So I finally got my Comptech B-Pipe installed and the mechanic said that the diameter of the Magnaflow high-flow cat is smaller than the b-pipe. I believe this is expected since the B-pipe is 2.5" and the Magnaflow 22643 is 2.25". Do you know for a fact that the Comptech B-pipe narrows to 2.25" to bolt up with what would be the stock cat?

 

The CT b-pipe is 2.5 all the way. What you probably got was a CL-P/Accord cat. The RT cat is the same way. Most people put a 2.25" cat on the 2.5" CL-S pipe because it doesn't require welding and because there is no bolt on CL-S cat.

Seems kind of counter productive, using a high flow cat but using a smaller diameter pipe.

 

Where the Comptech B-Pipe connects to the Cat it is 2.5", where it connects to the mufflers it is 2.25".

 

Good information, that being said even if I put the stock cat back on there will still be a discrepancy.

RooEng - I was almost certain the outlet was 2.25", which I why I bought the magnaflow over the RT.

 

I ran the stock axlebacks with comptech b-pipe, nice setup imo.

 

yea the cat is pretty much the bottleneck of the system I mremoved mine and I have 2.5 inches from the header downpipe to a 2.25" Y pipe. MY XS header downpipe is 2.5" as well

 

OK now I'm confused. OP said "b-pipe" which is the pipe between the cat and mufflers. The "downpipe" or "j-pipe" is what goes between the headers and the cat. The comptech downpipe is 2" the whole way, and the comptech b-pipe is 2.5" and splits to 2.25". The cat size isn't so important, it's nice to match, but it's not a big deal if it does not.

 

I thought the CT downpipe was 2" and XS copied the design from CT, hence it would be 2" also. Either way, sounds like L removed the cat and replaced it with a 2.5" test pipe.

My original question revolved around how restrictive the cat is with the 2.25" and the B-pipe being 2.5". All I know is the car sounds mean with the b-pipe and I definitely "feel" like gains were made.

 

I measured the diameter on my XS header down pipe and its 2.5" which is why I chose that size to go with for my B pipe. Technically I dont have a cat or a test pipe just and "exteneded" b pipe. My B pipe starts where the J pipe downpipe ends.

Sorry I went off topic, I had a bit to drink when I had replied to this thread last night

Im sure you felt gains from the addition to the B pipe because it helped open up that exhaust but I guarantee if you went with a 2.5" high flow cat or test pipe the gains would feel even better and show it on the dyno.

 

after looking at the headers it isnt the downpipe thats 2.5, its the part the flex pipe is on. Dunno what you call that

 

If you have the stock manifolds and a CT down pipe, the manifolds are the most restrictive in the whole exhaust system. You won't gain anything by going from a 2.25" cat to a 2.5". That's why everyone says there are very minimal gains with a cat back.

If you get headers with a 2.5" collector, now the restriction becomes the cat.

The only way to know, is to call Magnaflow and find out what the CFM difference between the 2.25" and 2.5" cat. There might not be any difference as the element is still the same size and is still more restrictive than a smaller straight pipe, but in your case it won't make a difference.

 

Oh I definitely have both the manifold and the j-pipe, no sense in having the j-pipe. I was just comparing piping and I will try to give magnaflow a call. I now need to figure out if I want the tb and im bored out and polished.