Question for Subi guys

[Kalstar]

I purchased a WRX donor car for my 818 build but I am now thinking of going NA. I can buy an 07 with 8000 miles (hit in the back) for $900.00.

My question, shorter exhaust, no parasitic lose from the a/c unit. With a few bolt ons like spacers, cold air intake, maybe lighter pullies and a tune....what would be the power increase over the stock 173hp?

[Joe Mush]

You come up with some great deals. That's awesome where did you find that?

[Silvertop]

I purchased a WRX donor car for my 818 build but I am now thinking of going NA. I can buy an 07 with 8000 miles (hit in the back) for $900.00.

My question, shorter exhaust, no parasitic lose from the a/c unit. With a few bolt ons like spacers, cold air intake, maybe lighter pullies and a tune....what would be the power increase over the stock 173hp?


I'm doing an NA build. My engine mods will include spacers and lightweight pulleys, cold air intake, plus a ported/polished intake manifold (Grimmspeed), a set of Techworks cams and equal length tuned exhaust. I'm hoping to achieve 200 honest flywheel horsepower compared to the original 165 that my '04 donor had, while retaining a nice broad torque curve.

One caveat. An NA ECU tune may be hard to find. Crawford was doing them, but they stopped. Your only choice may be via a piggyback or standalone unit (expensive., and not a lot of choices out there).

[Kalstar]

You come up with some great deals. That's awesome where did you find that?

Friend of a friend. Daughter drove it, since she lives in the household and was not on the issuance the insurance company did not cover the car when it was wrecked. Been parked for 5 years, I can buy it for what they still owe. Making payments on a crashed car for 5 years must have sucked.

[rjh2pd]

I dont think you will get too much of a boost without a cam change, then you really need a avls (active valve lift system) and i dont think any na came with it. if your looking for power I'd go turbo.

[Kalstar]

I figured 2-3 hp from no A/C, 1hp from the spacers 1hp from the crank pulley and 5-7hp from the exhaust/cai combo. Total of say 10-12hp increase. My target would be to match the Lotus Excege P/w of about 9lbs per HP. My guess is my final weight with the extras I want to put in will but me about 1700lbs. I'm I shooting high or low?

[riptide motorsport]

You could always go on a diet too!!:)

[Kalstar]

I thought we had Subaru geniuses in here? There has to be more knowledge then just the WRX models.

[HelluvaEngineer]

I thought we had Subaru geniuses in here? There has to be more knowledge then just the WRX models.

You may want to look at this forum. It is the Legacy GT web site, but this link is for the NA group there (http://legacygt.com/forums/forumdisplay.php/naturally-aspirated-powertrains-2-5i-3-0r-11.html). You will see a mix of 6 and 4 cylinders. But they have some good experience with the NA engines. I am probably going to do an NA build as well, but I will probably do a full rebuild and go higher compression. I am going to experiment with high MPG and still try to get good HP.

[longislandwrx]

With the mods you mention, minus the tune i'd expect to see about 6-8 hp gains at the wheels (if you are getting nice cold air)

Cobb had an accessport for the 2.5i for a while not sure if it's still available, gains were similar to the open source tunes... iirc about 12hp with all the bolt ons.

Getting rid of the close coupled cats will help as well. The EL Header on the 2.5i is supposed to be pretty good already.

Porting will make a noticible difference as well, as silvertop said, getting the intake manifold and throttle body gasket matched/ported/coated will be good for some top end power

Cam makers claim to make 20hp, but I think the only ones left in the game are Delta Cams or TechWorks Engineering. All the others have found that demand is virtually non existant and not worth the R&D. I think they both run about $1000

[apexanimal]

Tuning will make a big difference... Romraider stuff will certainly be needed to do what you want

El headers
2.25" exhaust
Phoenolic im spacers
Intake
Cams
Port/polish
TUNE

[metalmaker12]

To be honest it matters what you want out of it. The EJ series motors make decent power with no turbo. As it seems you like to get bargains so your going to sell your wrx donor and make out I presume lol. An na with an intake, possible larger throttle body and a open source tune will get you like 10 whp, maybe. Not worth cams, porting, etc etc, unless you want to spend more than it's even worth in actual power. I personally would never give up a wrx engine for any na . Jim if you go this route and a need a tune I can work that out for you.

[Kalstar]

To be honest it matters what you want out of it. The EJ series motors make decent power with no turbo. As it seems you like to get bargains so your going to sell your wrx donor and make out I presume lol. An na with an intake, possible larger throttle body and a open source tune will get you like 10 whp, maybe. Not worth cams, porting, etc etc, unless you want to spend more than it's even worth in actual power. I personally would never give up a wrx engine for any na . Jim if you go this route and a need a tune I can work that out for you.

I do love deals, though I think I would keep the WRX as a cheap toy. It's not bashed that bad. Besides no matter what I do your going to smoke me with your set up. You will give my GTM a run for its money. Thanx for the offer of help. 185hp would put me were I want to be if I do go NA. Will the short exhaust help or hurt? I know the engine needs some back pressure.

Thx for the advise so far guys!

[Ironhydroxide]

there are many accounts of high horsepower NA builds in the subie world. Most use the DOHC heads off the Boosted applications. there are a few sets of heads from the land of JDM that have the Variable valve, in the NA form.

If I were to build an engine NA for the 818, it would be a 2.7 stroked, 10:1CR, with Variable Valve heads, probably controlled by a megasquirt or the like.

[longislandwrx]

I think if you went conservative:

cold air intake $100-175
ported intake $175
ported throttle body $90
lightweight pulley $100
phenolic spacers $80
catless exhaust $?
custom pro tune $500
no ps or ac $free


you'd be able to hit your 185 number... a cooler tstat might help as well (as this wont be a winter driver I imagine)

[metalmaker12]

Jim, that is very doable, and that donor sounds like a great deal. I will talk to my bud Matt about the truth of tuning an Na ej and what he has done for little money that works.

Ps to Na lovers: I ended up with a 2.5 rs with as far as i can remember ported ej 207 spec c heads and it was stroked to a to a 2.7. I rebuilt the front end, painted the whole car and did all new bushings and coilovers. The engine was fully built and cost the kid like 8 grand. He ran out of money and lost his job, so I scored it cheap, I sold it for like 3 times the money. It made like 220 or so whp. This was like ten years ago, I have a complete list of parts somewhere in my files, hopefully I can find them. It was cool to drive and had a great torque curve, the top end was pretty strong even with the larger displacement.