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View Poll Results: Exhaust piping???
Just build a good full 3'' down/pipe and keep the Lachute 3'' exhaust 10 71.43%
Build a Full 3.5'' turbo/back exhaust 3 21.43%
Build a Full 4'' turbo/back exhaust 1 7.14%
Voters: 14. You may not vote on this poll

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Old 07-13-2008, 12:44 PM   #1
OB2
Scooby Newbie
 
Member#: 51500
Join Date: Dec 2003
Vehicle:
1999 impreza rs-t
sylver

Default exhaust question???

I do have a 99 RS-T with a ej257 forged engine, SOHC head and a GT3076R turbo that push around 345 whp!

I have a custom made Down-pipe starting at 2.5'' for 10 inch and go biger (3 inch) for the rest of pipe and everythink finish with a 3''Lachute Cat/Back !

The question is???: My car had alot of lag and not as much HP that I sould have for 22PSI on a GT30R turbo Do you think a biger Turbo/Back piping (full 3'' or 3.5'' or 4'')should help everythink?
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Old 07-13-2008, 01:25 PM   #2
KenSekiguchi
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Member#: 175331
Join Date: Mar 2008
Chapter/Region: MWSOC
Location: Rolling Meadows, IL
Vehicle:
2002 WRX STi - WRB
JDM V7 EJ207/13' Felt Z85

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Why wouldn't you just pick up a 4" TXS downpipe and then get the APS 3.5" catback? If it's not in your budget, then a custom 3" should be enough. I've read that anything over 3.5" - 4" won't get you anymore performance than a 3" unless you're running a huge turbo @ 30+ psi. Just my 2 cents though.
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Old 07-13-2008, 02:01 PM   #3
Dom'sGurl
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Member#: 150837
Join Date: Jun 2007
Chapter/Region: NWIC
Location: Lake Stevens
Vehicle:
2006 Legacy GT
Blue

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Quote:
Originally Posted by OB2 View Post
I do have a 99 RS-T with a ej257 forged engine, SOHC head and a GT3076R turbo that push around 345 whp!

I have a custom made Down-pipe starting at 2.5'' for 10 inch and go biger (3 inch) for the rest of pipe and everythink finish with a 3''Lachute Cat/Back !

The question is???: My car had alot of lag and not as much HP that I sould have for 22PSI on a GT30R turbo Do you think a biger Turbo/Back piping (full 3'' or 3.5'' or 4'')should help everythink?

Try cams. I had a lot of lag on my GT3076R and cams helped a ton. The TWE cams or even the Delta Regrinds work great. I have the same style downpipe as you with a Tial 38mm wastegate and I put down 406wtq and 367whp on a Mustang dyno.

what are you using for engine management?
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Old 07-13-2008, 03:53 PM   #4
OB2
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1999 impreza rs-t
sylver

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I allready have TWE Stage 3 cams but I have nothing before 4000RPM and everythink drop dead after 6500RPM! Look at my setup and my dyno graf and please help me to get 400over WHP???



MOTEUR:
Stock SOHC Head
TWE Stage 3 turbo Cams(272 HKS)
Wiseco 9.1@1 compression Piston
K1 Carrillo Rod
Cosworth bearing
Cometics head gasquet
ARP stud
Lachute Hi-Flow oil pump
Cosworth belt retaner
Gates Racing Belt

Lachute 3" Turbo/Back Exhaust
Zero Sport Radiator Wind Deflector
Halley Fuel Pump (650 hp)
K&N Air Filter and Intake
Turbo XS Blow off Valve
ASR 2.25" Up-Pipe
Gready Front Mont Intercooler
Garrett GT3076R ar.82 Turbo
Turbonetics Delta-Gate Wastgate
Turbonetics Manual Boost Controler (Set at 22 psi)
FAL Engine Cooler
Unorthodox Racing Full Pulley Kit
Power Entreprise 850cc Injectors
SUNO Automobile HYPER GROUND SYSTEM
Custom IC water foger
HYdra Nemesis EMS
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Old 07-13-2008, 10:54 PM   #5
Dom'sGurl
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Member#: 150837
Join Date: Jun 2007
Chapter/Region: NWIC
Location: Lake Stevens
Vehicle:
2006 Legacy GT
Blue

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Your graph is very interesting....

Seems like something else is going on.
Have you verified no boost leaks? Does your wastegate dump externally or recirc?

These heads are more efficient in the midrange as you can see by my graph above. I don't have any porting and my cams are only stage 2s. My turbo is also a GT3071R with a .63 A/R. So that would have a bit to do with the better spool on my setup. However, your larger cams should have helped out more than that.

I'm still shooting for a boost leak or a wastegate leak. You wanna shoot me an email with your tune file? Maybe I can see something in there.
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Old 07-14-2008, 01:49 AM   #6
reddevil
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Join Date: Jun 2004
Chapter/Region: NWIC
Location: portland
Vehicle:
1990 Legacy wagon
goes 12.387 @ 116.5

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Weird looking dynosheet to say the least.

I suspect tuning and mechanical issues.

Until recently I was using a 2.5" (or is it even smaller?!?!) NA Borla header with custom uppipe that was SMALL! and no problems spooling.
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Old 07-15-2008, 02:16 AM   #7
Dom'sGurl
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Member#: 150837
Join Date: Jun 2007
Chapter/Region: NWIC
Location: Lake Stevens
Vehicle:
2006 Legacy GT
Blue

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I'm using the borla N/A header as well with no issues.

something isn't right with the OP's engine or possibly the tune.
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