Im looking at replacing the catalytic converters on my 04 xjr. Its sitting on 105k mi and im sure theyre pretty well cooked by now. Also going to do the mina exhaust and replace the resonators with an x pipe.
On the cats
How many are there? I can see one on each side but read on one of these threads that the xjr had 4.
Also, i read the SC 4.2 has 600 cell while the Non SC has 400 cell cats.
Im thinking of doing the 400 cells as i dont want the exhaust too loud or wild like i assume a 100 or 200 would cause.
Does anyone know a part or model number for the oem 400 cells?

 

It may be a lot cheaper to do a dyno and see if the power is markedly down.

 

The programming in the ECM detects from the downstream sensor, cat efficiency. When they are past their useful life, the ECM will let you know via the CEL. As long as you don't poison them, or overheat them with raw fuel, they'll last quite some time. What should be considered at 100k miles, is 02 sensor replacement, both upstream and downstream.

 

David: For original poster and myself, please advise:

I have a bad RH cat (07 xjr; 102K miles):

- Should I replace both cats?

- Replace all four 02 sensors, based upon mileage?

- Regarding cats, I would like to keep my car as quiet as possible, but would consider weld in replacements. Any recommendations?

- Assume sealing rings (gaskets?) and new fasteners typically required for R&R?

 

Cats are designed to last the life of a car. If they fail, it's due to the engine not running correctly. Also fix the root cause of the problem when you replace the cat. Cheaper aftermarket cats are cheap for a reason, avoid them.

 

Wellll.... I don't think so. They're chosen to last "long enough", meaning that few will fail during some compromise period partly defined by any laws as to how long / miles they must last, customer expectations, etc.

Some then last longer. Maybe a lot longer. Some don't.

They fail for a variety of reasons not all of which are due to the engine not running correctly. (Though if there was ONE thing I'd advise people do every service besides the usual oil etc change it would be check your fuel trims.)

Overall, they commonly last a lot longer than was expected when they were first introduced.

Cheap aftermarket (any item) - you can get lucky but may not. Depends how cheap and why, for any item. E.g. I bought a Denso O2 sensor rather than OE so that's cheap aftermarket - though Denso made them for Jaguar for my car. Cost me about a third of Jaguar's dealer price though.

 

At the very least, definitely change your O2 sensors if you've never done so before. It made a huge difference in the way my car performed, especially in the braking dept, oddly enough.

 

Thanks, all

I bought my 07 XJR in March, at which time it had P028? DTC for bad RH cat. Interestingly, it seems that the RH cat is more likely to fail (based upon forum search)

The factory replacement cats are stupid expensive IIRC, and the aftermarket replacements undoubtedly sport generic cats anyhow.

I had thought to get a pair of ~ good quality 2 1/4'? generic ~ 200 cell cats and weld them in, but I'm afraid of making the old girl too noisy

Interesting about fuel trims. I just bought a Foxwell NT510 scanner (with LRJ software), and will study to see if this allows access to fuel trim data. I have no experience with fuel trims, and have done nothing with the engine other than plugs, filters, MAF cleaning. It seems to run well

Regarding new O2 sensors (which I will do), I puzzled awhile over improved braking until remembering that a slow return to idle speed can make braking less efficient. Maybe this is why? A failing O2 may cause this, even before setting a CEL code

 

Correct. Sometimes the rpms would drop too fast or sometimes too slow, both instances requiring more braking effort, and thus producing terribly loud creep groan. I was totally unable to come to a smooth stop no matter how I modulated the pedal. The new O2 sensors changed all that. And I never did get a CEL or code.

I've also been running the Nameless Performance 200 Cell cats for almost 3 months now and there is definitely a bit more get-up and go. I don't know if they actually added performance or if they just restored lost performance, but they definitely had an effect. The exhaust did become a bit louder, but still not obnoxious. Mind you, I'm also running an x-pipe and the Mina mufflers, so the sound and volume is totally different from stock.

I went with the Nameless because I wanted a simple bolt-on that I could swap in and out myself as needed when smog check time comes around. Of course, I kept my old OEMs for that purpose.

