FirstR

i have to make a decision now

7 weeks ago i blew my engine and 3 weeks ago i bought a recently rebuilt (has done ~ 2k miles) 2 litre STI V5 engine with V8 crank, forged pistons and rods, better oil pump, ACL bearings, lightened flywheel and more....

actually it was planned just to take the block and put my s-turbo heads on but now my mech asked me if i don´t want to take the whole engine and just put my s-turbo intake manifold on.

could be funny but i´m afraid all the low and mid range power is gone then. my old engine +vf34 had positive manifold pressure ~ 2100 and full boost round 2800. i really want to keep the vf34 but i have no idea when the sti engine would begin to boost then.

anyone an idea?

is it worth to use the sti heads or is it morelike a downgrade?

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI

 

Nich B

I believe that foresters have a softer cam profile than an STi

a known engine upgrade is to fit V3 top end to the standard block

You are now in the realms of seriosly changing the characteristics of the car, are you happy living day to day with that?

Personally that new motor sounds lovely, stick it in and be done with it, and fit your vf34

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My mods are worth more than the car

ther1guy

isnt the jdm 2 liter set up for twin scroll turbos? i'm just askin..

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04 XT 6MT
View Mod list here

Mark CSC

Nope only the new ones

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97 JDM S/tb with a proper gearbox ;)

The Rookie

You'll have slightly more aggresive cams so would loose a little bottom end torque, however the earlier exhaust valve opening would normally spool a turbo earlier all else being equal, however the STi is also 9:1 CR instead of 8:1 (0r 8.5:1 depending which spec you read) which will go some way to correcting the low end torque, so unless torque at 1000-200 is really important to you (and I love it!) go with the STi heads as well, be rude not to - but get it remapped before you loose a second engine!

Simon

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98 S-turbo, next mod decat D/P and hybrid turbo!

Nich B

seems like a no brainer as you already have the engine

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My mods are worth more than the car

FirstR

my 99 forester has 8.5:1 and i thought the sti has the same 8:1 like all the other calssic imprezas over here. are you sure about the 9:1, simon? must admit i didn´t really have much time to find out more.had tooo much to do at work the last two month and moving to the new flat cost a lot of time...

GC8 STIs are almost impossible to find over here so we don´t know much about them. would be great if it´s true with the 9:1



at the beginning the plan was to modify my old block with a 2.5 crank and rods and oversize pistons to get a 2.125 litre but then my mech said my open deck block is not the best choice to do that so we went for a semi closed deck and finally found that complete modified sti engine

i dont knwo how it will perform. i know lots of WRxs and some 2.5 STI imprezas but only one stock 2 litre sti - a bugeye with the stock vf35. i think it runs quite nice maybe the 6 speed tranny helps
don´t know if the vf34 would make it that much worse...

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI

The Rookie

Most the info I has says that the JDM's have a 9:1 CR, although having rechecked some sources, some state 8.5 and 8, so maybe its not as clear cut!

re the cam changes, could be worth reading XT cams in GT??

Simon

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98 S-turbo, next mod decat D/P and hybrid turbo!

FirstR

update!

my intake manifold doesn´t fit the 97/98 heads so we´ll keep my heads.

in some way i´m sad - 8000 revs could have been funny.
on the other hand it´s good to keep the low and mid range power as it´s my daily driver

don´t know how much boost i can run with that setup

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI

FirstR

i´m not so happy with my new engine. now with a CR of 8:1 instead of 8,5:1 it feels amazingly weak at low revs and it lost a lot of tourque. turbo seems to spool ~ 600-700 revs later later and even when i stab it at 3500 there´s a 3 second lag.

must admit i didn´t have the time for an ecutek remap yet and i´m not sure if it would help anyway, what do you think?

only good thing it revs much smoother up to 7000, sounds like a turbine and on a long trip to switzerland even loaded up with 780kg ( i know that was far too much) i managed 34.4 MPG

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI

The Rookie

The CR change shouldn't have that much effect on either low end torque (about 5% max, which you wouldn't feel through your seat) or the spool if your on the original heads, so it sounds to me like something else is wrong, cam timing would be the first check, especially give the eagerness at high rpm.

Simon

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98 S-turbo, next mod decat D/P and hybrid turbo!

FirstR

i´m going to Ecutek Hungary next thursday. they said they will have a look at that before the remap.

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI

FirstR

maybe i´ve found a problem with the MAP-sensor. yesterday i took out my GFB boost controller which was set to 1,15, just the same level as the ecutek guys set my ecu - at least they told that because on the way home from my remap with the stock solenoid in my (cheap) boost gauge showed me 1.4. i thought it must be the cheap gauge but to be sure i put a mnual boost controller in and set it down to 1.15.
tomorrow i´m going to the remap so i put the solenoid in again. once again my boost gauge showed me 1,4 hold. but when i tried two other different boost gauges they all showed me 1.4-1.5 hold


shouldn´t there already be a fuelcut? is there a way to clean or check the MAP sensor? the subaru select monitor says 1,15 but how can 3 different gauges be so wrong???

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greets, Alex
Mx-5 mkII 1.8
`99 S-turboSTI