View Full Version : still doing the homework...

Dark Anghell
04-15-2005, 11:58 PM
OK some may remember from the forums before the crash I was trying to figure out my best options for more power. After doing more research i have narrowed thngs down to the following:

Block and internals: EJ257

Head: my original SOHC heads ported and polished using stiffer valve springs.

Intake manifold: original SOHC manifold. Will STI or a WRX manifold work on the motor?

Turbo: this I'm not sure about. It will be at least the size of an STi turbo.

Here are some more questions:
stock ej257 pistons...are they pretty reliable? I understand that the rods are pretty beefy, but would it be wise to replace pistons with forged and possible ceramic coated ones?

turbo...I am hoping to get in the neighborhood of 250-350 at the wheels [I know it's a pretty big jump]. The HP depends on what the engine can handle without breaking down on me and what the drivetrain can handle [I will definately upgrade the clutch], for 250HP mark, and STI turbo would work, but if i decide to get more any suggestions on bigger turbos?

any other suggestions or things to consider would be great.

Thank you very much.

04-16-2005, 12:18 AM
dude, your really planing on pushing that ej257 block to some really big extremes. the first thing your going to have to consider if you go turbo is headgaskets. your going to have to get a custom reinforced one, especially if your going to go for port and polish. once you port that head and/or intake manifold things are really going to change so the gaskets have to change with the flow. probably should consider getting some better cams to if you go turbo. for 250-350 hp your looking at about 18psi from the turbo and the standard ej257 block is rated for about 6 or 8 max (someone please correct me if im wrong) so getting some ribbing and other reinforcement one the block is going to be a big issue especially for the valves, pistons and heads. its going to be alot of work to get 250-350 hp but will definitely be worth it in the end because your butt will go right into the back seat when you launch off a traffic light. good luck with the whole thing, keep us informed on the progress.

gator gt
04-16-2005, 12:30 AM
WRX/STi manifold. Period. You're doing turbo? Do the turbo intake.

If you are in fact going full on turbo (versus a turbo kit) then, you'll want the WRX/STi heads instead of yours. At 250-350 whp, you're kicking out more than a stock STi. Your minimum is quite a feat for OEM N/A heads, which may not take it at all; or may take it,...but won't be at all efficient.

The block will hold it. Its not forged....but it has hyper-cast pistons, which according to Subaru is stronger than their forged counterparts. But, its got to be tuned precisely or else they'll amount to a pile of crap. You don't need them to be forged or coated...it'll be all in the tuning. Not a job for fly-by-night shops.

what are your tranny thoughts? For something of this magnitude, you should be looking at the 6MT....not just your clutch. You could try keeping your case and moving up to RA gears....but you're back to the weak link....the case flex under high stress loads. The design of the 6MT eliminates that flex. With the 6MT comes a different rear diff to match the final drive.

If you're going to frakenstein it, the rumored street eater is the EJ257 with Ver7 RA Spec C or Ver8 heads. And if you want to make serious power, go with a Garret, Mitsubishi or AVO turbo. much better construction than the IHI (stock Subaru) turbos.


04-16-2005, 12:37 AM
I don't think the WRX intake manifold will bolt up to your EJ25 SOHC heads.

If you're going in excess of 250 whp you've really gotta think about upgrading the transmission. A clutch upgrade is only going to put more strain on the transmission.

If you want to eventually get 350 whp, you might as well start with a stronger block. Like I know Axis Power Racing here in St. Louis has all sorts of buildups of EJ257, EJ22T, etc. that can handle everything from 300-900 whp. http://www.axispowerracing.net/.

What are you going to do for engine management? Probably need a standalone? Might as well ditch the EJ25 heads then, if you're not going to be running on your stock ECU, and maybe go with WRX or STi heads?

The STi supposedly runs max 13.5 psi stock boost, and I think it normally dynos 225 or so whp? So you can start the numbers from there I think.

You're gonna need a new fuel pump probably too.

04-16-2005, 12:39 AM
Another alternative to the STi 6MT might be the Forester XT tranny? It would definitely be cheaper by the crate...

Dark Anghell
04-16-2005, 12:50 AM
I am trying to stay away from rewiring the entire car. I can do mechanical work without any poroblems, but as soon as it comes down to rewiring the entire car...I am not touching that.
I guess it would be a lot safer to go with only around 280-300 at the crank [very close to sti HP numbers].
So am i correct by saying that mitsubishi turbos bolt up? if so, then an EVo 3 16g turbo would be my safest bet [rated at 300-350hp]

04-16-2005, 09:38 AM
Yeah, then at some point you're going to hit the limits of using the stock ECU and piggybacking. Don't know where, don't have experience - car runs great at 7 psi on a WRX turbo even without extra ignition correction though :)

Definitely plan on some piggyback fuel management and ignition timing. You probably have to work out something for fuel injectors on those SOHC EJ25 heads, then, too.

Dark Anghell
04-16-2005, 12:15 PM
I am planning on using walbro 255 fuel pump or something along those lines, 555 fuel injectors or possibly stock ST injectsr [haven't researched what size they are], for fuel management...eiher SAFC II [cheapes way works well] or the UTEC if it can be plugged into my ECU.

After reading my own first post...I should clarify, the HP figures i was hopiing to get were at the crank not at the wheels.