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Old 08-02-2005, 12:43 PM   #1
Scooby Newbie
Member#: 78936
Join Date: Jan 2005
2005 WRX
Polar White

Default Is EM upgrade or utec need for Uppipe on 05 WRX 2.0 l

I am confused and have heard lots of conflicting stories on weather or not EM upgrade is needed when changing any pipes on the 2005 WRX. I have heard Subaru changed the pre boost enrichment parameters a bit for emission concerns, on the later 2004's and 2005's vesus the older 2003's. Interested in starting with an uppipe to cut lag but have been told that any decrease in turbo spool up time or reduction of lag, could widen gap of running lean with ECU everytime you go into boost. Bad on engine life. In short, I have heard that Subaru has extended a delay in fuel entry, a little eariler than on 2003's in pre boost condition to lean out emissions and get kudos with EPA. So I was told that the ECU would not immediately change its preboost enrichment. Based on this variance sounds like the faster turbo would create boost too fast for stock ECU on a 2005 to enrich mixture appropriately??? I have heard for a down pipe or stealthback and/or all pipes off stock turbo that EM is needed and can perhaps grasp that due to back pressure and a definitly more open system downstream off turbo. I am looking for an essentially faster than stock car and want to start with an uppipe only, question again is, will I need EM like cobb A/P or UTC or Vishnu and will I burn out the two stock cats down the line and fry rings?? Please help!!!! thanks!!
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Old 08-02-2005, 12:46 PM   #2
Scooby Guru
Member#: 23676
Join Date: Aug 2002
Chapter/Region: NESIC
Location: de_dust and Orgrimar


the up pipe should be done before any power mods on ANY wrx (not 06's )

I have replaced several up pipes/turbos due to the up pipe cat puking its guts into the turbo.

Then EM.

You will be ok without EM at this point with just teh up pipe. Do a downpipe though, and you need EM on 04-05 wrx's
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Old 08-02-2005, 12:57 PM   #3
Scooby Newbie
Member#: 78936
Join Date: Jan 2005
2005 WRX
Polar White

Default i have heard of cat crap getting into turbo......

Thanks for you input I hear you Dave on the cat guts nailing turbos, but for an uppipe on an a 2005 is true that this model year is so sensitive to any change in turbo spool with stock EM. I have 7600 miles on car and have done y pipes, crank case catch can, and perrin pannel filter. Will stock ECU code correct for faster turbo entry with all these mods is my main concern. Right now can't afford EM and a stealthback but eventually want it more towards end of factory warranty. This is my first subaru and i come from N/A land. My tendency in tuning up cars is to mod in stages this way from baseline you end up getting what you want without breaking the bank.
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