Building a 2.5" Turbo back exhaust parts?

[300D]

After my overly exhaustive search comparison of every single exhaust setup possible/available for 2003 wagon I have found a local VW guy who is going to fabricate a 304 stainless system for me for a decent price. I want it to be 2.5" and I want it to be inspection compliant and decently quiet, so I need a catalytic converter and a muffler.

Finding the exact parts for this setup is turning out to be difficult. Not many 2.5" diesel catalytic converters out there anymore. IDParts has one from Eastern Catalytic listed, but they are out of stock. I tried digging around the interwebs for a part number that would work, but couldn't find anything very specific. I called Eastern Catalytic and they told me that they no longer make ANY universal catalytic converters for small diesels! Neither them nor Catco who they own. So then I went down the Magnaflow route. They have a downpipe with cat that is 409 stainless and 2.16". I have found on a few sites a diesel catalytic converter for a 2.5" pipe, 93006D, but this one has also been discontinued. I called Magnaflow and they gave me a new part number, 93506, but this one is listed as gas or diesel. Is this a thing? I thought catalytic converters were different for different fuels?

Anyone have any recent experience in sourcing a good quality catalytic converter with 2.5" inlet/outlet?

Thanks.

 

[Rrusse11]

https://mufflerexpress.com/collections/all


You could try these people. I went with their performance 2.5" exhaust,
no kitty for me, but they may be able to help. My complete exhaust with
a resonator was about $600, fitment was excellent.
If you have a guy building a system, possibley a non OEM cat could be
adapted.

 

[300D]

https://mufflerexpress.com/collections/all
You could try these people. I went with their performance 2.5" exhaust,
no kitty for me, but they may be able to help. My complete exhaust with
a resonator was about $600, fitment was excellent.
If you have a guy building a system, possibley a non OEM cat could be
adapted.

Thanks for the link. Not a bad looking deal. Nice to have feedback too. Will be a bit more to add a catalytic converter and then there is no muffler either. Also it is 409 stainless rather than 304. My local guy is saying 700-750 complete with 304 stainless, cat, and muffler. Just need to find the right cat.

 

[flee]

When I went to a 2.5" exhaust I re-used the stock cat by trimming the funnels on
both ends to the new diameter and re-welding. They seem to flow enough and last.

 

[300D]

When I went to a 2.5" exhaust I re-used the stock cat by trimming the funnels on
both ends to the new diameter and re-welding. They seem to flow enough and last.

Do you think a 17 year old cat is still doing anything? This is not to open up the perennial can of emission worms on this forum, but I do like the idea of less stinky and a few less emissions. Plus, mine is rusty and leaking at the seams. Looks like someone has already been under there to fix stuff up once before.

 

[flee]

Do you think a 17 year old cat is still doing anything? This is not to open up the perennial can of emission worms on this forum, but I do like the idea of less stinky and a few less emissions. Plus, mine is rusty and leaking at the seams. Looks like someone has already been under there to fix stuff up once before.

Just from observation, the diesel smell is still controlled by the cat after 18 years.
They are made from a 400-series alloy so should be able to be repaired.
If the repairer didn't use stainless for welding it, that could cause more rusting, too.

 

[Rrusse11]

IIRC 304 SS is shinier, but subject to fatigue, 409 bends better and is more
weldable.

 

[Mongler98]

I did a 3" stair back with v clamps and hangers and flex joint for $100 in materials from mandrelbendingsolutions.com

 

[BobnOH]

I believe Buzzken sells those cats separate.

 

[300D]

I believe Buzzken sells those cats separate.

Buzzken is Tunemyeuro these days. They don't have a converter listed separately.

 

[300D]

Just a couple notes as I am taking a way too deep a dive into this.

I am in Maine and a lot of the exhaust companies are getting the rules for cats in Maine wrong. Maine requires that when you replace a catalytic converter you replace with one that matches the car's original emissions certificate. If the word California is on the sticker under your hood then you must replace with a CARB certified catalytic converter. If not, a regular old 49 state will do. My 2003's sticker has the word California on it.

But guess what? Maine's rules do not apply to diesels. Yeah. Nope. So, any old cat will do.I found this on a maine.gov website, and it was confirmed with the Maine state employee charged with overseeing this.

So back to finding the right part. I really do want the best emissions setup I can get outside of a VW OEM, $800 downpipe. I emailed back and forth with Magnaflow. At first they wouldn't even tell me anything because they think they can't sell any aftermarket cats in Maine at all. A few back and forths later I convinced them that diesels are exempt. Then they would only tell me the part #'s for stock sized exhaust, they wouldn't help me figure out one that would fit a 2.5". I imagine this has to do with the testing of parts for specific applications.

