Hi there everyone!

Our 2010 Altima 2.5 started throwing emmisions codes which our mechanic said was either the O2 sensors or the catalytic convertor that's integrated into the manifold. We replaced both O2 sensors but the error codes returned which the mechanic stated confirmed was indicative of needing to replace that catalytic convertor. Parts and labor quoted exceeds the value of the vehicle, unfortunately so we wondered how bad it would be for us to do the job to save the labor (my daughter loves the car and doesn't want to replace it). We're fairly mechanically inclined, do most of our work on our cars, own a decent set of tools but don't have access to a lift and do our work on a sloped gravel drive.

Is this a job someone in our position can do or is it something that is best left to the mechanic? What's the best deal we can get on that manifold/cat? We see huge differences in price and worry that we'll buy the wrong part.

Any insight would be greatly appreciated, thanks for your time!

The main risk in doing the cat on a QR25 is snapped studs, but you can very much minimize that with some PB Blaster and a couple of patient days to let it soak in. The 6mm's holding the heat shield on always snap, so have replacements on hand. The gasket ring is a crush type so don't try to re-use it. You should only need to lift the car enough to get at the studs holding the front section of flex pipe to the manifold. Get new studs for the manifold if the cat doesn't come with them, trying to extract and re-use the old ones is likely to be a bear. For aftermarket brands, some are good but stay away from the real bargain-basement stuff. My customers have had pretty good luck with both Bosal and Eastern Catalytic.

VStar650CL wrote: ↑

Fri Mar 05, 2021 1:13 pm

The main risk in doing the cat on a QR25 is snapped studs, but you can very much minimize that with some PB Blaster and a couple of patient days to let it soak in. The 6mm's holding the heat shield on always snap, so have replacements on hand. The gasket ring is a crush type so don't try to re-use it. You should only need to lift the car enough to get at the studs holding the front section of flex pipe to the manifold. Get new studs for the manifold if the cat doesn't come with them, trying to extract and re-use the old ones is likely to be a bear. For aftermarket brands, some are good but stay away from the real bargain-basement stuff. My customers have had pretty good luck with both Bosal and Eastern Catalytic.

Thanks very much for the help! Do you have any experience with the Evan Fischer brand? I found this two-cat kit for sale for roughly the same price as the single Eastern. It comes with the studs, gaskets, donut, etc and consists of some stainless construction so it seems like a well put-together kit. The vehicle has over 200k miles on it so realistically, I'm not looking to prep the vehicle for another 200k, I just need it to outlast the CVT.

schwim wrote: ↑

Fri Mar 05, 2021 5:45 pm

Do you have any experience with the Evan Fischer brand? I found this two-cat kit for sale for roughly the same price as the single Eastern. It comes with the studs, gaskets, donut, etc and consists of some stainless construction so it seems like a well put-together kit.

I have no experience with the brand, but they're all stainless, the temperatures make un-alloyed steel unusable. The thing about badly-constructed cats is that every technician can tell you a war story about one that failed inside of 10K miles. You pay your two-bits and take your chances.

I swapped out the engine in my 09 and replaced the cat with a Walker. No issues at all. I did spray everything down with kroil a few days before since I live in Ohio. I’m not sure what the mechanic quoted price wise but a decent pre cat can be had for a few hundred bucks and swapper in a few hrs.

Hello there everyone, I come with both progress and some questions!

I purchased the cheapest kit I could find. I have no complaints with the kit's assembly but do have a couple of questions, mostly relating to gaskets and a bit about heat wrap.

First off, from the header/cat to the second cat pipe, the vehicle originally had only the crush ring. I found soot denoting an exhaust leak at this point. The replacement system came with both a crush ring and a metal/material gasket. Should I use both the provided gasket and crush ring just the gasket or just the ring? Should I buy some exhaust sealer like Permatex sells?



Second, crush ring fitment: As per this little video shows, the fitment of the ring is a bit wiggly. I worry that It will be cockeyed when the two pieces together, causing a leak. I thought of using something like antiseaze or grinding paste just to secure it until I get them fastened together but thought there might be a trick to this that everyone knows.


Third, rear cat-to-muffler gasket: The gasket that came off of the car is the multi-layer metal sandwich. The one that shipped with the new pipe is the metal core with fiber material and the one from the local parts store is a fel-pro. Is the Fel-Pro the best solution of what I have?



Finally, heat shielding: Although the shield for the header/cat transferred over with only minor modification, there's really no way for me to transfer the second pipe's shielding over for quite a few reasons. First, they're welded on in places. Even if I grind the welds, the second issue is that although the header's shielding was a direct transfer, the second pipe is not. Originally oval in places, the new pipe is round throughought. The cat is a different shape as well. To do the best I could to retain some absorption, I bought a 50' roll of header wrap. and a bunch of hose clamps. I'm wondering if I should wrap the cat as well or whether it needs to remain in contact with air.