 

That makes sense about the rpm drop and braking. That may also be causing my transmission to hunt around between 1 and 2 when comming down to rolling speed (like in a traffic jam) hopefully thats whats going on there because thans an expenseive can of worms to get into lol

 

Thanks all. For an XJR 07:

The "Nameless Performance" cats look like a great option (~$1500 the pair)

Factory replacement cats? IIRC, about $2800 the pair

The NP cats look like 200 cell 2 1/2" SS generics welded into compatible sections (which neck down to ~ 2 1/4")

 

On my 07 XKR the 600 cell and the 400 cell bricks are in the same convertor. I spect yours are the same. One convertor, two individual bricks, first a 400 cell then the o2 sensor then a 600 cell brick.

 

ha , for the life of the car you say ? is that the same life span as the sealed for life trans fluid 100k miles/160k km ?
my cats were nearly completely blocked at 168000km .
i can't recommend 200cell cats enough !
let the big cat breath .

 

i done what you are about to do bar a few little differences . also being an STR .
i made a cat back system 2.5'' removed the center resonator and fitted a 2.5'' x-pipe in its place .2.5'' pipe right through to the rear and replaced the rear mufflers with much the same as mina's rear boxes , 2.5'' glass pack step through chambers. it started out a bit raspy, and got better with time rasp that is between 3k & 4k rpm! any ways about a year later i fitted 2 new magna flow 200cell cats and completed the 2.5'' systems . the sound was terrible !!! mad rasp huge resonance and drone. i had to do something as my neighbors were watching me leave for work through there curtains for the two mornings it was like that ! anyway the fix was easy , i moved the x-pipe forward to were it should be anyway as close to the trans as possible .
and fitted two 2.5'' silver bullet resonators were the original resonator was fitted . wow it sounds beautiful now .it has a real pulse to it now and not loud just deep and meaningful . also the power that it restored was unbelievable .
if you are planning on staying 2.1/4'' then leave the original center resonator alone . in fact i have read others going 2.5 and still leaving the factory resonator in . in my book thats a bottle neck .
sound laws here are strict and checked every warrant of fitness (wof) if suspect . mine passed at under 96 decibels and thats at 4000rpm .
it is much quieter than that at normal going to work or shopping commute driving styles . and probably a fair bit louder than that when I'm out in the country side bouncing off the limiter ! but it sounds amazing no drone in the car just a burble . in fact i really need the windows down to hear it over the road noise at any kind of speed that is .
the mina back boxes were not meant to have the center resonator deleted . trust me leave it in . and there is only 2 cats one in each pipe just after the manifold , as mentioned above there are two bricks in each factory cat.
if i was doing it again id still be fitting 200cell.

 

Catalytic converters don't just "go bad"... Blockage is generally caused by overheating and thermal shock. Overheating is generally caused by rich fuel mixtures and misfires. Thermal shock is self-defined. Poisoning can also cause issues and the easiest way to poison a cat is to introduce silicates, or additives in fuel/oils.

 

So, were I to weld in 2 1/4" ~ 400 cell generic cats (eg links below)with no other exhaust system changes) would the sound level be close to stock? No cat efficiency codes?

(I like fast, QUIET, stealthy cars)

Dynatech® PowerCat High Flow Catalytic Converter, 2-1/4 Inch In/Out - Free Shipping @ Speedway Motors

Magnaflow Catalytic Cat Converter 94105 2 25" 2 1 4" Universal OBD 2 | eBay




level

 

11.5" long will be a squeeze by the time you put an elbow on the out let . If you can get them with a pre angled outlet thay would work fine . Mine were strait 8" long and once the mandrel bend was on the out let it matched the original cats lenth , also it might be easier to go 2.5" cats then step down to 2.1/4" as the factory cats are 2.5" in 2.1/4" out !
Yes 400cell will be close to stock but louder than blocked stock !
No codes for me on 200cell thus far ! I think you'll be fine .

 

Thanks for the info. I was wandering about the resonator delete...my last car was a SRT8 Magnum with 3inch exhaust with the resonators deleted. Produced super drone at low speed enough to set off car alarms in parking garages lol it was fun in that car but id rather the Jag not do that
Just looking for that deep burble sound and not a lot of crackling F Type sound. I think my car has two resonators so i should leave them Both in?

 

Its like sailing, I guess. The kiwi's and aussie's are the best

Thanks for info. I will use 2 1/2" cats, plus neck down at outlet. Will post when I get 'er done