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Old 10-14-2019, 03:51 PM   #1
tsrapophis
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Default G25-660 Daily/autox bugeye build.

So after a predictable EJ205 failure during an Autocross late in 2018 I decided to build my 20002 WRX centered around Garrett's G25-660. The goal was to make a mid-range response monster with 400whp on pump gas that could be a locally competitive car but still driven to the track and work. I feel that I have accomplished that with this build and I've been super impressed with this turbo. The build, fabrication and tuning has all been done by me and/or friends except for the engine machining and assembly which was done by Gibson Performance in Spokane WA. Also a shoutout to both Fishhead performance and Tier 1 performance for the use of their dynos at various stages of the build.

Highlights.

- Dyno numbers - 397 whp at 7000 rpm and 345 ftlbs peak. The torque is above 300ftlbs from 4200-7000rpm. Dyno Dynamics (Stock STi is 215whp) On pump gas, 20psi and 11.9 AFR, 55F ambient temp, 2073 ft above sea level.

- Turbo system - Garrett G25-660 0.72 AR, custom rotated kit, Tial 38mm EWG, custom air to water (A2W) intercooler top mounted, cobb 3 port boost solenoid.

- Fuel system - ID 1300cc injectors, Aeromotive 340lph pump, stock tank, Cosworth fuel rails plumbed in series, stock lines from tank to filter and then -6 AN after that, Fuel lab regulator.

- Exhaust system - AFE 4-1 twisted headers (same as MAPerformance), Custom 2.5" upipe with a Y for the EWG, recirculated EWG to the downpipe, custom stainless 3" exhaust with a vibrant 18" resonator and magnaflow 14" muffler.

- Short Block - EJ257 with stock crank, Manley turbo tuff I beam rods, Mahle powerpak 99.5mm/ 4032 low expansion alloy, Killer bee oil pan and pickup.

- Heads - EJ257 heads with a die grinder port and polish by me, GSC S1 cams, ferrea springs, ferrea stainless valves stock size.

- Controls - Megasquirt MS3Pro based plug-n-play unit for 02 wrx, some custom integration and extra sensors by me, LC2 wideband O2 at stock rear O2 location.

- Drivetrain - 03 JDM 6 speed non DCCD w/3.90 final drive, R160 rear diff w/cusco LSD, DSS single piece aluminum driveshaft, DSS front OE replacement axles, stock rear axles, ACT 6 puck clutch w/sprung hub, ACT street lite flywheel.

- Brakes - 4pot/2pot conversion, EBC yellow pads and GD rotors, ABS delete, Wilwood bias valve.

- Suspension - Feal 441+ 1 way adjustable custom valved coilovers w/ spherical top mounts, bushings, lockdown bolts, STI control arms, Whiteline sway bars, Greddy Strut tower braces, the usual autocross stuff.

I have some tidying up left to do, it's been a bit of a thrash to get it ready before the end of season for testing; so this winter will be busy. Plans are to do a few more handling mods to tighten it up, Perrin PSRS, Delrin bushings, upgraded trailing arms and lateral links, solid subframe bushings. And I'll probably end up putting in some kind of cage. Half or full I am undecided but I have friend who won't ride with me until I let him cage it, lol. Unfortunately I can't go to bigger brakes without losing the ability to run my street and winter wheels; the car needs better brakes for the punishment I put it through. Some pics are here, I'll post more pictures and more detail of the individual systems soon.

https://i.imgur.com/KfqMHqe.jpg
Currently not utilizing AVCS, however that will come soon and fill in that curve a bit more.

https://i.imgur.com/6qEhLjA.jpg

https://i.imgur.com/2LoH8jb.jpg
G25-660 vs. VF24

https://i.imgur.com/7qIRzv8.jpg
Progress shot of the engine layout
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Last edited by tsrapophis; 10-14-2019 at 03:59 PM.
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Old 10-14-2019, 04:26 PM   #2
trueno92
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that dyno is intense. making power all the way to 7k!!!

nice wheel and tire choice. looks like u went up a size. what are you doing for Engine management? are you running carberry?
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Old 10-14-2019, 04:34 PM   #3
tsrapophis
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Quote:
Originally Posted by trueno92 View Post
that dyno is intense. making power all the way to 7k!!!

nice wheel and tire choice. looks like u went up a size. what are you doing for Engine management? are you running carberry?
Thanks! The wheels are Sparcos and my dailys and 16", I race on 17" RPF1's. The car makes power up to 7500 before it starts to fall off but I forgot to ask the dyno tech to run it up that high. He wasn't used to revving an EJ257 up like that lol.

