Basic Mods for a 2.5L DOHC...

[blackgtbeauty]

I just got a second DOHC engine for my Legacy that I want to start working on. I would like to keep it N/A, and keep it at about a stage one, what are some things I could do and keep the budget down, 1k - 2k would be ideal.
I also don't want to get into engine managment. Any idea?

[Wiscon_Mark]

Why no engine management?

[mr_choung]

basic's are...

obx equal length headers- 330 shipped
Custom wrx Catback- 100-150
Intake- Ebay w/cone -50
Perrin/Mr.Josh crank pulley 80-100
Total- roughly 600-650
the rest on built heads or even better, get a Phase II 2.5rs block off 99-01 rs.

[blackgtbeauty]

the dohc in my car now was rebuilt with a phase 2 style block, i could take that's block and just couple it with the new heads.

i guess maybe i want a stage 2, because i was thinking of mild cams and port polishing as well.

[sheepdog]

You'll want to mess with EM. Thats where you're going to take advantage of those mods, as well as the DOHC build. You should just rebuild it for high compression :twisted:

[rougeben83]

Ditch the wrx muffler, go full 2.5" piping to an STI exhaust for the catback. There's no point in wussing out on the exhaust if you decide to add more upgrades later.

You'll want a PP6 or equivalent for EM to take advantage of the cams and P&P. Buy one used, spend $50 for Rallitek to give you a stage 3 map you're set.

[Wiscon_Mark]

05+ WRX muffler is the same as an STi muffler (internally).

[blackgtbeauty]

Ditch the wrx muffler, go full 2.5" piping to an STI exhaust for the catback. There's no point in wussing out on the exhaust if you decide to add more upgrades later.

You'll want a PP6 or equivalent for EM to take advantage of the cams and P&P. Buy one used, spend $50 for Rallitek to give you a stage 3 map you're set.

hmmmmm... :twisted:

am i going to run into problems w/ the pp6 and my dohc/phase2 engine?

[Wiscon_Mark]

Why would you?

[blackgtbeauty]

i dunno that's why i'm asking :cool: .

[blackgtbeauty]

obx equal length headers- 330 shipped


bolt right up?

[Wiscon_Mark]

Yes, if you ditch the stock catalytic converter. The little pipe it has connected to it only looks like one. You can remove that and have a universal hi-flow attatched though.

[rougeben83]

Ditch the wrx muffler, go full 2.5" piping to an STI exhaust for the catback. There's no point in wussing out on the exhaust if you decide to add more upgrades later.

You'll want a PP6 or equivalent for EM to take advantage of the cams and P&P. Buy one used, spend $50 for Rallitek to give you a stage 3 map you're set.

hmmmmm... :twisted:

am i going to run into problems w/ the pp6 and my dohc/phase2 engine?

No, I meant is that Rallitek can send you the map that is for your particular setup for $50. Otherwise you'll have to tune the PP6 yourself.

[rougeben83]

05+ WRX muffler is the same as an STi muffler (internally).

Yeah, we'll need to start delineating that not ALL WRX mufflers are like the STI muffler; I think badasser confused which years had it and got the quiet one :grin:

Just to reiterate - single, big tip = STI/05+ muffler, dual tip = quiet 02-04 wrx muffler

:grin:

[sheepdog]

My personal opinion with EM solutions is to not bother with base maps. I've installed my share of UTECs, PP6, PP7, Accessports, etc, and flashed base maps on all of them. The purpose of the base map is to get the car on the road temporarily until you can go get it tuned on a dyno. One wrx I installed a utec has since died, the guy drove on a base stage 3 map for over six months. Get it tuned for real, its worth the money.

[Huffer]

+forty million on the EM + tuning.

[blackgtbeauty]

I understood about RalliTek remapping the pp6, I guess i'm still confused on the dohc/phase II situation.

Is it not that big a deal that I have that combination as far as tuning goes?

I can't find the thread this was discussed on here, i remember someone said high octane had to be run in it, etc etc...

please excuse my ignorance to this subject, i want to be educated on it so i don't eff the engine up.

[Huffer]

Stock motor has a 9.7:1 compression ratio. Going to a stage 2 type engine may not run on 87 octane, and furthermore, the stock ECU map may not be able to cope with more agressive cams and a higher compression ratio.

I do know that if you run a stock head with 10.2:1 pistons, (say a 99 RS shortblock), you will need to run a minimum of 89 octane to prevent detonation.

Tuned engine management will allow you to run the most, with the least danger. An untuned engine (one that constantly runs rich, or too lean) will eventually give up the ghost, and that's pretty expensive.

[sheepdog]

Yea, the EM is the solution to any problems you could potentially run into with the different compression with the phase 2 heads.

[TRReynz]

basic's are...

obx equal length headers- 330 shipped
Custom wrx Catback- 100-150
Intake- Ebay w/cone -50
Perrin/Mr.Josh crank pulley 80-100
Total- roughly 600-650
the rest on built heads or even better, get a Phase II 2.5rs block off 99-01 rs.

I've been reading up on the crank pulley upgrade and there are a lot of pros and cons on various boards.
I'm thinking of doing it to my 2000 LGT and was wondering if anyone here has done it and what their experience was (performace, reliability, etc).
Thanks!

[Wiscon_Mark]

What were some of the cons?

Besides improper installation leading to some serious problems.

[Huffer]

I've been reading up on the crank pulley upgrade and there are a lot of pros and cons on various boards.
I'm thinking of doing it to my 2000 LGT and was wondering if anyone here has done it and what their experience was (performace, reliability, etc).
Thanks!

