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How to get power out of your WRX/STI

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Getting sick of all the threads asking the same damn questions so here we go. I read a lot but can pass judgement to 227kw atw atm. Remember peak power isnt anything and power curve isnt everything its in the torque curve that you feel it. Racing dynos is a stupid game as theyre not comparable ever. Power figures Ive quoted are not accurate more of a reference than anything else. Plan long term so you dont end up paying to upgrade something a few times and its always better to stock pile the bits and do it in one hit.

Disclaimer: If you break your car it is not my fault in any way shape or form. Any change you make you really should tune your car for but many people run bad ass T3/T4 chinese jobs untuned and make less power than stock with 200rpm of power after 8k rpm where your heads want to fall apart anyway. My advice dont be a tard and do it right first time.

Stage 0

You need to get your engine up to a good spec first so refresh all the basics.

-Replace spark plugs and timing if it hasnt been done recently.

-Make sure it has good compression and turbo doesnt have issues.

-Make sure the bov doesnt leak at idle

-Cheeck all your sensors/coils/leads are working well and you dont have any CEL.

-Rocker cover gaskets - you dont want hot oil on your exhaust.

-Clean sump and make sure all hoses are up to par no leaks/blockages.

With a stock sti V3-6 you should have 160-170kw atw roughly. With non sti likely 120-140kw atw.

Stage 1

Best gains to be had on the stock ecu are in the breathing mods. These arent required but *sort of* help make more power and bring it to life quicker. You dont have to have these mods but I would recommend them highly but far better going straight to stage 2 at the same time.

-Silicon intake pipe and removing the flexi between the afm and the under mani pipe. Note when tuned this can spool the turbo too fast and bring it into surge.

-2.5-3" Exhaust turbo back. The downpipe gives the biggest gain here in this power bracket if you dont want a loud exhaust. You can make 3" free flow exhausts quieter than stock by using resonators though. By going to a freeflow exhaust you may notice a rise in the boost 1-2 psi.

-Split fuel rail - more of a safety thing you wont notice a gain in power. Search split rail on here theres plenty of info.

-Walbro or equivalent intank fuel pump.

-Upgrading the stock up pipe to a stock size 1.75" iirc that doesnt have the stock flexi restriction can net up to 10kw atw.

-A decent EBC will hold the internal gate shut for longer which gives more low/mid torque and can add 1-2psi safely but best checked on the dyno or with a wideband so you know its safe.

Unsure on the power this will give possibly 10-20kw atw but to make the most of it skip to stage 2.

Stage 2

Going to an aftermarket ecu will give you greater control over whats going on and keep everything a lot safer while giving you more in the low/mid and generally better boost control. It also means you can upgrade injectors so you can keep a low duty cycle and generally better economy. ...and if anything goes wrong its logged so you can pinpoint it a lot better.

-Tuneable ecu or piggyback - do your research.

-Yellow injectors at minimum.

-VF22/23/24/28/29/30/34 sti should have it stock.

-FMIC wouldnt be a silly idea at this stage but not required. Last thing you want is to sit at the lights and heatsoak the s*** out your tmic and not be able to get to 50 in 2 seconds. I have 20psi by 3.6k using closed loop G4 boost control so fmic wont make it laggy if its tuned. Plenty of info on flipping the mani to lose some piping - minimum gain would be losing 500mm of 2.5" pipe and thats a large volume of air. Flipping the comp housing also helps and keeps the piping away from the heat rising off the exhaust.

-Twisting the turbo is not necessary for this power level but helps when flipping the V5/6 mani and frees up the intake without buying the silicon under mani intake.

-An aftermarket 1.7:1 reg will push your injectors out further while keeping them at a safe duty cycle.

-A good set of tuned headers can net better results but Im not a header expert. I know EJ25 250T el back to back with stock uel I had boost faster and stronger and curve felt fatter right to the redline. This was in an untuned state.

When tuned you will see anywhere from 200-230kw atw with stock fuel reg, yellow 440cc injectors and tmic. With the ecu tuned you notice a lot more power over the whole curve and power comes on a lot smoother. For reference my TD04 was slower to spool on stock setup to 14psi than my VF22 to 20psi with the G4 boost control.

How long your stock block lasts will depend on how well it is tuned so dont get a cheap backyard job done.

Stage 3

This I have drawn from my own plans and others builds. Basically this is where it starts to get expensive. If spending bucks on turbos/etc you want to keep the rods in the block and pistons in one piece so think carefully and plan well.

-Minimum of a V7 sti shortblock up to a forged goodness and be silly not to run with at least sti heads. A V8 sti cross drilled crank and baffled sump isnt silly if youre tracking it along with larger oil pump/cooler etc.

-AVCS gives you more down low and helps spool bigger turbos but not a necessity.

