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Old 08-26-2007, 05:06 PM   #1
Scooby Specialist
Member#: 84443
Join Date: Apr 2005
Chapter/Region: NWIC
Location: Ducks, OR
2015 Forester XT

Default It's Hybrid Time for me Bugeye, but ?'s

I had always planned to go to a 2.5, but recent low compression test results (135 in #1 and #3 and like 23% and 32%, 2/4 were 150-152 12%/8%) have me accelerating my plans I am going to do a 2.5 STI SB Hybrid with OEM WRX heads.

Car runs great, but I don't pound on it much, or maybe I would have broken something by now (had from 15k-75k)? Just figured if I was to try and use my heads, I might as well do it sooner than later.

My questions are around what other changes might make sense while we are there and would best add to my set-up/new engine? I do not have too much budget to go beyond the block, head studs, gaskets, labor, etc...and am already leaning toward a new clutch.

Purpose: DD/2-4 autox/yr.
#'s: 288whp/278lbft @ 18psi 92
Goals: 295/295 - 310/310 range + low-end torque gains

Bits that matter: 16G(550cfm), FMIC, 860cc Inj, Walbro255, 3" tbe, STI up, CobbAP (PDX)

I am not considering plans that include P&P or heat wraps, my goals are modest and I just can't spare the extra $s vs other things. PDX Tuning will be doing the work to include the usual cleaning, etc. plus the new map.

What I am considering:

1. Clutch (original OEM is 75K, might as well) - OEM replacement or similar
2. Gruppe-S Unequal Headers - $350 (HKS would be 1st choice, but too much$$) - worth it or no? 200rpm+/- better spool? Addicted to boxer sound.
3. Lightweight Pulley - just not sure of real benefits, but for this set-up?
4. Engine mounts - replace OEMs for good measure

Comments on above or anything else that would make sense to consider?
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Old 08-27-2007, 09:41 PM   #2
Le Saboteur
Scooby Specialist
Member#: 142244
Join Date: Mar 2007
Chapter/Region: MAIC
Location: baltimore
2007 SWP STi
WFC #243


okay everyone has different opinions on what they THINK will work, but i can tell you first hand (as can other members of course) that this is a safe build as long as its done right
first, as long as you are using a stock 2.5, you dont really need headstuds
fmic is a good idea, the engine will be putting off a lot more heat
headers, too, to lower bay temps
bigger turbo, unless you dont mind the td dying at 5k rpm
exhaust +
bigger injectors +
fuel pump +
as far as management, i would go with the AP
uhh i think thats it although as ive said before im probably forgetting something hope this helps

+ clutch! exedy twin is a good choice, you could try similar ACT or something too, i wouldn't go with OEM
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Old 08-28-2007, 06:36 PM   #3
Scooby Newbie
Member#: 145138
Join Date: Apr 2007
Location: Stockton, California, 209
2002 Impreza WRX
WR Blue


I've been with the Hybrid setup for almost 2 weeks. Broke in the motor in a week and just got dyno tuned. here is what i did with my setup.

This is what my tuner recommended:
OEM STI short block
Machine 0.2L WRX heads
ARP Head studs
PE Timing belt
NGK Iridium plugs (one step colder)
New STi Gaskets
AP 2.0
STi oilpump (I upgraded to the cosworth pump)
STi Waterpump
Tensioner Pully

I added:
Overhaul gasket kit (since everything was open)
Invidia Up & Divorced down pipes
Apexi Noir catback.
Act Clutch Disk

lukasandrew is right in saying your engine bay temp will rise. But i havent seen an issue with it yet and it has been in the 100s lately. I imagine you would have no kind of issue since your in WA.

I would suggest dumping the headers and going with a bigger cams durations. You'll have more gains with cams. When setting up the hybrid it will fall short fast in the top end because of the restricted flow. You can combat it with a bigger turbo, but you'll have a way better top end if you had a better cam profile with a bigger turbo.

I was on a budget and didn't have enough for cams or a turbo/injectors/fuel pump/TMIC so i'll be doing that down the line after suspension and tranny work. But the TD04 is pretty much a pea shooter with the 2.5L block, but since your engine is open, you might as well work on the internals then focus on bolt-ons later.

Just my .02
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Old 08-29-2007, 12:21 PM   #4
Scooby Specialist
Member#: 84443
Join Date: Apr 2005
Chapter/Region: NWIC
Location: Ducks, OR
2015 Forester XT


Thanks for the feedback, I appreciate the insight. At the end of the day, budget and limited goals had me decide on:

Work being done by PDX Tuning:

EJ257 SB
WRX Heads
WRX Oil Pump
WRX Water Pump
New Gaskets (thicker HG to keep comp around 8:2)
New Head Stud Kit
New Timing Belt
New OEM WRX Clutch
HKS Headers - used for $300

What's already on:

Cobb AP - PDX 18psi map
16G (550cfm)
860cc Inj
Walbro 255
Perrin Fuel Rails
3" TBE
LGT 1st/2nd gear swap

Starting Thursday and hope to have done by Tues/Wed next week. Hopefully my heads check out or we will be delayed sourcing replacements.
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