engine swap - Subaru WRX Forum
 
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#1 Old 11-10-2007, 09:11 AM
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engine swap

I thinking of swapping to a 04 sti 2.5L engine(I currently have a 04 2.0L wrx engine.) that my friend is about to give me basically for free....He is gonna drop a fully built race engine in his sti. How hard is the swap? I would be getting his ecu and everything (including a cobb tuner for it.) It would be a turn key engine with the exception of the tranny. I'm thinking of redoing the gears in my tranny for the swap. or maybe sourcing a STI tranny from some where. any ideas would be helpful as it will probably happen with in the next 6 monthes. What turbo is best for it? 20g or a perrin gtr30 rotated kit? Any and all Ideas welcome...I'm not looking at drag racing with it. I basically want a killer cornering machine for autocross and time attacks and maybe some freeway runs. Help me out guys .Thanks -Big Jay.

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#2 Old 11-10-2007, 11:17 AM
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it will bolt right in... along with the ECU you will need the wire harness from the STI, because it is a little different. the STI has 2 cam position sensors and AVCS. and it is also drive by wire, so you will need everything that goes with that. Its doable but will take alot of work.

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#3 Old 11-10-2007, 12:18 PM
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Quote:
Originally Posted by BigJay View Post
I thinking of swapping to a 04 sti 2.5L engine(I currently have a 04 2.0L wrx engine.) that my friend is about to give me basically for free....He is gonna drop a fully built race engine in his sti. How hard is the swap? I would be getting his ecu and everything (including a cobb tuner for it.) It would be a turn key engine with the exception of the tranny. I'm thinking of redoing the gears in my tranny for the swap. or maybe sourcing a STI tranny from some where. any ideas would be helpful as it will probably happen with in the next 6 monthes. What turbo is best for it? 20g or a perrin gtr30 rotated kit? Any and all Ideas welcome...I'm not looking at drag racing with it. I basically want a killer cornering machine for autocross and time attacks and maybe some freeway runs. Help me out guys .Thanks -Big Jay.
The swap is fairly easy. The main issue will be drive by wire throttle which also requires pedals from a usdm sti. But you can just keep the intake manifold from your rex or replace a throttle body, or use wrx braket for the throttle cables, and retain your wrx pedals. If you are not upgrading the transmission at the time of the motor swap, you should just keep the stock sti turbo with everything. The power will be amazing right away and not too much extra stress on transmission. If you go even 20g, be prepared for new gears or tranny.
I am not sure on the vacuum lines and fuel lines, but since yours is same year as the donor car, it should all the same.
Hope this helps,
cheers!

drive = freedom
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#4 Old 11-10-2007, 09:07 PM
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Great thanks for the help ...any one know of a good source to find these parts used? Tranny, Wiring harness, etc......

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#5 Old 11-10-2007, 11:56 PM
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it would be way easier to just use your 2.0 heads and bolt it to the sti block and then you wont need to mess with a new wire harness...
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#6 Old 11-11-2007, 11:35 AM
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you can try junkyards, but it will be hard to find a wire harness, I imagine it would be aroud 500 from the dealer, but that is just a guess. i would wait and try to find a harness before i would use 2.0 heads on a 2.5. you want the AVCS

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#7 Old 11-12-2007, 12:34 AM
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Yeah i reallly want the Avcs ....Do I really need to change out the pedal set?

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#8 Old 11-12-2007, 10:16 AM
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the TPS is in the pedal so yes you will need that, youll only have to change the throttle pedal

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#9 Old 08-05-2008, 07:03 PM
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sorry to bump this thread but just need some more info.... ok so heres what i have:
ej257 motor complete
engine harness
ecu

all of this will be going into an 02 wrx.... what else am i going to need? i was told that i could just use my stock intake manifold and as long as TPS was hooked up that i wouldnt need to change the pedal..... and if i do have to change the pedal... whats involved in that??? thanks for your time!
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#10 Old 08-10-2008, 06:07 PM
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Anyone? I really need some help.... Could really use some info on the wiring and dbw... Thanks every!
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#11 Old 08-11-2008, 10:12 AM
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If you use the STi's heads, you need drive by wire setup which does mean the petal.

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#12 Old 08-11-2008, 11:22 AM
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Ok I got that 1 but what do I do? Just run wires from the pedal to the ecu? Is that all that's involved? Thanks!
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