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Discussion Starter #1
Right after my comment on the durability of Maserati cats, mine failed. I think it actually failed as I was writing the review on ML 2 weeks ago, in fact.

So, before taking my own advice and ordering a new exhaust bank, I did what any hood-rich Maserati owner would do and I paid a skilled exhaust shop to cut the guts out of each side. I cannot describe what a good choice this was.

Basically, according to a Fabspeed video, the secondary cats on the Cambio/Spyders are prone to failure and from what I've seen, the early QPs (2005-2006/7) used a dual-cat system that is equally prone. The secondary cat, which is downstream from the O2 sensors, is useless and serves the job of silencing the exhaust to the level of the average S-class Benz. Removing this 600-cell cat has measurably improved throttle response (and sound). IMPORTANT NOTE - the Automaticas have a single cat setup, so nothing that I am saying applies to those vehicles.

Now, it cost me a bit more than a used replacement because talking a legitimate shop into tampering with your cats in Florida takes a bit of money, but it was well worth it.

I will be posting a idling sound clip, however keep in mind I ALSO GUTTED MY MUFFLERS, so it is a bit aggressive. I will also post a driving clip as soon as possible. Personally, I feel it is tough to tastefully pull off a "loud" luxury car but with my current exterior mods, it just works. If it was a white "stock" QP, I probably wouldn't suggest going this far. Since the mod, however, I have had constant compliments, even from the Florida senior citizens who give me the thumbs up as I pass by.
 

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I have a 2006 QP Duoselect.

To be clear, you're talking about removing all of what's inside the second chamber of the cat, after the head?

That would be the part that has a white sticker on it in this photo?

If that's the case, and they are prone to failure as you say, why not remove all the guts of both chambers?

The cost may be more, but would it not be better in the long run to go with, say, Larini sport cats for QP, which would probably never fail, and are high quality stainless steel?

Also, how did you know that yours failed?

Thank you.
 

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Discussion Starter #5
I have a 2006 QP Duoselect.

To be clear, you're talking about removing all of what's inside the second chamber of the cat, after the head?

That would be the part that has a white sticker on it in this photo?

If that's the case, and they are prone to failure as you say, why not remove all the guts of both chambers?

The cost may be more, but would it not be better in the long run to go with, say, Larini sport cats for QP, which would probably never fail, and are high quality stainless steel?

Also, how did you know that yours failed?

Thank you.
1. Yes, you basically cut the "second chamber" along the weld line with a grinder wheel, remove the ceramic block, clean and reweld, leaving "chamber 1" intact.

2. Yes it's the one with the sticker and easily accessible from underneath the car.

3. If you tamper with the primary (first chamber) you will likely activate a CEL. The second chamber is not metered in any way.

4. I cannot attest to the quality of Larini. I have 106K miles on my cats and they performed well under street and track use. If someone has legitimately driven over 100K hard miles on anything aftermarket, I certainly would like to hear about it. Secondly, I am not a fan of Larini for these cars (personal choice). These cars are set up well with good headers and stainless components. The F430, for example, has a compromised header system with the catalyst integration - swapping that out make's a HUGE difference. So, on the QP, I can't see spending thousands on thousands on bent pipe on a front engine car, that doesn't require pretzel bending exhaust tubes to fit in a cramped engine bay, like in the 430, 458 or even 360. Makes no sense to me.

5. Mine started to rattle. Basically, the internal porcelain block broke free and started to rattle against the can. The dealer knew exactly what the sound was.

Seriously, though, cold start against a 458 is astonishingly similar. With the pumps running, you really can't tell them apart. Pretty awesome. Once they warm up and the pumps shut off, then the 458 quiets to a purr with an obvious flat-crack voice. The QP quiets down also with a slight rumble.

We'll see if I get tired of it. This setup ins't for everybody or just any car, but this time the dealer was right - it opened up the flow enough to FEEL the difference, it was easy to do (20 min), and it doesn't throw a code. Remember too, the Larini cat setup earns a large portion of its horsepower from the elimination of the cat that I removed.

Like I said, I will try to get a driving/shifting/downshifting vid posted soon so you all can judge for yourself.
 

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There was a similar "stealth" cat delete on one of my prior cars that the forum members referred to as the "magic mystery mod" The set up was headers- pre-cats- y-pipe - main cat - exhaust. And the process was to empty each pre-cat. If you removed the y-pipe, you could visualize the ceramic/platinum fill on one and easily bust it up with a long screw driver and remove via shop vac. The other one however had a 90 degree bend after the pre-cat and to empty it, you had to drill a hole at that elbow, take a length of hard wire that you put a 90 degree bend in, fish it up to the material and hook it into a drill to destroy the material, again sucking it out as it crumbled with a shop vac. All that was left then was to thread the hole and put a short bolt with exhaust sealing paste to prevent the leak. It did have a second set of O2 sensors down stream so you needed to splice a resistor inline with each to prevent the CELs but was a pretty simply process over all.
 

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Erik,

I think I'll just keep my cats intact like you did, until one of them develops a problem.

I'm still thinking though, that I should replace the resonator with an X-pipe on this QP5.

I did that on my 2002 Coupe, as well as secondary cat bypass, both with Fabspeed
and it made a huge difference.
.
 

