Not Magnaflow. I guess they are Larinis. Not cheap ones.

 

Xjr-99 and Datsport how much power are you pushing through yours and what's your AFR ratio? I'm at around 11.5 so think that pretty perfect for wot ,Yet these cats failed with minimum usage.

My guess is it just bad quality cats. I spend a good amount of money, for the set so definitely want to get to the bottom of this

 

My larinis lasted a bout 200Kmiles, I had to replace them as I couldn't get them thru the yearly emission test anymore, other then that they where still ok (no melt downs).
Quality certainly played a role that they lasted so long emission wise, these tests here are pretty tough.

For the ones that tune, you may want to add a EGT to monitor, as with changing parameters you also change the heat output, which could be a cause. Misfires etc (just google) could also add to melting cats.

I have only experience with the larinis on my car, and would buy them again in a heartbeat, but for now I have put my original cats back as it is not my main car anymore, and budgets have shifted.

 

well shoot. Maybe i will try the cats i got from magnaflow. I cant understand why they would die quickly. yes they are small but that shouldnt affect their ability to resist heat in normally running engine. heat is heat, right and a stock tune shouldnt be so lean its melting cats nor should it be rich.

I guess I will take the pipe off and see what cats are on there since its obvious someone replaced the stock cats

Does anyone have pics of stock STR cats that I can compare these ones too? i havent looked at mine well enough to see if there are any part numbers on them but I will.

I am not sure how to proceed just yet

 

Here is my plan.....i have same vehicle..,..after i smog this year i am having a no cat pipe made from manifold to x pipe with o2 sensor bungs ...i.have found a spacer that works great for all o2 sensors....i will run those pipes until smog again in 2 yrs.....muffler guy says i should be good to run pipes and have no codes....he has done it before on other European high power cars...the spacer is the key....it has a cat honeycomb built in and fools the o2 sensor....either way smog only uses the monitors to check for passing...cars are too low to see cats ......worse case scenerio is i put old pipes on for a day every 2 years.....he will make both pipes for 200 dollars and install....i am going to do this and a blower pulley and lower t stat at the same time....i will monitor trims and hopefully no engine light...any cat replacement has to be welded in so i will go with new straight pipes and save my old pipes....i trust his advice and experience....all this will happen before end of year.....i have 1 cat getting iffy, so i used a spacer on both o2 sensors as a test about a month ago, and now the readings are more stable, no codes and better trims....a test in progress, but looking good

 

Bad plan imo, the 2nd O2 sensor is also used for determination of the fuel mixture by the ECU, using the spacer you will influence these readings negatively which can cause a unwanted behavior at certain rpms/engine loads. Some have reported richer mixtures there which resulted into cat damage over time (Cambo for instance, and I know another case as well).

So it may work well for some time, but at some point you will have the consequences...

 

Thanks for input.....like i said it is a test....tests give different results......and there will be no cats to damage in the end.....i keep close tabs on trims for both sets of sensors.....right now i run 0 to +-.6 on the rears at varying loads....the final product will be catless....i trust your opinion too avos.....i will keep tabs as not to melt my existing cats

 

Sorry, I should have added that my comments are more for those who still go for 200 cell cats and extenders. As you say you are not using cats anymore so there running richer at some rpm ranges will be much less of a concern.

 

wait, isnt the first set of O2 sensors (the ones BEFORE the cats) the sensors that adjust the AFR? The second set of O2 sensors (after the cats) are in the clean air stream so they just measure cat efficiency and are not used for controlling the air/fuel mixture.

Am i wrong/

 

No worries avos, always glad for input.....i maybe barking the wrong tree by going catless and fooling the ecm.....but worth a try if the muffler guy is right....he also does smog so that's why i trust him.....he hateses the ca smog ripoff system and hates to see performance cars underperforming

 

I would suggest leaving them in as in stock o2 positions. If you trying not to get Cel lights. This is an easy fix in a tune I can help you with that.

 

thanks alexjag....i get my smog in december, so I figure after the 1st of the year I will be doing the mods...I will give you a shout for the thermostat and any other suggestions including tune...I have to take the current piping off so the muffler man can use them as templates for the new catless ones, so i will do that after smog...might do the pulley and thermo first...will keep you posted

 

Yes, you are wrong. As has been posted before (use Search) and as Jag say in their docs, the downstreams are also used for fuel trimming.

 

these jags by nature with stock tune do run rich .
if i were you i would get a higher quality set . those ones are just too cheep.
and not up to this kind of power and stock fuel-ing .
mine did not need down stream spacers with the magnaflows on. and ran great .
but does require spacers with the cats gutted . and runs a smidge richer again .
not ridiculous though .
still runs nice clean plugs , no fouling .
mine is on the stock tune . but with 3.5 more psi over stock boost . and way cooler charge temps than stock .
fact is you will struggle to find a tune for the early STR's with the DENSO PCM. so its going to be rich .
i believe my first set died early due to a bad MAF sensor . so it pays to make sure every coil , spark plug and fuel critical sensor is replaced .
as these to die with age .
but the second set of mine died early with zero explanation . all new sensors plugs . coils fuel pumps . and running good fuel pressure , AFR and trims .
quality cats cost more than those magnaflow cats . i should have figured that myself . but as i found a problem i figured it was worth another try .
truthfully that just made extra work . just like the sensors and coils it does not pay to skimp on cats
btw the stock cats are massive with two bricks inside . 1 600cell and 1 400 cell brick .
so they will by nature last a lot longer than the tiny generic honda civic ones you just purchased .
jagv8 is correct , the down stream o2's contribute to fuelling

 

Thanks for the responses! this is getting me somewhere! The suggestion to "use Search" is in my DNA. I use it religiously before I ever ask a question because this is a forum and besides a few smartie pants such as yourself and several others on here (and in this post), you can sometimes get off the wall statements so i always resort to google first.

That being said, that is what I had done but found tons of different or vague information especially when it comes to the Jag STR supercharged engine and it fuel control

Any links to describe the technical aspects of the system would be greatly appreciated. I am an electrical engineer by profession and I love all things electronic. And being a gearhead since i was born means i love all things engine related and i have spent a lifetime trying to learn.

That being said, I have found very little specifically talking about the STR O2 feedback and control for fuel trims so (once again) anything I can study up on would be invaluable to me.

I do know this- the upstream sensors are 4 wire, heated wideband sensors while the downstream or mid-cat O2 sensors are 4 wire, heated narrowband sensors.

If i know how a system works, I can fix it. So I have been trying to find the exact purposes for both the upstream and downstream O2 sensors. You said "according to the Jag doc" so this is my goal- to find those jag Docs! Do you have a link??

 

Good places to look for detailed info include the workshop manual, large file area, JagRepair.com - Jaguar Repair Information Resource (at least). All free downloads.

 

Also don't hesitate to use info from the XJR X350/358 forum too . they are identical to the STR's running gear . although the changes made to the STR was delayed a year or so from the XJR .
it's the same beast . the STR is rarely modded . and info on mods and aftermarkets are scarce .