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looking to put a full TBE on my 99 gt forester, i already have a 3" dump pipe, finding out whether a 2.5 or 3" is better? most performance?
turbo lag?
any feed back?
any other mods to coincide with this?
will be making a snorkel, out of 3" s/s exhuast pipe, that will help let better air in,

I hear that going too big can reduce the velocity of the exhaust gas and you actually get less performance. There's a fair bit of info on rslc and rexnet forums on what to do with the turbo exhausts

Make sure you take pics of your snorkel build, interested to see how you do it, what materials fasteners etc... Would be nice to have a little how-to thread

Turbo lag will be less with a freer flowing exhaust. Also come on boost slightly lower in rev range.

If you just put on a larger turbo without exhaust turbo lag would be much more pronounced.

With the exhaust use a nice big dump into 3 inch then 2.5 for rear muffler and tail pipe this will give a slightly better torque rating as was stated by using a smaller diameter pipe by keeping exhaust gases flowing better.
Add a resonator midway as wagons can be a little prone to exhaust drone.

I have been looking at a stealth system for our xt fozz basically utilises existing rear section of exhaust, Consisting of a large dump and 3 inch up to the tail section. Sounds similar to stock good flow only slightly less power then a full system not by much though but very quiet also.

Sleepers are so much more fun in traffic light wars;)

My experience is that large from the turbo to the cat and a size down from there to the back works well and doesn't seem to lose any performance .
My RX L Series is 3" to the rear of the cat (behind the gearbox) and 2.5 from there , not noisy at all compared to you average show off ram raider . No drones either .

Do not forget to use flex joints like Subaru does and yes you can get them in larger sizes . The braided flexi stuff is a cheap band aid and will eventually fail . The spring loaded carbon ring swivel joints are much better and are an easy place to disconnect the exhaust when required .

A .

well, im not sure if they would be putting on the resonator ot cat converter, as currently i run a dump pipe, with no cat or resonator,
im looking for plenty of power, but low noise output, was gonna run 3" to the back then just an avg performance muffler that wasnt tooo loud, i like a lil note but know how much wagons drone as my previous liberty had only no resonator and sports muffler, but almost woke the neighbourhood,

i would prefer to get it over the pits if possible, not that i have a sticker or anything,

should i have a cat converter and resonator or just leave them out?
appreciating your input so far guys,


as for snorkel, at this stage it will be mandrel bent s/s pipe, 2.3'3" mounted along the A frame, easy to do, pics will follow, along the fender *not looking forward to cutting the whole* and into the air filter, along the drivers side, removing the lil plastic air sump thats hidden behind the fender. there isnt much room to fir it, tight squeeze, but pretty sure it can be done

gonna leave the turbo as is,

*pipe, 2.5"/3" mounted*

just gonna by a snorkel top piece from safari snorkel or on ebay of something
and clamp it on

So you don't want it be loud or drone, but you don't want a cat or a resonator?
Then you need a big ar$e rear muffler with heaps of baffles to keep it quiet.

Why don't you want a resonator? It won't restrict power at all if its well designed.
Look at all the good exhausts out there and they all have resonators in them.

Tried a search on OzFoz and see what they do?

okay, so get a good resonator,
and cat aswell or no cat?

then 3", and possibly 2.5 after the rear dif?
or just leave it all 3"?

There should be no question about running a cat. They are mandatory on any car manufactured since about 1985

Driving a car without a cat is illegal and irresponsible.

Just stick to the tried and true design

3" dump into a highflow cat, 2.5" hotdog type resonator and piping to a sports muffler in the rear (please dont put a cannon on it)

okay, it goes in tomoro
i had a quick chat to a parts importer/wholesaler,
he rekons a 3" to the back will be fine,
but i might go the 3" dump with either 2.5" pipe from cat back, or diff back,
im sure either will be fine
and definately NO cannon, that was a given

I reckon 2 1/2 somewhere after the cat and before the resonator .
It's when the exhaust gasses cool and contract they they lose velocity , you step the tube size down before the rear to keep the gas speed up .
The reduced tube size (3 - 2 1/2) also makes it MUCH easier to muffle exhaust noise so you win with gas speed and sound reduction . Win win situation .

If it works for Michael South who rallys production class Rexs and works with my road only L RX Turbo I can't see why it wouldn't work for you .

A .

cheers for your help guys,
went with 3" dump with high flow cat, and res, and 2.5" diff back with a std sports muffler,
its not really that loud unless i really give it shit,
at idle very pleasant, and cruses well,
nice smooth acceleration increase,
going to monitor fuel consumption,
not as much power increase as i thought i'd get, but its the only mod i have done, so when a couple more come along later will be good to see how they all combine

will keep you updated with the air snorkel