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Discussion Starter #9
A quick note on the X-pipe.

I have commented on this over a year ago when I was looking to modify the exhaust. I simply do not like the sound of the QP with any aftermarket X-pipe. Even with gutted mufflers and no cats, the factory X-pipe/resonator does a very good job of "smoothing" out the sound of the car, where during acceleration, you get a smooth, trumpeting whine. All X-pipe replacements I have heard have a raspy sound to them which adds a bit of rumble to them. Makes the car sound too "American" in my opinion.

For example, when I removed the cats, it really didn't change the sound or tone at all - it just made it louder. Tampering with the X-pipe actually changes the sound of the car, which I am not looking to do.
 

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Discussion Starter #10
Also, the reason for my thread title of "must do," is that you WILL feel a difference in the car acceleration-wise. I'm sure Larini sport cats will offer the same performance gain (or maybe more), but this is a cheap and easy weekend mod that I recommend either before you spend the money on an upgrade, or after one of your cats fail anyway.
 

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To each his own.

I haven't tried it yet on the QP, but for the Coupe, I'd have to say that changing out the resonator to a true X-pipe was a must do.

It's a significant reduction in weight and increase in power. I did the mods one at a time to guage the results. First, the secondary cat bypass pipes, and then the X-pipe.

Yes, it did change the sound, but not for the worse, and it definitely added more power.

.
 

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Discussion Starter #12
To each his own.

I haven't tried it yet on the QP, but for the Coupe, I'd have to say that changing out the resonator to a true X-pipe was a must do.

It's a significant reduction in weight and increase in power. I did the mods one at a time to guage the results. First, the secondary cat bypass pipes, and then the X-pipe.

Yes, it did change the sound, but not for the worse, and it definitely added more power.

.
I do agree with you on this. On the CCs, I like the X-pipe with Tubi finals. I love Tubi on the coupes, hate them on the QP.

Question though, did you have a cabin drone on the Coupe? My friend has the setup I described and we can't get rid of the drone to save our lives! It's fine though as it adds to the "sport" of the car, but just curious if that was an issue you had.

It might be the Tubis. They kick off a hell of a vibration.
 

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I kept the stock mufflers on the Coupe.
It's definitely racier and somewhat louder, but not droning or vibrating.
The most important mod was getting rid of those squashed secondary cats, I think.
.
 

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Them damn CATS !
Mine failed a few months ago and bought replacements haven’t had time to get them installed. I might actually install them myself as I’m a DIYer...anyone know if they’re a pain to remove on the duo select QPs ?
 

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Discussion Starter #15
Them damn CATS !
Mine failed a few months ago and bought replacements haven’t had time to get them installed. I might actually install them myself as I’m a DIYer...anyone know if they’re a pain to remove on the duo select QPs ?
Well, that all depends on what you consider a "pain!" I think the most complicated part would be RR at the header side. The bolts may require access from the top, but maybe someone with experience can chime in on this. Fortunately, these cars are pretty standard - it's a conventional platform. If you chose to go to a shop to have the work done for example, they shouldn't need any Maserati experience. Just be sure to pick up new OEM gaskets before you go.
 

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Discussion Starter #16
sounds tinny as if something in the exhaust was broken...:|
You were right. Turns out that my left exhaust I had to bend back into position after someone hit me in a parking lot 2 years ago. It still is not perfect. I heard a slight rattling the other day during warm up and I tracked it down to the final bend in the left pipe - it was touching the rear sub frame. I re-adjusted and the rattling disappeared. Since the bends are not exact due to the accident, I just purchased a new rear final muffler/pipe and I am having that gutted as we speak. Once installed this weekend, I will get some better sound clips.
 

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Just gutted the secondary useless cats, and Omg what a difference in tone. Just when I thought the sound couldn't get any better. Drove to one of those muffler shops in the hood where I know gutting the cats wouldn't raise any problems. $200 bucks and 2 hrs later I drove off into the California sunset with the biggest smile. They cut along the bend just after the cat, then move the X pipe out the way to allow room for the drilled power cat destroyer. I helped by holding the shop Vac as the guts spewed out to avoid contaminating the air. My set up as follows: gutted secondary cats, Sport X pipe, gutted mufflers. I'll post a Vid as soon as possible.
 

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Just gutted the secondary useless cats, and Omg what a difference in tone. Just when I thought the sound couldn't get any better. Drove to one of those muffler shops in the hood where I know gutting the cats wouldn't raise any problems. $200 bucks and 2 hrs later I drove off into the California sunset with the biggest smile. They cut along the bend just after the cat, then move the X pipe out the way to allow room for the drilled power cat destroyer. I helped by holding the shop Vac as the guts spewed out to avoid contaminating the air. My set up as follows: gutted secondary cats, Sport X pipe, gutted mufflers. I'll post a Vid as soon as possible.
Hi there,

Did you have to remove the entire cats or it was done while in place? If it was removed, did you use a new gasket or used the same one?

Thanks!
 

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They don't remove the cats. They cut the pipe just aft of the secondary cat "see image". They use a power drill with a gnarly looking bit to gut the cat. The x pipe has to come off.
135415
 
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