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2008 XT Sport 5-speed
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418 Posts
Discussion Starter #1
Hi Everyone – I need some help figuring out my engine build. I’m looking to be in the 450-500 WHP range, but I’ve been out of the scene for so long that I don’t know what the parts and pieces are anymore. Let me give some background on the car first. (You can find the whole build thread here: https://www.subaruforester.org/vbulletin/f115/ultimate-daily-driver-project-99894/ ) but the short and sweet of it is the suspension is basically where I want it, and so now that I have pulled the car out of a 5-year storage, I’m ready to start on the engine. While the car was in storage it overheated badly. (As was reported to me by the person storing it for me.) I didn’t get to see, but when I pulled it out of storage, there was no sign of oil in the coolant (or any coolant for that matter) no sign of coolant In the oil, and no leaks under the car. So I’m not sure if the heads warped or not. If the heads did warp, I may just buy a staged block from IAG or someone similar, instead of dealing with getting the block and the heads machined. Either way, I’m looking for help on what I need to hit those numbers, and what the best companies are. Granted everyone will have different opinions, but usually, the best brands will stand out. So I’m going to make a list of the parts I’m already planning, and let me know if there are better products out there, what I’m missing, or if any of the parts I have planned don't play nice together. TIA (if this kind of stuff isn’t allowed anymore, feel free to delete.)
• Intake – Unknown
• Cosworth Forged pistons
• Fluidampr
• I wanted to go 18GXT-R, but I’m not sure if it will hit the numbers I want so maybe 3.0XT-R
• IAG Performance Competition series AOS
• IAG or Radium auto Top Feed Fuel Rail
• Radium Auto Fuel pump hanger
• Custom front mount intercooler from bellintercoolers
• KoyoRad aluminum radiator
• Subaru 68 degree racing thermostat
• Bline motorsports top mount oil cooler
• Killer B oil pan, pickup, & baffle
• Grimmspeed limited DP with thermal coating
• Grimmspeed exhaust manifold crossover with thermal coating
• Grimmspeed up pipe with thermal coating
• Injectors - unknown
• AMR Cast Turbo Inlet Tube
• AMR Un-Equal length header
• Cosworth air pump & tgv delete
• Prodrive 3-port boost control
• Omnipower 7 bar map sensor
• Fuel pump - Unknown
 

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07 FXT
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828 Posts
450-500 whp is hard to do. Pump gas and stock redline gets you to maybe 375 whp. To get more you will need higher octane fuel to turn up the boost, and/or upgraded heads/valvetrain to run higher RPM. Do you have access to E85? That would be a big help. If not probably need meth injection, or race gas. This discussion would be more beneficial to have with your tuner, you wont get there with bolt-ons. High boost/high RPM will both impact reliability. Your original thread stated this car is meant to be a daily driver, if that is true I'd consider lowering your goals. Have you had a high powered car before, and know what you want?

Not trying to sound like a negative Nancy, sorry.
 

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07 FXT
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828 Posts
And about your list, you have a header listed as well as a Grimmspeed crossover. The latter would not be needed. I would consider an equal length header instead, and maybe go external wastegate with the uppipe. I run a Perrin ELH, the Killer B header gets good press as well. Both are expensive upgrades for not a huge gain, but if you are going all out then you will need all the help you can get. At those power levels you might consider a rotated turbo setup, if you are doing a custom FMIC that would be more doable.
 

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2004 forester sti
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2,307 Posts
consider meth/water injection for this plus low compression for big boost big turbo application . imo this wont make a good road car unless its kept at higher revs.
as said above this is not achievable with a stock location turbo .
Water/Meth injection will allow you to run more timing and turn your pump fuel into race fuel for free , after the initial lay out.

apart from that virtually everything has been said in the above post.

1 last thing , bhp wins sales . torque wins races!
 

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2008 XT Sport 5-speed
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418 Posts
Discussion Starter #5 (Edited)
Thanks for the info. Some more background. When I first got the car it was my daily, and my original plan was to keep the power at about 350 crank. Then the car went into storage, and now I have a different daily driver, and the Forester is going to mostly be a fun car...It might see some daily use, but I only work 1.25 miles from my house, so I'm not as worried. I do want to stay with pump gas, and I don't want this to become a car that only has power in the last 800 RPM. So maybe I should shoot for 350 wheel instead of 350 crank. That seems like it might be more manageable. So back to the 18GXT-R, and any other suggestions you have.
 

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07 FXT
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828 Posts
350 whp is fun, it is about what my car does, and it can be reliable. You will want forged pistons. Your original list had a bunch of stuff that might well be good, but not absolutely necessary.