Running a Megasquirt MS3pro based setup. It's from their PNP lineup but I have had to make a lot of changes to it's original configuration. Love it so far though. Launch control is aggressive!
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Old 10-14-2019, 07:13 PM   #4
tsrapophis
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Head porting detail.

I used a long nosed die grinder with a couple different size and shape rotary files to do the bulk of the material removal. Afterwards everything was smoothed out with a couple stages of sand paper flapper wheels. 80 and 160 I believe. All the pictures are progress pieces. I didn't get any finished pics.

https://i.imgur.com/8DC9kVm.jpg
https://i.imgur.com/SpcJqBD.jpg
https://i.imgur.com/35d2uUZ.jpg

On the intake ports I port matched to the intake gasket, knife edged the divider and then carefully smoothed the transition on the back side of the valve seats. afterwards I polished everything until smooth, but not with the goal of enlargement.

https://i.imgur.com/hyuxgWM.jpg
https://i.imgur.com/GDGSEPK.jpg

Above is a bit of before and after on the valve seats pretty rough stuff on brand new subaru castings.

On the exhaust side, similar port match and valve seat smoothing procedure. I also paid extra attention to the rear most ports on cylinders 2 & 4. The rear most ports in the heads had quite a big kink in them compared to the nice and straight shots of the rest. So I took a decent amount of material out of the inside of the curve to try and reduce the backpressure.
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Old 10-17-2019, 09:33 AM   #5
vicious_fishes
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So I just saw this from another thread. How come you didn't up the redline? and I presume you kept the 2.0L capacity? Also curious as to why just 20psi, was it way out of efficiency past it or did you just feel like that was enough?
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Old 10-17-2019, 02:53 PM   #6
tsrapophis
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Originally Posted by vicious_fishes View Post
So I just saw this from another thread. How come you didn't up the redline? and I presume you kept the 2.0L capacity? Also curious as to why just 20psi, was it way out of efficiency past it or did you just feel like that was enough?
Its a 2.5L and the redline is 7500, It was a miscommunication with the dyno operator. Its still right in the meat of the efficiency but as I'm chasing the dream of "reliable 400hp" I didn't want to lean on it more than I needed to after I achieved my hp goal. It already feels stupid fast with the turbo response and torque band. Next year I'll set it up with flex fuel and tune on ethanol for some big numbers but it's not high on my priority list. E85 is kind of scarce around here so I'll have to buy a barrel of Thunderbolt when I want to do that.
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Old 10-18-2019, 02:49 AM   #7
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Gotcha. got a spool plot? very interested to compare to the old gtx3067
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Old 10-18-2019, 03:44 AM   #8
subaru_gc8
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are you running avcs?
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Old 10-18-2019, 05:39 PM   #9
tsrapophis
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Quote:
Originally Posted by vicious_fishes View Post
Gotcha. got a spool plot? very interested to compare to the old gtx3067
No spool plot, all I have is datalogs of MAP from an autocross. Full vacuum to full boost in 0.85s beginning at 4500rpm (35kpa-245kpa absolute).
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Old 10-18-2019, 05:42 PM   #10
tsrapophis
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Quote:
Originally Posted by subaru_gc8 View Post
are you running avcs?
I am not running avcs yet. I've been having a difficult time figuring out how to make the factory hall effect sensors work with my MS3. I only recently learned that the factory sensors switch polarity at random, which my ecu is not equipped to handle. Once I get over that hurdle I'll be able to start using AVCS and then I'll post another dyno plot.
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Old 10-22-2019, 08:58 AM   #11
PrinceVegeta
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Hey man thanks for the info

Your max boost is 20psi and hitting 20psi @ 4500rpm ?
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Old 10-23-2019, 05:45 PM   #12
tsrapophis
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Quote:
Originally Posted by PrinceVegeta View Post
Hey man thanks for the info

Your max boost is 20psi and hitting 20psi @ 4500rpm ?
It comes on slightly before, but I don't have the exact figure. I know that if I brake boost on the freeway I can make 15 lbs at 3700 RPM.
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Old 10-23-2019, 10:03 PM   #13
PrinceVegeta
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Cool.

I have a 2.0L 4EAT max RPM 7000

My dream turbo is the G25 660

I was wondering if I should go for the 0.49 T25 A/R or the 0.72 Vband A/R..

Not sure if the 0.49 A/R would be too small tho
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Old 10-24-2019, 01:34 PM   #14
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Quote:
Originally Posted by PrinceVegeta View Post
Cool.

I have a 2.0L 4EAT max RPM 7000

My dream turbo is the G25 660

I was wondering if I should go for the 0.49 T25 A/R or the 0.72 Vband A/R..

