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Discussion Starter · #1 ·
So I have a 2014 STI with 50k on the motor and it just blew. I just had GCH longblocks start my stage one longblock and need to know what else I'll need to hit the 500+ HP area. They said the longblock will handle around 620HP. What should I look for and what would I need to do to make that 500+ HP mark. Any help would be amazing. I'm new to the flat 4 world but have a good understanding of what it really takes to make good HP in the tuning world.
 

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what is the "stage 1" setup in their motor. i'd HIGHLY suggest going closed deck if GCH does it, i'm not at all familiar with their blocks. but most companies say the engine can handle 620, which means crankshaft power, it'll be less when going to the wheels, so 620 is approx 480whp accounting for roughly 22% drivetrain loss. that said, they may have enough in their longblocks that it will handle 620whp, which is why i ask what exactly it comes with.

the heads on the STi will be the weak point, specifically the valves/springs when running more than 24psi, so i'd make sure those are upgraded as well. they are actually pretty cheap to do vs the stock valves/springs.

there are quite a few different turbos that will get you there. do you plan to/have the budget to go rotated? if you do, i'd highly suggest that because the oem type housing on subarus is restrictive.

while you can make 500 on pump gas, it will be laggy, if you have e85 available set the car up to run e85/flex fuel.

and most importantly, what do you want to do with that 500, are you racing at all? if so what type of racing? or are you looking for just a fun street car?

i'm happy to get more specific and help guide you on this. i used to be the service advisor for mach v motorsports aka fastwrx dot com. and ive seen/helped with quite a few builds when i was there. ive also been in the subaru game for quite some time. let me know the answers to the questions above and i can make other suggestions on turbo/fuel setups from there.
 

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Discussion Starter · #3 ·
what is the "stage 1" setup in their motor. i'd HIGHLY suggest going closed deck if GCH does it, i'm not at all familiar with their blocks. but most companies say the engine can handle 620, which means crankshaft power, it'll be less when going to the wheels, so 620 is approx 480whp accounting for roughly 22% drivetrain loss. that said, they may have enough in their longblocks that it will handle 620whp, which is why i ask what exactly it comes with.

the heads on the STi will be the weak point, specifically the valves/springs when running more than 24psi, so i'd make sure those are upgraded as well. they are actually pretty cheap to do vs the stock valves/springs.

there are quite a few different turbos that will get you there. do you plan to/have the budget to go rotated? if you do, i'd highly suggest that because the oem type housing on subarus is restrictive.

while you can make 500 on pump gas, it will be laggy, if you have e85 available set the car up to run e85/flex fuel.

and most importantly, what do you want to do with that 500, are you racing at all? if so what type of racing? or are you looking for just a fun street car?

i'm happy to get more specific and help guide you on this. i used to be the service advisor for mach v motorsports aka fastwrx dot com. and ive seen/helped with quite a few builds when i was there. ive also been in the subaru game for quite some time. let me know the answers to the questions above and i can make other suggestions on turbo/fuel setups from there.

I can find out the exact build of the longblock. I'm not looking to do a lot of racing just more of a fun car to drive. I only wish I had real access to e85 so it will be pump gas for me. Even the 450 HP range is more than enough for me. I don't want to push the engine to hard because how easy it is to blow the engine. I'm hoping to get some info on supporting mods as well.
 

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I can find out the exact build of the longblock. I'm not looking to do a lot of racing just more of a fun car to drive. I only wish I had real access to e85 so it will be pump gas for me. Even the 450 HP range is more than enough for me. I don't want to push the engine to hard because how easy it is to blow the engine. I'm hoping to get some info on supporting mods as well.
let me know when you find out the exact build.

and it's really a myth that these cars are so easy to blow a motor, the overwhelming majority of the blown motors are user error, or bad tunes/maintenance. mine included in that, when my stock motor went it was 10000% my fault for getting so power hungry. if you are on pump gas you'll likely not be running super high boost levels. and likely a garrett gtx3576 will be a good turbo to hit that goal, although, without e85 you likely wont make 500. should be good for mid 400s on pump. maybe low 400s. but in that range. if you do get e85 in your area ever, it'll make upper 500s with ease. and if built properly, they will last quite a while. my oem motor lasted through abuse for 98k miles before it gave out, and my built motor has even more abuse for 42k so far with no issues whatsoever.

