im going to buy one but 2 friends said that if you do intake, exhaust or other mods the 04 sti computer is really touchy and the car will not run right at all. so they said get a regular wrx and you can save the money, but i really like the sti look.

now if you can mod it im going to do these mods and am i going the right route

1) cold air intake
2) down pipe
3) cat back exhaust
4) blow off valve(wondering if this is needed sorry im new at this car)
5) boost controller
6) turbo timer
and thats about it. now thing is im into american cars should i runa 3 inch down pipe to a 3 inch cat back and will it be annoying loud. i want a nice sounding set up that isnt crazy loud

also for intake whats a good cold air set up.

any help would be appreciated. if its true you can't do any mods to the car because of the cpu then i guess im stuck with the regular wrx

tony

 

1 word....


EcuTek


Well.. if thats a word...

 

Well your friends are half right. The STi's ECU is a very aggresive type, it will do everything imaginable to keep things at the preset "norm" If you modify, say, the intake it will be getting more air than it's used to and try to compinsate by adjusting A/F ratios. What most of us are waiting for with our STI's are engine management systems. Currently almost every major tuning company that is interested in a peice of the performance sedan market are busting there butts trying to get a system out there, but there not here yet. Oh, and don't get a WRX if you have the chance to get the STi. It's much more cost effective getting a STi for $31,500 than getting a WRX for $24,000 and dropping the diffrence into upgrades, even then the WRX won't be near on par with a STi.

 

Snowy's right. If you think about the bigger IC, Brembo brakes, wheels, IC Sprayer, the VF39 Turbo, the 2.5L, The STI is well worth the money compared to the WRX. Oh! And don't forget the $7300 6-speed tranny front differencial set up. Plus half the labor is already done for you and warrantied. I have 4.5" downpipe which tapers down to 3" by the time it reaches the midpipe. Catback is all 3" titanium. No Cats. It sounds great without the silence and it sounds like stock with one. I have a CEL and yes the ECU compensates by adjusting my Air/Fuel ratio by making the mixture richer. Gas milage went down about 3mpg. As for a Cold air intake...leave it as is. The cold air intake or short ram is definetely going to lean out the STI which will cause detonation, knock, ping, or whatever you want to call it. An S-AFC II may help but if you're planning on doing any mods then keep it simple until EcuTek, U-TEC or someother piggyback ECU comes out. As for the CEL's, Perrin will come out with a fix for that within a week or two and TurboXS plans on releasing it's STI U-Tec in 4-6 months. They say:
"the STI has a new ecu and connectors. It will be about 4-6 months before we have a US spec STI UTEC."
A Blow off valve is not neccessary. It comes with a recirculating dump valve but if you want that cool "shhhh" noise everytime you shift or lift then that's all a new BOV will be good for. A turbo timer is also not neccessary on the new Subarus or as Subaru puts it themselves:
"We do NOT recommend the installation of any aftermarket part into any of our vehicles. Doing so may affect your warranty, but only on related failures. Any problems caused by the installation or performance of an aftermarket product will not be covered by your warranty; thus, you would be responsible for the repairs. We do not offer or recommend a turbo timer, as it is not necessary."