Catalytic Converter Diameter Question

[u441105]

So after using this forum to pick out my Whisper Lid / SLP CAI and 2.5" Magnaflow Cat-back setup, I'm working my way from the ends to the middle.

After searching through the forums I've come to the conclusion that the Magnaflow / Carsound #94009 is recommended as the cat of choice as it is the same length as our stock cat? Would having a 3" ID in / out catalytic converter hurt me as the rest of my tubing is 2.5"? I understand that my exhaust is as good as the smallest part, but would going bigger cause any problems?

I've read that people said going with the 3" cat is easier because the stock Y-pipe collector and the Pacesetter Y-pipe collector is 3" and it is easier to reduce after the cat than before. Others have said that having 3" going into the 2.5" is one less part they have to replace in case a full 3" conversion happens down the line. I understand 3" is required for FI but I don't exactly plan on going that far into modding this daily driver.

So, in TLDR format, with a 2.5" cat-back, would having a 3" in / out cat and S-Pipe hurt me at all (flow or sound) or would it be the same as having a 2.5", maybe even better?

[Sean_99_3.8]

Re: Catalytic Converter Diameter Question

So after using this forum to pick out my Whisper Lid / SLP CAI and 2.5" Magnaflow Cat-back setup, I'm working my way from the ends to the middle.

After searching through the forums I've come to the conclusion that the Magnaflow / Carsound #94009 is recommended as the cat of choice as it is the same length as our stock cat? Would having a 3" ID in / out catalytic converter hurt me as the rest of my tubing is 2.5"? I understand that my exhaust is as good as the smallest part, but would going bigger cause any problems?

I've read that people said going with the 3" cat is easier because the stock Y-pipe collector and the Pacesetter Y-pipe collector is 3" and it is easier to reduce after the cat than before. Others have said that having 3" going into the 2.5" is one less part they have to replace in case a full 3" conversion happens down the line. I understand 3" is required for FI but I don't exactly plan on going that far into modding this daily driver.

So, in TLDR format, with a 2.5" cat-back, would having a 3" in / out cat and S-Pipe hurt me at all (flow or sound) or would it be the same as having a 2.5", maybe even better?

The magnaflow is shorter than the stock cat. No problems with 3in to 2.5in you just need a reducer. It will not hurt u going with 3in but make the job easier.
3in y-pipe->3in Cat->3in to 2.5 reducer->2.5in s-pipe(or 3in if you want)->cat back

[u441105]

Re: Catalytic Converter Diameter Question

Thank you, that's exactly what I was looking for, just some confirmation on what I found. If it won't be a problem then 3" it is. We do live in America, the bigger the better.

From what I understand and from what I've read here our cat is 12" long? The Magnaflow cat, #94009 3" in / out, is 12" or 16" counting the slip collar? I'm guessing that's where the dimensions are coming from from product descriptions and pictures. That should work?

And another question that goes along with this, grayman's 3" conversion guide says that he went with the #94039 cat, same dimensions but with an O2 sensor boss so that a bung would not have to be welded onto the S-Pipe. I did not see mention of this in the other threads that I searched through, but this would work for my specific application right?

Sorry if I'm being nit picky, just trying to make an informed buy.

[whitdog54]

Re: Catalytic Converter Diameter Question

I thought the pacesetter y pipes had a 2.5" outlet

http://store.summitracing.com/partde...5&autoview=sku

[u441105]

Re: Catalytic Converter Diameter Question

I believe that is the collector of the actual manifolds. I was confused about that too but searching through every vendor I could find I finally found out through the descriptions that the Y-Pipe collector is 3" and the manifolds is 2.5" going into a 2.5" Y-Pipe. Correct me if I'm wrong please.

[97rs4life]

Re: Catalytic Converter Diameter Question

yes the pacesetter ypipe is 3". Get the 94009 cat from carsound. http://www.gvperformance.com/store/i...d&productId=93

[u441105]

Re: Catalytic Converter Diameter Question

yes the pacesetter ypipe is 3". Get the 94009 cat from carsound. http://www.gvperformance.com/store/i...d&productId=93

Yeah that's the one I was looking at, Amazon of all places seems to have it really cheap for whatever reason. Not sure about the rules on links so I won't but they got one for around $50, not sure what's going on with that.

No go on the #94039 cat? I was thinking the O2 sensor boss already in it would help out the guys at the garage not having to cut and weld into the S-Pipe. Is that not that big of a deal?

[whitdog54]

Re: Catalytic Converter Diameter Question

? I dont think you need the 02 sensor boss in the CAT, im pretty sure the 02 sensors are before and after, not in the CAT.

this is what im going with

http://store.summitracing.com/partde...5&autoview=sku

[Sean_99_3.8]

Re: Catalytic Converter Diameter Question

Yeah that's the one I was looking at, Amazon of all places seems to have it really cheap for whatever reason. Not sure about the rules on links so I won't but they got one for around $50, not sure what's going on with that.

No go on the #94039 cat? I was thinking the O2 sensor boss already in it would help out the guys at the garage not having to cut and weld into the S-Pipe. Is that not that big of a deal?

o2 bungs are no big deal to weld in.
the o2 are before and after the cat.

[u441105]

Re: Catalytic Converter Diameter Question

So I went ahead and ordered the 94009 catalytic converter.

http://www.amazon.com/Magnaflow-9400.../dp/B000COTIKM

When I received it the packaging was labeled with part number 94009CA and the box says that it meets Carb and well as EPA requirements. I'm guessing this cat is the California equivalent of the 49-State cat that Magnaflow sells. Is there any major difference between the two? Since I don't live in California would I be better off with a 49-State cat or will this one be fine?

[IDoVoodoo]

Re: Catalytic Converter Diameter Question

the pacesetter collector is 3" inside diameter

edit: the y-pipe is 2.25" going to the collector

[u441105]

Re: Catalytic Converter Diameter Question

the pacesetter collector is 3" inside diameter

edit: the y-pipe is 2.25" going to the collector

Haha that kinda confused me until I remembered what the thread was about before I left to buy my cat.

Do you have any ideas about my updated question? Would a CA emissions 94009 Magnaflow cat be the same as a 49-State emissions cat of the same part number? I was thinking maybe better emissions means more restrictive flow.

[IDoVoodoo]

Re: Catalytic Converter Diameter Question

the 94009CA is a 50-state legal cat. The 49-state equivalent would be 94039 or 94069. They don't list any flow numbers for these cats.

[u441105]

Re: Catalytic Converter Diameter Question

These are the links to the two different emissions regulations found on the Magnaflow website. Almost identical it seems other than the Carb part.

49-State
http://www.car-sound.com/02product/universal/940.asp

California
http://www.car-sound.com/02product/u...alCARB/940.asp

[IDoVoodoo]

Re: Catalytic Converter Diameter Question

pages look pretty identical. I would call Magnaflow and ask them. I was just going by listings on summit racing, they don't even sell the non CA version.