2.5 turbo (2005) power rating

[Tuning Haus]

what are the 2.5 turbo motors rated to handle stock powerwise?

would 400-450HP be out of the question as far as staying within the stock bottom end/head?

[Huffer]

Stock engine in boosted form is tuned for around 250hp.

If you're looking to go to 400hp, then you would asking a factory engine to increase by nearly 100%.

I doubt that the stock bottom end or heads would be sufficient for that kind of power, reliably. However, I do know a number of Subaru STi owners who have had a lot of trouble maintaining 400hp+... typically chewing up bearings.

[deadlydave]

You could probably get 400hp at the crank without blowing anything up. Not at the wheels with the stock bottom end and heads, though.

What do you intend to use the car for? I autocross with a local guy that has a 430WHP (with braking and suspension mods to match) STi and the thing is utterly useless. The lag sucks away time, and when boost kicks in the tail hangs out all day.

[Tuning Haus]

i guess i'm very spoiled coming from the 6spd supra world. we were able to generate 750whp+ on a stock bottom end/tranny. :)

400 crank would even be pretty good.

i was just curious how stout these GT motors and trannies are.

sounds like anything above 300 is very questionable? not many guys putting much power down on these?

[deadlydave]

The 5-speed transmission will 'splode much easier than the STi's tranny. That's the first weak link.

The best place to look for dyno numbers on a stock legacy bottom end would be NASIOC.

Always remember, the AWD system will sap up to 1/3 of your power.

[Huffer]

Supra engines are built bigger, and heavier. Those things are tanks.

I would also hazard a guess that companies like Honda & Toyota have better facilities to design more reliable in-line or V-config engines. They've also poached/reverse engineered each other's cars multiple times.

Subaru has had no such competition to build a "better" engine - the only other manu. of flat-fours/sixes being Porsche (IIRC)...so the engine durability is not what you might expect from a H or Toymota.

"Power to the ground"

[AJM]

It's the difference between an Iron Block and an Alum block for one thing. The other is that Subarus are not drag queens but rally machines. 300 WHP is more than enough. The only Iron block Subaru ever made was a 2.2 years ago.

We all know our H motors may not be able to take the same amout of boost, but in stock form they can last with anyone else as far as long term life.

[jey]

What do you intend to use the car for? I autocross with a local guy that has a 430WHP (with braking and suspension mods to match) STi and the thing is utterly useless. The lag sucks away time, and when boost kicks in the tail hangs out all day.

It is possible to build a high-powered STi for autocross. The local Street Mod champion here for the last 4 straight years now is running a Deadbolt SZ49 and it dynoed 381 WHP on pump gas. The big Spearco TMIC got rid of the lag usually associated with a high-powered setup with a FMIC.

[SammyDaFish]

The only Iron block Subaru ever made was a 2.2 years ago.

you mean the 3.3 svx motor right? I think maybe the XT6 too.