What you need:

downpipe
upgraded TMIC
18G-XTR turbo (maybe consider the Dom 1.5 XTR, just slightly bigger)
injectors (ID1000s are good)
fuel pump
boost solenoid
a good tune


If funds allow:

Cold air intake
Equal length header


My opinion is to not change a bunch of stuff if not needed. Changing stuff increases the odds of messing something up, and the further from stock the more difficult it will be to fix if you get stranded somewhere and the local mechanic has no idea what you did.

Stock fuel rails are fine at this level.
Fluidamper? why second guess Subaru?
7 bar MAP sensor? not necessary at this level
Killer B pan? not really necessary, but I did go with their oil pickup
Aluminum radiator maybe, only because the stock one fails. Dont think it cools any better.
TMIC will be less trouble than FMIC
Turbo inlet needed if you tear the stock one, I like Samco, don't know about the AMR one
Stock T-stat is fine
TGV deletes are OK, I went with the JDM ones instead of grinding and plugging holes. Not sure I trust the plastic ones, but that is my own bias.
Definitely ditch the air pump & valves while you are in there. Keep the drivers side one with the pressure sensor.
Use whatever exhaust you like, an old STI is good enough and quiet, some can be painfully loud.
I get by fine with a stock clutch
AOS? Dunno if they do much, but I do have one.
Shouldn't need an external oil cooler for a DD
Maybe toss on a new MAF sensor if the current one has upwards of 100K on it

And I repeat, a good tune is paramount.
 

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MY05 Forester 2.5 XT 5MT
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2,847 Posts
Are you putting a 6 speed Getrag (Who makes the STI) gearbox) in or sticking with the 5 speed ?
 

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979 Posts
350 whp is fun, it is about what my car does, and it can be reliable. You will want forged pistons. Your original list had a bunch of stuff that might well be good, but not absolutely necessary.

What you need:

downpipe
upgraded TMIC
18G-XTR turbo (maybe consider the Dom 1.5 XTR, just slightly bigger)
injectors (ID1000s are good)
fuel pump
boost solenoid
a good tune


If funds allow:

Cold air intake
Equal length header


My opinion is to not change a bunch of stuff if not needed. Changing stuff increases the odds of messing something up, and the further from stock the more difficult it will be to fix if you get stranded somewhere and the local mechanic has no idea what you did.

Stock fuel rails are fine at this level.
Fluidamper? why second guess Subaru?
7 bar MAP sensor? not necessary at this level
Killer B pan? not really necessary, but I did go with their oil pickup
Aluminum radiator maybe, only because the stock one fails. Dont think it cools any better.
TMIC will be less trouble than FMIC
Turbo inlet needed if you tear the stock one, I like Samco, don't know about the AMR one
Stock T-stat is fine
TGV deletes are OK, I went with the JDM ones instead of grinding and plugging holes. Not sure I trust the plastic ones, but that is my own bias.
Definitely ditch the air pump & valves while you are in there. Keep the drivers side one with the pressure sensor.
Use whatever exhaust you like, an old STI is good enough and quiet, some can be painfully loud.
I get by fine with a stock clutch
AOS? Dunno if they do much, but I do have one.
Shouldn't need an external oil cooler for a DD
Maybe toss on a new MAF sensor if the current one has upwards of 100K on it

And I repeat, a good tune is paramount.
I pretty much second everything said here. This is basically my car, give or take a few bits and pieces. Very fun, good usable power, and reliable. IMO: aluminum radiator is a must-do. Agree that a GOOD tune is exigent. Don’t be cheap abou the tune, or your motor will pay the price.
 

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2008 XT Sport 5-speed
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418 Posts
Discussion Starter #9
Are you putting a 6 speed Getrag (Who makes the STI) gearbox) in or sticking with the 5 speed ?
I go back and forth between keeping the 5-speed, and putting stronger internals in or going 6 speed. I think the ultimate plan is to do a full STI swap underneath, so STI 6-speed, DCCD, axles, hubs, brembos...

I pretty much second everything said here. This is basically my car, give or take a few bits and pieces. Very fun, good usable power, and reliable. IMO: aluminum radiator is a must-do. Agree that a GOOD tune is exigent. Don’t be cheap abou the tune, or your motor will pay the price.
A Tune is a major part of the build. Fortunately, I've been friends with Matt Miner (one of the better tuners in New England) for a while, so I'll have him do the tune when the time comes.

Again thanks for the info everyone. Its good to know the basic pieces I will need. I tend to overbuild everything, so even if some of the stuff isn't necessary, it may still find it way onto the car. >:)
 

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2008 XT Sport 5-speed
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418 Posts
Discussion Starter #10
350 whp is fun, it is about what my car does, and it can be reliable. You will want forged pistons. Your original list had a bunch of stuff that might well be good, but not absolutely necessary.