That's it for now, I'm very sorry for the wall of questions, We're racing against rainy weather and I lay in the dirt to work on it so I'm hoping we beat the timer

Thanks for your time!

schwim wrote: ↑

Tue Apr 06, 2021 5:01 pm

First off, from the header/cat to the second cat pipe, the vehicle originally had only the crush ring. I found soot denoting an exhaust leak at this point. The replacement system came with both a crush ring and a metal/material gasket. Should I use both the provided gasket and crush ring just the gasket or just the ring? Should I buy some exhaust sealer like Permatex sells?

There's really no need for a gasket or sealer with both surfaces being new. The crush ring should work fine alone.

schwim wrote: ↑

Tue Apr 06, 2021 5:01 pm

Second, crush ring fitment: As per this little video shows, the fitment of the ring is a bit wiggly. I worry that It will be cockeyed when the two pieces together, causing a leak. I thought of using something like antiseaze or grinding paste just to secure it until I get them fastened together but thought there might be a trick to this that everyone knows.

It has to be wiggly. When crushed, the ID will shrink and the OD will expand.

schwim wrote: ↑

Tue Apr 06, 2021 5:01 pm

Third, rear cat-to-muffler gasket: The gasket that came off of the car is the multi-layer metal sandwich. The one that shipped with the new pipe is the metal core with fiber material and the one from the local parts store is a fel-pro. Is the Fel-Pro the best solution of what I have?

I've never been a fan of fiber in muffler systems except for asbestos, which of course isn't used anymore. However, FelPro generally knows what they're doing. That's your call. If it was my car, I'd use it and see how it holds up. You can always drop in an OEM set if it doesn't.

schwim wrote: ↑

Tue Apr 06, 2021 5:01 pm

Finally, heat shielding: Although the shield for the header/cat transferred over with only minor modification, there's really no way for me to transfer the second pipe's shielding over for quite a few reasons. First, they're welded on in places. Even if I grind the welds, the second issue is that although the header's shielding was a direct transfer, the second pipe is not. Originally oval in places, the new pipe is round throughought. The cat is a different shape as well. To do the best I could to retain some absorption, I bought a 50' roll of header wrap. and a bunch of hose clamps.

Wrap is okay on the back pipe but not the back cat (see below). The really important shields are the ones on the front cat, they keep the top of the engine and the harnesses there from baking when airflow stops. I've seen plenty of Alties with no shields at all south of the flex coupling and they seem to do fine.

schwim wrote: ↑

Tue Apr 06, 2021 5:01 pm

I'm wondering if I should wrap the cat as well or whether it needs to remain in contact with air.

Never wrap a cat, it will cause it to bake unnecessarily after shutdown and very much shorten its life.

Hello there and thanks again for all the help! I finished the install and just wanted to wrap things up in the topic for anyone that might come across the thread later while facing the same install. At the end of the day, it all works as it should(although I can't speak for how long the cats will last). The vehicle is quiet, it throws no cat errors(so far) and there was nothing wrong with the system I purchased, fitment wise.

The one thing I messed up is not modifying the top heat shield before install on the engine. I was unable to get the lower two bolts in while installed so I used some hose clamps at the bottom where the bolts were missing just to keep it from making any noise since I worried it would vibrate. In hindsight, that's the only thing I wish I had done differently.

I did wrap the pipe in the heat wrap, leaving the cat bare.



Thank you again for all the assistance, it wouldn't have gone nearly as well without your help.

schwim wrote: ↑

Wed Apr 07, 2021 3:58 pm

The one thing I messed up is not modifying the top heat shield before install on the engine. I was unable to get the lower two bolts in while installed so I used some hose clamps at the bottom where the bolts were missing just to keep it from making any noise since I worried it would vibrate. In hindsight, that's the only thing I wish I had done differently.

I did wrap the pipe in the heat wrap, leaving the cat bare.

Thank you again for all the assistance, it wouldn't have gone nearly as well without your help.

You're most welcome. Looks like a neat job, well done! Nothing wrong with band clamps on the top shield, having it in place is what matters (and yes, it would almost certainly have rattled if left unsecured). You might want to re-tighten the clamps after a few hundred miles, once the metal takes a set with the heat.

howwedrivecar wrote: ↑

Wed Apr 24, 2024 4:48 am

I found this Driving With A Bad Catalytic Converter risk on this site.

It can be way worse than what they show in that thread. Most Nissan engines are Miller-cycle, they manipulate valve overlap to suck a bit of exhaust back into the combustion chamber to avoid the need for an EGR Valve. These are actual pics of an Altima QR25 after inhaling pieces of a melted cat along with the exhaust. Needless to say, this engine was toast:

The spammer has been spaced. Carry on.