How much HP can a 04 STi handle - Subaru WRX Forum
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post #1 of 16 Old 12-18-2003, 11:19 PM Thread Starter
GAK
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Question How much HP can a 04 STi handle

I would like to run around 375 hp to my wheels on my 04 STi. A 75 hp gain is not that much but......ive heard about broken tranny's, smoked clutches, mounts etc.....With that said, what mods would I need to gain 75 hp to the wheels? Thanks

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post #2 of 16 Old 12-19-2003, 12:20 PM
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Re: How much HP can a 04 STi handle

Quote:
Originally posted by GAK
I would like to run around 375 hp to my wheels on my 04 STi. A 75 hp gain is not that much but......ive heard about broken tranny's, smoked clutches, mounts etc.....With that said, what mods would I need to gain 75 hp to the wheels? Thanks

GAK
I'm not sure how much an STi can handle before internal mods are needed but you are wrong with the 75 hp figure.

Stock the STi puts about 255-260 hp to the wheels the 300 is at the crank so you are looking at 115-120 hp increase to the wheels. That shouldn't be a big problem for it I would think. Many guys with WRX have 100+ additional hp to the wheels vs stock and the tranny in the WRX is weak.

Good luck
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post #3 of 16 Old 12-24-2003, 08:03 AM
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I was under the impression that 400-450 is easily capable in the STi. And there is no comparison between the standard Rex & STi. EVERYTHING in the STi is better & stronger, inside & out. I have a 2003 & I am running 325-350 at the crank. Again, you have stronger internals, .5 more liters & just an all around better car for tuning.
Just do as much research as possible. Call shops that tune these cars & will get a general idea of what you can & can't do. I call shops all over the country all the time. Have fun & good luck.
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post #4 of 16 Old 12-24-2003, 02:45 PM
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It will handle near 400-450 HP crank like sphinx said. I spoke with one guy at the track who had one and was telling me this . With the larger displacment it is hard to pump more PSI into the engine without doing pistons and things of that nature, due to the design of the engine. STI has a 18% - 20% drivetrain loss from what I heard. So 500hp crank = 400hp to the wheels.
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post #5 of 16 Old 12-24-2003, 04:53 PM
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Quote:
Originally posted by Sphinx1
I was under the impression that 400-450 is easily capable in the STi. And there is no comparison between the standard Rex & STi. EVERYTHING in the STi is better & stronger, inside & out. I have a 2003 & I am running 325-350 at the crank. Again, you have stronger internals, .5 more liters & just an all around better car for tuning.
Just do as much research as possible. Call shops that tune these cars & will get a general idea of what you can & can't do. I call shops all over the country all the time. Have fun & good luck.
Stronger, maybe. Better, no. Higher static compression means you can't run as much boost safely. Variable valve timing is the source of debate. Seems to help bottom end, but not as much as eliminating the tumble valves in a regular WRX. Basically, in my opinion, the STi is the car to buy if you intend to keep it stock or keep mods to a minimum. The WRX is the one to buy if you want to go crazy.
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post #6 of 16 Old 12-29-2003, 10:18 AM
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Ok. I ask this, what is safe, in terms of crank horse power, in the std. Rex Cosmo? Kobi is running 500hp. How is that possible to do safely w/o going internal?
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post #7 of 16 Old 12-29-2003, 10:37 AM
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ummm.....



no comment on that


no one has ever seen that setup....

i am at about 425crank hp...and i am currently waiting on parts to fix my tranny. however, i am going to be replacing this one with a STi with DCCD...if that tells you anything!
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post #8 of 16 Old 12-30-2003, 09:43 AM
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The tranny can't handle it???
There has got to be a threshold on what the internals before sh.. starts breaking down inside. 425hp w/ no worries?
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post #9 of 16 Old 12-30-2003, 05:36 PM
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reliably..it is best to go with a nice forged internal setup that is better then stock.....and change the damn valvetrain over to the shimless design that is in the STi.

other then that....not much needed to change...
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post #10 of 16 Old 01-02-2004, 09:58 AM
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I am at 322 whp on race fuel on my STi with stock turbo and stock cat back. I am installing a GT35R right now and although the turbo can lay down 500 whp I think I'll probably limit boost to something more block safe. I'd say 425-450 whp should be fine.

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post #11 of 16 Old 02-18-2004, 12:15 AM
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Quote:
Originally posted by god02
I am at 322 whp on race fuel on my STi with stock turbo and stock cat back. I am installing a GT35R right now and although the turbo can lay down 500 whp I think I'll probably limit boost to something more block safe. I'd say 425-450 whp should be fine.
I find it hard to believe that you are running 322 WHP with stock turbo and stock cat back. you're either off on your numbers, the dyno was way off, or your car is on the way to destruction make your time.

EDIT: race fuel - didn't see that at first. That'll make a diference. Sorry.

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post #12 of 16 Old 02-18-2004, 10:50 AM
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you ever heard of godspeed performance?
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post #13 of 16 Old 02-18-2004, 12:13 PM
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Quote:
Originally posted by fc735
you ever heard of godspeed performance?
i will refrain from sarcasm this time. yes, i have heard of godspeed performance. what i'm saying is that it has been my experience that the "packages" that are offered don't offer that kind of performance at regular premium pump gas levels. getting that performance from race gas, however, i admit that it is possible. again, i didn't see the fact that you said you get that on race gas.

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post #14 of 16 Old 02-20-2004, 09:32 PM
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Quote:
Originally posted by god02
I am at 322 whp on race fuel on my STi


Quote:
Originally posted by avatarr



EDIT: race fuel - didn't see that at first. That'll make a diference. Sorry.

-Jason



Quote:
Originally posted by avatarr


again, i didn't see the fact that you said you get that on race gas.

-Jason

ok....
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post #15 of 16 Old 03-08-2004, 09:40 AM
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Well we are almost done testing STi stuff so our STi will be for sale soon. Our GT35R kit is finished and we are working on some cool new items for both WRX and STi guys including some new ball bearing turbos that will kill the IHI turbos. As for my power numbers, 322 whp is correct on unleaded race fuel with stock turbo, stock engine, stock inlet pipe, stock cat back exhaust and all. Boost pressure was 16.7 PSI. We recommend upgrading internal on the STi at 350-360 whp. IT simply has not turned out to be any stronger than the standard WRX block. 400 whp is achievable but not recommended for long term durability. The pistons ar etoo weak as are the thin sleeves.

Dan
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