So my question to y'all is: Will a catalytic converter that is spec'd to another diesel vehicle that has a 2.5" exhaust standard work optimally for our diesels that are originally fitted with stock 2.125" exhausts? Do we need to match catalytic converters by exhaust gas temps? Rate of flow? Something else? Or will any cat that has a 2.5" inlet/outlet that is spec'd for a diesel work? Magnaflow even has a CARB compliant one that is reasonably priced. 447206 Listing says gas or diesel. https://www.dieselops.com/magnaflow-447206-catalytic-converter-oval-2-5-in-out-california-carb-obdii

 

[Rrusse11]

"will any cat that has a 2.5" inlet/outlet that is spec'd for a diesel work?"

Can't see why not. The only problem I can see is fitment under the car.
Certainly a reasonable price. I'd still be calling mufflerexpress.
I find speaking to people these days better than emails.

 

[300D]

"will any cat that has a 2.5" inlet/outlet that is spec'd for a diesel work?"

Can't see why not. The only problem I can see is fitment under the car.
Certainly a reasonable price. I'd still be calling mufflerexpress.
I find speaking to people these days better than emails.

I don’t quite understand. Why exactly should I call them? I have a local guy who does nice work, that will be cheaper than Muffler Express, and I won’t have to crawl around under my car in my gravel driveway in February in Maine.

Also, I have found info about cats being designed according to engine size. It would be great if I could find a listing that can be sorted by inlet/outlet size, fuel type, and engine size.

 

[IndigoBlueWagon]

Exhaust stuff for us is a $hitshow right now. Magnaflow acquired Bosal's aftermarket exhaust business a couple months ago and they're very slow to provide pricing and availbility. And that includes cats and mufflers that are Magnaflow branded, not Bosal.

As you know I recently replaced the exhaust on my wagon. 2" downpipe, no cat, stock muffler. Much, much quieter than when you drove it on New Year's day. And it doesn't smell at all that I've noticed, and the car is garaged, so I would think I'd smell it on start up. I often leave it running when picking up parts, and haven't smelled it then, either. Just sharing that info.

Most aftermarket cats are a lower grade stainless than what you're making the pipes from, so odds are they won't last as long as the pipe. Same with the flex pipe, because 304 stainless is too brittle to use in a flex, I'm told. I had a Magnaflow muffler on my car previously and my fabricator thought it was shot, as was the resonator. That was after about 100K miles. I'd probably try and get the biggest 2.5" muffler that will fit in the body of the car to keep it quiet.

If you're struggling to get the CAT and muffler I can see what I can source, although you may be able to currently get better pricing from Muffler Express.

 

[300D]

Exhaust stuff for us is a $hitshow right now. Magnaflow acquired Bosal's aftermarket exhaust business a couple months ago and they're very slow to provide pricing and availbility. And that includes cats and mufflers that are Magnaflow branded, not Bosal.

As you know I recently replaced the exhaust on my wagon. 2" downpipe, no cat, stock muffler. Much, much quieter than when you drove it on New Year's day. And it doesn't smell at all that I've noticed, and the car is garaged, so I would think I'd smell it on start up. I often leave it running when picking up parts, and haven't smelled it then, either. Just sharing that info.

Most aftermarket cats are a lower grade stainless than what you're making the pipes from, so odds are they won't last as long as the pipe. Same with the flex pipe, because 304 stainless is too brittle to use in a flex, I'm told. I had a Magnaflow muffler on my car previously and my fabricator thought it was shot, as was the resonator. That was after about 100K miles. I'd probably try and get the biggest 2.5" muffler that will fit in the body of the car to keep it quiet.

If you're struggling to get the CAT and muffler I can see what I can source, although you may be able to currently get better pricing from Muffler Express.

Thanks for the input Peter. As with most sites, on Muffler Express trying to pick a catalytic converter based upon inlet/outlet size and application range is impossible. One must input vehicle specifics and then it gives the recommendation. Muffler express does offer stuff in the 2.5", but doesn't seem to offer the cat separate from being included on a downpipe, nor any details about the cat that they do include.

I spoke with Eastern Catalytic and they have discontinued their cats for small diesels like ours.

Magnaflow does seem to have some 2.5" inlet cats that are spec'd for both diesel and gas, but with zero information that I can find about what exactly that means, I don't think I want to take the risk to find out myself.

My local guy has the 304 material already, so it seems that this is the best route. I will check in with him on what he thinks about all this.

My car is not garaged, which is why I am desiring the 304. I imagine 409 would do the trick pretty well too.

If I end up giving up on the search I will email you guys for help. Thanks so much.

 

[BobnOH]

Buzzken is Tunemyeuro these days. They don't have a converter listed separately.