as far as supporting mods, domtune cylinder 4 cooling mod, equal length headers (killer b is top dog here if you can afford it), a quality air oil separator aka AOS (IAG or KillerB here), and the killer b oil pickup/baffle combo, you can also get a killerb pan too if you'd like. i'd also suggest an oil cooler even on the street. you can build your own or perrin makes one that uses a setrab core which is nice.
 

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Discussion Starter · #5 ·
The build is as follows.
CP Custom Forged Pistons
New Wrist Pins
ACL race rod bearings
ACL race main bearings
GMC Spec high horsepower rated forged race rods
OEM crank
BC race valve springs
BC race valve spring retainers
Rave head studs
OEM MLS gaskets
OEM seals and O-Rings
OEM Timing
new water and oil pump.
 

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The build is as follows.
CP Custom Forged Pistons
New Wrist Pins
ACL race rod bearings
ACL race main bearings
GMC Spec high horsepower rated forged race rods
OEM crank
BC race valve springs
BC race valve spring retainers
Rave head studs
OEM MLS gaskets
OEM seals and O-Rings
OEM Timing
new water and oil pump.
that looks very similar to my build, are they h or i beam rods?

also, since your motor did blow i'd suggest swapping out every line in the oiling system, just to be sure theres not metal flakes that can hurt your new motor. when i built mine, IAG suggested that and I did it. i know if it blows and IAG builds it, they wont warranty if you dont replace all that.

if you can add a pocket port on the heads and get a better intake manifold/tgv deletes youll free up a bit of power. for intake manifold the corsa velose or however it's called is a nice one. basically a process west one but has a bit bigger plenums if i remember correctly.


you plan on rotated or staying stock location turbo?
 

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Discussion Starter · #7 ·
that looks very similar to my build, are they h or i beam rods?

also, since your motor did blow i'd suggest swapping out every line in the oiling system, just to be sure theres not metal flakes that can hurt your new motor. when i built mine, IAG suggested that and I did it. i know if it blows and IAG builds it, they wont warranty if you dont replace all that.

if you can add a pocket port on the heads and get a better intake manifold/tgv deletes youll free up a bit of power. for intake manifold the corsa velose or however it's called is a nice one. basically a process west one but has a bit bigger plenums if i remember correctly.


you plan on rotated or staying stock location turbo?
What should I do with the new turbo setup? What’s the biggest difference between the two options?
 

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What should I do with the new turbo setup? What’s the biggest difference between the two options?
cost and performance. a rotated kit will get you a new up/downpipe, and if you are staying tmic some will not work, some will, and some will require custom intercooler piping if you are top mount intercooler. if front mount you'll be good. a stock location drop in turbo will use a subaru oem type exhaust housing, which is restrictive and will limit spool/power capabilities. vs a rotated kit will allow you to use an aftermarket exhaust housing which will flow better and allow better spool and power. if you can afford it, go rotated. it's also alot easier to work on lol. for your goals/build i'd personally suggest either a garrett gtx3576 gen2 or a borg warner efr 7670. personally i prefer the garrett gtx, but the efrs are very nice as well. i know killerb prefers the garret. but some prefer the efr. alot of it is preference. ets makes a super high quality rotated kit, and personally this is what i'd suggest. it's what i'll go with when i have the funds. stock location will just be laggier, and i know for that power fp makes some of the best stock location turbos onthe market, although i'm not 100% sure which fp to suggest there. i'd have to refresh my memory on those, i want to say the fp black will be the best for that power on pump, but dont quote me on that one lol. rotated will also allow you to go vband which also makes wrenching alot easier, when you have to pull parts off and put them back on. rotated will be more expensive up front but it's 100% worth it

also how big are their headstuds. and do you plan on raising the rev limiter? i'd guess not based on the list but you could raise it a tad.
 

