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Discussion Starter #1
I have read a lot of conflictiong information on this
What are the differences/similarities?
Are they both using the same block?
 

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If the same holds true from the EJ205 and EJ207 comparisons. Then I'd say that the EJ257 probably has some forged internals. What exactly...I couldn't say. Some one correct me if i'm wrong, but...I believe the EJ255 is open deck and the EJ257 is semi-closed. The last thing that i've heard is that the EJ257s are using different cams then the EJ255s. I dunno, what i've heard could all be speculation. But, that's what i've heard and believe to be true. I haven't looked into it to much.
 

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http://www.wrxtuners.com/forums/212294-post9.html That's what I could find from another thread. Read the whole thread if your more curious....

Edit: Basically the cylinder walls are more supported or enclosed in semi-closed and closed decks. Which should allow it to not flex or warp a cylinder wall. The semi-closed isn't as big of a difference as closed deck is though.
 

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Discussion Starter #5
I always feel dumb asking questions
But how is it the Ej255 in the wrx and the Ej257 in the sti. I am still new to subarus and just trying to soak all the information I can in. So any insight/knowledge is apriciated.
 

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How is what? In a WRX and a STI? I'm assuming your asking which deck is in both versions? I'm pretty positive that it's.

WRX: open deck
STI: semi-closed

Edit: Man, I can't read. Yes, your correct.

WRX: EJ255
STI: EJ257
 

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The heads are also different. The STi heads (EJ257) flow better. Not that it matters at stock power levels of a WRX...
 

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Discussion Starter #8
all right so how much would it really matter on the open deck if i was wanting to go around 300-350 hp around what boost is aiming for i guess?

09 wrx if it matters
 

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The main difference that concerns you between the STi and the WRX is not the engine at all, it's the transmission. The WRX's 5-speed is fragile at that kind of power. It's nothing for the STi's 6-speed.

Also, numbers vary greatly between the flywheel (where car manufacturers rate them) and the road (where dynamometers measure them) so be specific. Also, numbers are just numbers.
 

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Very true....plus boost is relative. Like blackbeast has said for his 08. His AVO turbo makes more power with less boost then the stock turbo. So, magical PSI numbers are just numbers as well.

I'm not a expert at this. But, from what I've read in a flame war over on rs2.5 boards. Open deck Forced induction blocks with the lower compression are probably good to 350-400 crank. Open deck natural aspirated 2.5 engines with a turbo conversion probably 300 crank max. It's a highly debated subject over there for conversions or upgrades. Plus, most people over there still consider a wrx engine swap out or a STI SB hybrid for big numbers. Granted...they're still facing a weak transmission problem as well.
 

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Discussion Starter #11
opps i thought that i said at the wheels. so really the weak part would be transmission not the block or anything?
 

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Discussion Starter #13
So not that I am anywhere near needing to but would the sti 6 speed bolt up or are there other 6 speeds out there that bolt up correctly?

And the cylinder walls on the opendeck really don't pose much of a problem?
 

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I'm pretty sure it's the same as previous years. 90+%. It's not anywhere near a bolt on solution. It's cheaper to trade the WRX in for an STi. Although there are other options, some stronger even than the STi's 6-speed and many cheaper. Most WRX owners, even ones who broke their trannys, probably shouldn't be considering 6-speed swaps.

That said, you should be aware that the tranny is not indestructible, even at stock power levels. Launching your car can cause serious damage if you mess up.
 

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Discussion Starter #16
like i was saying i am no where near needing a stronger tranny at the moment
I was just curious. Just trying to learn a little more about Subaru and the setups.
If I could afford the STI i would have bought one though
 

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well, when the time comes you probably will want either another stocker (~200whp), upgrading to RA gears(~300whp), a PPG syncro'd helixial setup (~500whp), or a full out dog box (a lot).
 

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Discussion Starter #18
All right thanks for the info

Anything else I should know about the two engines and their differences?
 

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The blocks themselves are identical. The EJ257 and EJ255 share the same block castings, crank, and rods. The difference is the piston dish and heads. The combination of the small chamber EJ255 head and shorter piston dome make the 8.4:1 CR. The EJ257 has a deeper head and taller dome, making 8.2:1. Trust me, I've built motors with both EJ255 and EJ257 blocks and heads and the shortblock is identical with the exception of the piston.
 

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Uh? 06rexwagon. Is the ej255 deck semi closed? Just wondering, because I was under the impression that only the 257 deck was semi-closed. Kinda surprised if they didn't slip in any forged parts as well, just like the 207 layout.
 
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