Vocan

My car (997.1) has been getting an intermittent P0430 CEL (passenger side cat) maybe every 7-8 drives and I'm looking to get it resolved. I had my indy do some poking around and tested the O2 sensors and found they were in working order and he believes the cat is likely teetering on the borderline edge of needing replacement. I did some scouring of these forums on related topics and since these cars are now past the 8 year cat warranty and with increasingly more limited part availability I thought a new thread made sense. It seems I have a few different options here:

Option 1: Replace with OEM manifolds
My current passenger side manifold is part number 997.113.022.91. I can't find this part for sale online anywhere and I suspect it may be NLA. The PET lists both my part number and 997.113.022.AX and there are a few sites that list the AX version for sale. Does anyone know the difference between the .91 and the .AX and why the PET lists both? Are there different part numbers based on where the car was sold or did AX supersede .91? Assuming the AX part will work, the cheapest price I can find for just the passenger side is $2630 through Rose Passion, and it may require a core exchange (which may not even work since my part isn't an AX). Minor annoyance of having two very unmatched manifolds if I don't replace both.

Alternatively, if anyone has a good condition 997.1 passenger side manifold they're looking to unload I'd be very appreciative.

Option 2: Send both manifolds out to have cats replaced with HJS sport cats
A few shops appear to offer services where they'll gut the factory cats and replace them with 200 cell HJS sport cats. I've received quotes ranging from $1650 through $2000 for this service so far. It's fairly appealing to me since I'd get two brand new high quality cats for less than the cost of one new OEM manifold and who knows how far the driver's side is from failing as well. Presumably, I'd get some small power gains as well. While my state doesn't have a visual emissions inspection, it's also appealing that this setup would likely fly in all 50 states unless you get the most thorough emissions inspector in all of California who's looking for welds evidencing replacement. I do have questions of longevity and durability of the 200 cell cats in the factory manifolds and I found some very old threads discussing how using 100 cells in the OEM manifolds would cause issues with CELs. I know people have had success with this approach on non GT3s but I'm curious if anyone has done something similar on one of these cars and can speak to the longevity. I'm just afraid of having to re-do it all over again in a few years.

Option 3: Aftermarket manifolds with sport cats
Likely a similar net result as Option 2, though perhaps the shape and cat distance is more conducive to longevity of 200 cell cats. Most options are more expensive than either Option 1 or 2

Option 4: O2 Spacers/Mini Cats
Since my passenger side cat may very well just be borderline at this time, I may be able to get away with an O2 spacer or mini cat scrubber on the post-cat O2 line. This seems like I'm just buying myself some time with this approach but maybe some folks have had success using these longer term

Option 5: Ignore?
The CEL is very intermittent and clearing it isn't too big of a deal so I could just as easily live with it and tip toe around emissions testing dates.


Would appreciate some wisdom on the best way to proceed and if anyone has any other suggestions I'm all ears!

pputkowski

Personally I would buy these. Fixes your problem and an upgrade... win/win. https://rennlist.com/forums/market/1344508

Vocan

I saw those but they’re from a .2, which I believe use different o2 sensors than .1s so I’d potentially also need to buy all new o2 sensors but perhaps someone more knowledgeable than me can weigh in on whether that’s indeed the case or whether there would be any other compatibility issues.

noro

Can you swap the O2 sensor from side to side. Despite the shop's opinion I would 1st verify that it is in fact not going to move the CEL code over to the other bank. Unless of course this is exactly what the shop did to validate the O2 sensor being fine.

Option 3: Fabspeed sport cats (it's money but you are likely to get some power)

JG 996T

when my oem manifold cracked it caused intermittent cel.
before i learned it would be replaced under warranty, i was looking at your option 3.
if it happens again, i will do option 3.

Vocan

I think they at least checked the voltage output but I did ask about them swapping it side to side originally. With that being said from my stack of service invoices from the prior owner one of them was a replacement of all four o2 sensors about three years ago so my guess is that this has been an ongoing issue but I may still have them swap them anyways. You never know but based on the recent replacement I’m not holding my breath.

Spyerx

.2 headers fit fine. I ran .2 cup headers. They are 200 100 cell iirc and will cause check engine lights on stock tune. I modified mine with pre and post cat bungs. (see post a few responses down with link)
the .2 headers are a more durable cat material also.
4l headers are 300 cell.

you won’t pass in ca with anything but an oem looking product. I’ve never seen a smog guy check part numbers. But if you get flagged and have to go to the referee, they do.

if you are in ca stick oem.

Oh on my car, a 997.1RS, I have 997.2 gt3/rs headers on it. They fit and work fine. Why? Well, I got them cheap and the originals are on the shelf... these damn things are increasing in price at like 2-3x inflation rate.

RAudi Driver

I looked at those and it appears that those are the old Cartographic style headers. From my research, it didn't appear that they hook up to the stock side mufflers or deletes. You can compare the Cartographic header, add that cat and you'll see how it terminates further back than the stock system.




Stock Header:

RAudi Driver

The cats alone are going to be $1,500. Fabspeed will probably cost over $4,000 to do it.

Vocan

Fabspeed actually was around $4k. Carnewal was around $2200 including shipping and Cargraphic around $1850ish including shipping. Forgot the prices I mentioned earlier were in euros and didn't factor in the current exchange rate.

RAudi Driver

Cargraphic and Carnewal are using HJS cats also?

Vocan

Yes, that’s correct. Here’s the Cargraphic for reference (you may need to use google translate on this page):

https://www.cargraphic.de/en/your-ve...carp97gt3fkat/

Wonderdan

i got $650 for my old cats at junk, that helps with pricing a little.

Spyerx

ok, i think cup headers are 100 cell... just FYI, these are my old ones. A member/track buddy here got them (free like beer!) and replaced the cat membranes.

Anyway, 100 cell do trigger CEL. I suspect 200 may too.

https://rennlist.com/forums/997-gt2-...cats-fail.html