-Larger injectors - yellow sidefeed P2 440cc or pink top feed 565cc decapped come out anywhere between 800-950cc@43.5psi and support at least 330kw atw proven. I would suggest cleaning and flow testing so you know what youre working with. Cost me $98 shipped through tony@dtech. ID1000 also seem a popular choice.

-Larger turbo than VF series. TD05 20G seems a popular street choice along with TD06 variants and Garrett offerings. I wont get into that if youre looking at this sort of power I would be talking to your tuner and engine builder to get the best result overall.

-Likely you will need an external wastegate to get solid boost control.

-Possibly a twisted turbo set up to fit your new snail.

Power from here will be dictated by your turbo and engine choice but 250wkw+. 300kw has been seen on V8 sti bottom ends running hypereutectic pistons/tapered rods weaker then the V7 sti shorties. Stroker costs roughly the same as a forged build so have a good long hard think about what you really want out of your car. Remember your car is only as good as the parts and tune you put on it.

Any amendments reply below I cant be arsed proof reading this.

Edited by evowrx
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a pretty good write up Clint.

its really easy to make power but its hard and costs the most to hold that power in..

so my advice:

the 3 stages you\'ve got listed about smack on, but split them out into 2 groups for each stage:

Stage x

i: power making mods

ii: non power making mods recommended.

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 lunchie said:

bump the factory wrx dyno figures from 120-130 to 130-140kw atw.

Depends on the dyno - it\'s just an indicator anyway. I\'d expect to see less for the STi depending where you go too - it\'s just a ballpark place to start remember

Good write up though fo sho

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What about verifying a mod path for pre 2001/post 2001 vehicles

And add

note not to slap a intake or a fmic/ bigger injectors without tuning, or risk engine failure.

Goal = Xwhp/hp

Cost = X$$$

Parts = X recommended parts

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i think Clint has already got the goal (hp / kw) dimension mapped out to a reasonable margin - it varies so widely its hard to be specific. tbh.

the cost thing is a total waste of time, will only cause arguments.

parts - that comes under the mods bit, i think.

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nice right up man

just wondering about the silicone intake pipes.i installed one on my last Subaru and I didn\'t notice ALOT of difference,

ithink for the money and time could be spent else were enless the factory intake pipe is looking dodgy.iwould rather headers over a intake pipe

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Does a mod wanna sticky this somewhere? and maybe leave this thread as a discussion?

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this applies to gc8 models i presume?

could apply for newer as well with a few things evr so slightly different..

nice writeup tho

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 ADIKT said:

Does a mod wanna sticky this somewhere? and maybe leave this thread as a discussion?

worthwhile - let it run its course with some commentary and give Clint a chance to consider any updates and then it can be filed somewhere approp.

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 funkytown said:

a pretty good write up Clint.

its really easy to make power but its hard and costs the most to hold that power in..

so my advice:

the 3 stages you\'ve got listed about smack on, but split them out into 2 groups for each stage:

Stage x

i: power making mods

ii: non power making mods recommended.

I thought about that but its kind of hard to pin point with out back to back sheets to prove the diff.

Shit thing is even the best builds can fuck out with a spot of fuckin awful luck. Cars=lottery. Fast cars=shit odds.

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 gf8wagon said:

nice right up man

just wondering about the silicone intake pipes.i installed one on my last Subaru and I didn\'t notice ALOT of difference,

ithink for the money and time could be spent else were enless the factory intake pipe is looking dodgy.iwould rather headers over a intake pipe

Good feedback Ive seen various responses from wow to woohoo like the tax refund. The pipes get brittle with age and often break when you change turbo or muck around with the mani anyway. For the $150 if I was stock loc Id do it for sure.

Headers well you can go backwards with them esp the linglong with the sick lil johnny 3" up pipe.

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No offense at all but you get my point luck is shite sometimes. Money is expensive.

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In regards to stage 0...

I would put droping the sump and giving it a clean out along with oil pickup. The oil feed(s) pipes would be a good idea too.

Do the late ichi ban\'s trick and remove the mesh filter from oil feed and AVCS feed pipes if install.

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Thanks guys not that hard just seriously needed doing. Probably has I didnt search lol.

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Nice write up bro!

With the EBC whats the max "safe" boost without upgrading injectors I should aim for small power gains in a v2 sti with a TD05?

Cheers

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 jimme18 said:

Nice write up bro!

With the EBC whats the max "safe" boost without upgrading injectors I should aim for small power gains in a v2 sti with a TD05?

Cheers

A decent ebc will bring boost on faster as it holds gate shut as long as it can. You can often get 2-3psi safely but do it on a dyno to be safe. Them compressor taps that I have one of for sale work mint I havent had personal exp tho.

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This is obviously not important enough to sticky or idk what im on about so ill bump it instead.

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 evowrx said:

This is obviously not important enough to sticky or idk what im on about so ill bump it instead.

Bump. This is a very good write up can we please get it stickied as I couldn\'t find it anywhere...had to pm clint

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