Re jigged WRX exhaust bits on L RX-T .

[discopotato03]

Hi all , am trying to piece together an exhaust system for my L Series RX Turbo using mainly WRX and STi bits .

My reasons for doing it this way is that Fuji would know better than anyone else the sound signature of their water cooled Dak Dak engine so I aim to use bits from the later EJ engined cars that flow better .
From what I read early noughties (MY02/03) Impreza STi's are supposed to make around 195 engine Kw (260 Hp) and to do so means a production 2L engine has to have a reasonable exhaust system .
A little searching around shows that for each model year the main variation in STI exhausts was the last muffler and pipe - from the last flange joint back .

As we know the first of two cat converters in a WRX and STi is in the "dump pipe" , these are possibly not too bad but Rex's being what they are can have lead a pretty hard life and it's probably not possible to check the condition of the cat itself .

The dump pipe leads into a two piece "mid pipe" which has a secondary cat and what looks like an offset echo chamber - burble buster ?
The last flange joint leads under or over the rear NS drive shaft and into the last commonly called axle back/diff back muffler . It's here where STi's are I think a little larger in the tube size (54.2 OD) and a bit less restrictive in the single outlet muffler - which has perforated tubes rather than packing material in a very large "can" . I think they are a double pass design .

I think the basic tube size for the main part of the exhaust is ~ 60mm OD and ~ 57mm ID , my STi rear muffler has 54.2mm OD tube which probably works out to ~ 51ish mm ID or just over 2" which is 50.8mm .
Subaru (and switched on people in the afteremarket) step the exhaust size down in the last section of the exhaust because they know the gas has lost a lot of its heat so if the pipe size stays the same its velocity falls which is no good . To keep the gas speed up the pipe size has to reduce .

ATM I'm looking around at compact high flowing cats that will physically fit in the space taken by the std down pipe cat , APS's looks good though exy .
I want the space behind the first joint (in a turbo L) to use a resonator and I also want the swivel joint in the std position and in 60mm . RS Libs and WRX's have these joints but with the Impreza this joint is located at the back of the first "mid pipe" behind the secondary cat converter - not sure about turbo Libs .
My mid pipe just has to be plain tube behind the resonator and probably in 2.25" tube because its close to 60mm .

Out of all this I hope to get a quiet system with reasonable flow - which should be easy given that a turbo L exhaust is soooo restrictive - everywhere .

Thoughts , cheers A .