2.5i swap options

[tougefox]

I have a 2006 legacy 2.5i and unfortunately the motor is gone. Story can be found at legacygt.com. So now im replacing the motor so im wondering are there any NA options that will give me some more power or a better base to build on? Im an NA is best fan so i dont wanna go turbo. I thought of going with an sti block but thats gonna lower my compression. So if you subaru engine gurus can give me a hand on which direction to go, id greatly appreciate it......thanks.

2006 legacy 2.5i
4EAT

* Registered users of the site do not see these ads.

[mattwalters]

The STI block is hard as hell (closed deck, etc.) and designed to make power - you could have a set of high-compression pistons built for it and slap on a set of built DOHC heads - that could be a lot of fun. What's your budget / goal?

-Matt

[0deucedub]

STI BLOCK IS A MUST

stroker crank, (2.8 liter) forged high compression pistons, rods, 280/280 cams, dohc ported and polished heads, valve springs, ported and polished intake manifold, bigger throttle body. that could get you 300hp easy but its gonna cost you. lol.

[mattwalters]

..you owe me some new shorts. That engine would RULE.

-Matt

[EPskate]

Originally Posted by jonesboydamnit

The STI block is hard as hell (closed deck, etc.) and designed to make power - you could have a set of high-compression pistons built for it and slap on a set of built DOHC heads - that could be a lot of fun. What's your budget / goal?

-Matt

the usdm 2.5 sti block is not fully closed deck

[mslstixx]

What about the H6? I don't know much about engines, but I do know that the legacy comes with the H6 in certain trim levels. That would give you more HP without having to build the engine a lot, but Idk what other components would need to be replaced.

[piker28]

if you dont know alot about engines and etc i would just put what you had back in

[zavier]

the 3.0R is a nice motor...makes like 248bhp or something like that and some high comp pistons + some head work and you'd have a nice f'in N/A build...much better then a built EJ257 block...

or find a new tribecca motor.../yum 3.6L H6...that's a beast of a motor right there

[Division By Zero]

Wanting to stick with a NA Subaru is the wrong way to go. If your motor had variable valve lift and even variable camshaft advance then your goals would be a little bit more realistic. If you bought an NA Subaru as a basis of performance then you bought the wrong vehicle. Turbo Subarus OTOH, can be quite respectable

[Counterfit]

A) the 2006 2.5 DOES have variable lift, and 2) GTFO you FI weenie! :P

[0deucedub]

Originally Posted by tmarcel

Wanting to stick with a NA Subaru is the wrong way to go. If your motor had variable valve lift and even variable camshaft advance then your goals would be a little bit more realistic. If you bought an NA Subaru as a basis of performance then you bought the wrong vehicle. Turbo Subarus OTOH, can be quite respectable

Thats y we suggested a dohc head.

[Division By Zero]

Originally Posted by Counterfit

A) the 2006 2.5 DOES have variable lift, and 2) GTFO you FI weenie! :P

Are you kidding 2006 2.5 has variable valve lift? AVCS is a wee bit different than variable valve lift dude Come on man don't spout bad info.

[Division By Zero]

Originally Posted by 0deucedub

Thats y we suggested a dohc head.

So please tell the details. DOHC is a benefit because why? Jeez, you guys might want to think before posting

[0deucedub]

Originally Posted by tmarcel

So please tell the details. DOHC is a benefit because why? Jeez, you guys might want to think before posting

DOHC HEADS have variable cam advance and lift. THATS Y.

[bentwrench]

My advice is if you are going to build up from scratch look into a turbo. If you do it right it can be alot of fun...

You can usually find a usable engine in wreck if you aren't affraid to look around some. It can be a great place to start.

I mean you haven't bought anything yet, so it dosen't hurt to paln out a couple different options, then look at the work involved and costs.

If N/A is the only road you willing to look at, your gonna need high CR and cams. Lot of ways to do that, all depends on the $$$ you wanna spend.

[zavier]

the 2.5i's have iAVLS - Active Valve Lift System

the WRX and STi both have AVCS - Active Valve Control System

Originally Posted by tmarcel

If your motor had variable valve lift and even variable camshaft advance then your goals would be a little bit more realistic.

so i'm confused...here you state either or would be ideal (cause variable valve lift is what the 2.5i has and variable camshaft is what the sti has)...then you go on to say active valve lift is a bit different then avcs...which it is...making it seem like you want more then lift...so which is it?

