 225 V6: Painless Wiring Harness, Warn Overdrive & Hubs, 2" Lift, 31" Muds
Tshark299 is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.