Forum Index
Jeep Horizons HomeLinksJeep Horizons Tech Write-upsJeep newsLand useContact

 Watched TopicsWatched Topics   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

catless exhaust


 
Post new topic   Reply to topic     Forum Index -> Cherokee Forum
View previous topic :: View next topic  
Author Message
XT77
Member


Joined: 03 Aug 2007

PostPosted: Sat Aug 04, 2007 10:44 am    Post subject: catless exhaust Reply with quote

Hello to all!

First off I'd like to say what a great forum this is! I've been checking it out for a couple of days now, and decided to become a member. I bought a 1999 cherokee classic (4.0, auto, 4WD) back in april, and want to make a few mods, mostly for performance. I would like to replace the exhaust first with a free flow system, but I'm concerned about the O2 sensors up stream and down stream of the cat. If I remove the cat will the computer freak out without the sensors? If so, what can I do to fool the computer into believing they are still there?..Does somebody make dumby sensors?

I'm planning on piecing the exhaust system together myself w/ a do-it yourself pipe kit and a muffler of my choice. Does anyone have any suggestions on what muffler to use, and what diameter of pipe to go with? I would like to achieve a good low rubble, with no vibrating sounds!

Thank you in advance for any help or suggestions, XT77
Back to top
View user's profile Send private message
XT77
Member


Joined: 03 Aug 2007

PostPosted: Sat Aug 04, 2007 10:54 am    Post subject: Reply with quote

oops! I just realized I posted this on the grand cherokee forum, its suppose to be on the XJ forum...My apologizes.
Back to top
View user's profile Send private message
badger
Member


Joined: 16 Sep 2005
Location: Utah

PostPosted: Sat Aug 04, 2007 3:05 pm    Post subject: Reply with quote

no go on the cat removal .the computer is looking for the difference between the in-flow and out flow of the cat.if it doesn't see the cat doing its job it will throw a code .

as for what type of muffler i'm a fan of how the Flow Master Delta 40 sounds.
_________________
One Built XJ

Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
ThePhantum
Pissed-Off Admin
Pissed-Off Admin


Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Sat Aug 04, 2007 4:23 pm    Post subject: Reply with quote

Just go with a hi flow Cat...Random Technologies makes one that will accept the stock downstream sensor. I run one under mine...I'm also running a Flowmaster 40 with it and I'm very happy with the system.
_________________

97 XJ Sport with a bunch of stuff
Quote:
Never argue with idiots, they drag you down to their level and beat you with experience
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
badger
Member


Joined: 16 Sep 2005
Location: Utah

PostPosted: Sat Aug 04, 2007 7:14 pm    Post subject: Reply with quote

really the term high flow cat is redundant .pretty much all cats anymore are high flow .your not really gaining any extra flow while paying more for a cat with the term high flow slapped on it.

you are better off just going up to 2.25 pipe to the cat then 2.5 from ther muffler back.this way you keep just the right amount of back pressure while maintaining a nice free flowing exhaust.

a second part of a free flowing exhaust is a free flowing intake.getting spent gases out faster will do nothing for you if you can't get air in faster . you have to remember that an engine is basically a huge air pump.
_________________
One Built XJ

Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
Brad The Best
Member


Joined: 14 Jan 2007
Location: Kamloops B.C Canada

PostPosted: Sat Aug 04, 2007 9:30 pm    Post subject: Reply with quote

there is also the option of a dummy o2 sensor down stream that will fake a cat being in place .

this only works 50% of the time .

i would just put in a new cat . or buy and old Cherokee Smile
Back to top
View user's profile Send private message Send e-mail MSN Messenger
ThePhantum
Pissed-Off Admin
Pissed-Off Admin


Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Sun Aug 05, 2007 7:24 am    Post subject: Reply with quote

It's true that newer converters are not nearly as restrictive as they once were due to the use of monolith (brick) type cats over the pellet types that were used in the past. However, the density (cells per sq inch) and size (typically in length) of the bricks vs. the size/displacement of the engine is the determining factor in it's flow rate.

So it's correct that just buying any old cat labeled "hi flow", will not necessarily increase flow rate (as a matter of fact it might even increase the amount of emissions). However, a hi-flow cat, specifically designed for the engine in question, will have a higher CFM rate over the entire RPM range of the engine. OEM units, on the other hand, will be more restrictive at RPM's outside of the power band. In other words, an OEM cat will flow the same at say 3K RPM when the 4.0L is making max torque...but a high flow unit will flow better at lower RPM's.

Of course, it should also be noted that, unless your cat is shot (like mine was), none of this really makes sense unless you replace the downpipe going to the Cat. The factory put a big crimp in that pipe...which severely reduces airflow anyway. If you are going to replace the downpipe...you might as well put a header on too. Mr. Green
_________________

97 XJ Sport with a bunch of stuff
Quote:
Never argue with idiots, they drag you down to their level and beat you with experience
Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
badger
Member


Joined: 16 Sep 2005
Location: Utah

PostPosted: Sun Aug 05, 2007 7:37 am    Post subject: Reply with quote

all true

as for the down pipe thats why i was saying put some 2.25 to the cat then 2.5 from there out.i forget were i read it,i think it was another "Dr.Dyno" write up,the math was done and even a fully worked stroker wouldn't need more then 2.5 .anymore and you are really taking away because of lack of back pressure.
_________________
One Built XJ

Back to top
View user's profile Send private message AIM Address Yahoo Messenger MSN Messenger
XT77
Member


Joined: 03 Aug 2007

PostPosted: Sun Aug 05, 2007 7:26 pm    Post subject: Reply with quote

thanks for all the help and suggestions!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic     Forum Index -> Cherokee Forum All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Visit links4jeeps.com for write-ups, forums and clubs




Jeep®, Wrangler, Cherokee, Liberty and Grand Cherokee are copyrighted and trademarked to Chrysler LLC.
jeephorizons.com is not in any way associated with or endorsed by the Chrysler LLC.
All other content is copyright Jeep Horizons 2004-2008.
Tech write-ups Links Discussion board Land use News Site Map Terms of Use

Powered by phpBB © 2001, 2005 phpBB Group