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Old 02-13-2012, 05:13 PM   #1
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2.5/3.2 exhaust diameter

hi. did a search but didn't find anything. anyone know the inside diameter of the exhaust manifold secondaries for a 2.5? and whether this is the same for a 3.2?

cheers.

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Old 02-13-2012, 05:48 PM   #2
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I have my cats out so I can measure both intake side or muffler side.
Which one do you need ? Just note my car is a S.
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Old 02-14-2012, 07:20 AM   #3
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hi. i'm looking for inside diameter on the exhaust manifold where it connects to the mid-pipes. hoping to compare size from a 2.5 to a 3.2. i think that the 3.2 is 1-7/8, and that it is the same as the 2.5, but am uncertain.
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Old 02-14-2012, 07:26 AM   #4
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I believe their both the same. The only thing I know is that the S muffler itself flows better than a 2.5 muffler. I did not due the research on that but someone else has.
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Old 02-14-2012, 07:48 AM   #5
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that's what i was thinking. if so, if a person wants to do an inexpensive cat delete on their car but has issues with the quality of the cheap ebay headers, then using the manifolds from a 2.5 is a good option; compared to the 2.7/3.2 headers they will will flow better, be lighter, are inexpensive and higher quality than the $69 ebay offering.

if they are the same ID.

Last edited by The Radium King; 02-14-2012 at 08:47 AM.
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Old 02-14-2012, 07:56 AM   #6
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Last edited by madmods; 08-24-2013 at 06:41 AM.
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Old 02-14-2012, 08:13 AM   #7
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pipes to muffler are a match

A Boxster S muffler can be bolted right onto a stock 2.5 car's post-cat pipes, if that helps answer. Those pipes are the same diameter. I just did this swap because my 2.5 muffler hanger brackets were broken and a friend donated his old S muffler that was lying around. I did have to get the Porsche mounting adapter kit to hang it, though -- this kit is labeled for use mounting the PSE on a 2.5, but the reason is the same, to mate the S or PSE style muffler to the transmission hanger bolt locations. However, the pipes are a direct match.

Ah, my pictures and adapter part number at this link:

Used Boxster S muffler with mounting adapter by bombaydigital, on Flickr
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Old 02-14-2012, 09:00 AM   #8
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Quote:
Originally Posted by The Radium King View Post
hi. i'm looking for inside diameter on the exhaust manifold where it connects to the mid-pipes. hoping to compare size from a 2.5 to a 3.2. i think that the 3.2 is 1-7/8, and that it is the same as the 2.5, but am uncertain.
The 2.5 is smaller as it should be, I don't have any to measure but that is the reason the gaskets are different.
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Old 02-14-2012, 11:03 AM   #9
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so, perhaps the primaries are smaller on the 2.5 but the secondaries are the same as the 3.2?

one thing to note is that some ROW markets don't have cats on the headers of the 3.2 (ie, australia, germany) and the headers they use look suspiciaously like the 2.5 headers. here are some comparative images:



and



one is for a 2.5, one is for a german 3.2. differences?
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Old 02-14-2012, 12:27 PM   #10
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I think you are on the right track moving the cats out of the headers would improve flow. Put the cats in the mid pipes for a straight shot through. I would look into buying 3.2 take offs on a German site. I sniff around FVD once in a while.

I can measure the entrance to the 2000 3.2 secondary cats if you still need it...I have fabspeeds so I dropped them
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Old 02-16-2012, 08:01 AM   #11
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no one? ok, some more context to support my plea for info.

i've a line on an old tpc supercharger kit. it'll most likely be a ground-up redo (replace piggy-back computer and 7th injector with softronic ecu tune and larger injectors, increase cold-side piping diameter, add intercooler, etc.) but the actual supercharger and mounting brackets are good and will form the basis for the project.

the tpc supercharger was initially designed for the 2.5 and will not fit with aftermarket headers or with catted oem headers. so, i have three options:

1- custom headers. not going to happen.
2- oem row 3.2 headers without cats. impossible to find; there are only two on ebay but both for the same side.
3- 2.5 headers. lots around, but don't want to restrict airflow out my engine with smaller headers. however, i don't actually know if they are smaller or not. the 2.5 headers look exactly like the row 3.2 headers without cats. perhaps there is a size difference i can't see in crappy ebay photos. perhaps porsche decided to use smaller headers in the row market. perhaps the 2.5 headers are the same diameter as the 3.2. dunno. would love for someone to measure for me!
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Old 02-16-2012, 08:26 AM   #12
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i can still take the measurements for you, but i have the 3.2.
will that help, or you need the measurements from the 2.5?
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Old 02-16-2012, 09:51 AM   #13
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I measured my 2.5 stock header:
* primary pipe outer diameter is 35mm
* secondary pipe outer diameter is 41mm

My guess for pipe thickness is 1,5mm. So, inner diameters would be 32mm and 38mm (about 1-1/4IN and 1-1/2IN).
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Old 02-16-2012, 10:54 AM   #14
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Hey TRK,

Take a look at this page . Strange as this guy is, he's displays some interesting stats regarding exhaust diameters .

Boxster Header Systems
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Old 02-16-2012, 01:43 PM   #15
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thanks guys. if someone could confirm outside diameter of a primary and the secondary on a 3.2 header then we could comapre it to the info we have for the 2.5. everything i can find online leads me to belive pipe diameters are the same between the two, but i can also check when i get home.
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Old 02-16-2012, 04:48 PM   #16
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ok. here's a summary of findings. looking at primaries, OD is:

my 3.2 - 37 mm
ketsa's 2.5 - 35 mm
maxspeed motorsports lists both 34.5 mm and 36 mm on thier website.

is 2 mm (about 1/16") within margin of error and enough to say that they are equal?


looking at the secondary, OD is:

my 3.2 - 39 mm (this was hard to measure, so i used the mid-pipe diameter)
ketsa's 2.5 - 41 mm
maxspeed motorsports lists both 42 mm and 44.5 mm on their website.

here we are looking at a bigger difference - about 4.5 mm or 3/16". Again, close enough to say equal?
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Old 02-16-2012, 05:25 PM   #17
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King,

What are you brewing up ?
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Old 02-16-2012, 05:56 PM   #18
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see post #11 ...

Last edited by The Radium King; 02-16-2012 at 06:26 PM.
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Old 02-16-2012, 06:06 PM   #19
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Quote:
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no secrets - looking to hang a supercharger off the engine and need low-profile headers to make it fit ...
I assume that you're looking for a set of headers without the pre-cats ?
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Old 02-16-2012, 06:32 PM   #20
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i'm offically done with it. i'm not going to s/c a 3.2 then throttle the engine back with small exhaust. if anyone is interested, there is a tpc s/c kit on ebay for $2k obo. i know that he'll take $1.5k or less. it's missing part of the bracket to hang the s/c, but tpc will fab that for you (prolly $100). it's missing the controller (uses rpm and boost level to control fuel flow to a seventh injector) but you could probably get that for $500 or less. personally, i would delete the 7th injector stuff and just get 6 bigger injectors. softronic will do you a tune to run them properly as well as properly manage timing. ohterwise, you might want to do an air/water intercooler - your call.

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