I see these crazy built subbys that have 3,4, or even 500 horsepower. How do they pull this off and whats the quickest route to reach some of these staggering milestones?

The best way I know to achieve say 300-360hp is this... 1. Gotta get rid of the TD04. A VF39 or better yet 43 or 34 will do. Also an HTA68 does quite nicely for this. 2. Fuel. Get a wally 255lph high pressure pump and at least get 850cc fuel injectors, you will be needing them. Your OEM fuel rails will do just fine and remember a wideband AFR! 3. 3" turboback, catless up pipe (STi will do nice and be had for cheap.) If you keep your stock exhaust manifold get the grimmspeed crossover! 4. Get rid of that stock 2 port boost control solenoid and get the grimmspeed 3 port. 5. Aftermarket intake. I prefer the SPT or something similar. 6. You can opt for a front mount intercooler or to save money a better top mout will do nicely too! 7. Most important is the right tune! I suggest such big fuel injectors because you will be running E85 to reach this power level on the turbo's listed above. I prefer an opensource tune. The only equipment you may have to buy is the tactrix cable but a good reputible tuner should have his/her own. Remember this is on a stock block too, that is about as much power that a WRX will handle stock. Which reminds me... get that aftermarket clutch too! I know this list sounds pretty simple but you would have plenty of fun with that set up. If you want to go even higher I would start looking into doing away with the EJ205 2.0 and step up to the EJ257 from the STi with your WRX heads. Go with forged rods and pistons, Subaru's are known for weak pistons! Bigger cams to go along with a bigger turbo (ie, GT35R). You will probably want to do away with your 5 speed and snag the drive train from an STi or Legacy GT (Model years 05-08 for the Legacies) as they are stronger then the WRX transmission. Depending how much power you want will determine your tuning methods. I love open source, ACCESSport is awesome and stay away from piggy backs. If you are trying for huge numbers look into AEM for stand alone engine management, especially for custom setups. This should give you a good idea on what to reseach and look into for whatever your end goals may be. For some unknown reason it seems to be a bit harder to make good big power in Subaru's then say an Evo or DSM. But it can be done and its fun!!! I do miss my WRX.

Originally posted by MILOTEK

I see these crazy built subbys that have 3,4, or even 500 horsepower. How do they pull this off and whats the quickest route to reach some of these staggering milestones?

Well the short answer is there's definitely huge steps that you need to take. 300 can be (most likely, you'll have to refer to Talon or another Scooby guy) accomplished with simple bolt-ons and a good tune. The 400 mark can most likely be accomplished with a bigger turbo and supporting modifications. And then 500+ is where you start to really get into engine builds, i.e. cams, displacement, stroke mods, etc. The real question is - what exactly do you want in the end. Because now is the time to prep. But I see where the ? is going, so maybe this would be a good point for some of us to outline a basic guide for each "stage". Also, something to note would be are you referring to bhp (brake horsepower, or power @ the flywheel) or whp (hp @ the wheels). In an AWD application, the drivetrain losses are significant therefore it's a pretty big difference. Like I calculate my dt loss @ 25% with my AWD Volvo - makes you feel better (evil)

