How free flowing should the XJ exhaust be?

[gradon]

Last week I pulled the cat-back off to fix a leak @ that downpipe/cat junction and found that my 3 month old magnaflow was melted(fast $80). Half of the honeycomb came out from me shaking it and the other half my dad punched out. Now this cat was used for 2 months on my 4.0 w/o problems and a month on my 4.6. No lean codes, no pinging, but it wasn't smooth accelerating like it should've, so I felt it was running lean in the midrange. I installed the LT1 injectors after fixing the cat and now my stroker sounds and runs like a beast. I'll contact Magnaflow and see if the warranty applies w/ me being the installer and that I had to punch it out in order to drive.

 

[corbinafly]

Cats usually melt from running too rich don't they? Excess fuel burning off in the cat and all.........

 

[gradon]

I thought it was due to the hot temps of a lean mixture. It could've been due to me running a couple days w/o the heater circuit, thus ecu went into a rich safe mode. Regardless it's my fault and I'm gonna have to replace it. I definitely won't put another one on until it is tuned right.

 

[BBeach]

I thought it was due to the hot temps of a lean mixture. It could've been due to me running a couple days w/o the heater circuit, thus ecu went into a rich safe mode. Regardless it's my fault and I'm gonna have to replace it. I definitely won't put another one on until it is tuned right.

Good because im about to go install mine haha. At least its only $80.

 

[gradon]

It still hasn't thrown a code with the 98 ecu. I was thinking that the downstream o2 sensor would've notified the ecu that the cat wasn't doing it's job(being gutted), but I guess it's still within range(good).

 

[wolfpackjeeper]

thats why I ws glad to be stroking my 91 instead of an obd2 truck.

and since it has been about a week...

dyno numbers??? I would do my truck for you guys, I found a good shop to do it at at my new house, but since my truck is still 800 miles away it is gonna be a minute

 

[wolfpackjeeper]

clear......

ZAP!!!

 

[gradon]

I have about 1100 on the stroker now. I want to give it another 1000 and get that wideband and tune the psc1, then I'll get on a dyno.

 

[wolfpackjeeper]

I found a dyno, and I have the money to do it, but I am in Pensacola, and the jeep is in Raleigh...

 

[mikereid350]

well my 88 xj yard/farm jeep has no exhasut just the manifold and a short downpipe. its loud and loud..as per gas milage not shure it just runs around our land...but it seams that i don't go far on a few gallons of gas...

 

[Muddy-93]

Just jumping in with an addendum from Norway... My cat' is shot, and I am thinking about replacing it with a strait pipe, or an resonator. Talked to my local garage, an they said that exhaust-mesurements required here is within limits even with the cat' gone!? On my -93 XJ there are no sensors inside or after the cat', only in the downpipe. If you can't messure the difference, what's the use of replacing the damned thing?

 

[wolfpackjeeper]

some cars run clean without the cat, some cars stink to high heaven. It really comes down to your local laws and how you feel about it. Personally I feel that most of the vehicles I have had run better with the cats and a well built exhaust. And yes, all of them have been run without at one time or another so I do have a comparison to work with

 

[rjstiles]

Why did you get a cat with the O2 bungs in it already? What year is your XJ?
I am asking because i wanted to change the cat on my "01" for mileage reasons too. I have 124k on the motor and only get about 220 miles a tank of gas. All of my O2 bungs are in the exhuast and not the cat. Sorry for the Hijack.

Holy Moly, I thought my mileage was bad but I get right at 400 miles per tank. Mine is stock.
I just put Nitrogen in the tires, ordered the Edge products Trail Blazer kit with chip, throttle body and free flow air filter. I am thinking about adding a TB spacer and headers, downpipe and exhaust. With my luck I will spend a couple of grand to get 2-3 more miles per gallon :confused1 . Oh, I have 225,000 miles on my 2000 XJ.

 

[urban yan]

Speaking of Free Flowing... my 2.5" Kolak pipe arrived today.
I've been running a 2.5" magnaflow muffler and cat for a year
with the stock 2.25" pipe... I hope the larger pipe helps a little.

 

[wolfpackjeeper]

some maybe, not sure how much though

 

[alex22]

A bump for the dyno numbers on the exhaust system with no cats.