I see these posts on a weekly basis. We all do. It always makes me feel really aprehensive (sp?) when I read it. So I just wanted to put this out there for those that are asking this question.
Are you relatively new to the Subaru thing? Have you ever owned a TRUELY high performance import before? Have you ever owned any HIGH powered car before? Do you have fairly deep pockets?
If you say no to any or all of the above, then I beg you, please read on.
Many many times people have come into the Newbie forum and made the statement "My goal is 400whp" and they almost always JUST got the car.
It needs to be said, and anyone wanting 400whp needs to understand that 400whp is a LOT of power, and it takes a LOT to get there, and even more to do it reliably.
What will get you there?
Well, that depends on the dyno and tuner, along with how agressively you tune it. Dynos read differently and what makes 400whp on one dyny will make 450 on another, an 340 on yet others. Do you want 400whp on your local high reading dyno? Or do you want a TRUE 400whp that will make 400whp on almost any dyno out there?
In general you can hit 400whp on pump gas with something like (this is speaking of a 2.5L motor)
FP green turbocharger (this is larger than a 20G, its a 20G with a 49lb wheel)
Intake (GOOD intake, there are a few)
Front mount intercooler
turboback exhaust. Catless prefered for this turbo and power goal. 3" would definately be recommended but 2.5 wouldnt hold it back much if at all.
Headers or P&P manifold and better crossover pipe.
Larger/better up pipe Definately recommended.
Custom tune obviously, and to hit 400whp you will likely need 24+PSI.
If you run alcohol injection you will get there easier and safer at a little lower boost. This setup will not reach 400whp on all dynos, but it will get you there on most.
Or, and this would MUCH more easily hit 400whp, and on many more dynos. I consider this a "true" 400whp setup.
GT30R rotated mount turbo kit
Front mount intercooler
Header to go with whatever up pipe that setup uses, even better if they make a header specifically for their rotated kit.
Intake (this will be part of the rotated kit most likely)
Custom tune obviously.
Alcohol injection, again would allow lower boost/safer tune to hit 400whp, but this setup shouldnt have any problems hitting 400whp on pump gas by itself. Well over 400whp on race gas, I have seen 500whp on this setup with race gas on a semi high reading dyno.
So great, now you have 400whp.
Lets look at what the hidden costs are.
Clutch- Stock wont last long for 95% of people with this much power.
Flywheel- most do a light flywheel when they do a clutch. You may or may not.
Motor mounts are HIGHLY recommended at this point. Thats a lot of TQing around that the motor will be doing. The stock mounts were designed to hold a 300chp/300ctq motor still and keep noise at a reasonable level. If you are putting 400 to the WHEELS you are easily at 475 crank hp. Over 50% past what the stock mounts were made to handle.
Then lets look at the reliability limit of the stock motor.
400whp has been, since 2004 when the 2.5 came out shown itself to be the reliability limit of the stock pistons/rings. The rule of thumb is, upgrade the turbo, plan on a new shortblock. On something like a 20G or larger, at 20+PSI boost, its no longer a matter of IF, but when. There are of course some rare cases where someone makes 400whp for 50k+ miles, but believe me when I say this, that is RARE. Many with a good tune blow up well below 400whp. Best case scenario, pull the motor out and do pistons before you even install your 400whp setup. The crank/rods should be fine at this power level. Even so, doing a set of pistons can be a close to or just over $2000 investment, depending on what pistons and installer you use. Plan on at least $1500 to get some good forged pistons into your motor. Remember you will be paying for a full gasket kit, and with the motor apart a new timing belt and water pump is never a bad idea. Figure in oil and a filter as well. Small cost parts, but it adds up very quickly.
Then lets look at the safety aspect. 400whp is a LOT of power. In the hands of an unexperienced driver, it is quite litterally a deadly amount of power, especially so in an AWD car that can put the power down. 400whp in a RWD car is one thing, stomp on the gas at 40mph and you get massive wheelspin. Do it in an AWD car and you get hard acceleration. Are you experienced enough? The answer is in almost every case, no. Why? Lets use an example.
You are doing 65mph on the highway in a stock STI, or even light mods. You want to pass someone. Most will pass at roughly 85mph to get around that person. So you give it X amount of throttle, you dont look at the speedo because you have done it a million times, and you accelerate to 85mph.
Now lets swap that out for a 400whp car.
You are doing 65mph, you apply the same amount of throttle to do it, you are VERY quickly doing 90mph, you feel how hard it pulls so you back off a bit, but its all relative and even though it doesnt feel like its pulling as hard, its still pulling harder than it was when stock/lightly modded. You are doing well over 100mph by the time you get around that car.
Now someone comes over into your lane forcing you to turn and go around them while braking HARD. This is a delicate move.
Or, you decide you want to do a hard long pull. The kind that we all love, that puts a big dumb grin on our faces from feeling the seat pushing into our backs. You would have previously made it up to maybe 100-110mph.
So you are in the same place, same stretch of road. You do it again. Now you are doing 140 where you would have been doing 100. Go ahead, hit a bump at 140mph, and see how it feels. What was a "whump" at 100mph can quite litterally throw a 140mph vehicle into the air.
Your STI is a high performance vehicle that can handle high speeds and save your butt from a lot of dumb moves, but its not magic. AWD and the yaw sensors and such can only do so much, they arent miracle workers.
And if not for your own safety, think about what happens if you are doing the kinds of speeds you will EASILY hit with this kind of power and you hit another vehicle.
You may say "yeah but I wont do that kind of thing" That is all well and good, but the reality is that the more power you have, the more often you will drive at higher speeds than you did at the lower power level. I dont care who you are, its an almost 100% chance.
So lets review.
Do you REALLY know what this power goal will end up costing you?
Are you prepared to spend that kind of money?
Are you a good enough driver to handle that kind of power?
Have you even driven a 350whp STI?
My advice to those with a stock/lightly modded (like AP stage 2) STI/WRX, would be to take it in smaller steps. Most of the people I have met that wanted 400whp, were scared out of their mind when I took them out in a 330whp subby. Heck my 309whp 2.0Lwrx scared a lot of them.
Do this if you have a "stage 2" car (make sure you have these parts)
Custom tune. A GOOD custom tune. Do research before you pick a tuner. just because they own a shop doesnt make them good.
injectors and pump.
Because that will be as much or more than 90% of people here will ever want or need. If you want more, drive that around for 6 months to get a handle on what the power is like.
if you are bone stock,
GOOD custom tune
Of course much of this is opinion, however this is opinion coming from 18+ years of driving, 15+ of those in high powered cars, 10 years of import scene and tuning experience and 5 years of Subaru specific tuning/driving and really importantly in this case, Meeting and speaking to people on Nasioc. So I like to think that it holds SOME truth to it at least
Opinion or not, I assure you the message behind it holds true and you should really take it all to heart if 400whp is your true goal.