Not sure if the 0.49 A/R would be too small tho
i think think the 49 might be okay since youare not really going for ultimate power. if you want a better flowing turbo maybe the 550 would be a better choice.
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Old 10-24-2019, 01:54 PM   #15
PrinceVegeta
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Thanks!

I kinda want something in between. Good power and good spool. Hence maybe the 660 with the .49 a/r

What do you mean 550 is a "better flowing turbo" ?

You mean that in comparison to the 660 ?
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Old 10-26-2019, 12:19 AM   #16
PrinceVegeta
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Oh perhaps you mean that the 550 is a better spooling turbo than the 660?

I'm kinda looking more towards the 660 as I would like a little more headroom
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Old 10-27-2019, 12:57 PM   #17
bp05obxt
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Default G25-660 Daily/autox bugeye build.

Quote:
Originally Posted by PrinceVegeta View Post
Thanks!



I kinda want something in between. Good power and good spool. Hence maybe the 660 with the .49 a/r



What do you mean 550 is a "better flowing turbo" ?



You mean that in comparison to the 660 ?


I would highly suggest steering away from the t25 .49a/r. You will end up with increased back pressure for very little gain.

Overall EJís need to breathe to really shine the better the turbine flow the easier it is for the engine to breathe and make power. I gather that you want good spool, but I firmly believe that the .72 G25-660 would be the optimal setup for you; even with an EJ20. Good spool and should continue making power through redline even if redline is bumped up.
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Old 10-27-2019, 08:13 PM   #18
subaru_gc8
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Quote:
Originally Posted by bp05obxt View Post
I would highly suggest steering away from the t25 .49a/r. You will end up with increased back pressure for very little gain.

Overall EJís need to breathe to really shine the better the turbine flow the easier it is for the engine to breathe and make power. I gather that you want good spool, but I firmly believe that the .72 G25-660 would be the optimal setup for you; even with an EJ20. Good spool and should continue making power through redline even if redline is bumped up.
you know hes automatic right?
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Old 10-27-2019, 08:18 PM   #19
subaru_gc8
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Quote:
Originally Posted by PrinceVegeta View Post
Oh perhaps you mean that the 550 is a better spooling turbo than the 660?

I'm kinda looking more towards the 660 as I would like a little more headroom
what I mean be better flowing is you can have a bigger turbine housing with a smaller turbo because it spools faster so efficiency will be better on the top end (it will feel more linear)
Since your car is an auto it will be a dog til you hit 4000 or a little later with th 660. once again, youre not going to be happy going of r ulitmate power but you want something that is drivable. especially with an auto and that is why I suggested the smaller 550 with a larger turbine rather than a 660 with a smaller turbine housing

also im assuming you have a usdm not a jdm running avcs is that right?
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Old 10-28-2019, 01:12 AM   #20
bp05obxt
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Default G25-660 Daily/autox bugeye build.

Quote:
Originally Posted by subaru_gc8 View Post
you know hes automatic right?


Yes. Good thing there isnít much boost lost between shifts.... spool becomes less of an issue. Sluggish initially in first gear maybe? Still beats a manual running into the limiter and trying to go to second if we are talking all out pace. Might feel less exciting, but Iíd bet it would move along nicely.
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Old 10-28-2019, 03:13 AM   #21
PrinceVegeta
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Quote:
Originally Posted by bp05obxt View Post
I would highly suggest steering away from the t25 .49a/r. You will end up with increased back pressure for very little gain.

Overall EJís need to breathe to really shine the better the turbine flow the easier it is for the engine to breathe and make power. I gather that you want good spool, but I firmly believe that the .72 G25-660 would be the optimal setup for you; even with an EJ20. Good spool and should continue making power through redline even if redline is bumped up.
Thank you Sir.

I was also thinking of shooting for the .72 as it's in the middle of the .49 and .92

However my redline cannot be changed as it's limited by the TCU. Redline will always stay at 7000rpm
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Old 10-28-2019, 03:15 AM   #22
PrinceVegeta
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Quote:
Originally Posted by subaru_gc8 View Post
what I mean be better flowing is you can have a bigger turbine housing with a smaller turbo because it spools faster so efficiency will be better on the top end (it will feel more linear)
Since your car is an auto it will be a dog til you hit 4000 or a little later with th 660. once again, youre not going to be happy going of r ulitmate power but you want something that is drivable. especially with an auto and that is why I suggested the smaller 550 with a larger turbine rather than a 660 with a smaller turbine housing

also im assuming you have a usdm not a jdm running avcs is that right?
My car is RHD JDM 2008 WRX 4EAT (GH8)

It has Dual AVCS. U20 heads.

If I were to purchase Aftmkt cams, it would be the same part number as the 2008+ USDM STI
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