Call 'em. Many folks plumb this up with no cat or a resonator in it's place. Some even delete the muffler or add a 2nd resonator. If inspectors don't look for a cat, that's a good option. Most folks are unhappy with the sound of straight pipe.

 

[flee]

Buzzken is Tunemyeuro these days. They don't have a converter listed separately.

BuzzKen and TuneMyEuro both were very easy to contact and to deal with in the past.
I would give them a call and get the lowdown on a stand-alone cat purchase.

 

[300D]

Call 'em. Many folks plumb this up with no cat or a resonator in it's place. Some even delete the muffler or add a 2nd resonator. If inspectors don't look for a cat, that's a good option. Most folks are unhappy with the sound of straight pipe.

Just to clarify here on the second page of this thread. I am after a good performing, reliable, long lasting, quiet system that is to emissions standards. No cat is not an option.

I am actually leaning now toward a more OEM style system that gives me as low as sound as possible with the best emissions results I can figure out.

Interesting enough, earlier in the thread was mention of reusing my existing cat. I just found a research article where a citric acid solution was used on diesel cats to return them to like new performance with no downsides. Interesting.

https://www.nature.com/articles/news050425-10

 

[flee]

As I posted before, unless the cat is physically damaged it can be reused no prob.

 

[Rrusse11]

"As with most sites, on Muffler Express trying to pick a catalytic converter based upon inlet/outlet size and application range is impossible. One must input vehicle specifics and then it gives the recommendation. Muffler express does offer stuff in the 2.5", but doesn't seem to offer the cat separate from being included on a downpipe, nor any details about the cat that they do include."


"Why exactly should I call them?"

You just gave the reasons in the 1st quote for why you should.
Websites are getting increasingly difficult to use/decipher IMO.
Get someone on the phone (who knows what they are doing) for 5 minutes.
Go analogue!

 

[300D]

"As with most sites, on Muffler Express trying to pick a catalytic converter based upon inlet/outlet size and application range is impossible. One must input vehicle specifics and then it gives the recommendation. Muffler express does offer stuff in the 2.5", but doesn't seem to offer the cat separate from being included on a downpipe, nor any details about the cat that they do include."


"Why exactly should I call them?"

You just gave the reasons in the 1st quote for why you should.
Websites are getting increasingly difficult to use/decipher IMO.
Get someone on the phone (who knows what they are doing) for 5 minutes.
Go analogue!

I did a back and forth with someone at muffler express. The cats they use are eastern catalytic for the ceramic and catco for the metal. They don’t sell them separately. Also, the quietest exhaust they sell is their 2.25 with cat and muffler and he said it would be at least 50% louder than stock. So, not for me.

This is quite the journey.

 

[IndigoBlueWagon]

Because I needed to bug them anyway, I called Magnaflow and asked about universal catalytic converters. Nothing under 3" diameter. You could try a 3" with reducers, but I'd be concerned that it wouldn't fit in the exhaust tunnel. 2.5" is sometimes a tight fit.

 

[300D]

Because I needed to bug them anyway, I called Magnaflow and asked about universal catalytic converters. Nothing under 3" diameter. You could try a 3" with reducers, but I'd be concerned that it wouldn't fit in the exhaust tunnel. 2.5" is sometimes a tight fit.

Uh. That seems crazy. Not that you have to call them again, but their 93506 is the right size and is described on their amazon page as being for gas and diesel:


https://www.amazon.com/MagnaFlow-93506-Universal-Catalytic-Converter/dp/B000JKLESI


There is also a CARB compliant one

https://www.dieselops.com/magnaflow-447206-catalytic-converter-oval-2-5-in-out-california-carb-obdii

Same deal, gas and diesel.

What I wonder is if temp requirements and volume play a part and therefore makes everything more specific.

 

[IndigoBlueWagon]

I quizzed the Magnaflow rep pretty hard. I think that listing is incorrect.

 

[kajikidu]

https://www.idparts.com/25-inch-diesel-catalytic-converter-p-870.html

 

[Rrusse11]

https://www.idparts.com/25-inch-diesel-catalytic-converter-p-870.html

Problem solved, lol. The irony of cat skinning ehhhhh.

 

[300D]

https://www.idparts.com/25-inch-diesel-catalytic-converter-p-870.html

Out of stock and discontinued, hence why I am looking for another option and posting on the forum...

 

[Mongler98]

Out of stock and discontinued, hence why I am looking for another option and posting on the forum...

Nope. I can add to my cart no issues.

 

[300D]

Nope. I can add to my cart no issues.

That little red exclamation point that I circled? That means it’s not in stock.

 

[300D]

Also shows on the product page that it is on order. And IDParts has recently added a notify me feature. Which is super cool.