Originally posted by talonIV

The best way I know to achieve say 300-360hp is this... 1. Gotta get rid of the TD04. A VF39 or better yet 43 or 34 will do. Also an HTA68 does quite nicely for this. 2. Fuel. Get a wally 255lph high pressure pump and at least get 850cc fuel injectors, you will be needing them. Your OEM fuel rails will do just fine and remember a wideband AFR! 3. 3" turboback, catless up pipe (STi will do nice and be had for cheap.) If you keep your stock exhaust manifold get the grimmspeed crossover! 4. Get rid of that stock 2 port boost control solenoid and get the grimmspeed 3 port. 5. Aftermarket intake. I prefer the SPT or something similar. 6. You can opt for a front mount intercooler or to save money a better top mout will do nicely too! 7. Most important is the right tune! I suggest such big fuel injectors because you will be running E85 to reach this power level on the turbo's listed above. I prefer an opensource tune. The only equipment you may have to buy is the tactrix cable but a good reputible tuner should have his/her own. Remember this is on a stock block too, that is about as much power that a WRX will handle stock. Which reminds me... get that aftermarket clutch too! I know this list sounds pretty simple but you would have plenty of fun with that set up. If you want to go even higher I would start looking into doing away with the EJ205 2.0 and step up to the EJ257 from the STi with your WRX heads. Go with forged rods and pistons, Subaru's are known for weak pistons! Bigger cams to go along with a bigger turbo (ie, GT35R). You will probably want to do away with your 5 speed and snag the drive train from an STi or Legacy GT (Model years 05-08 for the Legacies) as they are stronger then the WRX transmission. Depending how much power you want will determine your tuning methods. I love open source, ACCESSport is awesome and stay away from piggy backs. If you are trying for huge numbers look into AEM for stand alone engine management, especially for custom setups. This should give you a good idea on what to reseach and look into for whatever your end goals may be. For some unknown reason it seems to be a bit harder to make good big power in Subaru's then say an Evo or DSM. But it can be done and its fun!!! I do miss my WRX.

Damn quick draw! Nice

Thanks Rocky! Oh that reminds me, try and stay away from "stage XXX" as its kinda pointless in my opinion. Find a good tuner in your area or if yoiu wanted to make the drive, I have an awesome guy here in town. But have them help ya with which mods to get in order to go from power level A to power level B and so on. The only reason I say "Stage XXX" is pointless is because there is no meadian for which to follow. "Stage 2" for a Subaru is about 240awhp with full exhaust and cold air/ short ram intake and tune, to where "Stage 2" on a DSM is something like full exhaust, intake, up graded turbo, tune/engine management, 300+awhp.

Yeah, stages are pretty pointless anymore imho. Back when it cost a grand to gain 30hp stages seemed cool, but when you can get things on craigslist, or even cheaply from the vendor. Like Rocky and Talon said, you have to figure out what power level you really want and start there. I think it is usually best to start with getting your logging/tuning items in order, wideband, boost gauge, whatever tuning solution you go with (above 400 you may have to go full standalone. I am not sure if Ru's have anything like DSMLink). Then I would get the engine breathing a bit better with a turbo back exhaust and less restrictive intake. Next would be getting the fuel system up to snuff. A wally 255, >800cc injectors and afpr would do for close to 500hp, but that is pushing the limits. Depending on the power levels that you are looking for you may need to beef up the engine internals as Talon said. At this point you have probably spent around $10 grand and have gained next to no horsepower, but now you have a solid platform to make 500hp. At this point it is finally time to get a bigger turbo (GT35R is pretty good for 500hp), and then turn up the boost and begin tuning!

Actually Subaru's ECU's are completly tunable! I have seen STi's go up to 600hp on the factory ECU and im not quite sure on the rex but they can get some good numbers from the factory ECU. I fully agree on getting tuning in order first, especially with Subaru's. They are a bit quirky with modification and tuning. Fickle would be a good word haha! But to acheive good numbers tuning is everything... just remember Subaru's do not tolerate any knock what so ever. Let me see if I can get a dyno sheet posted up for some good examples...

Here is an 05 STi my friend Will of Elevated Tuning did not too long ago... E85, stock turbo, greddy header, ported/polish w/ valve jhob heads, turboback, COBB SR, FIC 1100 injecors, 255 pump, TGV deletes. He is setup to go big with future mods. But 315 for what he has done is not too bad at all! This one is swapped with a 2.5L from a WRX and a VF39 turbo, External wastegate and ross 10:1 compression pistons. Eagle rods E85 Autronic, APS intake and a full turboback exhaust.

How do I modify my vehicle to run the E85 though? Wouldn't it ruin it if not properly set-up?

on a subie, I just suggest at least 850cc injectors and a walbro 255lph fuel pump. You can get a more heavy duty fuel line if ya like but the stock ones tend to stand up to the ethenol pretty well.