What you need:

downpipe
upgraded TMIC
18G-XTR turbo (maybe consider the Dom 1.5 XTR, just slightly bigger)
injectors (ID1000s are good)
fuel pump
boost solenoid
a good tune


If funds allow:

Cold air intake
Equal length header


My opinion is to not change a bunch of stuff if not needed. Changing stuff increases the odds of messing something up, and the further from stock the more difficult it will be to fix if you get stranded somewhere and the local mechanic has no idea what you did.

Stock fuel rails are fine at this level.
Fluidamper? why second guess Subaru?
7 bar MAP sensor? not necessary at this level
Killer B pan? not really necessary, but I did go with their oil pickup
Aluminum radiator maybe, only because the stock one fails. Dont think it cools any better.
TMIC will be less trouble than FMIC
Turbo inlet needed if you tear the stock one, I like Samco, don't know about the AMR one
Stock T-stat is fine
TGV deletes are OK, I went with the JDM ones instead of grinding and plugging holes. Not sure I trust the plastic ones, but that is my own bias.
Definitely ditch the air pump & valves while you are in there. Keep the drivers side one with the pressure sensor.
Use whatever exhaust you like, an old STI is good enough and quiet, some can be painfully loud.
I get by fine with a stock clutch
AOS? Dunno if they do much, but I do have one.
Shouldn't need an external oil cooler for a DD
Maybe toss on a new MAF sensor if the current one has upwards of 100K on it

And I repeat, a good tune is paramount.
Thanks for all the info, and breakdown of all the pieces...this will be a great list to use as I start collecting parts.
 

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07 FXT
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828 Posts
Note on the tranny. The 5 speed can last even at 350 whp, it is torque (and/or abuse) that is the real killer. Running the above mentioned turbos at 18 or 19 psi max boost is no harder on the driveline than running the same boost with a VF or even the stock turbo, the extra power comes from holding that boost all the way to redline. IMO one of the worst combos would be to run the stock TD04 with boost cranked way up with E85. You would have a huge torque spike that come on with a bang to break things, then the boost would fall off immediately and net you not much power. I also like keeping the stock clutch as a bit of a weak link in the system.
 

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I go back and forth between keeping the 5-speed, and putting stronger internals in or going 6 speed.
A note about the 5-speed: unless you are putting straight-cut gears into it: stronger internals will not make your transmission less failure-prone. The big weakness of the 5-speed tranny is that the case itself is not strong enough and tends to stretch under the (transverse?) load created by helical gears. Stonger internals will not fix that. Straight-cut gears WILL fix that but then you get to listen to them all the time. If this is truly just a joyride car then straight-cut gears might be an option for you ... but passengers might not enjoy them too much.
 

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2008 XT Sport 5-speed
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418 Posts
Discussion Starter #14
Note on the tranny. The 5 speed can last even at 350 whp, it is torque (and/or abuse) that is the real killer. Running the above mentioned turbos at 18 or 19 psi max boost is no harder on the driveline than running the same boost with a VF or even the stock turbo, the extra power comes from holding that boost all the way to redline. IMO one of the worst combos would be to run the stock TD04 with boost cranked way up with E85. You would have a huge torque spike that come on with a bang to break things, then the boost would fall off immediately and net you not much power. I also like keeping the stock clutch as a bit of a weak link in the system.
A note about the 5-speed: unless you are putting straight-cut gears into it: stronger internals will not make your transmission less failure-prone. The big weakness of the 5-speed tranny is that the case itself is not strong enough and tends to stretch under the (transverse?) load created by helical gears. Stonger internals will not fix that. Straight-cut gears WILL fix that but then you get to listen to them all the time. If this is truly just a joyride car then straight-cut gears might be an option for you ... but passengers might not enjoy them too much.
The straight cut gears are what I had meant, I just couldn't remember the name of them at the time. I've known a couple guys with the straight cut gears, and I'm not sure I could deal with that noise for any amount of time...The car is already loud, and adding another really loud noise would probably drive me nuts.

The clutch has already been replaced...the stocker didn't like my attempts at drifting and came apart, so I replaced it with one that is good to about 500hp. Its more of an on/off switch now than a clutch...so much so my wife refused to drive the car anymore after the new clutch went in. I have always planned to go 6-speed at some point, I guess now it is just a matter of which order do I go in...Do I do all the driveline bits first, and then the engine, or do the engine first and then the driveline once it lets go...some of it might depend on how much damage the overheating caused. If the heads are warped, then I'm doing the engine first...if everything checks out, then I'm not sure.
 
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