[mslstixx]

AVLS won't give you more power, it simply makes the engine more efficient in lower RPM/low valve lift situations.

OP says he wants NA, stop trying to tell him he meant to say turbo, he clearly said NA.

http://www.drivesubaru.com/Win05_WhatsInside.htm

According to this, several motors have the AVCS, including a 3liter H6, now that would be fun. I have heard that some JDM engines have dual avcs.

[EvoSpeed]

Originally Posted by mslstixx

AVLS won't give you more power, it simply makes the engine more efficient in lower RPM/low valve lift situations.

My understanding of Subarus iAVLS system is to get the most power down low AND on top.... while still getting the best possible gas mileage as a second thought.

Its the same idea as VTECH that everyone is following honda on. In Japan there is a tax for the more CC's your engine has. So VTECH (and iAVLS) are all about getting the most power out of a small engine. Japanese auto techs have developed this technology to get the most low end power, then switch to the other cam lobes to get the most top end power as well. Additionally the system also is designed to get the best gas mileage as a second thought.

My point is the comment "iAVLS wont give you more power" doesnt make sense. The same EJ25 NA wont have as much power without iAVLS.

[Sir-Knight]

Originally Posted by tougefox

I have a 2006 legacy 2.5i and unfortunately the motor is gone. Story can be found at legacygt.com. So now im replacing the motor so im wondering are there any NA options that will give me some more power or a better base to build on? Im an NA is best fan so i dont wanna go turbo. I thought of going with an sti block but thats gonna lower my compression. So if you subaru engine gurus can give me a hand on which direction to go, id greatly appreciate it......thanks.

2006 legacy 2.5i
4EAT

06 legacy...


What happened to your warranty?

[mslstixx]

Our NA motors have two intake valves and two exhaust valves. AVLS works on the intake side. In the standard "off" position one valve is at high lift and the second is at medium (lower) lift. When AVLS kicks in it increases the lift on the second valve to high lift.

AVLS makes the powerband smoother, and yes its possible it makes more power, but not a whole lot, 166hp w/out AVLS to 173 hp w/ AVLS.
"The same EJ25 NA wont have as much power without iAVLS."
While this may be true, the addition of AVLS coincided with the addition of equal length headers. Most people will agree that EL headers make more power than UEL headers and this difference between power output may be more due to this than AVLS. Either way its a small difference.

While my previous statement wasn't 100% true, I still contend that AVLS is not something to consider when building an engine for power. AVCS is expensive but can actually make significant power.

[mslstixx]

Furthermore VTEC seems to work like AVCS and AVLS combined: VTEC = variable valve timing and lift. AVCS=variable valve timing. AVLS variable valve lift

[EvoSpeed]

Originally Posted by mslstixx

"The same EJ25 NA wont have as much power without iAVLS."
While this may be true, the addition of AVLS coincided with the addition of equal length headers. Most people will agree that EL headers make more power than UEL headers

This is true.

[Division By Zero]

Originally Posted by 0deucedub

DOHC HEADS have variable cam advance and lift. THATS Y.

Oh that's "Y" - that's right, AVCS w/lift finally made it to production into the 4s. Regardless, it is cost prohibitive to make power even with the new valvetrain in non-turbo form (you could always spray on it but refills get old). Seems like a diluted version of Honda's i-Vtec considering max power doesn't come on nearly as strong, although power seems to be improved across the board.

I'm not here to battle with you guys on what's the right and wrong path to take. I came across this thread searching for NA parts actually. I happen to own a NA Legacy Subaru (well I did swap a turbo kit on it a couple of months ago). Ultimately, it boils down to how deep your pockets are and how much time you've got on your hands. I personally would advise against it with the current aftermarket support, or lack of.

[bentwrench]

I almost fear piping in on the variable valve geometry here...

The design criteria for these types of valve trains are to taylor the drivabilty of an engine and shift the torque curve. They want a motor you can tromp on and at the same time have a nice smooth mild sunday driver. In the truck world its all about the torque curve. But for us in the home brew power world variable valve geometry does nothing. If you want to build a motor to go fast you build it to go fast. To hell with the drivability and refinement crap.

Not that they don't get more power from variable valve geometry, but they could have done it with a simple cam change. Most likely it caused a rough idle or sogy lowend power, so they used the variable technique to correct it.

[EvoSpeed]

^^^Thats a really good statement I agree.

Yah my buddy just got new heads and a cam in his Z06 and he said its a super lopy idle and the lowend was affected.