I have a GFB lightweight pulley on my aged BD. No problems, and the install was done in my garage when we changed the timing belt. Been on there for half a year, and the car does a minimum 50mile commute per day.

Would I do it again? Maybe, probably not because I noticed no real difference.

[TRReynz]

I read that the factory pulley is harmonically balanced and when you change it with an aluminum one you run the risk of vibration at the crank which can cause damage to the oil pump.

An argument against that is because an aluminum pulley is so much lighter than the factory part the risk of vibration is much less.

Then of course there is the argument as to whether or not it even makes a difference.

Just trying to see if it's worth the effort.

Thanks.

[Wiscon_Mark]

I think it makes a noise difference, and that's about it.

If it's having serious vibration problems, then there's already a problem.

[badbasser98]

I think badasser confused which years had it and got the quiet one :grin:

Just to reiterate - single, big tip = STI/05+ muffler, dual tip = quiet 02-04 wrx muffler
I have a MY05 WRX muffler (single tip). Just the whole rest of the exhaust system is stock ATM... But not for a whole lot longer :wink:

[jey]

I read that the factory pulley is harmonically balanced and when you change it with an aluminum one you run the risk of vibration at the crank which can cause damage to the oil pump.

An argument against that is because an aluminum pulley is so much lighter than the factory part the risk of vibration is much less.

Then of course there is the argument as to whether or not it even makes a difference.

Just trying to see if it's worth the effort.

Thanks.

The pulley is acting as a harmonic dampener for the engine crankshaft - having a lighter pully doesn't reduce the need for a harmonic dampener. There is general consensus, though, that removing the harmonic dampener is not a big deal unless you're dealing with an engine with large amounts of power (like 300hp+).

[d1giPhux]

^ Nah, its not a harmonic dampener ... dont worry about that. You can get a lightened crank pulley like a perrin crank pulley, and it will make no difference.

http://forums.nasioc.com/forums/showthr ... did=444518 (http://forums.nasioc.com/forums/showthread.php?s=&threadid=444518)


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"Thank you for your patience as I checked with our Technical Services Department regarding your message below. They advised that the crank pulley is a pulley and nothing else. It is not used as a harmonic damper/balancer.

Thanks for the opportunity to be of assistance. If you need any future assistance, please feel free to contact us again."

Best wishes,

John J. Mergen
Customer Service Department
Subaru of America, Inc.

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There was HUGE discussion about this on NASIOC, and it ended when someone emailed subaru a few times and finally got a response back that the pulley WAS NOT a harmonic dampener. Although I cant verify this as COMPLETELY true.. a ton of people have looked into this, and that was the conclusion. By all means, someone should go ahead and re-email SOA and ask :grin:

I had a perrin lightweight pulley and it was great, never had any trouble!

[ten80]

I did the lightened pulley and wouldn't do it again. Absolutely no noticeable difference. If you look at your stock pulley, you will se NO harmonic ballancers. Just a big, heavy metal pulley with a little rubber, and that's it.

Here are the mods I have found to be very effective:

1. 1 step hotter spark plugs- dyno showed that I had a 10hp gain. NA subarus run rich and you can take advantage of this with a slightly more aggressive plug

2. 3" home made PVC intake from the stock airbox- retain the stock airbox for throttle response, but increase air flow and no CEL's

3. Light weight flywheel- although it doesn't increase horsepower, it will allow the engine to rev faster and the power to get to the wheels sooner.

4. OBX headers- no brainer for maximum power

5. High flow cat- get a magnaflow 2.25" spun cat- they practically have no restriction and are about the best cat you can get for $99 (ebay)

6. custom 2.25" exhaust all the way back to an aftermarket or single tip WRX/STi muffler. I have found that Prodrive mufflers are the only ones that keep the subaru sound with OBX headers (I've tried stromung, scoobysport, cobb, stock RS and stock WRX)

7. PP6 - pretty much the only viable engine control management for your car. everything else except i-speed reflash is either not OBDII compliant or does absolutely nothing (Like ProECM chip!).

8. cams, headwork, pistons - the really expensive part, but you can gain 25-40whp or so with these.

IMHO, there's not much else to do after these except suspension and handling stuff which can make your car feel faster and more agile!

-christophe
The very first mod you should do is put in 1 step hotter spark plugs, then make yourself a PVC cold air intake that retains the stock air box. Never ever ever ever use the stock, dual-tip WRX muffer- the exhaust path through it is like a maze and really not any better than the stock muffler.

[Wiscon_Mark]

Good post, Ten80.

I'm going to have to try these plugs.

[d1giPhux]

I noticed a good difference when I installed the lightweight crank pulley on my 99 BD. It was a lot better for acceleration in 1st and 2nd gear. It made the car feel a lot quicker from a stop. i dont know.. for $100.. thats a good deal to me. Also, its super easy to install.

[d1giPhux]

I noticed a good difference when I installed the lightweight crank pulley on my 99 BD. It was a lot better for acceleration in 1st and 2nd gear. It made the car feel a lot quicker from a stop. i dont know.. for $100.. thats a good deal to me. Also, its super easy to install.

[ten80]

forgot to mention that I use NGK BKRE4-11 plugs (2 steps hotter) and one step hotter in the plain coppers would be BKRE5-11, at least for SOHC. No point in getting irridium or platinum plugs since coppers are cheap and conduct the spark better. The only drawback is that you have to change them every 10-15k, but that takes 30 minutes tops.

[Wiscon_Mark]

Thanks, I was kinda wondering what "one step up" would mean when I go shopping for plugs.

[ten80]

www.sparkplugs.com (http://www.sparkplugs.com) is an excellent source for the plugs since they are rare in the hotter variations.