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Discussion Starter · #9 ·
cost and performance. a rotated kit will get you a new up/downpipe, and if you are staying tmic some will not work, some will, and some will require custom intercooler piping if you are top mount intercooler. if front mount you'll be good. a stock location drop in turbo will use a subaru oem type exhaust housing, which is restrictive and will limit spool/power capabilities. vs a rotated kit will allow you to use an aftermarket exhaust housing which will flow better and allow better spool and power. if you can afford it, go rotated. it's also alot easier to work on lol. for your goals/build i'd personally suggest either a garrett gtx3576 gen2 or a borg warner efr 7670. personally i prefer the garrett gtx, but the efrs are very nice as well. i know killerb prefers the garret. but some prefer the efr. alot of it is preference. ets makes a super high quality rotated kit, and personally this is what i'd suggest. it's what i'll go with when i have the funds. stock location will just be laggier, and i know for that power fp makes some of the best stock location turbos onthe market, although i'm not 100% sure which fp to suggest there. i'd have to refresh my memory on those, i want to say the fp black will be the best for that power on pump, but dont quote me on that one lol. rotated will also allow you to go vband which also makes wrenching alot easier, when you have to pull parts off and put them back on. rotated will be more expensive up front but it's 100% worth it

also how big are their headstuds. and do you plan on raising the rev limiter? i'd guess not based on the list but you could raise it a tad.
I don’t plan on raising the rev limiter at all. How much of the exhaust would I need to change? Would I need a different exhaust manifold? Or just a different setup from the turbo back?
 

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I don’t plan on raising the rev limiter at all. How much of the exhaust would I need to change? Would I need a different exhaust manifold? Or just a different setup from the turbo back?
For that type of power you’d need to change just about everything. Equal length headers would be highly suggested. Either killer b or ets are the top ones. Really I’d go killer b
 

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I'm not sure what kind of halves they are using. I can ask.
Yeah find out. If it’s not new case halves I’d honestly say you should look into an Iag long block instead. This one may be good but I’ve never heard of the shop
 

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Properly machined used cases are not as good or better? In iron block they used to be preferable. Course there's the issue of getting one properly machined . . . My 05 block was one of the first machined in-house at IAG and that was mostly their call to build my block rather than sell me a new one.
 

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Properly machined used cases are not as good or better? In iron block they used to be preferable. Course there's the issue of getting one properly machined . . . My 05 block was one of the first machined in-house at IAG and that was mostly their call to build my block rather than sell me a new one.
they could be just as good. but i know some of the older ones vs newer used a different material, which is why i asked.

What about the fuel system??
to support that power i'd suggest swapping out this as well. well it's necessary. people love ID injectors, ive heard good about FIC too. i know alot of tuners refuse to tune the car with DW fueling parts on it just cause thier quality control went down. and again, if you can afford it, look into a complete fuel system (rails, lines, hardwired pump, injectors, FPR).
 

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Discussion Starter · #18 ·
Yeah find out. If it’s not new case halves I’d honestly say you should look into an Iag long block instead. This one may be good but I’ve never heard of the shop

What do you think about the Precision 5858 turbo?
 

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What do you think about the Precision 5858 turbo?
I like PTE turbos, but the only experience ive had is installing them on friends cars. Ive never run one on a subaru, or at all personally. and from what ive seen the 5858 is slower spooling than the garrett gtx3076 its similar to, but will make more power, i havent directly compared it to the gtx3576 to see how they would be. but precision turbos are quality and if it meets your spool/power goals, you shouldnt have any issues with them at all, i have 3-4 friends who have run them on multiple different setups and all are strong and long lasting.
 

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Make useable real power in an STI means replacing everything . . . - nobody has mentioned a clutch for example. Anyway it is expensive. Budgets first, then decide what you want to do. Not doing the work yourself will cost more, and doing it piecemeal will too . . .
 
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