Subaru exhaust ID stats

[DJ]

(Info from DaveG2)
We need a solid convention of ID vs OD to end this! US exhaust piping has been measured in OD for as long as I can remember. However this is not true for Japanese cars; they use ID. 60mm ID is almost 2.5" OD. 2.25" OD is 55mm ID. 2.1" OD is 50mm ID.

Headers:
Stock MY00 RS header - 45mm collector, 35mm primaries
Borla header (2.5L) - 50mm collector
Borla header (2.2L) - 63.5mm collector, 45mm primaries

OBX Header:
Primary tubes= 1.650" OD/=41.91mm OD
Secondary after collector= 2.243" OD/=56.97mm OD
Ports at head exhaust= 1.5" ID/=38.1mm ID
ID at collector exhuast was flared out and I'm calling it 2.25"/=57.150mm ID

MRT primaries: 1.85" OD and 1.6" ID or (for those metric types) 4.71cm OD 4.07cm ID

Cats:
Stock MY99 L wagon - 1 7/8" front and back
Stock MY00 RS cat - 45mm
Random Technology SHF CAT is 55mm (or 2.17" in and 2.25" out)
Stromung HFC - 2.25" in, 1 7/8" out

Midpipe (front is larger due to cat connection/graphite donut):
Stock MY01 RS midpipe - 47.6mm front, 45mm rear
Stock MY03 WRX midpipe - 57mm front, 62mm rear

Axleback:
Stock MY00 RS - 45mm
MY04 WRX STI CAT back is 60mm

In inches, for those not cool enough for metrics

45mm is 1.77". 50mm is roughly 2". 55mm is 2.165". 63.5mm is 2.5".

From cueball89 - the id for the borlas i got are 1.709 and 1.68, and the collector is 2.15. the stock are 1. 565, 1.542, and the collector is 1.786.

More info to be added to this post as more info is found.

[DJ]

When I swap out my STi axleback for my WRX catback (modified... don't ask), I'll measure everything involved and add. If anyone else has info, please post up and I'll add it to the original post.

[anonymous_wolf]

when i installed the WRX axleback on my apex'i N1 midpipe i noticed the WRX axleback is a little bit smaller (i could put the tube of the WRX axleback inside the N1 pipe)
the apexi is 60mm ID, so i think WRX axleback is 60mm OD

[DJ]

"I think" doesn't work for me. I want solid measured numbers...

[DaveG2]

Also post model year (of doner vehicle and recipient vehicle) or year and manufacturer of the exhaust parts..... Use calipers or at least a fabric tape to measure the OD of the piping in a straight section (divide outside circumference by 3.14 to get outside diameter)...flanges are flared so they will not give the right dimensions for tubing size (ID).

[puckaveli]

Once you get some more solid numbers and MY's I'll be happy to stick this Doug.

[DJ]

Originally Posted by DaveG2

Also post model year (of doner vehicle and recipient vehicle) or year and manufacturer of the exhaust parts..... Use calipers or at least a fabric tape to measure the OD of the piping in a straight section (divide outside circumference by 3.14 to get outside diameter)...flanges are flared so they will not give the right dimensions for tubing size (ID).

When I get my numbers, I'll be using calipers and posting the MYs of the cars involved.
As for info already posted, the aftermarket ones should stay the same, and the one stock part has MY listed.

Thanks Judd.

[DaveG2]

This should give all users a matrix of info for planning exhaust mods when it's done....

[cueball89]

My borla headers for my 2.2 l wagon came yesterday. The spec sheet on the borlas said the primary tubes are 1.75" and the collector is 2.5".

A note if anyone is going with these headers the flange needs to be drilled out, alot.

[DaveG2]

Measured my old ('00 2.5 RS) exhaust parts today.... 45 mm ID for stock header (35 mm primaries), 45 mm cat section ID, 45 mm ID mid pipe and 45 mm axel back ID