Cats removed - what to do next?
 

I took my '07 XKR around a race track a month or so ago and the following day had a check engine light and P0430. After a bit of diagnosis it appeared that the catalyst on bank 2 was stuffed.

After doing a bit of research on this forum I was considering buying some 200 cell cats to replace them but my mechanic recommended just chopping the existing ones out and replacing them with straight through pipes. I got the car back yesterday and they have done a neat job but in his own words "you aren't going to like this, it is too loud".

You can hear the results here:


What does the collective wisdom of the internet think I should do next. We don't have emission testing here so I don't need to replace the cats. I have put fuse 19 back in which has got rid of a lot of the snarl but it is still quite raucous off the line until the valves close and even then it is quite loud. It sounds a bit like the AWD F-Type R I test drove in hooligan mode but at least you can turn that off!

Without watching the video, do right by the planet and install cats.

I have my secondary exhaust valves permanently shut this does help alot with reducing the sound

Thanks for the suggestion - I did wonder if that might be an option while I was lying in bed this morning. I just had a look at mine and on the XKR they have quite a strong spring on them forcing them open so I would have to overcome that somehow.

I didn't like the original noise transition from open to closed with the active exhaust valves which was one of my reasons for removing fuse 19 so would want to either come up with a solution that had them permanently open or closed. I have only driven the car once since getting it back but I think it will probably still be too loud with them closed though so will have to look at some sort of intermediate silencer if I don't put another cat back.

I noticed when I had a look inside one of the cats once it was off the car that there was a piece of foam dangling inside one of them so I wonder if that is normally wrapped around the cat but got blown out with my high speed runs round the race track because the cat was too blocked? That would then allow the exhaust gases to bypass the cat causing the P0430 code. It is turning in to a very expensive day out!

Drop the rear muffler disconnect the exhaust valve and permanently shut it by tying it off with wire

Thanks. That actually took less time than expected. I had a quick play while waiting for Xmas lunch to be cooked and, once I had sussed it out, the second side only took a couple of minutes and I didn't need to jack the car up to do it. The rod from the valve can just be pushed up and out then the valve arm can be rotated and wired shut.

The bad news is that the sound isn't very pleasant so I am going to have to sort something else out. Trying to get a decent sound looks like it is going to be a real case of trial and error.

It doesn't sound too bad in the video but at what I guess is around 3,000 rpm's the exhaust note is quite tinny and fluttery with a bit of a rasp:

Ok we got that sorted that's good

Are you running any mid pipe resonator or have they also been deleted?

Ps merry Christmas from oz

Merry Xmas to you too!

The rest of the exhaust is standard at the moment but when I picked the car up my mechanic was suggesting removing the mid pipe resonator section and getting something custom made to replace it. Not sure how you would go about choosing something suitable though?

The system seems to be lacking base now with the adaptive valves permanently closed so I think my preference would be to put them back as they were and take fuse 19 out then try and get the rest of the system tuned. At least the exhaust is a little quieter now so I am less likely to get pulled over until I can sort something out.

I've had my resonators removed and an x-pipe installed yes its louder but it does produce a silkier sound

On a technical note (excuse the pun) it balances out the exhaust banks improving low down torque and free up some hp

Thanks, I did wonder about getting an x-pipe installed. Louder might not be good though!

Here's a 4.2 XKR, no cats and x-pipe


Has a tune in it though

That is definitely loud! Do you know if he put it on a dyno once the cats were removed to see what the difference in power was because I note on another thread that you made a comment about some people experiencing loss of power and responsiveness when removing the cats?

I have 200 cell cats & x-pipe with the original muffler. With the valves closed the exhaust sounds bizarre and weak and a little tinny. With the valves open it is really loud. The valve switch over certainly sounds a lot better with the full factory exhaust. I have not yet decided what to do or what can be done to further refine the exhaust note.

I'll let you know when I do a dyno run next week as I have a baseline from before the cats were installed.

That would be great to find out, thanks. I didn't think it was worth baselining mine as one of the cats seemed to be stuffed and I suspect the other one was quite blocked as well so it wouldn't have been a good comparison. It was all done in a bit of a rush anyway as I needed to get it 'fixed' before the Xmas break.

That is a good description and is why I have taken the wire off the valves and reconnected them for now so at least they are open some of the time. Most of my driving is around town so I get a nice burble as I go from traffic light to traffic light and I am learning to ease on the throttle slowly and wait for the valves to close if I want 'stealth mode'.

I think I have the perfect set up. 'growly' and 'snarky' but not obnoxious. And truly, everywhere I go I get compliments on the rumble. Even the Jag meets.
300 cell cats and the remainder of the exhaust stock.

FWIW

u102768, after re-reading your initial post and my response, I think I should apologize.

A little too judgy on my part. Not the purpose of the forum to judge, but to help. So wile I think you should use the cats, I could have offered a kinder response. My apologies.

And since I'm satisfied with stock, I have no suggestions to add.

Dyno today. Did not really see any loss of power but did not see any gain either. Definitely louder though and smellier.

Thanks very much for confirming that. I had thought that the exhaust fumes were more noticeable as well.

My mechanic will hopefully be back from his Xmas break this week so I will try and catch up with him and see what he thinks we should do next. He was talking about replacing the two resonators with something else but if there is little or no performance gain running with no cats it might be worth starting with 200 cell cats and seeing what it sounds like after that.

A week on, I like the rumble of the current setup at low throttle but anything more than that is stupidly harsh and loud and really doesn't suit the car. I miss being able to floor it off the lights without drawing so much attention to myself.

Jahummer so I take it its not worth upgrading the stock cats? Did you see if AFRs shifted at all? Maybe AFR are now richer with opened up cats thus lack of gain? Just a thought....